diff options
Diffstat (limited to 'sys/netinet/tcp_output.c')
| -rw-r--r-- | sys/netinet/tcp_output.c | 1556 |
1 files changed, 1556 insertions, 0 deletions
diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c new file mode 100644 index 0000000..bcfed8a --- /dev/null +++ b/sys/netinet/tcp_output.c @@ -0,0 +1,1556 @@ +/*- + * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 + * The Regents of the University of California. All rights reserved. + * + * 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_output.c 8.4 (Berkeley) 5/24/95 + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include "opt_inet.h" +#include "opt_inet6.h" +#include "opt_ipsec.h" +#include "opt_tcpdebug.h" + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/domain.h> +#include <sys/hhook.h> +#include <sys/kernel.h> +#include <sys/lock.h> +#include <sys/mbuf.h> +#include <sys/mutex.h> +#include <sys/protosw.h> +#include <sys/socket.h> +#include <sys/socketvar.h> +#include <sys/sysctl.h> + +#include <net/if.h> +#include <net/route.h> +#include <net/vnet.h> + +#include <netinet/cc.h> +#include <netinet/in.h> +#include <netinet/in_systm.h> +#include <netinet/ip.h> +#include <netinet/in_pcb.h> +#include <netinet/ip_var.h> +#include <netinet/ip_options.h> +#ifdef INET6 +#include <netinet6/in6_pcb.h> +#include <netinet/ip6.h> +#include <netinet6/ip6_var.h> +#endif +#define TCPOUTFLAGS +#include <netinet/tcp_fsm.h> +#include <netinet/tcp_seq.h> +#include <netinet/tcp_timer.h> +#include <netinet/tcp_var.h> +#include <netinet/tcpip.h> +#ifdef TCPDEBUG +#include <netinet/tcp_debug.h> +#endif +#ifdef TCP_OFFLOAD +#include <netinet/tcp_offload.h> +#endif + +#ifdef IPSEC +#include <netipsec/ipsec.h> +#endif /*IPSEC*/ + +#include <machine/in_cksum.h> + +#include <security/mac/mac_framework.h> + +VNET_DEFINE(int, path_mtu_discovery) = 1; +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, + &VNET_NAME(path_mtu_discovery), 1, + "Enable Path MTU Discovery"); + +VNET_DEFINE(int, tcp_do_tso) = 1; +#define V_tcp_do_tso VNET(tcp_do_tso) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, + &VNET_NAME(tcp_do_tso), 0, + "Enable TCP Segmentation Offload"); + +VNET_DEFINE(int, tcp_sendspace) = 1024*32; +#define V_tcp_sendspace VNET(tcp_sendspace) +SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_RW, + &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); + +VNET_DEFINE(int, tcp_do_autosndbuf) = 1; +#define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, + &VNET_NAME(tcp_do_autosndbuf), 0, + "Enable automatic send buffer sizing"); + +VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; +#define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, + &VNET_NAME(tcp_autosndbuf_inc), 0, + "Incrementor step size of automatic send buffer"); + +VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; +#define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) +SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, + &VNET_NAME(tcp_autosndbuf_max), 0, + "Max size of automatic send buffer"); + +static void inline hhook_run_tcp_est_out(struct tcpcb *tp, + struct tcphdr *th, struct tcpopt *to, + long len, int tso); +static void inline cc_after_idle(struct tcpcb *tp); + +/* + * Wrapper for the TCP established output helper hook. + */ +static void inline +hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, + struct tcpopt *to, long len, int tso) +{ + struct tcp_hhook_data hhook_data; + + if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { + hhook_data.tp = tp; + hhook_data.th = th; + hhook_data.to = to; + hhook_data.len = len; + hhook_data.tso = tso; + + hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, + tp->osd); + } +} + +/* + * CC wrapper hook functions + */ +static void inline +cc_after_idle(struct tcpcb *tp) +{ + INP_WLOCK_ASSERT(tp->t_inpcb); + + if (CC_ALGO(tp)->after_idle != NULL) + CC_ALGO(tp)->after_idle(tp->ccv); +} + +/* + * Tcp output routine: figure out what should be sent and send it. + */ +int +tcp_output(struct tcpcb *tp) +{ + struct socket *so = tp->t_inpcb->inp_socket; + long len, recwin, sendwin; + int off, flags, error = 0; /* Keep compiler happy */ + struct mbuf *m; + struct ip *ip = NULL; + struct ipovly *ipov = NULL; + struct tcphdr *th; + u_char opt[TCP_MAXOLEN]; + unsigned ipoptlen, optlen, hdrlen; +#ifdef IPSEC + unsigned ipsec_optlen = 0; +#endif + int idle, sendalot; + int sack_rxmit, sack_bytes_rxmt; + struct sackhole *p; + int tso, mtu; + struct tcpopt to; +#if 0 + int maxburst = TCP_MAXBURST; +#endif +#ifdef INET6 + struct ip6_hdr *ip6 = NULL; + int isipv6; + + isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; +#endif + + INP_WLOCK_ASSERT(tp->t_inpcb); + +#ifdef TCP_OFFLOAD + if (tp->t_flags & TF_TOE) + return (tcp_offload_output(tp)); +#endif + + /* + * Determine length of data that should be transmitted, + * and flags that will be used. + * If there is some data or critical controls (SYN, RST) + * to send, then transmit; otherwise, investigate further. + */ + idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); + if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) + cc_after_idle(tp); + tp->t_flags &= ~TF_LASTIDLE; + if (idle) { + if (tp->t_flags & TF_MORETOCOME) { + tp->t_flags |= TF_LASTIDLE; + idle = 0; + } + } +again: + /* + * If we've recently taken a timeout, snd_max will be greater than + * snd_nxt. There may be SACK information that allows us to avoid + * resending already delivered data. Adjust snd_nxt accordingly. + */ + if ((tp->t_flags & TF_SACK_PERMIT) && + SEQ_LT(tp->snd_nxt, tp->snd_max)) + tcp_sack_adjust(tp); + sendalot = 0; + tso = 0; + mtu = 0; + off = tp->snd_nxt - tp->snd_una; + sendwin = min(tp->snd_wnd, tp->snd_cwnd); + + flags = tcp_outflags[tp->t_state]; + /* + * Send any SACK-generated retransmissions. If we're explicitly trying + * to send out new data (when sendalot is 1), bypass this function. + * If we retransmit in fast recovery mode, decrement snd_cwnd, since + * we're replacing a (future) new transmission with a retransmission + * now, and we previously incremented snd_cwnd in tcp_input(). + */ + /* + * Still in sack recovery , reset rxmit flag to zero. + */ + sack_rxmit = 0; + sack_bytes_rxmt = 0; + len = 0; + p = NULL; + if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && + (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { + long cwin; + + cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; + if (cwin < 0) + cwin = 0; + /* Do not retransmit SACK segments beyond snd_recover */ + if (SEQ_GT(p->end, tp->snd_recover)) { + /* + * (At least) part of sack hole extends beyond + * snd_recover. Check to see if we can rexmit data + * for this hole. + */ + if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { + /* + * Can't rexmit any more data for this hole. + * That data will be rexmitted in the next + * sack recovery episode, when snd_recover + * moves past p->rxmit. + */ + p = NULL; + goto after_sack_rexmit; + } else + /* Can rexmit part of the current hole */ + len = ((long)ulmin(cwin, + tp->snd_recover - p->rxmit)); + } else + len = ((long)ulmin(cwin, p->end - p->rxmit)); + off = p->rxmit - tp->snd_una; + KASSERT(off >= 0,("%s: sack block to the left of una : %d", + __func__, off)); + if (len > 0) { + sack_rxmit = 1; + sendalot = 1; + TCPSTAT_INC(tcps_sack_rexmits); + TCPSTAT_ADD(tcps_sack_rexmit_bytes, + min(len, tp->t_maxseg)); + } + } +after_sack_rexmit: + /* + * Get standard flags, and add SYN or FIN if requested by 'hidden' + * state flags. + */ + if (tp->t_flags & TF_NEEDFIN) + flags |= TH_FIN; + if (tp->t_flags & TF_NEEDSYN) + flags |= TH_SYN; + + SOCKBUF_LOCK(&so->so_snd); + /* + * If in persist timeout with window of 0, send 1 byte. + * Otherwise, if window is small but nonzero + * and timer expired, we will send what we can + * and go to transmit state. + */ + if (tp->t_flags & TF_FORCEDATA) { + if (sendwin == 0) { + /* + * If we still have some data to send, then + * clear the FIN bit. Usually this would + * happen below when it realizes that we + * aren't sending all the data. However, + * if we have exactly 1 byte of unsent data, + * then it won't clear the FIN bit below, + * and if we are in persist state, we wind + * up sending the packet without recording + * that we sent the FIN bit. + * + * We can't just blindly clear the FIN bit, + * because if we don't have any more data + * to send then the probe will be the FIN + * itself. + */ + if (off < so->so_snd.sb_cc) + flags &= ~TH_FIN; + sendwin = 1; + } else { + tcp_timer_activate(tp, TT_PERSIST, 0); + tp->t_rxtshift = 0; + } + } + + /* + * If snd_nxt == snd_max and we have transmitted a FIN, the + * offset will be > 0 even if so_snd.sb_cc is 0, resulting in + * a negative length. This can also occur when TCP opens up + * its congestion window while receiving additional duplicate + * acks after fast-retransmit because TCP will reset snd_nxt + * to snd_max after the fast-retransmit. + * + * In the normal retransmit-FIN-only case, however, snd_nxt will + * be set to snd_una, the offset will be 0, and the length may + * wind up 0. + * + * If sack_rxmit is true we are retransmitting from the scoreboard + * in which case len is already set. + */ + if (sack_rxmit == 0) { + if (sack_bytes_rxmt == 0) + len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); + else { + long cwin; + + /* + * We are inside of a SACK recovery episode and are + * sending new data, having retransmitted all the + * data possible in the scoreboard. + */ + len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) + - off); + /* + * Don't remove this (len > 0) check ! + * We explicitly check for len > 0 here (although it + * isn't really necessary), to work around a gcc + * optimization issue - to force gcc to compute + * len above. Without this check, the computation + * of len is bungled by the optimizer. + */ + if (len > 0) { + cwin = tp->snd_cwnd - + (tp->snd_nxt - tp->sack_newdata) - + sack_bytes_rxmt; + if (cwin < 0) + cwin = 0; + len = lmin(len, cwin); + } + } + } + + /* + * Lop off SYN bit if it has already been sent. However, if this + * is SYN-SENT state and if segment contains data and if we don't + * know that foreign host supports TAO, suppress sending segment. + */ + if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { + if (tp->t_state != TCPS_SYN_RECEIVED) + flags &= ~TH_SYN; + off--, len++; + } + + /* + * Be careful not to send data and/or FIN on SYN segments. + * This measure is needed to prevent interoperability problems + * with not fully conformant TCP implementations. + */ + if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { + len = 0; + flags &= ~TH_FIN; + } + + if (len < 0) { + /* + * If FIN has been sent but not acked, + * but we haven't been called to retransmit, + * len will be < 0. Otherwise, window shrank + * after we sent into it. If window shrank to 0, + * cancel pending retransmit, pull snd_nxt back + * to (closed) window, and set the persist timer + * if it isn't already going. If the window didn't + * close completely, just wait for an ACK. + */ + len = 0; + if (sendwin == 0) { + tcp_timer_activate(tp, TT_REXMT, 