diff options
Diffstat (limited to 'sys/netinet/tcp_input.c')
| -rw-r--r-- | sys/netinet/tcp_input.c | 3729 |
1 files changed, 3729 insertions, 0 deletions
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c new file mode 100644 index 0000000..a7b6ced --- /dev/null +++ b/sys/netinet/tcp_input.c @@ -0,0 +1,3729 @@ +/*- + * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 + * The Regents of the University of California. All rights reserved. + * Copyright (c) 2007-2008,2010 + * Swinburne University of Technology, Melbourne, Australia. + * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> + * Copyright (c) 2010 The FreeBSD Foundation + * Copyright (c) 2010-2011 Juniper Networks, Inc. + * All rights reserved. + * + * Portions of this software were developed at the Centre for Advanced Internet + * Architectures, Swinburne University of Technology, by Lawrence Stewart, + * James Healy and David Hayes, made possible in part by a grant from the Cisco + * University Research Program Fund at Community Foundation Silicon Valley. + * + * Portions of this software were developed at the Centre for Advanced + * Internet Architectures, Swinburne University of Technology, Melbourne, + * Australia by David Hayes under sponsorship from the FreeBSD Foundation. + * + * Portions of this software were developed by Robert N. M. Watson under + * contract to Juniper Networks, Inc. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include "opt_ipfw.h" /* for ipfw_fwd */ +#include "opt_inet.h" +#include "opt_inet6.h" +#include "opt_ipsec.h" +#include "opt_tcpdebug.h" + +#include <sys/param.h> +#include <sys/kernel.h> +#include <sys/hhook.h> +#include <sys/malloc.h> +#include <sys/mbuf.h> +#include <sys/proc.h> /* for proc0 declaration */ +#include <sys/protosw.h> +#include <sys/signalvar.h> +#include <sys/socket.h> +#include <sys/socketvar.h> +#include <sys/sysctl.h> +#include <sys/syslog.h> +#include <sys/systm.h> + +#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ + +#include <vm/uma.h> + +#include <net/if.h> +#include <net/route.h> +#include <net/vnet.h> + +#define TCPSTATES /* for logging */ + +#include <netinet/cc.h> +#include <netinet/in.h> +#include <netinet/in_pcb.h> +#include <netinet/in_systm.h> +#include <netinet/in_var.h> +#include <netinet/ip.h> +#include <netinet/ip_icmp.h> /* required for icmp_var.h */ +#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ +#include <netinet/ip_var.h> +#include <netinet/ip_options.h> +#include <netinet/ip6.h> +#include <netinet/icmp6.h> +#include <netinet6/in6_pcb.h> +#include <netinet6/ip6_var.h> +#include <netinet6/nd6.h> +#include <netinet/tcp_fsm.h> +#include <netinet/tcp_seq.h> +#include <netinet/tcp_timer.h> +#include <netinet/tcp_var.h> +#include <netinet6/tcp6_var.h> +#include <netinet/tcpip.h> +#include <netinet/tcp_syncache.h> +#ifdef TCPDEBUG +#include <netinet/tcp_debug.h> +#endif /* TCPDEBUG */ +#ifdef TCP_OFFLOAD +#include <netinet/tcp_offload.h> +#endif + +#ifdef IPSEC +#include <netipsec/ipsec.h> +#include <netipsec/ipsec6.h> +#endif /*IPSEC*/ + +#include <machine/in_cksum.h> + +#include <security/mac/mac_framework.h> + +const int tcprexmtthresh = 3; + +int tcp_log_in_vain = 0; +SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, + &tcp_log_in_vain, 0, + "Log all incoming TCP segments to closed ports"); + +VNET_DEFINE(int, blackhole) = 0; +#define V_blackhole VNET(blackhole) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, + &VNET_NAME(blackhole), 0, + "Do not send RST on segments to closed ports"); + +VNET_DEFINE(int, tcp_delack_enabled) = 1; +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, + &VNET_NAME(tcp_delack_enabled), 0, + "Delay ACK to try and piggyback it onto a data packet"); + +VNET_DEFINE(int, drop_synfin) = 0; +#define V_drop_synfin VNET(drop_synfin) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, + &VNET_NAME(drop_synfin), 0, + "Drop TCP packets with SYN+FIN set"); + +VNET_DEFINE(int, tcp_do_rfc3042) = 1; +#define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, + &VNET_NAME(tcp_do_rfc3042), 0, + "Enable RFC 3042 (Limited Transmit)"); + +VNET_DEFINE(int, tcp_do_rfc3390) = 1; +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, + &VNET_NAME(tcp_do_rfc3390), 0, + "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); + +SYSCTL_NODE(_net_inet_tcp, OID_AUTO, experimental, CTLFLAG_RW, 0, + "Experimental TCP extensions"); + +VNET_DEFINE(int, tcp_do_initcwnd10) = 1; +SYSCTL_VNET_INT(_net_inet_tcp_experimental, OID_AUTO, initcwnd10, CTLFLAG_RW, + &VNET_NAME(tcp_do_initcwnd10), 0, + "Enable draft-ietf-tcpm-initcwnd-05 (Increasing initial CWND to 10)"); + +VNET_DEFINE(int, tcp_do_rfc3465) = 1; +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW, + &VNET_NAME(tcp_do_rfc3465), 0, + "Enable RFC 3465 (Appropriate Byte Counting)"); + +VNET_DEFINE(int, tcp_abc_l_var) = 2; +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW, + &VNET_NAME(tcp_abc_l_var), 2, + "Cap the max cwnd increment during slow-start to this number of segments"); + +static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); + +VNET_DEFINE(int, tcp_do_ecn) = 0; +SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW, + &VNET_NAME(tcp_do_ecn), 0, + "TCP ECN support"); + +VNET_DEFINE(int, tcp_ecn_maxretries) = 1; +SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW, + &VNET_NAME(tcp_ecn_maxretries), 0, + "Max retries before giving up on ECN"); + +VNET_DEFINE(int, tcp_insecure_rst) = 0; +#define V_tcp_insecure_rst VNET(tcp_insecure_rst) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, + &VNET_NAME(tcp_insecure_rst), 0, + "Follow the old (insecure) criteria for accepting RST packets"); + +VNET_DEFINE(int, tcp_recvspace) = 1024*64; +#define V_tcp_recvspace VNET(tcp_recvspace) +SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_RW, + &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); + +VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; +#define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, + &VNET_NAME(tcp_do_autorcvbuf), 0, + "Enable automatic receive buffer sizing"); + +VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; +#define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, + &VNET_NAME(tcp_autorcvbuf_inc), 0, + "Incrementor step size of automatic receive buffer"); + +VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; +#define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, + &VNET_NAME(tcp_autorcvbuf_max), 0, + "Max size of automatic receive buffer"); + +VNET_DEFINE(struct inpcbhead, tcb); +#define tcb6 tcb /* for KAME src sync over BSD*'s */ +VNET_DEFINE(struct inpcbinfo, tcbinfo); + +static void tcp_dooptions(struct tcpopt *, u_char *, int, int); +static void tcp_do_segment(struct mbuf *, struct tcphdr *, + struct socket *, struct tcpcb *, int, int, uint8_t, + int); +static void tcp_dropwithreset(struct mbuf *, struct tcphdr *, + struct tcpcb *, int, int); +static void tcp_pulloutofband(struct socket *, + struct tcphdr *, struct mbuf *, int); +static void tcp_xmit_timer(struct tcpcb *, int); +static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); +static void inline tcp_fields_to_host(struct tcphdr *); +#ifdef TCP_SIGNATURE +static void inline tcp_fields_to_net(struct tcphdr *); +static int inline tcp_signature_verify_input(struct mbuf *, int, int, + int, struct tcpopt *, struct tcphdr *, u_int); +#endif +static void inline cc_ack_received(struct tcpcb *tp, struct tcphdr *th, + uint16_t type); +static void inline cc_conn_init(struct tcpcb *tp); +static void inline cc_post_recovery(struct tcpcb *tp, struct tcphdr *th); +static void inline hhook_run_tcp_est_in(struct tcpcb *tp, + struct tcphdr *th, struct tcpopt *to); + +/* + * TCP statistics are stored in struct tcpstat_p, which is + * an "array" of counter(9)s. Although it isn't a real + * array, we treat it as array to reduce code bloat. + */ +VNET_DEFINE(struct tcpstat_p, tcpstatp); + +static void +vnet_tcpstatp_init(const void *unused) +{ + counter_u64_t *c; + int i; + + for (i = 0, c = (counter_u64_t *)&V_tcpstatp; + i < sizeof(V_tcpstatp) / sizeof(counter_u64_t); + i++, c++) { + *c = counter_u64_alloc(M_WAITOK); + counter_u64_zero(*c); + } +} +VNET_SYSINIT(vnet_tcpstatp_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, + vnet_tcpstatp_init, NULL); + +#ifdef VIMAGE +static void +vnet_tcpstatp_uninit(const void *unused) +{ + counter_u64_t *c; + int i; + + for (i = 0, c = (counter_u64_t *)&V_tcpstatp; + i < sizeof(V_tcpstatp) / sizeof(counter_u64_t); + i++, c++) + counter_u64_free(*c); +} +VNET_SYSUNINIT(vnet_tcpstatp_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, + vnet_tcpstatp_uninit, NULL); +#endif /* VIMAGE */ + +static int +tcpstat_sysctl(SYSCTL_HANDLER_ARGS) +{ + struct tcpstat tcpstat; + counter_u64_t *c; + uint64_t *v; + int i; + + for (i = 0, c = (counter_u64_t *)&V_tcpstatp, v = (uint64_t *)&tcpstat; + i < sizeof(V_tcpstatp) / sizeof(counter_u64_t); + i++, c++, v++) { + *v = counter_u64_fetch(*c); + if (req->newptr) + counter_u64_zero(*c); + } + + return (SYSCTL_OUT(req, &tcpstat, sizeof(tcpstat))); +} + +SYSCTL_VNET_PROC(_net_inet_tcp, TCPCTL_STATS, stats, CTLTYPE_OPAQUE | + CTLFLAG_RW, NULL, 0, tcpstat_sysctl, "I", + "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); + +/* + * Kernel module interface for updating tcpstat. The argument is an index + * into tcpstat treated as an array. + */ +void +kmod_tcpstat_inc(int statnum) +{ + + counter_u64_add((counter_u64_t )&V_tcpstatp + statnum, 1); +} + +/* + * Wrapper for the TCP established input helper hook. + */ +static void inline +hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) +{ + struct tcp_hhook_data hhook_data; + + if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { + hhook_data.tp = tp; + hhook_data.th = th; + hhook_data.to = to; + + hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, + tp->osd); + } +} + +/* + * CC wrapper hook functions + */ +static void inline +cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type) +{ + INP_WLOCK_ASSERT(tp->t_inpcb); + + tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); + if (tp->snd_cwnd <= tp->snd_wnd) + tp->ccv->flags |= CCF_CWND_LIMITED; + else + tp->ccv->flags &= ~CCF_CWND_LIMITED; + + if (type == CC_ACK) { + if (tp->snd_cwnd > tp->snd_ssthresh) { + tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, + V_tcp_abc_l_var * tp->t_maxseg); + if (tp->t_bytes_acked >= tp->snd_cwnd) { + tp->t_bytes_acked -= tp->snd_cwnd; + tp->ccv->flags |= CCF_ABC_SENTAWND; + } + } else { + tp->ccv->flags &= ~CCF_ABC_SENTAWND; + tp->t_bytes_acked = 0; + } + } + + if (CC_ALGO(tp)->ack_received != NULL) { + /* XXXLAS: Find a way to live without this */ + tp->ccv->curack = th->th_ack; + CC_ALGO(tp)->ack_received(tp->ccv, type); + } +} + +static void inline +cc_conn_init(struct tcpcb *tp) +{ + struct hc_metrics_lite metrics; + struct inpcb *inp = tp->t_inpcb; + int rtt; + + INP_WLOCK_ASSERT(tp->t_inpcb); + + tcp_hc_get(&inp->inp_inc, &metrics); + + if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { + tp->t_srtt = rtt; + tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; + TCPSTAT_INC(tcps_usedrtt); + if (metrics.rmx_rttvar) { + tp->t_rttvar = metrics.rmx_rttvar; + TCPSTAT_INC(tcps_usedrttvar); + } else { + /* default variation is +- 1 rtt */ + tp->t_rttvar = + tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; + } + TCPT_RANGESET(tp->t_rxtcur, + ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, + tp->t_rttmin, TCPTV_REXMTMAX); + } + if (metrics.rmx_ssthresh) { + /* + * There's some sort of gateway or interface + * buffer limit on the path. Use this to set + * the slow start threshhold, but set the + * threshold to no less than 2*mss. + */ + tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh); + TCPSTAT_INC(tcps_usedssthresh); + } + + /* + * Set the initial slow-start flight size. + * + * RFC5681 Section 3.1 specifies the default conservative values. + * RFC3390 specifies slightly more aggressive values. + * Draft-ietf-tcpm-initcwnd-05 increases it to ten segments. + * + * If a SYN or SYN/ACK was lost and retransmitted, we have to + * reduce the initial CWND to one segment as congestion is likely + * requiring us to be cautious. + */ + if (tp->snd_cwnd == 1) + tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */ + else if (V_tcp_do_initcwnd10) + tp->snd_cwnd = min(10 * tp->t_maxseg, + max(2 * tp->t_maxseg, 14600)); + else if (V_tcp_do_rfc3390) + tp->snd_cwnd = min(4 * tp->t_maxseg, + max(2 * tp->t_maxseg, 4380)); + else { + /* Per RFC5681 Section 3.1 */ + if (tp->t_maxseg > 2190) + tp->snd_cwnd = 2 * tp->t_maxseg; + else if (tp->t_maxseg > 1095) + tp->snd_cwnd = 3 * tp->t_maxseg; + else + tp->snd_cwnd = 4 * tp->t_maxseg; + } + + if (CC_ALGO(tp)->conn_init != NULL) + CC_ALGO(tp)->conn_init(tp->ccv); +} + +void inline +cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) +{ + INP_WLOCK_ASSERT(tp->t_inpcb); + + switch(type) { + case CC_NDUPACK: + if (!IN_FASTRECOVERY(tp->t_flags)) { + tp->snd_recover = tp->snd_max; + if (tp->t_flags & TF_ECN_PERMIT) + tp->t_flags |= TF_ECN_SND_CWR; + } + break; + case CC_ECN: + if (!IN_CONGRECOVERY(tp->t_flags)) { + TCPSTAT_INC(tcps_ecn_rcwnd); + tp->snd_recover = tp->snd_max; + if (tp->t_flags & TF_ECN_PERMIT) + tp->t_flags |= TF_ECN_SND_CWR; + } + break; + case CC_RTO: + tp->t_dupacks = 0; + tp->t_bytes_acked = 0; + EXIT_RECOVERY(tp->t_flags); + tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / + tp->t_maxseg) * tp->t_maxseg; + tp->snd_cwnd = tp->t_maxseg; + break; + case CC_RTO_ERR: + TCPSTAT_INC(tcps_sndrexmitbad); + /* RTO was unnecessary, so reset everything. */ + tp->snd_cwnd = tp->snd_cwnd_prev; + tp->snd_ssthresh = tp->snd_ssthresh_prev; + tp->snd_recover = tp->snd_recover_prev; + if (tp->t_flags & TF_WASFRECOVERY) + ENTER_FASTRECOVERY(tp->t_flags); + if (tp->t_flags & TF_WASCRECOVERY) + ENTER_CONGRECOVERY(tp->t_flags); + tp->snd_nxt = tp->snd_max; + tp->t_flags &= ~TF_PREVVALID; + tp->t_badrxtwin = 0; + break; + } + + if (CC_ALGO(tp)->cong_signal != NULL) { + if (th != NULL) + tp->ccv->curack = th->th_ack; + CC_ALGO(tp)->cong_signal(tp->ccv, type); + } +} + +static void inline +cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) +{ + INP_WLOCK_ASSERT(tp->t_inpcb); + + /* XXXLAS: KASSERT that we're in recovery? */ + + if (CC_ALGO(tp)->post_recovery != NULL) { + tp->ccv->curack = th->th_ack; + CC_ALGO(tp)->post_recovery(tp->ccv); + } + /* XXXLAS: EXIT_RECOVERY ? */ + tp->t_bytes_acked = 0; +} + +static inline void +tcp_fields_to_host(struct tcphdr *th) +{ + + th->th_seq = ntohl(th->th_seq); + th->th_ack = ntohl(th->th_ack); + th->th_win = ntohs(th->th_win); + th->th_urp = ntohs(th->th_urp); +} + +#ifdef TCP_SIGNATURE +static inline void +tcp_fields_to_net(struct tcphdr *th) +{ + + th->th_seq = htonl(th->th_seq); + th->th_ack = htonl(th->th_ack); + th->th_win = htons(th->th_win); + th->th_urp = htons(th->th_urp); +} + +static inline int +tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen, + struct tcpopt *to, struct tcphdr *th, u_int tcpbflag) +{ + int ret; + + tcp_fields_to_net(th); + ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag); + tcp_fields_to_host(th); + return (ret); +} +#endif + +/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ +#ifdef INET6 +#define ND6_HINT(tp) \ +do { \ + if ((tp) && (tp)->t_inpcb && \ + ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ + nd6_nud_hint(NULL, NULL, 0); \ +} while (0) +#else +#define ND6_HINT(tp) +#endif + +/* + * Indicate whether this ack should be delayed. We can delay the ack if + * - there is no delayed ack timer in progress and + * - our last ack wasn't a 0-sized window. We never want to delay + * the ack that opens up a 0-sized window and + * - delayed acks are enabled or + * - this is a half-synchronized T/TCP connection. + */ +#define DELAY_ACK(tp) \ + ((!tcp_timer_active(tp, TT_DELACK) && \ + (tp->t_flags & TF_RXWIN0SENT) == 0) && \ + (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) + +/* + * TCP input handling is split into multiple parts: + * tcp6_input is a thin wrapper around tcp_input for the extended + * ip6_protox[] call format in ip6_input + * tcp_input handles primary segment validation, inpcb lookup and + * SYN processing on listen sockets + * tcp_do_segment processes the ACK and text of the segment for + * establishing, established and closing connections + */ +#ifdef INET6 +int +tcp6_input(struct mbuf **mp, int *offp, int proto) +{ + struct mbuf *m = *mp; + struct in6_ifaddr *ia6; + + IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); + + /* + * draft-itojun-ipv6-tcp-to-anycast + * better place to put this in? + */ + ia6 = ip6_getdstifaddr(m); + if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { + struct ip6_hdr *ip6; + + ifa_free(&ia6->ia_ifa); + ip6 = mtod(m, struct ip6_hdr *); + icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, + (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); + return IPPROTO_DONE; + } + if (ia6) + ifa_free(&ia6->ia_ifa); + + tcp_input(m, *offp); + return IPPROTO_DONE; +} +#endif /* INET6 */ + +void +tcp_input(struct mbuf *m, int off0) +{ + struct tcphdr *th = NULL; + struct ip *ip = NULL; + struct inpcb *inp = NULL; + struct tcpcb *tp = NULL; + struct socket *so = NULL; + u_char *optp = NULL; + int optlen = 0; +#ifdef INET + int len; +#endif + int tlen = 0, off; + int drop_hdrlen; + int thflags; + int rstreason = 0; /* For badport_bandlim accounting purposes */ +#ifdef TCP_SIGNATURE + uint8_t sig_checked = 0; +#endif + uint8_t iptos = 0; + struct m_tag *fwd_tag = NULL; +#ifdef INET6 + struct ip6_hdr *ip6 = NULL; + int isipv6; +#else + const void *ip6 = NULL; +#endif /* INET6 */ + struct tcpopt to; /* options in this segment */ + char *s = NULL; /* address and port logging */ + int ti_locked; +#define TI_UNLOCKED 1 +#define TI_WLOCKED 2 + +#ifdef TCPDEBUG + /* + * The size of tcp_saveipgen must be the size of the max ip header, + * now IPv6. + */ + u_char tcp_saveipgen[IP6_HDR_LEN]; + struct tcphdr tcp_savetcp; + short ostate = 0; +#endif + +#ifdef INET6 + isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; +#endif + + to.to_flags = 0; + TCPSTAT_INC(tcps_rcvtotal); + +#ifdef INET6 + if (isipv6) { + /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ + + if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { + m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); + if (m == NULL) { + TCPSTAT_INC(tcps_rcvshort); + return; + } + } + + ip6 = mtod(m, struct ip6_hdr *); + th = (struct tcphdr *)((caddr_t)ip6 + off0); + tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; + if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { + if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) + th->th_sum = m->m_pkthdr.csum_data; + else + th->th_sum = in6_cksum_pseudo(ip6, tlen, + IPPROTO_TCP, m->m_pkthdr.csum_data); + th->th_sum ^= 0xffff; + } else + th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); + if (th->th_sum) { + TCPSTAT_INC(tcps_rcvbadsum); + goto drop; + } + + /* + * Be proactive about unspecified IPv6 address in source. + * As we use all-zero to indicate unbounded/unconnected pcb, + * unspecified IPv6 address can be used to confuse us. + * + * Note that packets with unspecified IPv6 destination is + * already dropped in ip6_input. + */ + if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { + /* XXX stat */ + goto drop; + } + } +#endif +#if defined(INET) && defined(INET6) + else +#endif +#ifdef INET + { + /* + * Get IP and TCP header together in first mbuf. + * Note: IP leaves IP header in first mbuf. + */ + if (off0 > sizeof (struct ip)) { + ip_stripoptions(m); + off0 = sizeof(struct ip); + } + if (m->m_len < sizeof (struct tcpiphdr)) { + if ((m = m_pullup(m, sizeof (struct tcpiphdr))) + == NULL) { + TCPSTAT_INC(tcps_rcvshort); + return; + } + } + ip = mtod(m, struct ip *); + th = (struct tcphdr *)((caddr_t)ip + off0); + tlen = ntohs(ip->ip_len) - off0; + + if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { + if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) + th->th_sum = m->m_pkthdr.csum_data; + else + th->th_sum = in_pseudo(ip->ip_src.s_addr, + ip->ip_dst.s_addr, + htonl(m->m_pkthdr.csum_data + tlen + + IPPROTO_TCP)); + th->th_sum ^= 0xffff; + } else { + struct ipovly *ipov = (struct ipovly *)ip; + + /* + * Checksum extended TCP header and data. + */ + len = off0 + tlen; + bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); + ipov->ih_len = htons(tlen); + th->th_sum = in_cksum(m, len); + } + if (th->th_sum) { + TCPSTAT_INC(tcps_rcvbadsum); + goto drop; + } + /* Re-initialization for later version check */ + ip->ip_v = IPVERSION; + } +#endif /* INET */ + +#ifdef INET6 + if (isipv6) + iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; +#endif +#if defined(INET) && defined(INET6) + else +#endif +#ifdef INET + iptos = ip->ip_tos; +#endif + + /* + * Check that TCP offset makes sense, + * pull out TCP options and adjust length. XXX + */ + off = th->th_off << 2; + if (off < sizeof (struct tcphdr) || off > tlen) { + TCPSTAT_INC(tcps_rcvbadoff); + goto drop; + } + tlen -= off; /* tlen is used instead of ti->ti_len */ + if (off > sizeof (struct tcphdr)) { +#ifdef INET6 + if (isipv6) { + IP6_EXTHDR_CHECK(m, off0, off, ); + ip6 = mtod(m, struct ip6_hdr *); + th = (struct tcphdr *)((caddr_t)ip6 + off0); + } +#endif +#if defined(INET) && defined(INET6) + else +#endif +#ifdef INET + { + if (m->m_len < sizeof(struct ip) + off) { + if ((m = m_pullup(m, sizeof (struct ip) + off)) + == NULL) { + TCPSTAT_INC(tcps_rcvshort); + return; + } + ip = mtod(m, struct ip *); + th = (struct tcphdr *)((caddr_t)ip + off0); + } + } +#endif + optlen = off - sizeof (struct tcphdr); + optp = (u_char *)(th + 1); + } + thflags = th->th_flags; + + /* + * Convert TCP protocol specific fields to host format. + */ + tcp_fields_to_host(th); + + /* + * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. + */ + drop_hdrlen = off0 + off; + + /* + * Locate pcb for segment; if we're likely to add or remove a + * connection then first acquire pcbinfo lock. There are two cases + * where we might discover later we need a write lock despite the + * flags: ACKs moving a connection out of the syncache, and ACKs for + * a connection in TIMEWAIT. + */ + if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) { + INP_INFO_WLOCK(&V_tcbinfo); + ti_locked = TI_WLOCKED; + } else + ti_locked = TI_UNLOCKED; + + /* + * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. + */ + if ( +#ifdef INET6 + (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) +#ifdef INET + || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) +#endif +#endif +#if defined(INET) && !defined(INET6) + (m->m_flags & M_IP_NEXTHOP) +#endif + ) + fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); + +findpcb: +#ifdef INVARIANTS + if (ti_locked == TI_WLOCKED) { + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + } else { + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); + } +#endif +#ifdef INET6 + if (isipv6 && fwd_tag != NULL) { + struct sockaddr_in6 *next_hop6; + + next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); + /* + * Transparently forwarded. Pretend to be the destination. + * Already got one like this? + */ + inp = in6_pcblookup_mbuf(&V_tcbinfo, + &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, + INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); + if (!inp) { + /* + * It's new. Try to find the ambushing socket. + * Because we've rewritten the destination address, + * any hardware-generated hash is ignored. + */ + inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, + th->th_sport, &next_hop6->sin6_addr, + next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : + th->th_dport, INPLOOKUP_WILDCARD | + INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); + } + } else if (isipv6) { + inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, + th->th_sport, &ip6->ip6_dst, th->th_dport, + INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, + m->m_pkthdr.rcvif, m); + } +#endif /* INET6 */ +#if defined(INET6) && defined(INET) + else +#endif +#ifdef INET + if (fwd_tag != NULL) { + struct sockaddr_in *next_hop; + + next_hop = (struct sockaddr_in *)(fwd_tag+1); + /* + * Transparently forwarded. Pretend to be the destination. + * already got one like this? + */ + inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, + ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, + m->m_pkthdr.rcvif, m); + if (!inp) { + /* + * It's new. Try to find the ambushing socket. + * Because we've rewritten the destination address, + * any hardware-generated hash is ignored. + */ + inp = in_pcblookup(&V_tcbinfo, ip->ip_src, + th->th_sport, next_hop->sin_addr, + next_hop->sin_port ? ntohs(next_hop->sin_port) : + th->th_dport, INPLOOKUP_WILDCARD | + INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); + } + } else + inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, + th->th_sport, ip->ip_dst, th->th_dport, + INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, + m->m_pkthdr.rcvif, m); +#endif /* INET */ + + /* + * If the INPCB does not exist then all data in the incoming + * segment is discarded and an appropriate RST is sent back. + * XXX MRT Send RST using which routing table? + */ + if (inp == NULL) { + /* + * Log communication attempts to ports that are not + * in use. + */ + if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || + tcp_log_in_vain == 2) { + if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) + log(LOG_INFO, "%s; %s: Connection attempt " + "to closed port\n", s, __func__); + } + /* + * When blackholing do not respond with a RST but + * completely ignore the segment and drop it. + */ + if ((V_blackhole == 1 && (thflags & TH_SYN)) || + V_blackhole == 2) + goto dropunlock; + + rstreason = BANDLIM_RST_CLOSEDPORT; + goto dropwithreset; + } + INP_WLOCK_ASSERT(inp); + if (!