Initial import of modified Linux 2.6.28 tree

Original upstream URL:
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git | branch linux-2.6.28.y

1 files changed, 1059 insertions, 0 deletions

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
new file mode 100644
index 0000000..e3dfdda
--- /dev/null
+++ b/net/dccp/ipv4.c
@@ -0,0 +1,1059 @@
+/*
+ *  net/dccp/ipv4.c
+ *
+ *  An implementation of the DCCP protocol
+ *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/dccp.h>
+#include <linux/icmp.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/random.h>
+
+#include <net/icmp.h>
+#include <net/inet_common.h>
+#include <net/inet_hashtables.h>
+#include <net/inet_sock.h>
+#include <net/protocol.h>
+#include <net/sock.h>
+#include <net/timewait_sock.h>
+#include <net/tcp_states.h>
+#include <net/xfrm.h>
+
+#include "ackvec.h"
+#include "ccid.h"
+#include "dccp.h"
+#include "feat.h"
+
+/*
+ * The per-net dccp.v4_ctl_sk socket is used for responding to
+ * the Out-of-the-blue (OOTB) packets. A control sock will be created
+ * for this socket at the initialization time.
+ */
+
+int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct dccp_sock *dp = dccp_sk(sk);
+	const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
+	struct rtable *rt;
+	__be32 daddr, nexthop;
+	int tmp;
+	int err;
+
+	dp->dccps_role = DCCP_ROLE_CLIENT;
+
+	if (addr_len < sizeof(struct sockaddr_in))
+		return -EINVAL;
+
+	if (usin->sin_family != AF_INET)
+		return -EAFNOSUPPORT;
+
+	nexthop = daddr = usin->sin_addr.s_addr;
+	if (inet->opt != NULL && inet->opt->srr) {
+		if (daddr == 0)
+			return -EINVAL;
+		nexthop = inet->opt->faddr;
+	}
+
+	tmp = ip_route_connect(&rt, nexthop, inet->saddr,
+			       RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
+			       IPPROTO_DCCP,
+			       inet->sport, usin->sin_port, sk, 1);
+	if (tmp < 0)
+		return tmp;
+
+	if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
+		ip_rt_put(rt);
+		return -ENETUNREACH;
+	}
+
+	if (inet->opt == NULL || !inet->opt->srr)
+		daddr = rt->rt_dst;
+
+	if (inet->saddr == 0)
+		inet->saddr = rt->rt_src;
+	inet->rcv_saddr = inet->saddr;
+
+	inet->dport = usin->sin_port;
+	inet->daddr = daddr;
+
+	inet_csk(sk)->icsk_ext_hdr_len = 0;
+	if (inet->opt != NULL)
+		inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
+	/*
+	 * Socket identity is still unknown (sport may be zero).
+	 * However we set state to DCCP_REQUESTING and not releasing socket
+	 * lock select source port, enter ourselves into the hash tables and
+	 * complete initialization after this.
+	 */
+	dccp_set_state(sk, DCCP_REQUESTING);
+	err = inet_hash_connect(&dccp_death_row, sk);
+	if (err != 0)
+		goto failure;
+
+	err = ip_route_newports(&rt, IPPROTO_DCCP, inet->sport, inet->dport,
+				sk);
+	if (err != 0)
+		goto failure;
+
+	/* OK, now commit destination to socket.  */
+	sk_setup_caps(sk, &rt->u.dst);
+
+	dp->dccps_iss = secure_dccp_sequence_number(inet->saddr, inet->daddr,
+						    inet->sport, inet->dport);
+	inet->id = dp->dccps_iss ^ jiffies;
+
+	err = dccp_connect(sk);
+	rt = NULL;
+	if (err != 0)
+		goto failure;
+out:
+	return err;
+failure:
+	/*
+	 * This unhashes the socket and releases the local port, if necessary.
+	 */
+	dccp_set_state(sk, DCCP_CLOSED);
+	ip_rt_put(rt);
+	sk->sk_route_caps = 0;
+	inet->dport = 0;
+	goto out;
+}
+
+EXPORT_SYMBOL_GPL(dccp_v4_connect);
+
+/*
+ * This routine does path mtu discovery as defined in RFC1191.
