Import of Linux 2.2.12 subset (ipv4 stack and related)

1 files changed, 2432 insertions, 0 deletions

diff --git a/pfinet/linux-src/net/ipv4/tcp_input.c b/pfinet/linux-src/net/ipv4/tcp_input.c
new file mode 100644
index 00000000..a753b128
--- /dev/null
+++ b/pfinet/linux-src/net/ipv4/tcp_input.c
@@ -0,0 +1,2432 @@
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		Implementation of the Transmission Control Protocol(TCP).
+ *
+ * Version:	$Id: tcp_input.c,v 1.164.2.7 1999/08/13 16:14:27 davem Exp $
+ *
+ * Authors:	Ross Biro, <bir7@leland.Stanford.Edu>
+ *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
+ *		Mark Evans, <evansmp@uhura.aston.ac.uk>
+ *		Corey Minyard <wf-rch!minyard@relay.EU.net>
+ *		Florian La Roche, <flla@stud.uni-sb.de>
+ *		Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
+ *		Linus Torvalds, <torvalds@cs.helsinki.fi>
+ *		Alan Cox, <gw4pts@gw4pts.ampr.org>
+ *		Matthew Dillon, <dillon@apollo.west.oic.com>
+ *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
+ *		Jorge Cwik, <jorge@laser.satlink.net>
+ */
+
+/*
+ * Changes:
+ *		Pedro Roque	:	Fast Retransmit/Recovery.
+ *					Two receive queues.
+ *					Retransmit queue handled by TCP.
+ *					Better retransmit timer handling.
+ *					New congestion avoidance.
+ *					Header prediction.
+ *					Variable renaming.
+ *
+ *		Eric		:	Fast Retransmit.
+ *		Randy Scott	:	MSS option defines.
+ *		Eric Schenk	:	Fixes to slow start algorithm.
+ *		Eric Schenk	:	Yet another double ACK bug.
+ *		Eric Schenk	:	Delayed ACK bug fixes.
+ *		Eric Schenk	:	Floyd style fast retrans war avoidance.
+ *		David S. Miller	:	Don't allow zero congestion window.
+ *		Eric Schenk	:	Fix retransmitter so that it sends
+ *					next packet on ack of previous packet.
+ *		Andi Kleen	:	Moved open_request checking here
+ *					and process RSTs for open_requests.
+ *		Andi Kleen	:	Better prune_queue, and other fixes.
+ *		Andrey Savochkin:	Fix RTT measurements in the presnce of
+ *					timestamps.
+ *		Andrey Savochkin:	Check sequence numbers correctly when
+ *					removing SACKs due to in sequence incoming
+ *					data segments.
+ *		Andi Kleen:		Make sure we never ack data there is not
+ *					enough room for. Also make this condition
+ *					a fatal error if it might still happen.
+ *		Andi Kleen:		Add tcp_measure_rcv_mss to make 
+ *					connections with MSS<min(MTU,ann. MSS)
+ *					work without delayed acks. 
+ *		Andi Kleen:		Process packets with PSH set in the
+ *					fast path.
+ */
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/sysctl.h>
+#include <net/tcp.h>
+#include <linux/ipsec.h>
+
+#ifdef CONFIG_SYSCTL
+#define SYNC_INIT 0 /* let the user enable it */
+#else
+#define SYNC_INIT 1
+#endif
+
+extern int sysctl_tcp_fin_timeout;
+
+/* These are on by default so the code paths get tested.