(inp->inp_flags & INP_HW_FLOWID) + && (m->m_flags & M_FLOWID) + && ((inp->inp_socket == NULL) + || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) { + inp->inp_flags |= INP_HW_FLOWID; + inp->inp_flags &= ~INP_SW_FLOWID; + inp->inp_flowid = m->m_pkthdr.flowid; + } +#ifdef IPSEC +#ifdef INET6 + if (isipv6 && ipsec6_in_reject(m, inp)) { + V_ipsec6stat.in_polvio++; + goto dropunlock; + } else +#endif /* INET6 */ + if (ipsec4_in_reject(m, inp) != 0) { + V_ipsec4stat.in_polvio++; + goto dropunlock; + } +#endif /* IPSEC */ + + /* + * Check the minimum TTL for socket. + */ + if (inp->inp_ip_minttl != 0) { +#ifdef INET6 + if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) + goto dropunlock; + else +#endif + if (inp->inp_ip_minttl > ip->ip_ttl) + goto dropunlock; + } + + /* + * A previous connection in TIMEWAIT state is supposed to catch stray + * or duplicate segments arriving late. If this segment was a + * legitimate new connection attempt, the old INPCB gets removed and + * we can try again to find a listening socket. + * + * At this point, due to earlier optimism, we may hold only an inpcb + * lock, and not the inpcbinfo write lock. If so, we need to try to + * acquire it, or if that fails, acquire a reference on the inpcb, + * drop all locks, acquire a global write lock, and then re-acquire + * the inpcb lock. We may at that point discover that another thread + * has tried to free the inpcb, in which case we need to loop back + * and try to find a new inpcb to deliver to. + * + * XXXRW: It may be time to rethink timewait locking. + */ +relocked: + if (inp->inp_flags & INP_TIMEWAIT) { + if (ti_locked == TI_UNLOCKED) { + if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) { + in_pcbref(inp); + INP_WUNLOCK(inp); + INP_INFO_WLOCK(&V_tcbinfo); + ti_locked = TI_WLOCKED; + INP_WLOCK(inp); + if (in_pcbrele_wlocked(inp)) { + inp = NULL; + goto findpcb; + } + } else + ti_locked = TI_WLOCKED; + } + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + + if (thflags & TH_SYN) + tcp_dooptions(&to, optp, optlen, TO_SYN); + /* + * NB: tcp_twcheck unlocks the INP and frees the mbuf. + */ + if (tcp_twcheck(inp, &to, th, m, tlen)) + goto findpcb; + INP_INFO_WUNLOCK(&V_tcbinfo); + return; + } + /* + * The TCPCB may no longer exist if the connection is winding + * down or it is in the CLOSED state. Either way we drop the + * segment and send an appropriate response. + */ + tp = intotcpcb(inp); + if (tp == NULL || tp->t_state == TCPS_CLOSED) { + rstreason = BANDLIM_RST_CLOSEDPORT; + goto dropwithreset; + } + +#ifdef TCP_OFFLOAD + if (tp->t_flags & TF_TOE) { + tcp_offload_input(tp, m); + m = NULL; /* consumed by the TOE driver */ + goto dropunlock; + } +#endif + + /* + * We've identified a valid inpcb, but it could be that we need an + * inpcbinfo write lock but don't hold it. In this case, attempt to + * acquire using the same strategy as the TIMEWAIT case above. If we + * relock, we have to jump back to 'relocked' as the connection might + * now be in TIMEWAIT. + */ +#ifdef INVARIANTS + if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); +#endif + if (tp->t_state != TCPS_ESTABLISHED) { + if (ti_locked == TI_UNLOCKED) { + if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) { + in_pcbref(inp); + INP_WUNLOCK(inp); + INP_INFO_WLOCK(&V_tcbinfo); + ti_locked = TI_WLOCKED; + INP_WLOCK(inp); + if (in_pcbrele_wlocked(inp)) { + inp = NULL; + goto findpcb; + } + goto relocked; + } else + ti_locked = TI_WLOCKED; + } + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + } + +#ifdef MAC + INP_WLOCK_ASSERT(inp); + if (mac_inpcb_check_deliver(inp, m)) + goto dropunlock; +#endif + so = inp->inp_socket; + KASSERT(so != NULL, ("%s: so == NULL", __func__)); +#ifdef TCPDEBUG + if (so->so_options & SO_DEBUG) { + ostate = tp->t_state; +#ifdef INET6 + if (isipv6) { + bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); + } else +#endif + bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); + tcp_savetcp = *th; + } +#endif /* TCPDEBUG */ + /* + * When the socket is accepting connections (the INPCB is in LISTEN + * state) we look into the SYN cache if this is a new connection + * attempt or the completion of a previous one. Because listen + * sockets are never in TCPS_ESTABLISHED, the V_tcbinfo lock will be + * held in this case. + */ + if (so->so_options & SO_ACCEPTCONN) { + struct in_conninfo inc; + + KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " + "tp not listening", __func__)); + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + + bzero(&inc, sizeof(inc)); +#ifdef INET6 + if (isipv6) { + inc.inc_flags |= INC_ISIPV6; + inc.inc6_faddr = ip6->ip6_src; + inc.inc6_laddr = ip6->ip6_dst; + } else +#endif + { + inc.inc_faddr = ip->ip_src; + inc.inc_laddr = ip->ip_dst; + } + inc.inc_fport = th->th_sport; + inc.inc_lport = th->th_dport; + inc.inc_fibnum = so->so_fibnum; + + /* + * Check for an existing connection attempt in syncache if + * the flag is only ACK. A successful lookup creates a new + * socket appended to the listen queue in SYN_RECEIVED state. + */ + if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { + /* + * Parse the TCP options here because + * syncookies need access to the reflected + * timestamp. + */ + tcp_dooptions(&to, optp, optlen, 0); + /* + * NB: syncache_expand() doesn't unlock + * inp and tcpinfo locks. + */ + if (!syncache_expand(&inc, &to, th, &so, m)) { + /* + * No syncache entry or ACK was not + * for our SYN/ACK. Send a RST. + * NB: syncache did its own logging + * of the failure cause. + */ + rstreason = BANDLIM_RST_OPENPORT; + goto dropwithreset; + } + if (so == NULL) { + /* + * We completed the 3-way handshake + * but could not allocate a socket + * either due to memory shortage, + * listen queue length limits or + * global socket limits. Send RST + * or wait and have the remote end + * retransmit the ACK for another + * try. + */ + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "Socket allocation failed due to " + "limits or memory shortage, %s\n", + s, __func__, + V_tcp_sc_rst_sock_fail ? + "sending RST" : "try again"); + if (V_tcp_sc_rst_sock_fail) { + rstreason = BANDLIM_UNLIMITED; + goto dropwithreset; + } else + goto dropunlock; + } + /* + * Socket is created in state SYN_RECEIVED. + * Unlock the listen socket, lock the newly + * created socket and update the tp variable. + */ + INP_WUNLOCK(inp); /* listen socket */ + inp = sotoinpcb(so); + INP_WLOCK(inp); /* new connection */ + tp = intotcpcb(inp); + KASSERT(tp->t_state == TCPS_SYN_RECEIVED, + ("%s: ", __func__)); +#ifdef TCP_SIGNATURE + if (sig_checked == 0) { + tcp_dooptions(&to, optp, optlen, + (thflags & TH_SYN) ? TO_SYN : 0); + if (!tcp_signature_verify_input(m, off0, tlen, + optlen, &to, th, tp->t_flags)) { + + /* + * In SYN_SENT state if it receives an + * RST, it is allowed for further + * processing. + */ + if ((thflags & TH_RST) == 0 || + (tp->t_state == TCPS_SYN_SENT) == 0) + goto dropunlock; + } + sig_checked = 1; + } +#endif + + /* + * Process the segment and the data it + * contains. tcp_do_segment() consumes + * the mbuf chain and unlocks the inpcb. + */ + tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, + iptos, ti_locked); + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); + return; + } + /* + * Segment flag validation for new connection attempts: + * + * Our (SYN|ACK) response was rejected. + * Check with syncache and remove entry to prevent + * retransmits. + * + * NB: syncache_chkrst does its own logging of failure + * causes. + */ + if (thflags & TH_RST) { + syncache_chkrst(&inc, th); + goto dropunlock; + } + /* + * We can't do anything without SYN. + */ + if ((thflags & TH_SYN) == 0) { + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "SYN is missing, segment ignored\n", + s, __func__); + TCPSTAT_INC(tcps_badsyn); + goto dropunlock; + } + /* + * (SYN|ACK) is bogus on a listen socket. + */ + if (thflags & TH_ACK) { + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "SYN|ACK invalid, segment rejected\n", + s, __func__); + syncache_badack(&inc); /* XXX: Not needed! */ + TCPSTAT_INC(tcps_badsyn); + rstreason = BANDLIM_RST_OPENPORT; + goto dropwithreset; + } + /* + * If the drop_synfin option is enabled, drop all + * segments with both the SYN and FIN bits set. + * This prevents e.g. nmap from identifying the + * TCP/IP stack. + * XXX: Poor reasoning. nmap has other methods + * and is constantly refining its stack detection + * strategies. + * XXX: This is a violation of the TCP specification + * and was used by RFC1644. + */ + if ((thflags & TH_FIN) && V_drop_synfin) { + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "SYN|FIN segment ignored (based on " + "sysctl setting)\n", s, __func__); + TCPSTAT_INC(tcps_badsyn); + goto dropunlock; + } + /* + * Segment's flags are (SYN) or (SYN|FIN). + * + * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored + * as they do not affect the state of the TCP FSM. + * The data pointed to by TH_URG and th_urp is ignored. + */ + KASSERT((thflags & (TH_RST|TH_ACK)) == 0, + ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); + KASSERT(thflags & (TH_SYN), + ("%s: Listen socket: TH_SYN not set", __func__)); +#ifdef INET6 + /* + * If deprecated address is forbidden, + * we do not accept SYN to deprecated interface + * address to prevent any new inbound connection from + * getting established. + * When we do not accept SYN, we send a TCP RST, + * with deprecated source address (instead of dropping + * it). We compromise it as it is much better for peer + * to send a RST, and RST will be the final packet + * for the exchange. + * + * If we do not forbid deprecated addresses, we accept + * the SYN packet. RFC2462 does not suggest dropping + * SYN in this case. + * If we decipher RFC2462 5.5.4, it says like this: + * 1. use of deprecated addr with existing + * communication is okay - "SHOULD continue to be + * used" + * 2. use of it with new communication: + * (2a) "SHOULD NOT be used if alternate address + * with sufficient scope is available" + * (2b) nothing mentioned otherwise. + * Here we fall into (2b) case as we have no choice in + * our source address selection - we must obey the peer. + * + * The wording in RFC2462 is confusing, and there are + * multiple description text for deprecated address + * handling - worse, they are not exactly the same. + * I believe 5.5.4 is the best one, so we follow 5.5.4. + */ + if (isipv6 && !V_ip6_use_deprecated) { + struct in6_ifaddr *ia6; + + ia6 = ip6_getdstifaddr(m); + if (ia6 != NULL && + (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { + ifa_free(&ia6->ia_ifa); + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "Connection attempt to deprecated " + "IPv6 address rejected\n", + s, __func__); + rstreason = BANDLIM_RST_OPENPORT; + goto dropwithreset; + } + if (ia6) + ifa_free(&ia6->ia_ifa); + } +#endif /* INET6 */ + /* + * Basic sanity checks on incoming SYN requests: + * Don't respond if the destination is a link layer + * broadcast according to RFC1122 4.2.3.10, p. 104. + * If it is from this socket it must be forged. + * Don't respond if the source or destination is a + * global or subnet broad- or multicast address. + * Note that it is quite possible to receive unicast + * link-layer packets with a broadcast IP address. Use + * in_broadcast() to find them. + */ + if (m->m_flags & (M_BCAST|M_MCAST)) { + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "Connection attempt from broad- or multicast " + "link layer address ignored\n", s, __func__); + goto dropunlock; + } +#ifdef INET6 + if (isipv6) { + if (th->th_dport == th->th_sport && + IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "Connection attempt to/from self " + "ignored\n", s, __func__); + goto dropunlock; + } + if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || + IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "Connection attempt from/to multicast " + "address ignored\n", s, __func__); + goto dropunlock; + } + } +#endif +#if defined(INET) && defined(INET6) + else +#endif +#ifdef INET + { + if (th->th_dport == th->th_sport && + ip->ip_dst.s_addr == ip->ip_src.s_addr) { + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "Connection attempt from/to self " + "ignored\n", s, __func__); + goto dropunlock; + } + if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || + IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || + ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || + in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { + if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) + log(LOG_DEBUG, "%s; %s: Listen socket: " + "Connection attempt from/to broad- " + "or multicast address ignored\n", + s, __func__); + goto dropunlock; + } + } +#endif + /* + * SYN appears to be valid. Create compressed TCP state + * for syncache. + */ +#ifdef TCPDEBUG + if (so->so_options & SO_DEBUG) + tcp_trace(TA_INPUT, ostate, tp, + (void *)tcp_saveipgen, &tcp_savetcp, 0); +#endif + tcp_dooptions(&to, optp, optlen, TO_SYN); + syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); + /* + * Entry added to syncache and mbuf consumed. + * Everything already unlocked by syncache_add(). + */ + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); + return; + } else if (tp->t_state == TCPS_LISTEN) { + /* + * When a listen socket is torn down the SO_ACCEPTCONN + * flag is removed first while connections are drained + * from the accept queue in a unlock/lock cycle of the + * ACCEPT_LOCK, opening a race condition allowing a SYN + * attempt go through unhandled. + */ + goto dropunlock; + } + +#ifdef TCP_SIGNATURE + if (sig_checked == 0) { + tcp_dooptions(&to, optp, optlen, + (thflags & TH_SYN) ? TO_SYN : 0); + if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to, + th, tp->t_flags)) { + + /* + * In SYN_SENT state if it receives an RST, it is + * allowed for further processing. + */ + if ((thflags & TH_RST) == 0 || + (tp->t_state == TCPS_SYN_SENT) == 0) + goto dropunlock; + } + sig_checked = 1; + } +#endif + + /* + * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later + * state. tcp_do_segment() always consumes the mbuf chain, unlocks + * the inpcb, and unlocks pcbinfo. + */ + tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); + return; + +dropwithreset: + if (ti_locked == TI_WLOCKED) { + INP_INFO_WUNLOCK(&V_tcbinfo); + ti_locked = TI_UNLOCKED; + } +#ifdef INVARIANTS + else { + KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " + "ti_locked: %d", __func__, ti_locked)); + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); + } +#endif + + if (inp != NULL) { + tcp_dropwithreset(m, th, tp, tlen, rstreason); + INP_WUNLOCK(inp); + } else + tcp_dropwithreset(m, th, NULL, tlen, rstreason); + m = NULL; /* mbuf chain got consumed. */ + goto drop; + +dropunlock: + if (ti_locked == TI_WLOCKED) { + INP_INFO_WUNLOCK(&V_tcbinfo); + ti_locked = TI_UNLOCKED; + } +#ifdef INVARIANTS + else { + KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " + "ti_locked: %d", __func__, ti_locked)); + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); + } +#endif + + if (inp != NULL) + INP_WUNLOCK(inp); + +drop: + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); + if (s != NULL) + free(s, M_TCPLOG); + if (m != NULL) + m_freem(m); +} + +static void +tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, + struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, + int ti_locked) +{ + int thflags, acked, ourfinisacked, needoutput = 0; + int rstreason, todrop, win; + u_long tiwin; + struct tcpopt to; + +#ifdef TCPDEBUG + /* + * The size of tcp_saveipgen must be the size of the max ip header, + * now IPv6. + */ + u_char tcp_saveipgen[IP6_HDR_LEN]; + struct tcphdr tcp_savetcp; + short ostate = 0; +#endif + thflags = th->th_flags; + tp->sackhint.last_sack_ack = 0; + + /* + * If this is either a state-changing packet or current state isn't + * established, we require a write lock on tcbinfo. Otherwise, we + * allow the tcbinfo to be in either alocked or unlocked, as the + * caller may have unnecessarily acquired a write lock due to a race. + */ + if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || + tp->t_state != TCPS_ESTABLISHED) { + KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for " + "SYN/FIN/RST/!EST", __func__, ti_locked)); + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + } else { +#ifdef INVARIANTS + if (ti_locked == TI_WLOCKED) + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + else { + KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST " + "ti_locked: %d", __func__, ti_locked)); + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); + } +#endif + } + INP_WLOCK_ASSERT(tp->t_inpcb); + KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", + __func__)); + KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", + __func__)); + + /* + * Segment received on connection. + * Reset idle time and keep-alive timer. + * XXX: This should be done after segment + * validation to ignore broken/spoofed segs. + */ + tp->t_rcvtime = ticks; + if (TCPS_HAVEESTABLISHED(tp->t_state)) + tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); + + /* + * Unscale the window into a 32-bit value. + * For the SYN_SENT state the scale is zero. + */ + tiwin = th->th_win << tp->snd_scale; + + /* + * TCP ECN processing. + */ + if (tp->t_flags & TF_ECN_PERMIT) { + if (thflags & TH_CWR) + tp->t_flags &= ~TF_ECN_SND_ECE; + switch (iptos & IPTOS_ECN_MASK) { + case IPTOS_ECN_CE: + tp->t_flags |= TF_ECN_SND_ECE; + TCPSTAT_INC(tcps_ecn_ce); + break; + case IPTOS_ECN_ECT0: + TCPSTAT_INC(tcps_ecn_ect0); + break; + case IPTOS_ECN_ECT1: + TCPSTAT_INC(tcps_ecn_ect1); + break; + } + /* Congestion experienced. */ + if (thflags & TH_ECE) { + cc_cong_signal(tp, th, CC_ECN); + } + } + + /* + * Parse options on any incoming segment. + */ + tcp_dooptions(&to, (u_char *)(th + 1), + (th->th_off << 2) - sizeof(struct tcphdr), + (thflags & TH_SYN) ? TO_SYN : 0); + + /* + * If echoed timestamp is later than the current time, + * fall back to non RFC1323 RTT calculation. Normalize + * timestamp if syncookies were used when this connection + * was established. + */ + if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { + to.to_tsecr -= tp->ts_offset; + if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) + to.to_tsecr = 0; + } + + /* + * Process options only when we get SYN/ACK back. The SYN case + * for incoming connections is handled in tcp_syncache. + * According to RFC1323 the window field in a SYN (i.e., a <SYN> + * or <SYN,ACK>) segment itself is never scaled. + * XXX this is traditional behavior, may need to be cleaned up. + */ + if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { + if ((to.to_flags & TOF_SCALE) && + (tp->t_flags & TF_REQ_SCALE)) { + tp->t_flags |= TF_RCVD_SCALE; + tp->snd_scale = to.to_wscale; + } + /* + * Initial send window. It will be updated with + * the next incoming segment to the scaled value. + */ + tp->snd_wnd = th->th_win; + if (to.to_flags & TOF_TS) { + tp->t_flags |= TF_RCVD_TSTMP; + tp->ts_recent = to.to_tsval; + tp->ts_recent_age = tcp_ts_getticks(); + } + if (to.to_flags & TOF_MSS) + tcp_mss(tp, to.to_mss); + if ((tp->t_flags & TF_SACK_PERMIT) && + (to.to_flags & TOF_SACKPERM) == 0) + tp->t_flags &= ~TF_SACK_PERMIT; + } + + /* + * Header prediction: check for the two common cases + * of a uni-directional data xfer. If the packet has + * no control flags, is in-sequence, the window didn't + * change and we're not retransmitting, it's a + * candidate. If the length is zero and the ack moved + * forward, we're the sender side of the xfer. Just + * free the data acked & wake any higher level process + * that was blocked waiting for space. If the length + * is non-zero and the ack didn't move, we're the + * receiver side. If we're getting packets in-order + * (the reassembly queue is empty), add the data to + * the socket buffer and note that we need a delayed ack. + * Make sure that the hidden state-flags are also off. + * Since we check for TCPS_ESTABLISHED first, it can only + * be TH_NEEDSYN. + */ + if (tp->t_state == TCPS_ESTABLISHED && + th->th_seq == tp->rcv_nxt && + (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && + tp->snd_nxt == tp->snd_max && + tiwin && tiwin == tp->snd_wnd && + ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && + LIST_EMPTY(&tp->t_segq) && + ((to.to_flags & TOF_TS) == 0 || + TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { + + /* + * If last ACK falls within this segment's sequence numbers, + * record the timestamp. + * NOTE that the test is modified according to the latest + * proposal of the tcplw@cray.com list (Braden 1993/04/26). + */ + if ((to.to_flags & TOF_TS) != 0 && + SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { + tp->ts_recent_age = tcp_ts_getticks(); + tp->ts_recent = to.to_tsval; + } + + if (tlen == 0) { + if (SEQ_GT(th->th_ack, tp->snd_una) && + SEQ_LEQ(th->th_ack, tp->snd_max) && + !IN_RECOVERY(tp->t_flags) && + (to.to_flags & TOF_SACK) == 0 && + TAILQ_EMPTY(&tp->snd_holes)) { + /* + * This is a pure ack for outstanding data. + */ + if (ti_locked == TI_WLOCKED) + INP_INFO_WUNLOCK(&V_tcbinfo); + ti_locked = TI_UNLOCKED; + + TCPSTAT_INC(tcps_predack); + + /* + * "bad retransmit" recovery. + */ + if (tp->t_rxtshift == 1 && + tp->t_flags & TF_PREVVALID && + (int)(ticks - tp->t_badrxtwin) < 0) { + cc_cong_signal(tp, th, CC_RTO_ERR); + } + + /* + * Recalculate the transmit timer / rtt. + * + * Some boxes send broken timestamp replies + * during the SYN+ACK phase, ignore + * timestamps of 0 or we could calculate a + * huge RTT and blow up the retransmit timer. + */ + if ((to.to_flags & TOF_TS) != 0 && + to.to_tsecr) { + u_int t; + + t = tcp_ts_getticks() - to.to_tsecr; + if (!tp->t_rttlow || tp->t_rttlow > t) + tp->t_rttlow = t; + tcp_xmit_timer(tp, + TCP_TS_TO_TICKS(t) + 1); + } else if (tp->t_rtttime && + SEQ_GT(th->th_ack, tp->t_rtseq)) { + if (!tp->t_rttlow || + tp->t_rttlow > ticks - tp->t_rtttime) + tp->t_rttlow = ticks - tp->t_rtttime; + tcp_xmit_timer(tp, + ticks - tp->t_rtttime); + } + acked = BYTES_THIS_ACK(tp, th); + + /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ + hhook_run_tcp_est_in(tp, th, &to); + + TCPSTAT_INC(tcps_rcvackpack); + TCPSTAT_ADD(tcps_rcvackbyte, acked); + sbdrop(&so->so_snd, acked); + if (SEQ_GT(tp->snd_una, tp->snd_recover) && + SEQ_LEQ(th->th_ack, tp->snd_recover)) + tp->snd_recover = th->th_ack - 1; + + /* + * Let the congestion control algorithm update + * congestion control related information. This + * typically means increasing the congestion + * window. + */ + cc_ack_received(tp, th, CC_ACK); + + tp->snd_una = th->th_ack; + /* + * Pull snd_wl2 up to prevent seq wrap relative + * to th_ack. + */ + tp->snd_wl2 = th->th_ack; + tp->t_dupacks = 0; + m_freem(m); + ND6_HINT(tp); /* Some progress has been made. */ + + /* + * If all outstanding data are acked, stop + * retransmit timer, otherwise restart timer + * using current (possibly backed-off) value. + * If process is waiting for space, + * wakeup/selwakeup/signal. If data + * are ready to send, let tcp_output + * decide between more output or persist. + */ +#ifdef TCPDEBUG + if (so->so_options & SO_DEBUG) + tcp_trace(TA_INPUT, ostate, tp, + (void *)tcp_saveipgen, + &tcp_savetcp, 0); +#endif + if (tp->snd_una == tp->snd_max) + tcp_timer_activate(tp, TT_REXMT, 0); + else if (!tcp_timer_active(tp, TT_PERSIST)) + tcp_timer_activate(tp, TT_REXMT, + tp->t_rxtcur); + sowwakeup(so); + if (so->so_snd.sb_cc) + (void) tcp_output(tp); + goto check_delack; + } + } else if (th->th_ack == tp->snd_una && + tlen <= sbspace(&so->so_rcv)) { + int newsize = 0; /* automatic sockbuf scaling */ + + /* + * This is a pure, in-sequence data packet with + * nothing on the reassembly queue and we have enough + * buffer space to take it. + */ + if (ti_locked == TI_WLOCKED) + INP_INFO_WUNLOCK(&V_tcbinfo); + ti_locked = TI_UNLOCKED; + + /* Clean receiver SACK report if present */ + if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) + tcp_clean_sackreport(tp); + TCPSTAT_INC(tcps_preddat); + tp->rcv_nxt += tlen; + /* + * Pull snd_wl1 up to prevent seq wrap relative to + * th_seq. + */ + tp->snd_wl1 = th->th_seq; + /* + * Pull rcv_up up to prevent seq wrap relative to + * rcv_nxt. + */ + tp->rcv_up = tp->rcv_nxt; + TCPSTAT_INC(tcps_rcvpack); + TCPSTAT_ADD(tcps_rcvbyte, tlen); + ND6_HINT(tp); /* Some progress has been made */ +#ifdef TCPDEBUG + if (so->so_options & SO_DEBUG) + tcp_trace(TA_INPUT, ostate, tp, + (void *)tcp_saveipgen, &tcp_savetcp, 0); +#endif + /* + * Automatic sizing of receive socket buffer. Often the send + * buffer size is not optimally adjusted to the actual network + * conditions at hand (delay bandwidth product). Setting the + * buffer size too small limits throughput on links with high + * bandwidth and high delay (eg. trans-continental/oceanic links). + * + * On the receive side the socket buffer memory is only rarely + * used to any significant extent. This allows us to be much + * more aggressive in scaling the receive socket buffer. For + * the case that the buffer space is actually used to a large + * extent and we run out of kernel memory we can simply drop + * the new segments; TCP on the sender will just retransmit it + * later. Setting the buffer size too big may only consume too + * much kernel memory if the application doesn't read() from + * the socket or packet loss or reordering makes use of the + * reassembly queue. + * + * The criteria to step up the receive buffer one notch are: + * 1. the number of bytes received during the time it takes + * one timestamp to be reflected back to us (the RTT); + * 2. received bytes per RTT is within seven eighth of the + * current socket buffer size; + * 3. receive buffer size has not hit maximal automatic size; + * + * This algorithm does one step per RTT at most and only if + * we receive a bulk stream w/o packet losses or reorderings. + * Shrinking the buffer during idle times is not necessary as + * it doesn't consume any memory when idle. + * + * TODO: Only step up if the application is actually serving + * the buffer to better manage the socket buffer resources. + */ + if (V_tcp_do_autorcvbuf && + to.to_tsecr && + (so->so_rcv.sb_flags & SB_AUTOSIZE)) { + if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) && + to.to_tsecr - tp->rfbuf_ts < hz) { + if (tp->rfbuf_cnt > + (so->so_rcv.sb_hiwat / 8 * 7) && + so->so_rcv.sb_hiwat < + V_tcp_autorcvbuf_max) { + newsize = + min(so->so_rcv.sb_hiwat + + V_tcp_autorcvbuf_inc, + V_tcp_autorcvbuf_max); + } + /* Start over with next RTT. */ + tp->rfbuf_ts = 0; + tp->rfbuf_cnt = 0; + } else + tp->rfbuf_cnt += tlen; /* add up */ + } + + /* Add data to socket buffer. */ + SOCKBUF_LOCK(&so->so_rcv); + if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { + m_freem(m); + } else { + /* + * Set new socket