+ */
+static inline void dccp_do_pmtu_discovery(struct sock *sk,
+					  const struct iphdr *iph,
+					  u32 mtu)
+{
+	struct dst_entry *dst;
+	const struct inet_sock *inet = inet_sk(sk);
+	const struct dccp_sock *dp = dccp_sk(sk);
+
+	/* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
+	 * send out by Linux are always < 576bytes so they should go through
+	 * unfragmented).
+	 */
+	if (sk->sk_state == DCCP_LISTEN)
+		return;
+
+	/* We don't check in the destentry if pmtu discovery is forbidden
+	 * on this route. We just assume that no packet_to_big packets
+	 * are send back when pmtu discovery is not active.
+	 * There is a small race when the user changes this flag in the
+	 * route, but I think that's acceptable.
+	 */
+	if ((dst = __sk_dst_check(sk, 0)) == NULL)
+		return;
+
+	dst->ops->update_pmtu(dst, mtu);
+
+	/* Something is about to be wrong... Remember soft error
+	 * for the case, if this connection will not able to recover.
+	 */
+	if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
+		sk->sk_err_soft = EMSGSIZE;
+
+	mtu = dst_mtu(dst);
+
+	if (inet->pmtudisc != IP_PMTUDISC_DONT &&
+	    inet_csk(sk)->icsk_pmtu_cookie > mtu) {
+		dccp_sync_mss(sk, mtu);
+
+		/*
+		 * From RFC 4340, sec. 14.1:
+		 *
+		 *	DCCP-Sync packets are the best choice for upward
+		 *	probing, since DCCP-Sync probes do not risk application
+		 *	data loss.
+		 */
+		dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
+	} /* else let the usual retransmit timer handle it */
+}
+
+/*
+ * This routine is called by the ICMP module when it gets some sort of error
+ * condition. If err < 0 then the socket should be closed and the error
+ * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
+ * After adjustment header points to the first 8 bytes of the tcp header. We
+ * need to find the appropriate port.
+ *
+ * The locking strategy used here is very "optimistic". When someone else
+ * accesses the socket the ICMP is just dropped and for some paths there is no
+ * check at all. A more general error queue to queue errors for later handling
+ * is probably better.
+ */
+static void dccp_v4_err(struct sk_buff *skb, u32 info)
+{
+	const struct iphdr *iph = (struct iphdr *)skb->data;
+	const u8 offset = iph->ihl << 2;
+	const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset);
+	struct dccp_sock *dp;
+	struct inet_sock *inet;
+	const int type = icmp_hdr(skb)->type;
+	const int code = icmp_hdr(skb)->code;
+	struct sock *sk;
+	__u64 seq;
+	int err;
+	struct net *net = dev_net(skb->dev);
+
+	if (skb->len < offset + sizeof(*dh) ||
+	    skb->len < offset + __dccp_basic_hdr_len(dh)) {
+		ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
+		return;
+	}
+
+	sk = inet_lookup(net, &dccp_hashinfo,
+			iph->daddr, dh->dccph_dport,
+			iph->saddr, dh->dccph_sport, inet_iif(skb));
+	if (sk == NULL) {
+		ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
+		return;
+	}
+
+	if (sk->sk_state == DCCP_TIME_WAIT) {
+		inet_twsk_put(inet_twsk(sk));
+		return;
+	}
+
+	bh_lock_sock(sk);
+	/* If too many ICMPs get dropped on busy
+	 * servers this needs to be solved differently.
+	 */
+	if (sock_owned_by_user(sk))
+		NET_INC_STATS_BH(net, LINUX_MIB_LOCKDROPPEDICMPS);
+
+	if (sk->sk_state == DCCP_CLOSED)
+		goto out;
+
+	dp = dccp_sk(sk);
+	seq = dccp_hdr_seq(dh);
+	if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
+	    !between48(seq, dp->dccps_awl, dp->dccps_awh)) {
+		NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
+		goto out;
+	}
+
+	switch (type) {
+	case ICMP_SOURCE_QUENCH:
+		/* Just silently ignore these. */
+		goto out;
+	case ICMP_PARAMETERPROB:
+		err = EPROTO;
+		break;
+	case ICMP_DEST_UNREACH:
+		if (code > NR_ICMP_UNREACH)
+			goto out;
+
+		if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
+			if (!sock_owned_by_user(sk))
+				dccp_do_pmtu_discovery(sk, iph, info);
+			goto out;
+		}
+
+		err = icmp_err_convert[code].errno;
+		break;
+	case ICMP_TIME_EXCEEDED:
+		err = EHOSTUNREACH;
+		break;
+	default:
+		goto out;
+	}
+
+	switch (sk->sk_state) {
+		struct request_sock *req , **prev;
+	case DCCP_LISTEN:
+		if (sock_owned_by_user(sk))
+			goto out;
+		req = inet_csk_search_req(sk, &prev, dh->dccph_dport,
+					  iph->daddr, iph->saddr);
+		if (!req)
+			goto out;
+
+		/*
+		 * ICMPs are not backlogged, hence we cannot get an established
+		 * socket here.