+ * For the final 2.2 this may be undone at our discretion. -DaveM
+ */
+int sysctl_tcp_timestamps = 1;
+int sysctl_tcp_window_scaling = 1;
+int sysctl_tcp_sack = 1;
+
+int sysctl_tcp_syncookies = SYNC_INIT; 
+int sysctl_tcp_stdurg;
+int sysctl_tcp_rfc1337;
+
+static int prune_queue(struct sock *sk);
+
+/* There is something which you must keep in mind when you analyze the
+ * behavior of the tp->ato delayed ack timeout interval.  When a
+ * connection starts up, we want to ack as quickly as possible.  The
+ * problem is that "good" TCP's do slow start at the beginning of data
+ * transmission.  The means that until we send the first few ACK's the
+ * sender will sit on his end and only queue most of his data, because
+ * he can only send snd_cwnd unacked packets at any given time.  For
+ * each ACK we send, he increments snd_cwnd and transmits more of his
+ * queue.  -DaveM
+ */
+static void tcp_delack_estimator(struct tcp_opt *tp)
+{
+	if(tp->ato == 0) {
+		tp->lrcvtime = tcp_time_stamp;
+
+		/* Help sender leave slow start quickly,
+		 * and also makes sure we do not take this
+		 * branch ever again for this connection.
+		 */
+		tp->ato = 1;
+		tcp_enter_quickack_mode(tp);
+	} else {
+		int m = tcp_time_stamp - tp->lrcvtime;
+
+		tp->lrcvtime = tcp_time_stamp;
+		if(m <= 0)
+			m = 1;
+		if(m > tp->rto)
+			tp->ato = tp->rto;
+		else {
+			/* This funny shift makes sure we
+			 * clear the "quick ack mode" bit.
+			 */
+			tp->ato = ((tp->ato << 1) >> 2) + m;
+		}
+	}
+}
+
+/* 
+ * Remember to send an ACK later.
+ */
+static __inline__ void tcp_remember_ack(struct tcp_opt *tp, struct tcphdr *th, 
+					struct sk_buff *skb)
+{
+	tp->delayed_acks++; 
+
+	/* Tiny-grams with PSH set artifically deflate our
+	 * ato measurement, but with a lower bound.
+	 */
+	if(th->psh && (skb->len < (tp->mss_cache >> 1))) {
+		/* Preserve the quickack state. */
+		if((tp->ato & 0x7fffffff) > HZ/50)
+			tp->ato = ((tp->ato & 0x80000000) |
+				   (HZ/50));
+	}
+} 
+
+/* Called to compute a smoothed rtt estimate. The data fed to this
+ * routine either comes from timestamps, or from segments that were
+ * known _not_ to have been retransmitted [see Karn/Partridge
+ * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
+ * piece by Van Jacobson.
+ * NOTE: the next three routines used to be one big routine.
+ * To save cycles in the RFC 1323 implementation it was better to break
+ * it up into three procedures. -- erics
+ */
+
+static __inline__ void tcp_rtt_estimator(struct tcp_opt *tp, __u32 mrtt)
+{
+	long m = mrtt; /* RTT */
+
+	/*	The following amusing code comes from Jacobson's
+	 *	article in SIGCOMM '88.  Note that rtt and mdev
+	 *	are scaled versions of rtt and mean deviation.
+	 *	This is designed to be as fast as possible 
+	 *	m stands for "measurement".
+	 *
+	 *	On a 1990 paper the rto value is changed to:
+	 *	RTO = rtt + 4 * mdev
+	 */
+	if(m == 0)
+		m = 1;
+	if (tp->srtt != 0) {
+		m -= (tp->srtt >> 3);	/* m is now error in rtt est */
+		tp->srtt += m;		/* rtt = 7/8 rtt + 1/8 new */
+		if (m < 0)
+			m = -m;		/* m is now abs(error) */
+		m -= (tp->mdev >> 2);   /* similar update on mdev */
+		tp->mdev += m;	    	/* mdev = 3/4 mdev + 1/4 new */
+	} else {
+		/* no previous measure. */
+		tp->srtt = m<<3;	/* take the measured time to be rtt */
+		tp->mdev = m<<2;	/* make sure rto = 3*rtt */
+	}
+}
+
+/* Calculate rto without backoff.  This is the second half of Van Jacobson's
+ * routine referred to above.