buffer size. + * Give up when limit is reached. + */ + if (newsize) + if (!sbreserve_locked(&so->so_rcv, + newsize, so, NULL)) + so->so_rcv.sb_flags &= ~SB_AUTOSIZE; + m_adj(m, drop_hdrlen); /* delayed header drop */ + sbappendstream_locked(&so->so_rcv, m); + } + /* NB: sorwakeup_locked() does an implicit unlock. */ + sorwakeup_locked(so); + if (DELAY_ACK(tp)) { + tp->t_flags |= TF_DELACK; + } else { + tp->t_flags |= TF_ACKNOW; + tcp_output(tp); + } + goto check_delack; + } + } + + /* + * Calculate amount of space in receive window, + * and then do TCP input processing. + * Receive window is amount of space in rcv queue, + * but not less than advertised window. + */ + win = sbspace(&so->so_rcv); + if (win < 0) + win = 0; + tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); + + /* Reset receive buffer auto scaling when not in bulk receive mode. */ + tp->rfbuf_ts = 0; + tp->rfbuf_cnt = 0; + + switch (tp->t_state) { + + /* + * If the state is SYN_RECEIVED: + * if seg contains an ACK, but not for our SYN/ACK, send a RST. + */ + case TCPS_SYN_RECEIVED: + if ((thflags & TH_ACK) && + (SEQ_LEQ(th->th_ack, tp->snd_una) || + SEQ_GT(th->th_ack, tp->snd_max))) { + rstreason = BANDLIM_RST_OPENPORT; + goto dropwithreset; + } + break; + + /* + * If the state is SYN_SENT: + * if seg contains an ACK, but not for our SYN, drop the input. + * if seg contains a RST, then drop the connection. + * if seg does not contain SYN, then drop it. + * Otherwise this is an acceptable SYN segment + * initialize tp->rcv_nxt and tp->irs + * if seg contains ack then advance tp->snd_una + * if seg contains an ECE and ECN support is enabled, the stream + * is ECN capable. + * if SYN has been acked change to ESTABLISHED else SYN_RCVD state + * arrange for segment to be acked (eventually) + * continue processing rest of data/controls, beginning with URG + */ + case TCPS_SYN_SENT: + if ((thflags & TH_ACK) && + (SEQ_LEQ(th->th_ack, tp->iss) || + SEQ_GT(th->th_ack, tp->snd_max))) { + rstreason = BANDLIM_UNLIMITED; + goto dropwithreset; + } + if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) + tp = tcp_drop(tp, ECONNREFUSED); + if (thflags & TH_RST) + goto drop; + if (!(thflags & TH_SYN)) + goto drop; + + tp->irs = th->th_seq; + tcp_rcvseqinit(tp); + if (thflags & TH_ACK) { + TCPSTAT_INC(tcps_connects); + soisconnected(so); +#ifdef MAC + mac_socketpeer_set_from_mbuf(m, so); +#endif + /* Do window scaling on this connection? */ + if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == + (TF_RCVD_SCALE|TF_REQ_SCALE)) { + tp->rcv_scale = tp->request_r_scale; + } + tp->rcv_adv += imin(tp->rcv_wnd, + TCP_MAXWIN << tp->rcv_scale); + tp->snd_una++; /* SYN is acked */ + /* + * If there's data, delay ACK; if there's also a FIN + * ACKNOW will be turned on later. + */ + if (DELAY_ACK(tp) && tlen != 0) + tcp_timer_activate(tp, TT_DELACK, + tcp_delacktime); + else + tp->t_flags |= TF_ACKNOW; + + if ((thflags & TH_ECE) && V_tcp_do_ecn) { + tp->t_flags |= TF_ECN_PERMIT; + TCPSTAT_INC(tcps_ecn_shs); + } + + /* + * Received <SYN,ACK> in SYN_SENT[*] state. + * Transitions: + * SYN_SENT --> ESTABLISHED + * SYN_SENT* --> FIN_WAIT_1 + */ + tp->t_starttime = ticks; + if (tp->t_flags & TF_NEEDFIN) { + tp->t_state = TCPS_FIN_WAIT_1; + tp->t_flags &= ~TF_NEEDFIN; + thflags &= ~TH_SYN; + } else { + tp->t_state = TCPS_ESTABLISHED; + cc_conn_init(tp); + tcp_timer_activate(tp, TT_KEEP, + TP_KEEPIDLE(tp)); + } + } else { + /* + * Received initial SYN in SYN-SENT[*] state => + * simultaneous open. If segment contains CC option + * and there is a cached CC, apply TAO test. + * If it succeeds, connection is * half-synchronized. + * Otherwise, do 3-way handshake: + * SYN-SENT -> SYN-RECEIVED + * SYN-SENT* -> SYN-RECEIVED* + * If there was no CC option, clear cached CC value. + */ + tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); + tcp_timer_activate(tp, TT_REXMT, 0); + tp->t_state = TCPS_SYN_RECEIVED; + } + + KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: " + "ti_locked %d", __func__, ti_locked)); + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + INP_WLOCK_ASSERT(tp->t_inpcb); + + /* + * Advance th->th_seq to correspond to first data byte. + * If data, trim to stay within window, + * dropping FIN if necessary. + */ + th->th_seq++; + if (tlen > tp->rcv_wnd) { + todrop = tlen - tp->rcv_wnd; + m_adj(m, -todrop); + tlen = tp->rcv_wnd; + thflags &= ~TH_FIN; + TCPSTAT_INC(tcps_rcvpackafterwin); + TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); + } + tp->snd_wl1 = th->th_seq - 1; + tp->rcv_up = th->th_seq; + /* + * Client side of transaction: already sent SYN and data. + * If the remote host used T/TCP to validate the SYN, + * our data will be ACK'd; if so, enter normal data segment + * processing in the middle of step 5, ack processing. + * Otherwise, goto step 6. + */ + if (thflags & TH_ACK) + goto process_ACK; + + goto step6; + + /* + * If the state is LAST_ACK or CLOSING or TIME_WAIT: + * do normal processing. + * + * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. + */ + case TCPS_LAST_ACK: + case TCPS_CLOSING: + break; /* continue normal processing */ + } + + /* + * States other than LISTEN or SYN_SENT. + * First check the RST flag and sequence number since reset segments + * are exempt from the timestamp and connection count tests. This + * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix + * below which allowed reset segments in half the sequence space + * to fall though and be processed (which gives forged reset + * segments with a random sequence number a 50 percent chance of + * killing a connection). + * Then check timestamp, if present. + * Then check the connection count, if present. + * Then check that at least some bytes of segment are within + * receive window. If segment begins before rcv_nxt, + * drop leading data (and SYN); if nothing left, just ack. + * + * + * If the RST bit is set, check the sequence number to see + * if this is a valid reset segment. + * RFC 793 page 37: + * In all states except SYN-SENT, all reset (RST) segments + * are validated by checking their SEQ-fields. A reset is + * valid if its sequence number is in the window. + * Note: this does not take into account delayed ACKs, so + * we should test against last_ack_sent instead of rcv_nxt. + * The sequence number in the reset segment is normally an + * echo of our outgoing acknowlegement numbers, but some hosts + * send a reset with the sequence number at the rightmost edge + * of our receive window, and we have to handle this case. + * Note 2: Paul Watson's paper "Slipping in the Window" has shown + * that brute force RST attacks are possible. To combat this, + * we use a much stricter check while in the ESTABLISHED state, + * only accepting RSTs where the sequence number is equal to + * last_ack_sent. In all other states (the states in which a + * RST is more likely), the more permissive check is used. + * If we have multiple segments in flight, the initial reset + * segment sequence numbers will be to the left of last_ack_sent, + * but they will eventually catch up. + * In any case, it never made sense to trim reset segments to + * fit the receive window since RFC 1122 says: + * 4.2.2.12 RST Segment: RFC-793 Section 3.4 + * + * A TCP SHOULD allow a received RST segment to include data. + * + * DISCUSSION + * It has been suggested that a RST segment could contain + * ASCII text that encoded and explained the cause of the + * RST. No standard has yet been established for such + * data. + * + * If the reset segment passes the sequence number test examine + * the state: + * SYN_RECEIVED STATE: + * If passive open, return to LISTEN state. + * If active open, inform user that connection was refused. + * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: + * Inform user that connection was reset, and close tcb. + * CLOSING, LAST_ACK STATES: + * Close the tcb. + * TIME_WAIT STATE: + * Drop the segment - see Stevens, vol. 2, p. 964 and + * RFC 1337. + */ + if (thflags & TH_RST) { + if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && + SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { + switch (tp->t_state) { + + case TCPS_SYN_RECEIVED: + so->so_error = ECONNREFUSED; + goto close; + + case TCPS_ESTABLISHED: + if (V_tcp_insecure_rst == 0 && + !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) && + SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) && + !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && + SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) { + TCPSTAT_INC(tcps_badrst); + goto drop; + } + /* FALLTHROUGH */ + case TCPS_FIN_WAIT_1: + case TCPS_FIN_WAIT_2: + case TCPS_CLOSE_WAIT: + so->so_error = ECONNRESET; + close: + KASSERT(ti_locked == TI_WLOCKED, + ("tcp_do_segment: TH_RST 1 ti_locked %d", + ti_locked)); + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + + tp->t_state = TCPS_CLOSED; + TCPSTAT_INC(tcps_drops); + tp = tcp_close(tp); + break; + + case TCPS_CLOSING: + case TCPS_LAST_ACK: + KASSERT(ti_locked == TI_WLOCKED, + ("tcp_do_segment: TH_RST 2 ti_locked %d", + ti_locked)); + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + + tp = tcp_close(tp); + break; + } + } + goto drop; + } + + /* + * RFC 1323 PAWS: If we have a timestamp reply on this segment + * and it's less than ts_recent, drop it. + */ + if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && + TSTMP_LT(to.to_tsval, tp->ts_recent)) { + + /* Check to see if ts_recent is over 24 days old. */ + if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { + /* + * Invalidate ts_recent. If this segment updates + * ts_recent, the age will be reset later and ts_recent + * will get a valid value. If it does not, setting + * ts_recent to zero will at least satisfy the + * requirement that zero be placed in the timestamp + * echo reply when ts_recent isn't valid. The + * age isn't reset until we get a valid ts_recent + * because we don't want out-of-order segments to be + * dropped when ts_recent is old. + */ + tp->ts_recent = 0; + } else { + TCPSTAT_INC(tcps_rcvduppack); + TCPSTAT_ADD(tcps_rcvdupbyte, tlen); + TCPSTAT_INC(tcps_pawsdrop); + if (tlen) + goto dropafterack; + goto drop; + } + } + + /* + * In the SYN-RECEIVED state, validate that the packet belongs to + * this connection before trimming the data to fit the receive + * window. Check the sequence number versus IRS since we know + * the sequence numbers haven't wrapped. This is a partial fix + * for the "LAND" DoS attack. + */ + if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { + rstreason = BANDLIM_RST_OPENPORT; + goto dropwithreset; + } + + todrop = tp->rcv_nxt - th->th_seq; + if (todrop > 0) { + /* + * If this is a duplicate SYN for our current connection, + * advance over it and pretend and it's not a SYN. + */ + if (thflags & TH_SYN && th->th_seq == tp->irs) { + thflags &= ~TH_SYN; + th->th_seq++; + if (th->th_urp > 1) + th->th_urp--; + else + thflags &= ~TH_URG; + todrop--; + } + /* + * Following if statement from Stevens, vol. 2, p. 960. + */ + if (todrop > tlen + || (todrop == tlen && (thflags & TH_FIN) == 0)) { + /* + * Any valid FIN must be to the left of the window. + * At this point the FIN must be a duplicate or out + * of sequence; drop it. + */ + thflags &= ~TH_FIN; + + /* + * Send an ACK to resynchronize and drop any data. + * But keep on processing for RST or ACK. + */ + tp->t_flags |= TF_ACKNOW; + todrop = tlen; + TCPSTAT_INC(tcps_rcvduppack); + TCPSTAT_ADD(tcps_rcvdupbyte, todrop); + } else { + TCPSTAT_INC(tcps_rcvpartduppack); + TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); + } + drop_hdrlen += todrop; /* drop from the top afterwards */ + th->th_seq += todrop; + tlen -= todrop; + if (th->th_urp > todrop) + th->th_urp -= todrop; + else { + thflags &= ~TH_URG; + th->th_urp = 0; + } + } + + /* + * If new data are received on a connection after the + * user processes are gone, then RST the other end. + */ + if ((so->so_state & SS_NOFDREF) && + tp->t_state > TCPS_CLOSE_WAIT && tlen) { + char *s; + + KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && " + "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + + if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) { + log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data after socket " + "was closed, sending RST and removing tcpcb\n", + s, __func__, tcpstates[tp->t_state], tlen); + free(s, M_TCPLOG); + } + tp = tcp_close(tp); + TCPSTAT_INC(tcps_rcvafterclose); + rstreason = BANDLIM_UNLIMITED; + goto dropwithreset; + } + + /* + * If segment ends after window, drop trailing data + * (and PUSH and FIN); if nothing left, just ACK. + */ + todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); + if (todrop > 0) { + TCPSTAT_INC(tcps_rcvpackafterwin); + if (todrop >= tlen) { + TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); + /* + * If window is closed can only take segments at + * window edge, and have to drop data and PUSH from + * incoming segments. Continue processing, but + * remember to ack. Otherwise, drop segment + * and ack. + */ + if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { + tp->t_flags |= TF_ACKNOW; + TCPSTAT_INC(tcps_rcvwinprobe); + } else + goto