+		 */
+		WARN_ON(req->sk);
+
+		if (seq != dccp_rsk(req)->dreq_iss) {
+			NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
+			goto out;
+		}
+		/*
+		 * Still in RESPOND, just remove it silently.
+		 * There is no good way to pass the error to the newly
+		 * created socket, and POSIX does not want network
+		 * errors returned from accept().
+		 */
+		inet_csk_reqsk_queue_drop(sk, req, prev);
+		goto out;
+
+	case DCCP_REQUESTING:
+	case DCCP_RESPOND:
+		if (!sock_owned_by_user(sk)) {
+			DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
+			sk->sk_err = err;
+
+			sk->sk_error_report(sk);
+
+			dccp_done(sk);
+		} else
+			sk->sk_err_soft = err;
+		goto out;
+	}
+
+	/* If we've already connected we will keep trying
+	 * until we time out, or the user gives up.
+	 *
+	 * rfc1122 4.2.3.9 allows to consider as hard errors
+	 * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
+	 * but it is obsoleted by pmtu discovery).
+	 *
+	 * Note, that in modern internet, where routing is unreliable
+	 * and in each dark corner broken firewalls sit, sending random
+	 * errors ordered by their masters even this two messages finally lose
+	 * their original sense (even Linux sends invalid PORT_UNREACHs)
+	 *
+	 * Now we are in compliance with RFCs.
+	 *							--ANK (980905)
+	 */
+
+	inet = inet_sk(sk);
+	if (!sock_owned_by_user(sk) && inet->recverr) {
+		sk->sk_err = err;
+		sk->sk_error_report(sk);
+	} else /* Only an error on timeout */
+		sk->sk_err_soft = err;
+out:
+	bh_unlock_sock(sk);
+	sock_put(sk);
+}
+
+static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
+				      __be32 src, __be32 dst)
+{
+	return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
+}
+
+void dccp_v4_send_check(struct sock *sk, int unused, struct sk_buff *skb)
+{
+	const struct inet_sock *inet = inet_sk(sk);
+	struct dccp_hdr *dh = dccp_hdr(skb);
+
+	dccp_csum_outgoing(skb);
+	dh->dccph_checksum = dccp_v4_csum_finish(skb, inet->saddr, inet->daddr);
+}
+
+EXPORT_SYMBOL_GPL(dccp_v4_send_check);
+
+static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
+{
+	return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
+					   ip_hdr(skb)->saddr,
+					   dccp_hdr(skb)->dccph_dport,
+					   dccp_hdr(skb)->dccph_sport);
+}
+
+/*
+ * The three way handshake has completed - we got a valid ACK or DATAACK -
+ * now create the new socket.