0); + tp->t_rxtshift = 0; + tp->snd_nxt = tp->snd_una; + if (!tcp_timer_active(tp, TT_PERSIST)) + tcp_setpersist(tp); + } + } + + /* len will be >= 0 after this point. */ + KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); + + /* + * Automatic sizing of send 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). Setting the + * buffer size too big consumes too much real kernel memory, + * especially with many connections on busy servers. + * + * The criteria to step up the send buffer one notch are: + * 1. receive window of remote host is larger than send buffer + * (with a fudge factor of 5/4th); + * 2. send buffer is filled to 7/8th with data (so we actually + * have data to make use of it); + * 3. send buffer fill has not hit maximal automatic size; + * 4. our send window (slow start and cogestion controlled) is + * larger than sent but unacknowledged data in send buffer. + * + * The remote host receive window scaling factor may limit the + * growing of the send buffer before it reaches its allowed + * maximum. + * + * It scales directly with slow start or congestion window + * and does at most one step per received ACK. This fast + * scaling has the drawback of growing the send buffer beyond + * what is strictly necessary to make full use of a given + * delay*bandwith product. However testing has shown this not + * to be much of an problem. At worst we are trading wasting + * of available bandwith (the non-use of it) for wasting some + * socket buffer memory. + * + * TODO: Shrink send buffer during idle periods together + * with congestion window. Requires another timer. Has to + * wait for upcoming tcp timer rewrite. + */ + if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { + if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && + so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && + so->so_snd.sb_cc < V_tcp_autosndbuf_max && + sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { + if (!sbreserve_locked(&so->so_snd, + min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, + V_tcp_autosndbuf_max), so, curthread)) + so->so_snd.sb_flags &= ~SB_AUTOSIZE; + } + } + + /* + * Decide if we can use TCP Segmentation Offloading (if supported by + * hardware). + * + * TSO may only be used if we are in a pure bulk sending state. The + * presence of TCP-MD5, SACK retransmits, SACK advertizements and + * IP options prevent using TSO. With TSO the TCP header is the same + * (except for the sequence number) for all generated packets. This + * makes it impossible to transmit any options which vary per generated + * segment or packet. + */ +#ifdef IPSEC + /* + * Pre-calculate here as we save another lookup into the darknesses + * of IPsec that way and can actually decide if TSO is ok. + */ + ipsec_optlen = ipsec_hdrsiz_tcp(tp); +#endif + if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && + ((tp->t_flags & TF_SIGNATURE) == 0) && + tp->rcv_numsacks == 0 && sack_rxmit == 0 && +#ifdef IPSEC + ipsec_optlen == 0 && +#endif + tp->t_inpcb->inp_options == NULL && + tp->t_inpcb->in6p_options == NULL) + tso = 1; + + if (sack_rxmit) { + if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) + flags &= ~TH_FIN; + } else { + if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) + flags &= ~TH_FIN; + } + + recwin = sbspace(&so->so_rcv); + + /* + * Sender silly window avoidance. We transmit under the following + * conditions when len is non-zero: + * + * - We have a full segment (or more with TSO) + * - This is the last buffer in a write()/send() and we are + * either idle or running NODELAY + * - we've timed out (e.g. persist timer) + * - we have more then 1/2 the maximum send window's worth of + * data (receiver may be limited the window size) + * - we need to retransmit + */ + if (len) { + if (len >= tp->t_maxseg) + goto send; + /* + * NOTE! on localhost connections an 'ack' from the remote + * end may occur synchronously with the output and cause + * us to flush a buffer queued with moretocome. XXX + * + * note: the len + off check is almost certainly unnecessary. + */ + if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ + (idle || (tp->t_flags & TF_NODELAY)) && + len + off >= so->so_snd.sb_cc && + (tp->t_flags & TF_NOPUSH) == 0) { + goto send; + } + if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ + goto send; + if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) + goto send; + if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ + goto send; + if (sack_rxmit) + goto send; + } + + /* + * Sending of standalone window updates. + * + * Window updates are important when we close our window due to a + * full socket buffer and are opening it again after the application + * reads data from it. Once the window has opened again and the + * remote end starts to send again the ACK clock takes over and + * provides the most current window information. + * + * We must avoid the silly window syndrome whereas every read + * from the receive buffer, no matter how small, causes a window + * update to be sent. We also should avoid sending a flurry of + * window updates when the socket buffer had queued a lot of data + * and the application is doing small reads. + * + * Prevent a flurry of pointless window updates by only sending + * an update when we can increase the advertized window by more + * than 1/4th of the socket buffer capacity. When the buffer is + * getting full or is very small be more aggressive and send an + * update whenever we can increase by two mss sized segments. + * In all other situations the ACK's to new incoming data will + * carry further window increases. + * + * Don't send an independent window update if a delayed + * ACK is pending (it will get piggy-backed on it) or the + * remote side already has done a half-close and won't send + * more data. Skip this if the connection is in T/TCP + * half-open state. + */ + if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && + !(tp->t_flags & TF_DELACK) && + !TCPS_HAVERCVDFIN(tp->t_state)) { + /* + * "adv" is the amount we could increase the window, + * taking into account that we are limited by + * TCP_MAXWIN << tp->rcv_scale. + */ + long adv; + int oldwin; + + adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); + if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { + oldwin = (tp->rcv_adv - tp->rcv_nxt); + adv -= oldwin; + } else + oldwin = 0; + + /* + * If the new window size ends up being the same as the old + * size when it is scaled, then don't force a window update. + */ + if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) + goto dontupdate; + + if (adv >= (long)(2 * tp->t_maxseg) && + (adv >= (long)(so->so_rcv.sb_hiwat / 4) || + recwin <= (long)(so->so_rcv.sb_hiwat / 8) || + so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) + goto send; + } +dontupdate: + + /* + * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW + * is also a catch-all for the retransmit timer timeout case. + */ + if (tp->t_flags & TF_ACKNOW) + goto send; + if ((flags & TH_RST) || + ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) + goto send; + if (SEQ_GT(tp->snd_up, tp->snd_una)) + goto send; + /* + * If our state indicates that FIN should be sent + * and we have not yet done so, then we need to send. + */ + if (flags & TH_FIN && + ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) + goto send; + /* + * In SACK, it is possible for tcp_output to fail to send a segment + * after the retransmission timer has been turned off. Make sure + * that the retransmission timer is set. + */ + if ((tp->t_flags & TF_SACK_PERMIT) && + SEQ_GT(tp->snd_max, tp->snd_una) && + !tcp_timer_active(tp, TT_REXMT) && + !tcp_timer_active(tp, TT_PERSIST)) { + tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); + goto just_return; + } + /* + * TCP window updates are not reliable, rather a polling protocol + * using ``persist'' packets is used to insure receipt of window + * updates. The three ``states'' for the output side are: + * idle not doing retransmits or persists + * persisting to move a small or zero window + * (re)transmitting and thereby not persisting + * + * tcp_timer_active(tp, TT_PERSIST) + * is true when we are in persist state. + * (tp->t_flags & TF_FORCEDATA) + * is set when we are called to send a persist packet. + * tcp_timer_active(tp, TT_REXMT) + * is set when we are retransmitting + * The output side is idle when both timers are zero. + * + * If send window is too small, there is data to transmit, and no + * retransmit or persist is pending, then go to persist state. + * If nothing happens soon, send when timer expires: + * if window is nonzero, transmit what we can, + * otherwise force out a byte. + */ + if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && + !tcp_timer_active(tp, TT_PERSIST)) { + tp->t_rxtshift = 0; + tcp_setpersist(tp); + } + + /* + * No reason to send a segment, just return. + */ +just_return: + SOCKBUF_UNLOCK(&so->so_snd); + return (0); + +send: + SOCKBUF_LOCK_ASSERT(&so->so_snd); + /* + * Before ESTABLISHED, force sending of initial options + * unless TCP set not to do any options. + * NOTE: we assume that the IP/TCP header plus TCP options + * always fit in a single mbuf, leaving room for a maximum + * link header, i.e. + * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES + */ + optlen = 0; +#ifdef INET6 + if (isipv6) + hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); + else +#endif + hdrlen = sizeof (struct tcpiphdr); + + /* + * Compute options for segment. + * We only have to care about SYN and established connection + * segments. Options for SYN-ACK segments are handled in TCP + * syncache. + */ + if ((tp->t_flags & TF_NOOPT) == 0) { + to.to_flags = 0; + /* Maximum segment size. */ + if (flags & TH_SYN) { + tp->snd_nxt = tp->iss; + to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); + to.to_flags |= TOF_MSS; + } + /* Window scaling. */ + if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { + to.to_wscale = tp->request_r_scale; + to.to_flags |= TOF_SCALE; + } + /* Timestamps. */ + if ((tp->t_flags & TF_RCVD_TSTMP) || + ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { + to.to_tsval = tcp_ts_getticks() + tp->ts_offset; + to.to_tsecr = tp->ts_recent; + to.to_flags |= TOF_TS; + /* Set receive buffer autosizing timestamp. */ + if (tp->rfbuf_ts == 0 && + (so->so_rcv.sb_flags & SB_AUTOSIZE)) + tp->rfbuf_ts = tcp_ts_getticks(); + } + /* Selective ACK's. */ + if (tp->t_flags & TF_SACK_PERMIT) { + if (flags & TH_SYN) + to.to_flags |= TOF_SACKPERM; + else if (TCPS_HAVEESTABLISHED(tp->t_state) && + (tp->t_flags & TF_SACK_PERMIT) && + tp->rcv_numsacks > 0) { + to.to_flags |= TOF_SACK; + to.to_nsacks = tp->rcv_numsacks; + to.to_sacks = (u_char *)tp->sackblks; + } + } +#ifdef TCP_SIGNATURE + /* TCP-MD5 (RFC2385). */ + if (tp->t_flags & TF_SIGNATURE) + to.to_flags |= TOF_SIGNATURE; +#endif /* TCP_SIGNATURE */ + + /* Processing the options. */ + hdrlen += optlen = tcp_addoptions(&to, opt); + } + +#ifdef INET6 + if (isipv6) + ipoptlen = ip6_optlen(tp->t_inpcb); + else +#endif + if (tp->t_inpcb->inp_options) + ipoptlen = tp->t_inpcb->inp_options->m_len - + offsetof(struct ipoption, ipopt_list); + else + ipoptlen = 0; +#ifdef IPSEC + ipoptlen += ipsec_optlen; +#endif + + /* + * Adjust data length if insertion of options will + * bump the packet length beyond the t_maxopd length. + * Clear the FIN bit because we cut off the tail of + * the segment. + */ + if (len + optlen + ipoptlen > tp->t_maxopd) { + flags &= ~TH_FIN; + + if (tso) { + KASSERT(ipoptlen == 0, + ("%s: TSO can't do IP options", __func__)); + + /* + * Limit a burst to IP_MAXPACKET minus IP, + * TCP and options length to keep ip->ip_len + * from overflowing. + */ + if (len > IP_MAXPACKET - hdrlen) { + len = IP_MAXPACKET - hdrlen; + sendalot = 1; + } + + /* + * Prevent the last segment from being + * fractional unless the send sockbuf can + * be emptied. + */ + if (sendalot && off + len < so->so_snd.sb_cc) { + len -= len % (tp->t_maxopd - optlen); + sendalot = 1; + } + + /* + * Send the FIN in a separate segment + * after the bulk sending is done. + * We don't trust the TSO implementations + * to clear the FIN flag on all but the + * last segment. + */ + if (tp->t_flags & TF_NEEDFIN) + sendalot = 1; + + } else { + len = tp->t_maxopd - optlen - ipoptlen; + sendalot = 1; + } + } else + tso = 0; + + KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, + ("%s: len > IP_MAXPACKET", __func__)); + +/*#ifdef DIAGNOSTIC*/ +#ifdef INET6 + if (max_linkhdr + hdrlen > MCLBYTES) +#else + if (max_linkhdr + hdrlen > MHLEN) +#endif + panic("tcphdr too big"); +/*#endif*/ + + /* + * This KASSERT is here to catch edge cases at a well defined place. + * Before, those had triggered (random) panic conditions further down. + */ + KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); + + /* + * Grab a header mbuf, attaching a copy of data to + * be transmitted, and initialize the header from + * the template for sends on this connection. + */ + if (len) { + struct mbuf *mb; + u_int moff; + + if ((tp->t_flags & TF_FORCEDATA) && len == 1) + TCPSTAT_INC(tcps_sndprobe); + else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { + tp->t_sndrexmitpack++; + TCPSTAT_INC(tcps_sndrexmitpack); + TCPSTAT_ADD(tcps_sndrexmitbyte, len); + } else { + TCPSTAT_INC(tcps_sndpack); + TCPSTAT_ADD(tcps_sndbyte, len); + } +#ifdef INET6 + if (MHLEN < hdrlen + max_linkhdr) + m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); + else +#endif + m = m_gethdr(M_NOWAIT, MT_DATA); + + if (m == NULL) { + SOCKBUF_UNLOCK(&so->so_snd); + error = ENOBUFS; + goto out; + } + + m->m_data += max_linkhdr; + m->m_len = hdrlen; + + /* + * Start the m_copy functions from the closest mbuf + * to the offset in the socket buffer chain. + */ + mb = sbsndptr(&so->so_snd, off, len, &moff); + + if (len <= MHLEN - hdrlen - max_linkhdr) { + m_copydata(mb, moff, (int)len, + mtod(m, caddr_t) + hdrlen); + m->m_len += len; + } else { + m->m_next = m_copy(mb, moff, (int)len); + if (m->m_next == NULL) { + SOCKBUF_UNLOCK(&so->so_snd); + (void) m_free(m); + error = ENOBUFS; + goto out; + } + } + + /* + * If we're sending everything we've got, set PUSH. + * (This will keep happy those implementations which only + * give data to the user when a buffer fills or + * a PUSH comes in.) + */ + if (off + len == so->so_snd.sb_cc) + flags |= TH_PUSH; + SOCKBUF_UNLOCK(&so->so_snd); + } else { + SOCKBUF_UNLOCK(&so->so_snd); + if (tp->t_flags & TF_ACKNOW) + TCPSTAT_INC(tcps_sndacks); + else if (flags & (TH_SYN|TH_FIN|TH_RST)) + TCPSTAT_INC(tcps_sndctrl); + else if (SEQ_GT(tp->snd_up, tp->snd_una)) + TCPSTAT_INC(tcps_sndurg); + else + TCPSTAT_INC(tcps_sndwinup); + + m = m_gethdr(M_NOWAIT, MT_DATA); + if (m == NULL) { + error = ENOBUFS; + goto out; + } +#ifdef INET6 + if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && + MHLEN >= hdrlen) { + MH_ALIGN(m, hdrlen); + } else +#endif + m->m_data += max_linkhdr; + m->m_len = hdrlen; + } + SOCKBUF_UNLOCK_ASSERT(&so->so_snd); + m->m_pkthdr.rcvif = (struct ifnet *)0; +#ifdef MAC + mac_inpcb_create_mbuf(tp->t_inpcb, m); +#endif +#ifdef INET6 + if (isipv6) { + ip6 = mtod(m, struct ip6_hdr *); + th = (struct tcphdr *)(ip6 + 1); + tcpip_fillheaders(tp->t_inpcb, ip6, th); + } else +#endif /* INET6 */ + { + ip = mtod(m, struct ip *); + ipov = (struct ipovly *)ip; + th = (struct tcphdr *)(ip + 1); + tcpip_fillheaders(tp->t_inpcb, ip, th); + } + + /* + * Fill in fields, remembering maximum advertised + * window for use in delaying messages about window sizes. + * If resending a FIN, be sure not to use a new sequence number. + */ + if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && + tp->snd_nxt == tp->snd_max) + tp->snd_nxt--; + /* + * If we are starting a connection, send ECN setup + * SYN packet. If we are on a retransmit, we may + * resend those bits a number of times as per + * RFC 3168. + */ + if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { + if (tp->t_rxtshift >= 1) { + if (tp->t_rxtshift <= V_tcp_ecn_maxretries) + flags |= TH_ECE|TH_CWR; + } else + flags |= TH_ECE|TH_CWR; + } + + if (tp->t_state == TCPS_ESTABLISHED && + (tp->t_flags & TF_ECN_PERMIT)) { + /* + * If the peer has ECN, mark data packets with + * ECN capable transmission (ECT). + * Ignore pure ack packets, retransmissions and window probes. + */ + if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && + !((tp->t_flags & TF_FORCEDATA) && len == 1)) { +#ifdef INET6 + if (isipv6) + ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); + else +#endif + ip->ip_tos |= IPTOS_ECN_ECT0; + TCPSTAT_INC(tcps_ecn_ect0); + } + + /* + * Reply with proper ECN notifications. + */ + if (tp->t_flags & TF_ECN_SND_CWR) { + flags |= TH_CWR; + tp->t_flags &= ~TF_ECN_SND_CWR; + } + if (tp->t_flags & TF_ECN_SND_ECE) + flags |= TH_ECE; + } + + /* + * If we are doing retransmissions, then snd_nxt will + * not reflect the first unsent octet. For ACK only + * packets, we do not want the sequence number of the + * retransmitted packet, we want the sequence number + * of the next unsent octet. So, if there is no data + * (and no SYN or FIN), use snd_max instead of snd_nxt + * when filling in ti_seq. But if we are in persist + * state, snd_max might reflect one byte beyond the + * right edge of the window, so use snd_nxt in that + * case, since we know we aren't doing a retransmission. + * (retransmit and persist are mutually exclusive...) + */ + if (sack_rxmit == 0) { + if (len || (flags & (TH_SYN|TH_FIN)) || + tcp_timer_active(tp, TT_PERSIST)) + th->th_seq = htonl(tp->snd_nxt); + else + th->th_seq = htonl(tp->snd_max); + } else { + th->th_seq = htonl(p->rxmit); + p->rxmit += len; + tp->sackhint.sack_bytes_rexmit += len; + } + th->th_ack = htonl(tp->rcv_nxt); + if (optlen) { + bcopy(opt, th + 1, optlen); + th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; + } + th->th_flags = flags; + /* + * Calculate receive window. Don't shrink window, + * but avoid silly window syndrome. + */ + if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && + recwin < (long)tp->t_maxseg) + recwin = 0; + if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && + recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) + recwin = (long)(tp->rcv_adv - tp->rcv_nxt); + if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) + recwin = (long)TCP_MAXWIN << tp->rcv_scale; + + /* + * According to RFC1323 the window field in a SYN (i.e., a <SYN> + * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> + * case is handled in syncache. + */ + if (flags & TH_SYN) + th->th_win = htons((u_short) + (min(sbspace(&so->so_rcv), TCP_MAXWIN))); + else + th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); + + /* + * Adjust the RXWIN0SENT flag - indicate that we have advertised + * a 0 window. This may cause the remote transmitter to stall. This + * flag tells soreceive() to disable delayed acknowledgements when + * draining the buffer. This can occur if the receiver is attempting + * to read more data than can be buffered prior to transmitting on + * the connection. + */ + if (th->th_win == 0) { + tp->t_sndzerowin++; + tp->t_flags |= TF_RXWIN0SENT; + } else + tp->t_flags &= ~TF_RXWIN0SENT; + if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { + th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); + th->th_flags |= TH_URG; + } else + /* + * If no urgent pointer to send, then we pull + * the urgent pointer to the left edge of the send window + * so that it doesn't drift into the send window on sequence + * number wraparound. + */ + tp->snd_up = tp->snd_una; /* drag it along */ + +#ifdef TCP_SIGNATURE + if (tp->t_flags & TF_SIGNATURE) { + int sigoff = to.to_signature - opt; + tcp_signature_compute(m, 0, len, optlen, + (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); + } +#endif + + /* + * Put TCP length in extended header, and then + * checksum extended header and data. + */ + m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ + m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); +#ifdef INET6 + if (isipv6) { + /* + * ip6_plen is not need to be filled now, and will be filled + * in ip6_output. + */ + m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; + th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + + optlen + len, IPPROTO_TCP, 0); + } +#endif +#if defined(INET6) && defined(INET) + else +#endif +#ifdef INET + { + m->m_pkthdr.csum_flags = CSUM_TCP; + th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, + htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); + + /* IP version must be set here for ipv4/ipv6 checking later */ + KASSERT(ip->ip_v == IPVERSION, + ("%s: IP version incorrect: %d", __func__, ip->ip_v)); + } +#endif + + /* + * Enable TSO and specify the size of the segments. + * The TCP pseudo header checksum is always provided. + * XXX: Fixme: This is currently not the case for IPv6. + */ + if (tso) { + KASSERT(len > tp->t_maxopd - optlen, + ("%s: len <= tso_segsz", __func__)); + m->m_pkthdr.csum_flags |= CSUM_TSO; + m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; + } + +#ifdef IPSEC + KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), + ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u", + __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); +#else + KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), + ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u", + __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); +#endif + + /* + * In transmit state, time the transmission and arrange for + * the retransmit. In persist state, just set snd_max. + */ + if ((tp->t_flags & TF_FORCEDATA) == 0 || + !tcp_timer_active(tp, TT_PERSIST)) { + tcp_seq startseq = tp->snd_nxt; + + /* + * Advance snd_nxt over sequence space of this segment. + */ + if (flags & (TH_SYN|TH_FIN)) { + if (flags & TH_SYN) + tp->snd_nxt++; + if (flags & TH_FIN) { + tp->snd_nxt++; + tp->t_flags |= TF_SENTFIN; + } + } + if (sack_rxmit) + goto timer; + tp->snd_nxt += len; + if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { + tp->snd_max = tp->snd_nxt; + /* + * Time this transmission if not a retransmission and + * not currently timing anything. + */ + if (tp->t_rtttime == 0) { + tp->t_rtttime = ticks; + tp->t_rtseq = startseq; + TCPSTAT_INC(tcps_segstimed); + } + } + + /* + * Set retransmit timer if not currently set, + * and not doing a pure ack or a keep-alive probe. + * Initial value for retransmit timer is smoothed + * round-trip time + 2 * round-trip time variance. + * Initialize shift counter which is used for backoff + * of retransmit time. + */ +timer: + if (!tcp_timer_active(tp, TT_REXMT) && + ((sack_rxmit && tp->snd_nxt != tp->snd_max) || + (tp->snd_nxt != tp->snd_una))) { + if (tcp_timer_active(tp, TT_PERSIST)) { + tcp_timer_activate(tp, TT_PERSIST, 0); + tp->t_rxtshift = 0; + } + tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); + } + } else { + /* + * Persist case, update snd_max but since we are in + * persist mode (no window) we do not update snd_nxt. + */ + int xlen = len; + if (flags & TH_SYN) + ++xlen; + if (flags & TH_FIN) { + ++xlen; + tp->t_flags |= TF_SENTFIN; + } + if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) + tp->snd_max = tp->snd_nxt + len; + } + + /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ + hhook_run_tcp_est_out(tp, th, &to, len, tso); + +#ifdef TCPDEBUG + /* + * Trace. + */ + if (so->so_options & SO_DEBUG) { + u_short save = 0; +#ifdef INET6 + if (!isipv6) +#endif + { + save = ipov->ih_len; + ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); + } + tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); +#ifdef INET6 + if (!isipv6) +#endif + ipov->ih_len = save; + } +#endif /* TCPDEBUG */ + + /* + * Fill in IP length and desired time to live and + * send to IP level. There should be a better way + * to handle ttl and tos; we could keep them in + * the template, but need a way to checksum without them. + */ + /* + * m->m_pkthdr.len should have been set before cksum calcuration, + * because in6_cksum() need it. + */ +#ifdef INET6 + if (isipv6) { + struct route_in6 ro; + + bzero(&ro, sizeof(ro)); + /* + * we separately set hoplimit for every segment, since the + * user might want to change the value via setsockopt. + * Also, desired default hop limit might be changed via + * Neighbor Discovery. + */ + ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); + + /* TODO: IPv6 IP6TOS_ECT bit on */ + error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, + ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), + NULL, NULL, tp->t_inpcb); + + if (error == EMSGSIZE && ro.ro_rt != NULL) + mtu = ro.ro_rt->rt_rmx.rmx_mtu; + RO_RTFREE(&ro); + } +#endif /* INET6 */ +#if defined(INET) && defined(INET6) + else +#endif +#ifdef INET + { + struct route ro; + + bzero(&ro, sizeof(ro)); + ip->ip_len = htons(m->m_pkthdr.len); +#ifdef INET6 + if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) + ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); +#endif /* INET6 */ + /* + * If we do path MTU discovery, then we set DF on every packet. + * This might not be the best thing to do according to RFC3390 + * Section 2. However the tcp hostcache migitates the problem + * so it affects only the first tcp connection with a host. + * + * NB: Don't set DF on small MTU/MSS to have a safe fallback. + */ + if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) + ip->ip_off |= htons(IP_DF); + + error = ip_output(m, tp->t_inpcb->inp_options, &ro, + ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, + tp->t_inpcb); + + if (error == EMSGSIZE && ro.ro_rt != NULL) + mtu = ro.ro_rt->rt_rmx.rmx_mtu; + RO_RTFREE(&ro); + } +#endif /* INET */ + if (error) { + + /* + * We know that the packet was lost, so back out the + * sequence number advance, if any. + * + * If the error is EPERM the packet got blocked by the + * local firewall. Normally we should terminate the + * connection but the blocking may have been spurious + * due to a firewall reconfiguration cycle. So we treat + * it like a packet loss and let the retransmit timer and + * timeouts do their work over time. + * XXX: It is a POLA question whether calling tcp_drop right + * away would be the really correct behavior instead. + */ + if (((tp->t_flags & TF_FORCEDATA) == 0 || + !tcp_timer_active(tp, TT_PERSIST)) && + ((flags & TH_SYN) == 0) && + (error != EPERM)) { + if (sack_rxmit) { + p->rxmit -= len; + tp->sackhint.sack_bytes_rexmit -= len; + KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, + ("sackhint bytes rtx >= 0")); + } else + tp->snd_nxt -= len; + } +out: + SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ + switch (error) { + case EPERM: + tp->t_softerror = error; + return (error); + case ENOBUFS: + if (!tcp_timer_active(tp, TT_REXMT) && + !tcp_timer_active(tp, TT_PERSIST)) + tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); + tp->snd_cwnd = tp->t_maxseg; + return (0); + case EMSGSIZE: + /* + * For some reason the interface we used initially + * to send segments changed to another or lowered + * its MTU. + * If TSO was active we either got an interface + * without TSO capabilits or TSO was turned off. + * If we obtained mtu from ip_output() then update + * it and try again. + */ + if (tso) + tp->t_flags &= ~TF_TSO; + if (mtu != 0) { + tcp_mss_update(tp, -1, mtu, NULL, NULL); + goto again; + } + return (error); + case EHOSTDOWN: + case EHOSTUNREACH: + case ENETDOWN: + case ENETUNREACH: + if (TCPS_HAVERCVDSYN(tp->t_state)) { + tp->t_softerror = error; + return (0); + } + /* FALLTHROUGH */ + default: + return (error); + } + } + TCPSTAT_INC(tcps_sndtotal); + + /* + * Data sent (as far as we can tell). + * If this advertises a larger window than any other segment, + * then