dropafterack; + } else + TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); + m_adj(m, -todrop); + tlen -= todrop; + thflags &= ~(TH_PUSH|TH_FIN); + } + + /* + * If last ACK falls within this segment's sequence numbers, + * record its timestamp. + * NOTE: + * 1) That the test incorporates suggestions from the latest + * proposal of the tcplw@cray.com list (Braden 1993/04/26). + * 2) That updating only on newer timestamps interferes with + * our earlier PAWS tests, so this check should be solely + * predicated on the sequence space of this segment. + * 3) That we modify the segment boundary check to be + * Last.ACK.Sent <= SEG.SEQ + SEG.Len + * instead of RFC1323's + * Last.ACK.Sent < SEG.SEQ + SEG.Len, + * This modified check allows us to overcome RFC1323's + * limitations as described in Stevens TCP/IP Illustrated + * Vol. 2 p.869. In such cases, we can still calculate the + * RTT correctly when RCV.NXT == Last.ACK.Sent. + */ + if ((to.to_flags & TOF_TS) != 0 && + SEQ_LEQ(th->th_seq, tp->last_ack_sent) && + SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + + ((thflags & (TH_SYN|TH_FIN)) != 0))) { + tp->ts_recent_age = tcp_ts_getticks(); + tp->ts_recent = to.to_tsval; + } + + /* + * If a SYN is in the window, then this is an + * error and we send an RST and drop the connection. + */ + if (thflags & TH_SYN) { + KASSERT(ti_locked == TI_WLOCKED, + ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + + tp = tcp_drop(tp, ECONNRESET); + rstreason = BANDLIM_UNLIMITED; + goto drop; + } + + /* + * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN + * flag is on (half-synchronized state), then queue data for + * later processing; else drop segment and return. + */ + if ((thflags & TH_ACK) == 0) { + if (tp->t_state == TCPS_SYN_RECEIVED || + (tp->t_flags & TF_NEEDSYN)) + goto step6; + else if (tp->t_flags & TF_ACKNOW) + goto dropafterack; + else + goto drop; + } + + /* + * Ack processing. + */ + switch (tp->t_state) { + + /* + * In SYN_RECEIVED state, the ack ACKs our SYN, so enter + * ESTABLISHED state and continue processing. + * The ACK was checked above. + */ + case TCPS_SYN_RECEIVED: + + TCPSTAT_INC(tcps_connects); + soisconnected(so); + /* Do window scaling? */ + if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == + (TF_RCVD_SCALE|TF_REQ_SCALE)) { + tp->rcv_scale = tp->request_r_scale; + tp->snd_wnd = tiwin; + } + /* + * Make transitions: + * SYN-RECEIVED -> ESTABLISHED + * SYN-RECEIVED* -> FIN-WAIT-1 + */ + tp->t_starttime = ticks; + if (tp->t_flags & TF_NEEDFIN) { + tp->t_state = TCPS_FIN_WAIT_1; + tp->t_flags &= ~TF_NEEDFIN; + } else { + tp->t_state = TCPS_ESTABLISHED; + cc_conn_init(tp); + tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); + } + /* + * If segment contains data or ACK, will call tcp_reass() + * later; if not, do so now to pass queued data to user. + */ + if (tlen == 0 && (thflags & TH_FIN) == 0) + (void) tcp_reass(tp, (struct tcphdr *)0, 0, + (struct mbuf *)0); + tp->snd_wl1 = th->th_seq - 1; + /* FALLTHROUGH */ + + /* + * In ESTABLISHED state: drop duplicate ACKs; ACK out of range + * ACKs. If the ack is in the range + * tp->snd_una < th->th_ack <= tp->snd_max + * then advance tp->snd_una to th->th_ack and drop + * data from the retransmission queue. If this ACK reflects + * more up to date window information we update our window information. + */ + case TCPS_ESTABLISHED: + case TCPS_FIN_WAIT_1: + case TCPS_FIN_WAIT_2: + case TCPS_CLOSE_WAIT: + case TCPS_CLOSING: + case TCPS_LAST_ACK: + if (SEQ_GT(th->th_ack, tp->snd_max)) { + TCPSTAT_INC(tcps_rcvacktoomuch); + goto dropafterack; + } + if ((tp->t_flags & TF_SACK_PERMIT) && + ((to.to_flags & TOF_SACK) || + !TAILQ_EMPTY(&tp->snd_holes))) + tcp_sack_doack(tp, &to, th->th_ack); + + /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ + hhook_run_tcp_est_in(tp, th, &to); + + if (SEQ_LEQ(th->th_ack, tp->snd_una)) { + if (tlen == 0 && tiwin == tp->snd_wnd) { + TCPSTAT_INC(tcps_rcvdupack); + /* + * If we have outstanding data (other than + * a window probe), this is a completely + * duplicate ack (ie, window info didn't + * change), the ack is the biggest we've + * seen and we've seen exactly our rexmt + * threshhold of them, assume a packet + * has been dropped and retransmit it. + * Kludge snd_nxt & the congestion + * window so we send only this one + * packet. + * + * We know we're losing at the current + * window size so do congestion avoidance + * (set ssthresh to half the current window + * and pull our congestion window back to + * the new ssthresh). + * + * Dup acks mean that packets have left the + * network (they're now cached at the receiver) + * so bump cwnd by the amount in the receiver + * to keep a constant cwnd packets in the + * network. + * + * When using TCP ECN, notify the peer that + * we reduced the cwnd. + */ + if (!tcp_timer_active(tp, TT_REXMT) || + th->th_ack != tp->snd_una) + tp->t_dupacks = 0; + else if (++tp->t_dupacks > tcprexmtthresh || + IN_FASTRECOVERY(tp->t_flags)) { + cc_ack_received(tp, th, CC_DUPACK); + if ((tp->t_flags & TF_SACK_PERMIT) && + IN_FASTRECOVERY(tp->t_flags)) { + int awnd; + + /* + * Compute the amount of data in flight first. + * We can inject new data into the pipe iff + * we have less than 1/2 the original window's + * worth of data in flight. + */ + awnd = (tp->snd_nxt - tp->snd_fack) + + tp->sackhint.sack_bytes_rexmit; + if (awnd < tp->snd_ssthresh) { + tp->snd_cwnd += tp->t_maxseg; + if (tp->snd_cwnd > tp->snd_ssthresh) + tp->snd_cwnd = tp->snd_ssthresh; + } + } else + tp->snd_cwnd += tp->t_maxseg; + if ((thflags & TH_FIN) && + (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { + /* + * If its a fin we need to process + * it to avoid a race where both + * sides enter FIN-WAIT and send FIN|ACK + * at the same time. + */ + break; + } + (void) tcp_output(tp); + goto drop; + } else if (tp->t_dupacks == tcprexmtthresh) { + tcp_seq onxt = tp->snd_nxt; + + /* + * If we're doing sack, check to + * see if we're already in sack + * recovery. If we're not doing sack, + * check to see if we're in newreno + * recovery. + */ + if (tp->t_flags & TF_SACK_PERMIT) { + if (IN_FASTRECOVERY(tp->t_flags)) { + tp->t_dupacks = 0; + break; + } + } else { + if (SEQ_LEQ(th->th_ack, + tp->snd_recover)) { + tp->t_dupacks = 0; + break; + } + } + /* Congestion signal before ack. */ + cc_cong_signal(tp, th, CC_NDUPACK); + cc_ack_received(tp, th, CC_DUPACK); + tcp_timer_activate(tp, TT_REXMT, 0); + tp->t_rtttime = 0; + if (tp->t_flags & TF_SACK_PERMIT) { + TCPSTAT_INC( + tcps_sack_recovery_episode); + tp->sack_newdata = tp->snd_nxt; + tp->snd_cwnd = tp->t_maxseg; + (void) tcp_output(tp); + goto drop; + } + tp->snd_nxt = th->th_ack; + tp->snd_cwnd = tp->t_maxseg; + if ((thflags & TH_FIN) && + (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { + /* + * If its a fin we need to process + * it to avoid a race where both + * sides enter FIN-WAIT and send FIN|ACK + * at the same time. + */ + break; + } + (void) tcp_output(tp); + KASSERT(tp->snd_limited <= 2, + ("%s: tp->snd_limited too big", + __func__)); + tp->snd_cwnd = tp->snd_ssthresh + + tp->t_maxseg * + (tp->t_dupacks - tp->snd_limited); + if (SEQ_GT(onxt, tp->snd_nxt)) + tp->snd_nxt = onxt; + goto drop; + } else if (V_tcp_do_rfc3042) { + cc_ack_received(tp, th, CC_DUPACK); + u_long oldcwnd = tp->snd_cwnd; + tcp_seq oldsndmax = tp->snd_max; + u_int sent; + + KASSERT(tp->t_dupacks == 1 || + tp->t_dupacks == 2, + ("%s: dupacks not 1 or 2", + __func__)); + if (tp->t_dupacks == 1) + tp->snd_limited = 0; + tp->snd_cwnd = + (tp->snd_nxt - tp->snd_una) + + (tp->t_dupacks - tp->snd_limited) * + tp->t_maxseg; + if ((thflags & TH_FIN) && + (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { + /* + * If its a fin we need to process + * it to avoid a race where both + * sides enter FIN-WAIT and send FIN|ACK + * at the same time. + */ + break; + } + (void) tcp_output(tp); + sent = tp->snd_max - oldsndmax; + if (sent > tp->t_maxseg) { + KASSERT((tp->t_dupacks == 2 && + tp->snd_limited == 0) || + (sent == tp->t_maxseg + 1 && + tp->t_flags & TF_SENTFIN), + ("%s: sent too much", + __func__)); + tp->snd_limited = 2; + } else if (sent > 0) + ++tp->snd_limited; + tp->snd_cwnd = oldcwnd; + goto drop; + } + } else + tp->t_dupacks = 0; + break; + } + + KASSERT(SEQ_GT(th->th_ack, tp->snd_una), + ("%s: th_ack <= snd_una", __func__)); + + /* + * If the congestion window was inflated to account + * for the other side's cached packets, retract it. + */ + if (IN_FASTRECOVERY(tp->t_flags)) { + if (SEQ_LT(th->th_ack, tp->snd_recover)) { + if (tp->t_flags & TF_SACK_PERMIT) + tcp_sack_partialack(tp, th); + else + tcp_newreno_partial_ack(tp, th); + } else + cc_post_recovery(tp, th); + } + tp->t_dupacks = 0; + /* + * If we reach this point, ACK is not a duplicate, + * i.e., it ACKs something we sent. + */ + if (tp->t_flags & TF_NEEDSYN) { + /* + * T/TCP: Connection was half-synchronized, and our + * SYN has been ACK'd (so connection is now fully + * synchronized). Go to non-starred state, + * increment snd_una for ACK of SYN, and check if + * we can do window scaling. + */ + tp->t_flags &= ~TF_NEEDSYN; + tp->snd_una++; + /* Do window scaling? */ + if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == + (TF_RCVD_SCALE|TF_REQ_SCALE)) { + tp->rcv_scale = tp->request_r_scale; + /* Send window already scaled. */ + } + } + +process_ACK: + INP_WLOCK_ASSERT(tp->t_inpcb); + + acked = BYTES_THIS_ACK(tp, th); + TCPSTAT_INC(tcps_rcvackpack); + TCPSTAT_ADD(tcps_rcvackbyte, acked); + + /* + * If we just performed our first retransmit, and the ACK + * arrives within our recovery window, then it was a mistake + * to do the retransmit in the first place. Recover our + * original cwnd and ssthresh, and proceed to transmit where + * we left off. + */ + if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && + (int)(ticks - tp->t_badrxtwin) < 0) + cc_cong_signal(tp, th, CC_RTO_ERR); + + /* + * If we have a timestamp reply, update smoothed + * round trip time. If no timestamp is present but + * transmit timer is running and timed sequence + * number was acked, update smoothed round trip time. + * Since we now have an rtt measurement, cancel the + * timer backoff (cf., Phil Karn's retransmit alg.). + * Recompute the initial retransmit timer. + * + * Some boxes send broken timestamp replies + * during the SYN+ACK phase, ignore + * timestamps of 0 or we could calculate a + * huge RTT and blow up the retransmit timer. + */ + if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { + u_int t; + + t = tcp_ts_getticks() - to.to_tsecr; + if (!tp->t_rttlow || tp->t_rttlow > t) + tp->t_rttlow = t; + tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); + } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { + if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) + tp->t_rttlow = ticks - tp->t_rtttime; + tcp_xmit_timer(tp, ticks - tp->t_rtttime); + } + + /* + * If all outstanding data is acked, stop retransmit + * timer and remember to restart (more output or persist). + * If there is more data to be acked, restart retransmit + * timer, using current (possibly backed-off) value. + */ + if (th->th_ack == tp->snd_max) { + tcp_timer_activate(tp, TT_REXMT, 0); + needoutput = 1; + } else if (!tcp_timer_active(tp, TT_PERSIST)) + tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); + + /* + * If no data (only SYN) was ACK'd, + * skip rest of ACK processing. + */ + if (acked == 0) + goto step6; + + /* + * Let the congestion control algorithm update congestion + * control related information. This typically means increasing + * the congestion window. + */ + cc_ack_received(tp, th, CC_ACK); + + SOCKBUF_LOCK(&so->so_snd); + if (acked > so->so_snd.sb_cc) { + tp->snd_wnd -= so->so_snd.sb_cc; + sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); + ourfinisacked = 1; + } else { + sbdrop_locked(&so->so_snd, acked); + tp->snd_wnd -= acked; + ourfinisacked = 0; + } + /* NB: sowwakeup_locked() does an implicit unlock. */ + sowwakeup_locked(so); + /* Detect una wraparound. */ + if (!IN_RECOVERY(tp->t_flags) && + SEQ_GT(tp->snd_una, tp->snd_recover) && + SEQ_LEQ(th->th_ack, tp->snd_recover)) + tp->snd_recover = th->th_ack - 1; + /* XXXLAS: Can this be moved up into cc_post_recovery? */ + if (IN_RECOVERY(tp->t_flags) && + SEQ_GEQ(th->th_ack, tp->snd_recover)) { + EXIT_RECOVERY(tp->t_flags); + } + tp->snd_una = th->th_ack; + if (tp->t_flags & TF_SACK_PERMIT) { + if (SEQ_GT(tp->snd_una, tp->snd_recover)) + tp->snd_recover = tp->snd_una; + } + if (SEQ_LT(tp->snd_nxt, tp->snd_una)) + tp->snd_nxt = tp->snd_una; + + switch (tp->t_state) { + + /* + * In FIN_WAIT_1 STATE in addition to the processing + * for the ESTABLISHED state if our FIN is now acknowledged + * then enter FIN_WAIT_2. + */ + case TCPS_FIN_WAIT_1: + if (ourfinisacked) { + /* + * If we can't receive any more + * data, then closing user can proceed. + * Starting the timer is contrary to the + * specification, but if we don't get a FIN + * we'll hang forever. + * + * XXXjl: + * we should release the tp also, and use a + * compressed state. + */ + if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { + soisdisconnected(so); + tcp_timer_activate(tp, TT_2MSL, + (tcp_fast_finwait2_recycle ? + tcp_finwait2_timeout : + TP_MAXIDLE(tp))); + } + tp->t_state = TCPS_FIN_WAIT_2; + } + break; + + /* + * In CLOSING STATE in addition to the processing for + * the ESTABLISHED state if the ACK acknowledges our FIN + * then enter the TIME-WAIT state, otherwise ignore + * the segment. + */ + case TCPS_CLOSING: + if (ourfinisacked) { + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + tcp_twstart(tp); + INP_INFO_WUNLOCK(&V_tcbinfo); + m_freem(m); + return; + } + break; + + /* + * In LAST_ACK, we may still be waiting for data to drain + * and/or to be acked, as well as for the ack of our FIN. + * If our FIN is now acknowledged, delete the TCB, + * enter the closed state and return. + */ + case TCPS_LAST_ACK: + if (ourfinisacked) { + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + tp = tcp_close(tp); + goto drop; + } + break; + } + } + +step6: + INP_WLOCK_ASSERT(tp->t_inpcb); + + /* + * Update window information. + * Don't look at window if no ACK: TAC's send garbage on first SYN. + */ + if ((thflags & TH_ACK) && + (SEQ_LT(tp->snd_wl1, th->th_seq) || + (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || + (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { + /* keep track of pure window updates */ + if (tlen == 0 && + tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) + TCPSTAT_INC(tcps_rcvwinupd); + tp->snd_wnd = tiwin; + tp->snd_wl1 = th->th_seq; + tp->snd_wl2 = th->th_ack; + if (tp->snd_wnd > tp->max_sndwnd) + tp->max_sndwnd = tp->snd_wnd; + needoutput = 1; + } + + /* + * Process segments with URG. + */ + if ((thflags & TH_URG) && th->th_urp && + TCPS_HAVERCVDFIN(tp->t_state) == 0) { + /* + * This is a kludge, but if we receive and accept + * random urgent pointers, we'll crash in + * soreceive. It's hard to imagine someone + * actually wanting to send this much urgent data. + */ + SOCKBUF_LOCK(&so->so_rcv); + if (th->th_urp + so->so_rcv.sb_cc > sb_max) { + th->th_urp = 0; /* XXX */ + thflags &= ~TH_URG; /* XXX */ + SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ + goto dodata; /* XXX */ + } + /* + * If this segment advances the known urgent pointer, + * then mark the data stream. This should not happen + * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since + * a FIN has been received from the remote side. + * In these states we ignore the URG. + * + * According to RFC961 (Assigned Protocols), + * the urgent pointer points to the last octet + * of urgent data. We continue, however, + * to consider it to indicate the first octet + * of data past the urgent section as the original + * spec states (in one of two places). + */ + if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { + tp->rcv_up = th->th_seq + th->th_urp; + so->so_oobmark = so->so_rcv.sb_cc + + (tp->rcv_up - tp->rcv_nxt) - 1; + if (so->so_oobmark == 0) + so->so_rcv.sb_state |= SBS_RCVATMARK; + sohasoutofband(so); + tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); + } + SOCKBUF_UNLOCK(&so->so_rcv); + /* + * Remove out of band data so doesn't get presented to user. + * This can happen independent of advancing the URG pointer, + * but if two URG's are pending at once, some out-of-band + * data may creep in... ick. + */ + if (th->th_urp <= (u_long)tlen && + !(so->so_options & SO_OOBINLINE)) { + /* hdr drop is delayed */ + tcp_pulloutofband(so, th, m, drop_hdrlen); + } + } else { + /* + * If no out of band data is expected, + * pull receive urgent pointer along + * with the receive window. + */ + if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) + tp->rcv_up = tp->rcv_nxt; + } +dodata: /* XXX */ + INP_WLOCK_ASSERT(tp->t_inpcb); + + /* + * Process the segment text, merging it into the TCP sequencing queue, + * and arranging for acknowledgment of receipt if necessary. + * This process logically involves adjusting tp->rcv_wnd as data + * is presented to the user (this happens in tcp_usrreq.c, + * case PRU_RCVD). If a FIN has already been received on this + * connection then we just ignore the text. + */ + if ((tlen || (thflags & TH_FIN)) && + TCPS_HAVERCVDFIN(tp->t_state) == 0) { + tcp_seq save_start = th->th_seq; + m_adj(m, drop_hdrlen); /* delayed header drop */ + /* + * Insert segment which includes th into TCP reassembly queue + * with control block tp. Set thflags to whether reassembly now + * includes a segment with FIN. This handles the common case + * inline (segment is the next to be received on an established + * connection, and the queue is empty), avoiding linkage into + * and removal from the queue and repetition of various + * conversions. + * Set DELACK for segments received in order, but ack + * immediately when segments are out of order (so + * fast retransmit can work). + */ + if (th->th_seq == tp->rcv_nxt && + LIST_EMPTY(&tp->t_segq) && + TCPS_HAVEESTABLISHED(tp->t_state)) { + if (DELAY_ACK(tp)) + tp->t_flags |= TF_DELACK; + else + tp->t_flags |= TF_ACKNOW; + tp->rcv_nxt += tlen; + thflags = th->th_flags & TH_FIN; + TCPSTAT_INC(tcps_rcvpack); + TCPSTAT_ADD(tcps_rcvbyte, tlen); + ND6_HINT(tp); + SOCKBUF_LOCK(&so->so_rcv); + if (so->so_rcv.sb_state & SBS_CANTRCVMORE) + m_freem(m); + else + sbappendstream_locked(&so->so_rcv, m); + /* NB: sorwakeup_locked() does an implicit unlock. */ + sorwakeup_locked(so); + } else { + /* + * XXX: Due to the header drop above "th" is + * theoretically invalid by now. Fortunately + * m_adj() doesn't actually frees any mbufs + * when trimming from the head. + */ + thflags = tcp_reass(tp, th, &tlen, m); + tp->t_flags |= TF_ACKNOW; + } + if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) + tcp_update_sack_list(tp, save_start, save_start + tlen); +#if 0 + /* + * Note the amount of data that peer has sent into + * our window, in order to estimate the sender's + * buffer size. + * XXX: Unused. + */ + if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) + len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); + else + len = so->so_rcv.sb_hiwat; +#endif + } else { + m_freem(m); + thflags &= ~TH_FIN; + } + + /* + * If FIN is received ACK the FIN and let the user know + * that the connection is closing. + */ + if (thflags & TH_FIN) { + if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { + socantrcvmore(so); + /* + * If connection is half-synchronized + * (ie NEEDSYN flag on) then delay ACK, + * so it may be piggybacked when SYN is sent. + * Otherwise, since we received a FIN then no + * more input can be expected, send ACK now. + */ + if (tp->t_flags & TF_NEEDSYN) + tp->t_flags |= TF_DELACK; + else + tp->t_flags |= TF_ACKNOW; + tp->rcv_nxt++; + } + switch (tp->t_state) { + + /* + * In SYN_RECEIVED and ESTABLISHED STATES + * enter the CLOSE_WAIT state. + */ + case TCPS_SYN_RECEIVED: + tp->t_starttime = ticks; + /* FALLTHROUGH */ + case TCPS_ESTABLISHED: + tp->t_state = TCPS_CLOSE_WAIT; + break; + + /* + * If still in FIN_WAIT_1 STATE FIN has not been acked so + * enter the CLOSING state. + */ + case TCPS_FIN_WAIT_1: + tp->t_state = TCPS_CLOSING; + break; + + /* + * In FIN_WAIT_2 state enter the TIME_WAIT state, + * starting the time-wait timer, turning off the other + * standard timers. + */ + case TCPS_FIN_WAIT_2: + INP_INFO_WLOCK_ASSERT(&V_tcbinfo); + KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata " + "TCP_FIN_WAIT_2 ti_locked: %d", __func__, + ti_locked)); + + tcp_twstart(tp); + INP_INFO_WUNLOCK(&V_tcbinfo); + return; + } + } + if (ti_locked == TI_WLOCKED) + INP_INFO_WUNLOCK(&V_tcbinfo); + ti_locked = TI_UNLOCKED; + +#ifdef TCPDEBUG + if (so->so_options & SO_DEBUG) + tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, + &tcp_savetcp, 0); +#endif + + /* + * Return any desired output. + */ + if (needoutput || (tp->t_flags & TF_ACKNOW)) + (void) tcp_output(tp); + +check_delack: + KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", + __func__, ti_locked)); + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); + INP_WLOCK_ASSERT(tp->t_inpcb); + + if (tp->t_flags & TF_DELACK) { + tp->t_flags &= ~TF_DELACK; + tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); + } + INP_WUNLOCK(tp->t_inpcb); + return; + +dropafterack: + /* + * Generate an ACK dropping incoming segment if it occupies + * sequence space, where the ACK reflects our state. + * + * We can now skip the test for the RST flag since all + * paths to this code happen after packets containing + * RST have been dropped. + * + * In the SYN-RECEIVED state, don't send an ACK unless the + * segment we received passes the SYN-RECEIVED ACK test. + * If it fails send a RST. This breaks the loop in the + * "LAND" DoS attack, and also prevents an ACK storm + * between two listening ports that have been sent forged + * SYN segments, each with the source address of the other. + */ + if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && + (SEQ_GT(tp->snd_una, th->th_ack) || + SEQ_GT(th->th_ack, tp->snd_max)) ) { + rstreason = BANDLIM_RST_OPENPORT; + goto dropwithreset; + } +#ifdef TCPDEBUG + if (so->so_options & SO_DEBUG) + tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, + &tcp_savetcp, 0); +#endif + if (ti_locked == TI_WLOCKED) + INP_INFO_WUNLOCK(&V_tcbinfo); + ti_locked = TI_UNLOCKED; + + tp->t_flags |= TF_ACKNOW; + (void) tcp_output(tp); + INP_WUNLOCK(tp->t_inpcb); + m_freem(m); + return; + +dropwithreset: + if (ti_locked == TI_WLOCKED) + INP_INFO_WUNLOCK(&V_tcbinfo); + ti_locked = TI_UNLOCKED; + + if (tp != NULL) { + tcp_dropwithreset(m, th, tp, tlen, rstreason); + INP_WUNLOCK(tp->t_inpcb); + } else + tcp_dropwithreset(m, th, NULL, tlen, rstreason); + return; + +drop: + if (ti_locked == TI_WLOCKED) { + INP_INFO_WUNLOCK(&V_tcbinfo); + ti_locked = TI_UNLOCKED; + } +#ifdef INVARIANTS + else + INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); +#endif + + /* + * Drop space held by incoming segment and return. + */ +#ifdef TCPDEBUG + if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) + tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, + &tcp_savetcp, 0); +#endif + if (tp != NULL) + INP_WUNLOCK(tp->t_inpcb); + m_freem(m); +} + +/* + * Issue RST and make ACK acceptable to originator of segment. + * The mbuf must still include the original packet header. + * tp may be NULL. + */ +static void +tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, + int tlen, int rstreason) +{ +#ifdef INET + struct ip *ip; +#endif +#ifdef INET6 + struct ip6_hdr *ip6; +#endif + + if (tp != NULL) { + INP_WLOCK_ASSERT(tp->t_inpcb); + } + + /* Don't bother if destination was broadcast/multicast. */ + if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) + goto drop; +#ifdef INET6 + if (mtod(m, struct ip *)->ip_v == 6) { + ip6 = mtod(m, struct ip6_hdr *); + if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || + IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) + goto drop; + /* IPv6 anycast check is done at tcp6_input() */ + } +#endif +#if defined(INET) && defined(INET6) + else +#endif +#ifdef INET + { + ip = mtod(m, struct ip *); + if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || + IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || + ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || + in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) + goto drop; + } +#endif + + /* Perform bandwidth limiting. */ + if (badport_bandlim(rstreason) < 0) + goto drop; + + /* tcp_respond consumes the mbuf chain. */ + if (th->th_flags & TH_ACK) { + tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, + th->th_ack, TH_RST); + } else { + if (th->th_flags & TH_SYN) + tlen++; + tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, + (tcp_seq)0, TH_RST|TH_ACK); + } + return; +drop: + m_freem(m); +} + +/* + * Parse TCP options and place in tcpopt. + */ +static void +tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) +{ + int opt, optlen; + + to->to_flags = 0; + for (; cnt > 0; cnt -= optlen, cp += optlen) { + opt = cp[0]; + if (opt == TCPOPT_EOL) + break; + if (opt == TCPOPT_NOP) + optlen = 1; + else { + if (cnt < 2) + break; + optlen = cp[1]; + if (optlen < 2 || optlen > cnt) + break; + } + switch (opt) { + case TCPOPT_MAXSEG: + if (optlen != TCPOLEN_MAXSEG) + continue; + if (!(flags & TO_SYN)) + continue; + to->to_flags |= TOF_MSS; + bcopy((char *)cp + 2, + (char *)&to->to_mss, sizeof(to->to_mss)); + to->to_mss = ntohs(to->to_mss); + break; + case TCPOPT_WINDOW: + if (optlen != TCPOLEN_WINDOW) + continue; + if (!(flags & TO_SYN)) + continue; + to->to_flags |= TOF_SCALE; + to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); + break; + case TCPOPT_TIMESTAMP: + if (optlen != TCPOLEN_TIMESTAMP) + continue; + to->to_flags |= TOF_TS; + bcopy((char *)cp + 2, + (char *)&to->to_tsval, sizeof(to->to_tsval)); + to->to_tsval = ntohl(to->to_tsval); + bcopy((char *)cp + 6, + (char *)&to->to_tsecr, sizeof(to->to_tsecr)); + to->to_tsecr = ntohl(to->to_tsecr); + break; +#ifdef TCP_SIGNATURE + /* + * XXX In order to reply to a host which has set the + * TCP_SIGNATURE option in its initial SYN, we have to + * record the fact that the option was observed here + * for the syncache code to perform the correct response. + */ + case TCPOPT_SIGNATURE: + if (optlen != TCPOLEN_SIGNATURE) + continue; + to->to_flags |= TOF_SIGNATURE; + to->to_signature = cp + 2; + break; +#endif + case TCPOPT_SACK_PERMITTED: + if (optlen != TCPOLEN_SACK_PERMITTED) + continue; + if (!