+ *
+ * This is the equivalent of TCP's tcp_v4_syn_recv_sock
+ */
+struct sock *dccp_v4_request_recv_sock(struct sock *sk, struct sk_buff *skb,
+				       struct request_sock *req,
+				       struct dst_entry *dst)
+{
+	struct inet_request_sock *ireq;
+	struct inet_sock *newinet;
+	struct sock *newsk;
+
+	if (sk_acceptq_is_full(sk))
+		goto exit_overflow;
+
+	if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
+		goto exit;
+
+	newsk = dccp_create_openreq_child(sk, req, skb);
+	if (newsk == NULL)
+		goto exit;
+
+	sk_setup_caps(newsk, dst);
+
+	newinet		   = inet_sk(newsk);
+	ireq		   = inet_rsk(req);
+	newinet->daddr	   = ireq->rmt_addr;
+	newinet->rcv_saddr = ireq->loc_addr;
+	newinet->saddr	   = ireq->loc_addr;
+	newinet->opt	   = ireq->opt;
+	ireq->opt	   = NULL;
+	newinet->mc_index  = inet_iif(skb);
+	newinet->mc_ttl	   = ip_hdr(skb)->ttl;
+	newinet->id	   = jiffies;
+
+	dccp_sync_mss(newsk, dst_mtu(dst));
+
+	__inet_hash_nolisten(newsk);
+	__inet_inherit_port(sk, newsk);
+
+	return newsk;
+
+exit_overflow:
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
+exit:
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
+	dst_release(dst);
+	return NULL;
+}
+
+EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);
+
+static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
+{
+	const struct dccp_hdr *dh = dccp_hdr(skb);
+	const struct iphdr *iph = ip_hdr(skb);
+	struct sock *nsk;
+	struct request_sock **prev;
+	/* Find possible connection requests. */
+	struct request_sock *req = inet_csk_search_req(sk, &prev,
+						       dh->dccph_sport,
+						       iph->saddr, iph->daddr);
+	if (req != NULL)
+		return dccp_check_req(sk, skb, req, prev);
+
+	nsk = inet_lookup_established(sock_net(sk), &dccp_hashinfo,
+				      iph->saddr, dh->dccph_sport,
+				      iph->daddr, dh->dccph_dport,
+				      inet_iif(skb));
+	if (nsk != NULL) {
+		if (nsk->sk_state != DCCP_TIME_WAIT) {
+			bh_lock_sock(nsk);
+			return nsk;
+		}
+		inet_twsk_put(inet_twsk(nsk));
+		return NULL;
+	}
+
+	return sk;
+}
+
+static struct dst_entry* dccp_v4_route_skb(struct net *net, struct sock *sk,
+					   struct sk_buff *skb)
+{
+	struct rtable *rt;
+	struct flowi fl = { .oif = skb->rtable->rt_iif,
+			    .nl_u = { .ip4_u =
+				      { .daddr = ip_hdr(skb)->saddr,
+					.saddr = ip_hdr(skb)->daddr,
+					.tos = RT_CONN_FLAGS(sk) } },
+			    .proto = sk->sk_protocol,
+			    .uli_u = { .ports =
+				       { .sport = dccp_hdr(skb)->dccph_dport,
+					 .dport = dccp_hdr(skb)->dccph_sport }
+				     }
+			  };
+
+	security_skb_classify_flow(skb, &fl);
+	if (ip_route_output_flow(net, &rt, &fl, sk, 0)) {
+		IP_INC_STATS_BH(net, IPSTATS_MIB_OUTNOROUTES);
+		return NULL;
+	}
+
+	return &rt->u.dst;
+}
+
+static int dccp_v4_send_response(struct sock *sk, struct request_sock *req)
+{
+	int err = -1;
+	struct sk_buff *skb;
+	struct dst_entry *dst;
+
+	dst = inet_csk_route_req(sk, req);
+	if (dst == NULL)
+		goto out;
+
+	skb = dccp_make_response(sk, dst, req);
+	if (skb != NULL) {
+		const struct inet_request_sock *ireq = inet_rsk(req);
+		struct dccp_hdr *dh = dccp_hdr(skb);
+
+		dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,
+							      ireq->rmt_addr);
+		err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
+					    ireq->rmt_addr,
+					    ireq->opt);
+		err = net_xmit_eval(err);
+	}
+
+out:
+	dst_release(dst);
+	return err;
+}
+
+static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
+{
+	int err;
+	const struct iphdr *rxiph;
+	struct sk_buff *skb;
+	struct dst_entry *dst;
+	struct net *net = dev_net(rxskb->dst->dev);
+	struct sock *ctl_sk = net->dccp.v4_ctl_sk;
+
+	/* Never send a reset in response to a reset. */
+	if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
+		return;
+
+	if (rxskb->rtable->rt_type != RTN_LOCAL)
+		return;
+
+	dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
+	if (dst == NULL)
+		return;
+
+	skb = dccp_ctl_make_reset(ctl_sk, rxskb);
+	if (skb == NULL)
+		goto out;
+
+	rxiph = ip_hdr(rxskb);
+	dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
+								 rxiph->daddr);
+	skb->dst = dst_clone(dst);
+
+	bh_lock_sock(ctl_sk);
+	err = ip_build_and_send_pkt(skb, ctl_sk,
+				    rxiph->daddr, rxiph->saddr, NULL);
+	bh_unlock_sock(ctl_sk);
+
+	if (net_xmit_eval(err) == 0) {
+		DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
+		DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
+	}
+out:
+	 dst_release(dst);
+}
+
+static void dccp_v4_reqsk_destructor(struct request_sock *req)
+{
+	kfree(inet_rsk(req)->opt);
+}
+
+static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
+	.family		= PF_INET,
+	.obj_size	= sizeof(struct dccp_request_sock),
+	.rtx_syn_ack	= dccp_v4_send_response,
+	.send_ack	= dccp_reqsk_send_ack,
+	.destructor	= dccp_v4_reqsk_destructor,
+	.send_reset	= dccp_v4_ctl_send_reset,
+};
+
+int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
+{
+	struct inet_request_sock *ireq;
+	struct request_sock *req;
+	struct dccp_request_sock *dreq;
+	const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
+	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
+
+	/* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
+	if (skb->rtable->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
+		return 0;	/* discard, don't send a reset here */
+
+	if (dccp_bad_service_code(sk, service)) {
+		dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
+		goto drop;
+	}
+	/*
+	 * TW buckets are converted to open requests without
+	 * limitations, they conserve resources and peer is
+	 * evidently real one.