remember the size of the advertised window. + * Any pending ACK has now been sent. + */ + if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) + tp->rcv_adv = tp->rcv_nxt + recwin; + tp->last_ack_sent = tp->rcv_nxt; + tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); + if (tcp_timer_active(tp, TT_DELACK)) + tcp_timer_activate(tp, TT_DELACK, 0); +#if 0 + /* + * This completely breaks TCP if newreno is turned on. What happens + * is that if delayed-acks are turned on on the receiver, this code + * on the transmitter effectively destroys the TCP window, forcing + * it to four packets (1.5Kx4 = 6K window). + */ + if (sendalot && --maxburst) + goto again; +#endif + if (sendalot) + goto again; + return (0); +} + +void +tcp_setpersist(struct tcpcb *tp) +{ + int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; + int tt; + + tp->t_flags &= ~TF_PREVVALID; + if (tcp_timer_active(tp, TT_REXMT)) + panic("tcp_setpersist: retransmit pending"); + /* + * Start/restart persistance timer. + */ + TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], + TCPTV_PERSMIN, TCPTV_PERSMAX); + tcp_timer_activate(tp, TT_PERSIST, tt); + if (tp->t_rxtshift < TCP_MAXRXTSHIFT) + tp->t_rxtshift++; +} + +/* + * Insert TCP options according to the supplied parameters to the place + * optp in a consistent way. Can handle unaligned destinations. + * + * The order of the option processing is crucial for optimal packing and + * alignment for the scarce option space. + * + * The optimal order for a SYN/SYN-ACK segment is: + * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + + * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. + * + * The SACK options should be last. SACK blocks consume 8*n+2 bytes. + * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). + * At minimum we need 10 bytes (to generate 1 SACK block). If both + * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, + * we only have 10 bytes for SACK options (40 - (12 + 18)). + */ +int +tcp_addoptions(struct tcpopt *to, u_char *optp) +{ + u_int mask, optlen = 0; + + for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { + if ((to->to_flags & mask) != mask) + continue; + if (optlen == TCP_MAXOLEN) + break; + switch (to->to_flags & mask) { + case TOF_MSS: + while (optlen % 4) { + optlen += TCPOLEN_NOP; + *optp++ = TCPOPT_NOP; + } + if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) + continue; + optlen += TCPOLEN_MAXSEG; + *optp++ = TCPOPT_MAXSEG; + *optp++ = TCPOLEN_MAXSEG; + to->to_mss = htons(to->to_mss); + bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); + optp += sizeof(to->to_mss); + break; + case TOF_SCALE: + while (!optlen || optlen % 2 != 1) { + optlen += TCPOLEN_NOP; + *optp++ = TCPOPT_NOP; + } + if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) + continue; + optlen += TCPOLEN_WINDOW; + *optp++ = TCPOPT_WINDOW; + *optp++ = TCPOLEN_WINDOW; + *optp++ = to->to_wscale; + break; + case TOF_SACKPERM: + while (optlen % 2) { + optlen += TCPOLEN_NOP; + *optp++ = TCPOPT_NOP; + } + if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) + continue; + optlen += TCPOLEN_SACK_PERMITTED; + *optp++ = TCPOPT_SACK_PERMITTED; + *optp++ = TCPOLEN_SACK_PERMITTED; + break; + case TOF_TS: + while (!optlen || optlen % 4 != 2) { + optlen += TCPOLEN_NOP; + *optp++ = TCPOPT_NOP; + } + if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) + continue; + optlen += TCPOLEN_TIMESTAMP; + *optp++ = TCPOPT_TIMESTAMP; + *optp++ = TCPOLEN_TIMESTAMP; + to->to_tsval = htonl(to->to_tsval); + to->to_tsecr = htonl(to->to_tsecr); + bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); + optp += sizeof(to->to_tsval); + bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); + optp += sizeof(to->to_tsecr); + break; + case TOF_SIGNATURE: + { + int siglen = TCPOLEN_SIGNATURE - 2; + + while (!optlen || optlen % 4 != 2) { + optlen += TCPOLEN_NOP; + *optp++ = TCPOPT_NOP; + } + if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) + continue; + optlen += TCPOLEN_SIGNATURE; + *optp++ = TCPOPT_SIGNATURE; + *optp++ = TCPOLEN_SIGNATURE; + to->to_signature = optp; + while (siglen--) + *optp++ = 0; + break; + } + case TOF_SACK: + { + int sackblks = 0; + struct sackblk *sack = (struct sackblk *)to->to_sacks; + tcp_seq sack_seq; + + while (!optlen || optlen % 4 != 2) { + optlen += TCPOLEN_NOP; + *optp++ = TCPOPT_NOP; + } + if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) + continue; + optlen += TCPOLEN_SACKHDR; + *optp++ = TCPOPT_SACK; + sackblks = min(to->to_nsacks, + (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); + *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; + while (sackblks--) { + sack_seq = htonl(sack->start); + bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); + optp += sizeof(sack_seq); + sack_seq = htonl(sack->end); + bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); + optp += sizeof(sack_seq); + optlen += TCPOLEN_SACK; + sack++; + } + TCPSTAT_INC(tcps_sack_send_blocks); + break; + } + default: + panic("%s: unknown TCP option type", __func__); + break; + } + } + + /* Terminate and pad TCP options to a 4 byte boundary. */ + if (optlen % 4) { + optlen += TCPOLEN_EOL; + *optp++ = TCPOPT_EOL; + } + /* + * According to RFC 793 (STD0007): + * "The content of the header beyond the End-of-Option option + * must be header padding (i.e., zero)." + * and later: "The padding is composed of zeros." + */ + while (optlen % 4) { + optlen += TCPOLEN_PAD; + *optp++ = TCPOPT_PAD; + } + + KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); + return (optlen); +} |