(flags & TO_SYN)) + continue; + if (!V_tcp_do_sack) + continue; + to->to_flags |= TOF_SACKPERM; + break; + case TCPOPT_SACK: + if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) + continue; + if (flags & TO_SYN) + continue; + to->to_flags |= TOF_SACK; + to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; + to->to_sacks = cp + 2; + TCPSTAT_INC(tcps_sack_rcv_blocks); + break; + default: + continue; + } + } +} + +/* + * Pull out of band byte out of a segment so + * it doesn't appear in the user's data queue. + * It is still reflected in the segment length for + * sequencing purposes. + */ +static void +tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, + int off) +{ + int cnt = off + th->th_urp - 1; + + while (cnt >= 0) { + if (m->m_len > cnt) { + char *cp = mtod(m, caddr_t) + cnt; + struct tcpcb *tp = sototcpcb(so); + + INP_WLOCK_ASSERT(tp->t_inpcb); + + tp->t_iobc = *cp; + tp->t_oobflags |= TCPOOB_HAVEDATA; + bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); + m->m_len--; + if (m->m_flags & M_PKTHDR) + m->m_pkthdr.len--; + return; + } + cnt -= m->m_len; + m = m->m_next; + if (m == NULL) + break; + } + panic("tcp_pulloutofband"); +} + +/* + * Collect new round-trip time estimate + * and update averages and current timeout. + */ +static void +tcp_xmit_timer(struct tcpcb *tp, int rtt) +{ + int delta; + + INP_WLOCK_ASSERT(tp->t_inpcb); + + TCPSTAT_INC(tcps_rttupdated); + tp->t_rttupdated++; + if (tp->t_srtt != 0) { + /* + * srtt is stored as fixed point with 5 bits after the + * binary point (i.e., scaled by 8). The following magic + * is equivalent to the smoothing algorithm in rfc793 with + * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed + * point). Adjust rtt to origin 0. + */ + delta = ((rtt - 1) << TCP_DELTA_SHIFT) + - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); + + if ((tp->t_srtt += delta) <= 0) + tp->t_srtt = 1; + + /* + * We accumulate a smoothed rtt variance (actually, a + * smoothed mean difference), then set the retransmit + * timer to smoothed rtt + 4 times the smoothed variance. + * rttvar is stored as fixed point with 4 bits after the + * binary point (scaled by 16). The following is + * equivalent to rfc793 smoothing with an alpha of .75 + * (rttvar = rttvar*3/4 + |delta| / 4). This replaces + * rfc793's wired-in beta. + */ + if (delta < 0) + delta = -delta; + delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); + if ((tp->t_rttvar += delta) <= 0) + tp->t_rttvar = 1; + if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) + tp->t_rttbest = tp->t_srtt + tp->t_rttvar; + } else { + /* + * No rtt measurement yet - use the unsmoothed rtt. + * Set the variance to half the rtt (so our first + * retransmit happens at 3*rtt). + */ + tp->t_srtt = rtt << TCP_RTT_SHIFT; + tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); + tp->t_rttbest = tp->t_srtt + tp->t_rttvar; + } + tp->t_rtttime = 0; + tp->t_rxtshift = 0; + + /* + * the retransmit should happen at rtt + 4 * rttvar. + * Because of the way we do the smoothing, srtt and rttvar + * will each average +1/2 tick of bias. When we compute + * the retransmit timer, we want 1/2 tick of rounding and + * 1 extra tick because of +-1/2 tick uncertainty in the + * firing of the timer. The bias will give us exactly the + * 1.5 tick we need. But, because the bias is + * statistical, we have to test that we don't drop below + * the minimum feasible timer (which is 2 ticks). + */ + TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), + max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); + + /* + * We received an ack for a packet that wasn't retransmitted; + * it is probably safe to discard any error indications we've + * received recently. This isn't quite right, but close enough + * for now (a route might have failed after we sent a segment, + * and the return path might not be symmetrical). + */ + tp->t_softerror = 0; +} + +/* + * Determine a reasonable value for maxseg size. + * If the route is known, check route for mtu. + * If none, use an mss that can be handled on the outgoing interface + * without forcing IP to fragment. If no route is found, route has no mtu, + * or the destination isn't local, use a default, hopefully conservative + * size (usually 512 or the default IP max size, but no more than the mtu + * of the interface), as we can't discover anything about intervening + * gateways or networks. We also initialize the congestion/slow start + * window to be a single segment if the destination isn't local. + * While looking at the routing entry, we also initialize other path-dependent + * parameters from pre-set or cached values in the routing entry. + * + * Also take into account the space needed for options that we + * send regularly. Make maxseg shorter by that amount to assure + * that we can send maxseg amount of data even when the options + * are present. Store the upper limit of the length of options plus + * data in maxopd. + * + * NOTE that this routine is only called when we process an incoming + * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS + * settings are handled in tcp_mssopt(). + */ +void +tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, + struct hc_metrics_lite *metricptr, int *mtuflags) +{ + int mss = 0; + u_long maxmtu = 0; + struct inpcb *inp = tp->t_inpcb; + struct hc_metrics_lite metrics; + int origoffer; +#ifdef INET6 + int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; + size_t min_protoh = isipv6 ? + sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : + sizeof (struct tcpiphdr); +#else + const size_t min_protoh = sizeof(struct tcpiphdr); +#endif + + INP_WLOCK_ASSERT(tp->t_inpcb); + + if (mtuoffer != -1) { + KASSERT(offer == -1, ("%s: conflict", __func__)); + offer = mtuoffer - min_protoh; + } + origoffer = offer; + + /* Initialize. */ +#ifdef INET6 + if (isipv6) { + maxmtu = tcp_maxmtu6(&inp->inp_inc, mtuflags); + tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt; + } +#endif +#if defined(INET) && defined(INET6) + else +#endif +#ifdef INET + { + maxmtu = tcp_maxmtu(&inp->inp_inc, mtuflags); + tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt; + } +#endif + + /* + * No route to sender, stay with default mss and return. + */ + if (maxmtu == 0) { + /* + * In case we return early we need to initialize metrics + * to a defined state as tcp_hc_get() would do for us + * if there was no cache hit. + */ + if (metricptr != NULL) + bzero(metricptr, sizeof(struct hc_metrics_lite)); + return; + } + + /* What have we got? */ + switch (offer) { + case 0: + /* + * Offer == 0 means that there was no MSS on the SYN + * segment, in this case we use tcp_mssdflt as + * already assigned to t_maxopd above. + */ + offer = tp->t_maxopd; + break; + + case -1: + /* + * Offer == -1 means that we didn't receive SYN yet. + */ + /* FALLTHROUGH */ + + default: + /* + * Prevent DoS attack with too small MSS. Round up + * to at least minmss. + */ + offer = max(offer, V_tcp_minmss); + } + + /* + * rmx information is now retrieved from tcp_hostcache. + */ + tcp_hc_get(&inp->inp_inc, &metrics); + if (metricptr != NULL) + bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); + + /* + * If there's a discovered mtu int tcp hostcache, use it + * else, use the link mtu. + */ + if (metrics.rmx_mtu) + mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; + else { +#ifdef INET6 + if (isipv6) { + mss = maxmtu - min_protoh; + if (!V_path_mtu_discovery && + !in6_localaddr(&inp->in6p_faddr)) + mss = min(mss, V_tcp_v6mssdflt); + } +#endif +#if defined(INET) && defined(INET6) + else +#endif +#ifdef INET + { + mss = maxmtu - min_protoh; + if (!V_path_mtu_discovery && + !in_localaddr(inp->inp_faddr)) + mss = min(mss, V_tcp_mssdflt); + } +#endif + /* + * XXX - The above conditional (mss = maxmtu - min_protoh) + * probably violates the TCP spec. + * The problem is that, since we don't know the + * other end's MSS, we are supposed to use a conservative + * default. But, if we do that, then MTU discovery will + * never actually take place, because the conservative + * default is much less than the MTUs typically seen + * on the Internet today. For the moment, we'll sweep + * this under the carpet. + * + * The conservative default might not actually be a problem + * if the only case this occurs is when sending an initial + * SYN with options and data to a host we've never talked + * to before. Then, they will reply with an MSS value which + * will get recorded and the new parameters should get + * recomputed. For Further Study. + */ + } + mss = min(mss, offer); + + /* + * Sanity check: make sure that maxopd will be large + * enough to allow some data on segments even if the + * all the option space is used (40bytes). Otherwise + * funny things may happen in tcp_output. + */ + mss = max(mss, 64); + + /* + * maxopd stores the maximum length of data AND options + * in a segment; maxseg is the amount of data in a normal + * segment. We need to store this value (maxopd) apart + * from maxseg, because now every segment carries options + * and thus we normally have somewhat less data in segments. + */ + tp->t_maxopd = mss; + + /* + * origoffer==-1 indicates that no segments were received yet. + * In this case we just guess. + */ + if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && + (origoffer == -1 || + (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) + mss -= TCPOLEN_TSTAMP_APPA; + + tp->t_maxseg = mss; +} + +void +tcp_mss(struct tcpcb *tp, int offer) +{ + int mss; + u_long bufsize; + struct inpcb *inp; + struct socket *so; + struct hc_metrics_lite metrics; + int mtuflags = 0; + + KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); + + tcp_mss_update(tp, offer, -1, &metrics, &mtuflags); + + mss = tp->t_maxseg; + inp = tp->t_inpcb; + + /* + * If there's a pipesize, change the socket buffer to that size, + * don't change if sb_hiwat is different than default (then it + * has been changed on purpose with setsockopt). + * Make the socket buffers an integral number of mss units; + * if the mss is larger than the socket buffer, decrease the mss. + */ + so = inp->inp_socket; + SOCKBUF_LOCK(&so->so_snd); + if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) + bufsize = metrics.rmx_sendpipe; + else + bufsize = so->so_snd.sb_hiwat; + if (bufsize < mss) + mss = bufsize; + else { + bufsize = roundup(bufsize, mss); + if (bufsize > sb_max) + bufsize = sb_max; + if (bufsize > so->so_snd.sb_hiwat) + (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); + } + SOCKBUF_UNLOCK(&so->so_snd); + tp->t_maxseg = mss; + + SOCKBUF_LOCK(&so->so_rcv); + if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) + bufsize = metrics.rmx_recvpipe; + else + bufsize = so->so_rcv.sb_hiwat; + if (bufsize > mss) { + bufsize = roundup(bufsize, mss); + if (bufsize > sb_max) + bufsize = sb_max; + if (bufsize > so->so_rcv.sb_hiwat) + (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); + } + SOCKBUF_UNLOCK(&so->so_rcv); + + /* Check the interface for TSO capabilities. */ + if (mtuflags & CSUM_TSO) + tp->t_flags |= TF_TSO; +} + +/* + * Determine the MSS option to send on an outgoing SYN. + */ +int +tcp_mssopt(struct in_conninfo *inc) +{ + int mss = 0; + u_long maxmtu = 0; + u_long thcmtu = 0; + size_t min_protoh; + + KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); + +#ifdef INET6 + if (inc->inc_flags & INC_ISIPV6) { + mss = V_tcp_v6mssdflt; + maxmtu = tcp_maxmtu6(inc, NULL); + min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); + } +#endif +#if defined(INET) && defined(INET6) + else +#endif +#ifdef INET + { + mss = V_tcp_mssdflt; + maxmtu = tcp_maxmtu(inc, NULL); + min_protoh = sizeof(struct tcpiphdr); + } +#endif +#if defined(INET6) || defined(INET) + thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ +#endif + + if (maxmtu && thcmtu) + mss = min(maxmtu, thcmtu) - min_protoh; + else if (maxmtu || thcmtu) + mss = max(maxmtu, thcmtu) - min_protoh; + + return (mss); +} + + +/* + * On a partial ack arrives, force the retransmission of the + * next unacknowledged segment. Do not clear tp->t_dupacks. + * By setting snd_nxt to ti_ack, this forces retransmission timer to + * be started again. + */ +static void +tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) +{ + tcp_seq onxt = tp->snd_nxt; + u_long ocwnd = tp->snd_cwnd; + + INP_WLOCK_ASSERT(tp->t_inpcb); + + tcp_timer_activate(tp, TT_REXMT, 0); + tp->t_rtttime = 0; + tp->snd_nxt = th->th_ack; + /* + * Set snd_cwnd to one segment beyond acknowledged offset. + * (tp->snd_una has not yet been updated when this function is called.) + */ + tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th); + tp->t_flags |= TF_ACKNOW; + (void) tcp_output(tp); + tp->snd_cwnd = ocwnd; + if (SEQ_GT(onxt, tp->snd_nxt)) + tp->snd_nxt = onxt; + /* + * Partial window deflation. Relies on fact that tp->snd_una + * not updated yet. + */ + if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) + tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); + else + tp->snd_cwnd = 0; + tp->snd_cwnd += tp->t_maxseg; +} |