+	 */
+	dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
+	if (inet_csk_reqsk_queue_is_full(sk))
+		goto drop;
+
+	/*
+	 * Accept backlog is full. If we have already queued enough
+	 * of warm entries in syn queue, drop request. It is better than
+	 * clogging syn queue with openreqs with exponentially increasing
+	 * timeout.
+	 */
+	if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
+		goto drop;
+
+	req = inet_reqsk_alloc(&dccp_request_sock_ops);
+	if (req == NULL)
+		goto drop;
+
+	dccp_reqsk_init(req, skb);
+
+	dreq = dccp_rsk(req);
+	if (dccp_parse_options(sk, dreq, skb))
+		goto drop_and_free;
+
+	if (security_inet_conn_request(sk, skb, req))
+		goto drop_and_free;
+
+	ireq = inet_rsk(req);
+	ireq->loc_addr = ip_hdr(skb)->daddr;
+	ireq->rmt_addr = ip_hdr(skb)->saddr;
+
+	/*
+	 * Step 3: Process LISTEN state
+	 *
+	 * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
+	 *
+	 * In fact we defer setting S.GSR, S.SWL, S.SWH to
+	 * dccp_create_openreq_child.
+	 */
+	dreq->dreq_isr	   = dcb->dccpd_seq;
+	dreq->dreq_iss	   = dccp_v4_init_sequence(skb);
+	dreq->dreq_service = service;
+
+	if (dccp_v4_send_response(sk, req))
+		goto drop_and_free;
+
+	inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
+	return 0;
+
+drop_and_free:
+	reqsk_free(req);
+drop:
+	DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
+	return -1;
+}
+
+EXPORT_SYMBOL_GPL(dccp_v4_conn_request);
+
+int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
+{
+	struct dccp_hdr *dh = dccp_hdr(skb);
+
+	if (sk->sk_state == DCCP_OPEN) { /* Fast path */
+		if (dccp_rcv_established(sk, skb, dh, skb->len))
+			goto reset;
+		return 0;
+	}
+
+	/*
+	 *  Step 3: Process LISTEN state
+	 *	 If P.type == Request or P contains a valid Init Cookie option,
+	 *	      (* Must scan the packet's options to check for Init
+	 *		 Cookies.  Only Init Cookies are processed here,
+	 *		 however; other options are processed in Step 8.  This
+	 *		 scan need only be performed if the endpoint uses Init
+	 *		 Cookies *)
+	 *	      (* Generate a new socket and switch to that socket *)
+	 *	      Set S := new socket for this port pair
+	 *	      S.state = RESPOND
+	 *	      Choose S.ISS (initial seqno) or set from Init Cookies
+	 *	      Initialize S.GAR := S.ISS
+	 *	      Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
+	 *	      Continue with S.state == RESPOND
+	 *	      (* A Response packet will be generated in Step 11 *)
+	 *	 Otherwise,
+	 *	      Generate Reset(No Connection) unless P.type == Reset
+	 *	      Drop packet and return
+	 *
+	 * NOTE: the check for the packet types is done in
+	 *	 dccp_rcv_state_process
+	 */
+	if (sk->sk_state == DCCP_LISTEN) {
+		struct sock *nsk = dccp_v4_hnd_req(sk, skb);
+
+		if (nsk == NULL)
+			goto discard;
+
+		if (nsk != sk) {
+			if (dccp_child_process(sk, nsk, skb))
+				goto reset;
+			return 0;
+		}
+	}
+
+	if (dccp_rcv_state_process(sk, skb, dh, skb->len))
+		goto reset;
+	return 0;
+
+reset:
+	dccp_v4_ctl_send_reset(sk, skb);
+discard:
+	kfree_skb(skb);
+	return 0;
+}
+
+EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);
+
+/**
+ *	dccp_invalid_packet  -  check for malformed packets
+ *	Implements RFC 4340, 8.5:  Step 1: Check header basics
+ *	Packets that fail these checks are ignored and do not receive Resets.
+ */
+int dccp_invalid_packet(struct sk_buff *skb)
+{
+	const struct dccp_hdr *dh;
+	unsigned int cscov;
+
+	if (skb->pkt_type != PACKET_HOST)
+		return 1;
+
+	/* If the packet is shorter than 12 bytes, drop packet and return */
+	if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
+		DCCP_WARN("pskb_may_pull failed\n");
+		return 1;
+	}
+
+	dh = dccp_hdr(skb);
+
+	/* If P.type is not understood, drop packet and return */
+	if (dh->dccph_type >= DCCP_PKT_INVALID) {
+		DCCP_WARN("invalid packet type\n");
+		return 1;
+	}
+
+	/*
+	 * If P.Data Offset is too small for packet type, drop packet and return
+	 */
+	if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
+		DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
+		return 1;
+	}
+	/*
+	 * If P.Data Offset is too too large for packet, drop packet and return
+	 */
+	if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
+		DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
+		return 1;
+	}
+
+	/*
+	 * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
+	 * has short sequence numbers), drop packet and return
+	 */
+	if ((dh->dccph_type < DCCP_PKT_DATA    ||
+	    dh->dccph_type > DCCP_PKT_DATAACK) && dh->dccph_x == 0)  {
+		DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
+			  dccp_packet_name(dh->dccph_type));
+		return 1;
+	}
+
+	/*
+	 * If P.CsCov is too large for the packet size, drop packet and return.
+	 * This must come _before_ checksumming (not as RFC 4340 suggests).
+	 */
+	cscov = dccp_csum_coverage(skb);
+	if (cscov > skb->len) {
+		DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
+			  dh->dccph_cscov, skb->len);
+		return 1;
+	}
+
+	/* If header checksum is incorrect, drop packet and return.
+	 * (This step is completed in the AF-dependent functions.) */
+	skb->csum = skb_checksum(skb, 0, cscov, 0);
+
+	return 0;
+}
+
+EXPORT_SYMBOL_GPL(dccp_invalid_packet);
+
+/* this is called when real data arrives */
+static int dccp_v4_rcv(struct sk_buff *skb)
+{
+	const struct dccp_hdr *dh;
+	const struct iphdr *iph;
+	struct sock *sk;
+	int min_cov;
+
+	/* Step 1: Check header basics */
+
+	if (dccp_invalid_packet(skb))
+		goto discard_it;
+
+	iph = ip_hdr(skb);
+	/* Step 1: If header checksum is incorrect, drop packet and return */
+	if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
+		DCCP_WARN("dropped packet with invalid checksum\n");
+		goto discard_it;
+	}
+
+	dh = dccp_hdr(skb);
+
+	DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
+	DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
+
+	dccp_pr_debug("%8.8s "
+		      "src=%u.%u.%u.%u@%-5d "
+		      "dst=%u.%u.%u.%u@%-5d seq=%llu",
+		      dccp_packet_name(dh->dccph_type),
+		      NIPQUAD(iph->saddr), ntohs(dh->dccph_sport),
+		      NIPQUAD(iph->daddr), ntohs(dh->dccph_dport),
+		      (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
+
+	if (dccp_packet_without_ack(skb)) {
+		DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
+		dccp_pr_debug_cat("\n");
+	} else {
+		DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
+		dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
+				  DCCP_SKB_CB(skb)->dccpd_ack_seq);
+	}
+
+	/* Step 2:
+	 *	Look up flow ID in table and get corresponding socket */
+	sk = __inet_lookup_skb(&dccp_hashinfo, skb,
+			       dh->dccph_sport, dh->dccph_dport);
+	/*
+	 * Step 2:
+	 *	If no socket ...
+	 */
+	if (sk == NULL) {
+		dccp_pr_debug("failed to look up flow ID in table and "
+			      "get corresponding socket\n");
+		goto no_dccp_socket;
+	}
+
+	/*
+	 * Step 2:
+	 *	... or S.state == TIMEWAIT,
+	 *		Generate Reset(No Connection) unless P.type == Reset
+	 *		Drop packet and return
+	 */
+	if (sk->sk_state == DCCP_TIME_WAIT) {
+		dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
+		inet_twsk_put(inet_twsk(sk));
+		goto no_dccp_socket;
+	}
+
+	/*
+	 * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
+	 *	o if MinCsCov = 0, only packets with CsCov = 0 are accepted
+	 *	o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
+	 */
+	min_cov = dccp_sk(sk)->dccps_pcrlen;
+	if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
+		dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
+			      dh->dccph_cscov, min_cov);
+		/* FIXME: "Such packets SHOULD be reported using Data Dropped
+		 *         options (Section 11.7) with Drop Code 0, Protocol
+		 *         Constraints."                                     */
+		goto discard_and_relse;
+	}
+
+	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
+		goto discard_and_relse;
+	nf_reset(skb);
+
+	return sk_receive_skb(sk, skb, 1);
+
+no_dccp_socket:
+	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
+		goto discard_it;
+	/*
+	 * Step 2:
+	 *	If no socket ...
+	 *		Generate Reset(No Connection) unless P.type == Reset
+	 *		Drop packet and return
+	 */
+	if (dh->dccph_type != DCCP_PKT_RESET) {
+		DCCP_SKB_CB(skb)->dccpd_reset_code =
+					DCCP_RESET_CODE_NO_CONNECTION;
+		dccp_v4_ctl_send_reset(sk, skb);
+	}
+
+discard_it:
+	kfree_skb(skb);
+	return 0;
+
+discard_and_relse:
+	sock_put(sk);
+	goto discard_it;
+}
+
+static struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
+	.queue_xmit	   = ip_queue_xmit,
+	.send_check	   = dccp_v4_send_check,
+	.rebuild_header	   = inet_sk_rebuild_header,
+	.conn_request	   = dccp_v4_conn_request,
+	.syn_recv_sock	   = dccp_v4_request_recv_sock,
+	.net_header_len	   = sizeof(struct iphdr),
+	.setsockopt	   = ip_setsockopt,
+	.getsockopt	   = ip_getsockopt,
+	.addr2sockaddr	   = inet_csk_addr2sockaddr,
+	.sockaddr_len	   = sizeof(struct sockaddr_in),
+	.bind_conflict	   = inet_csk_bind_conflict,
+#ifdef CONFIG_COMPAT
+	.compat_setsockopt = compat_ip_setsockopt,
+	.compat_getsockopt = compat_ip_getsockopt,
+#endif
+};
+
+static int dccp_v4_init_sock(struct sock *sk)
+{
+	static __u8 dccp_v4_ctl_sock_initialized;
+	int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);
+
+	if (err == 0) {
+		if (unlikely(!dccp_v4_ctl_sock_initialized))
+			dccp_v4_ctl_sock_initialized = 1;
+		inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
+	}
+
+	return err;
+}
+
+static struct timewait_sock_ops dccp_timewait_sock_ops = {
+	.twsk_obj_size	= sizeof(struct inet_timewait_sock),
+};
+
+static struct proto dccp_v4_prot = {
+	.name			= "DCCP",
+	.owner			= THIS_MODULE,
+	.close			= dccp_close,
+	.connect		= dccp_v4_connect,
+	.disconnect		= dccp_disconnect,
+	.ioctl			= dccp_ioctl,
+	.init			= dccp_v4_init_sock,
+	.setsockopt		= dccp_setsockopt,
+	.getsockopt		= dccp_getsockopt,
+	.sendmsg		= dccp_sendmsg,
+	.recvmsg		= dccp_recvmsg,
+	.backlog_rcv		= dccp_v4_do_rcv,
+	.hash			= inet_hash,
+	.unhash			= inet_unhash,
+	.accept			= inet_csk_accept,
+	.get_port		= inet_csk_get_port,
+	.shutdown		= dccp_shutdown,
+	.destroy		= dccp_destroy_sock,
+	.orphan_count		= &dccp_orphan_count,
+	.max_header		= MAX_DCCP_HEADER,
+	.obj_size		= sizeof(struct dccp_sock),
+	.rsk_prot		= &dccp_request_sock_ops,
+	.twsk_prot		= &dccp_timewait_sock_ops,
+	.h.hashinfo		= &dccp_hashinfo,
+#ifdef CONFIG_COMPAT
+	.compat_setsockopt	= compat_dccp_setsockopt,
+	.compat_getsockopt	= compat_dccp_getsockopt,
+#endif
+};
+
+static struct net_protocol dccp_v4_protocol = {
+	.handler	= dccp_v4_rcv,
+	.err_handler	= dccp_v4_err,
+	.no_policy	= 1,
+	.netns_ok	= 1,
+};
+
+static const struct proto_ops inet_dccp_ops = {
+	.family		   = PF_INET,
+	.owner		   = THIS_MODULE,
+	.release	   = inet_release,
+	.bind		   = inet_bind,
+	.connect	   = inet_stream_connect,
+	.socketpair	   = sock_no_socketpair,
+	.accept		   = inet_accept,
+	.getname	   = inet_getname,
+	/* FIXME: work on tcp_poll to rename it to inet_csk_poll */
+	.poll		   = dccp_poll,
+	.ioctl		   = inet_ioctl,
+	/* FIXME: work on inet_listen to rename it to sock_common_listen */
+	.listen		   = inet_dccp_listen,
+	.shutdown	   = inet_shutdown,
+	.setsockopt	   = sock_common_setsockopt,
+	.getsockopt	   = sock_common_getsockopt,
+	.sendmsg	   = inet_sendmsg,
+	.recvmsg	   = sock_common_recvmsg,
+	.mmap		   = sock_no_mmap,
+	.sendpage	   = sock_no_sendpage,
+#ifdef CONFIG_COMPAT
+	.compat_setsockopt = compat_sock_common_setsockopt,
+	.compat_getsockopt = compat_sock_common_getsockopt,
+#endif
+};
+
+static struct inet_protosw dccp_v4_protosw = {
+	.type		= SOCK_DCCP,
+	.protocol	= IPPROTO_DCCP,
+	.prot		= &dccp_v4_prot,
+	.ops		= &inet_dccp_ops,
+	.capability	= -1,
+	.no_check	= 0,
+	.flags		= INET_PROTOSW_ICSK,
+};
+
+static int dccp_v4_init_net(struct net *net)
+{
+	int err;
+
+	err = inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
+				   SOCK_DCCP, IPPROTO_DCCP, net);
+	return err;
+}
+
+static void dccp_v4_exit_net(struct net *net)
+{
+	inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
+}
+
+static struct pernet_operations dccp_v4_ops = {
+	.init	= dccp_v4_init_net,
+	.exit	= dccp_v4_exit_net,
+};
+
+static int __init dccp_v4_init(void)
+{
+	int err = proto_register(&dccp_v4_prot, 1);
+
+	if (err != 0)
+		goto out;
+
+	err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
+	if (err != 0)
+		goto out_proto_unregister;
+
+	inet_register_protosw(&dccp_v4_protosw);
+
+	err = register_pernet_subsys(&dccp_v4_ops);
+	if (err)
+		goto out_destroy_ctl_sock;
+out:
+	return err;
+out_destroy_ctl_sock:
+	inet_unregister_protosw(&dccp_v4_protosw);
+	inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
+out_proto_unregister:
+	proto_unregister(&dccp_v4_prot);
+	goto out;
+}
+
+static void __exit dccp_v4_exit(void)
+{
+	unregister_pernet_subsys(&dccp_v4_ops);
+	inet_unregister_protosw(&dccp_v4_protosw);
+	inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
+	proto_unregister(&dccp_v4_prot);
+}
+
+module_init(dccp_v4_init);
+module_exit(dccp_v4_exit);
+
+/*
+ * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
+ * values directly, Also cover the case where the protocol is not specified,
+ * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
+ */
+MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
+MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
+MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");