+ */
+
+static __inline__ void tcp_set_rto(struct tcp_opt *tp)
+{
+	tp->rto = (tp->srtt >> 3) + tp->mdev;
+	tp->rto += (tp->rto >> 2) + (tp->rto >> (tp->snd_cwnd-1));
+}
+ 
+
+/* Keep the rto between HZ/5 and 120*HZ. 120*HZ is the upper bound
+ * on packet lifetime in the internet. We need the HZ/5 lower
+ * bound to behave correctly against BSD stacks with a fixed
+ * delayed ack.
+ * FIXME: It's not entirely clear this lower bound is the best
+ * way to avoid the problem. Is it possible to drop the lower
+ * bound and still avoid trouble with BSD stacks? Perhaps
+ * some modification to the RTO calculation that takes delayed
+ * ack bias into account? This needs serious thought. -- erics
+ */
+static __inline__ void tcp_bound_rto(struct tcp_opt *tp)
+{
+	if (tp->rto > 120*HZ)
+		tp->rto = 120*HZ;
+	if (tp->rto < HZ/5)
+		tp->rto = HZ/5;
+}
+
+/* WARNING: this must not be called if tp->saw_timestamp was false. */
+extern __inline__ void tcp_replace_ts_recent(struct sock *sk, struct tcp_opt *tp,
+					     __u32 start_seq, __u32 end_seq)
+{
+	/* It is start_seq <= last_ack_seq combined
+	   with in window check. If start_seq<=last_ack_seq<=rcv_nxt,
+	   then segment is in window if end_seq>=rcv_nxt.
+	 */
+	if (!after(start_seq, tp->last_ack_sent) &&
+	    !before(end_seq, tp->rcv_nxt)) {
+		/* PAWS bug workaround wrt. ACK frames, the PAWS discard
+		 * extra check below makes sure this can only happen
+		 * for pure ACK frames.  -DaveM
+		 *
+		 * Plus: expired timestamps.
+		 *
+		 * Plus: resets failing PAWS.
+		 */
+		if((s32)(tp->rcv_tsval - tp->ts_recent) >= 0) {
+			tp->ts_recent = tp->rcv_tsval;
+			tp->ts_recent_stamp = tcp_time_stamp;
+		}
+	}
+}
+
+#define PAWS_24DAYS	(HZ * 60 * 60 * 24 * 24)
+
+extern __inline__ int tcp_paws_discard(struct tcp_opt *tp, struct tcphdr *th, unsigned len)
+{
+	return ((s32)(tp->rcv_tsval - tp->ts_recent) < 0 &&
+		(s32)(tcp_time_stamp - tp->ts_recent_stamp) < PAWS_24DAYS &&
+		/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM */
+		len != (th->doff * 4));
+}
+
+
+static int __tcp_sequence(struct tcp_opt *tp, u32 seq, u32 end_seq)
+{
+	u32 end_window = tp->rcv_wup + tp->rcv_wnd;
+
+	if (tp->rcv_wnd &&
+	    after(end_seq, tp->rcv_nxt) &&
+	    before(seq, end_window))
+		return 1;
+	if (seq != end_window)
+		return 0;
+	return (seq == end_seq);
+}
+
+/* This functions checks to see if the tcp header is actually acceptable. */
+extern __inline__ int tcp_sequence(struct tcp_opt *tp, u32 seq, u32 end_seq)
+{
+	if (seq == tp->rcv_nxt)
+		return (tp->rcv_wnd || (end_seq == seq));
+
+	return __tcp_sequence(tp, seq, end_seq);
+}
+
+/* When we get a reset we do this. */
+static void tcp_reset(struct sock *sk)
+{
+	sk->zapped = 1;
+
+	/* We want the right error as BSD sees it (and indeed as we do). */
+	switch (sk->state) {
+		case TCP_SYN_SENT:
+			sk->err = ECONNREFUSED;
+			break;
+		case TCP_CLOSE_WAIT:
+			sk->err = EPIPE;
+			break;
+		default:
+			sk->err = ECONNRESET;
+	};
+	tcp_set_state(sk, TCP_CLOSE);
+	sk->shutdown = SHUTDOWN_MASK;
+	if (!sk->dead) 
+		sk->state_change(sk);
+}
+
+/* This tags the retransmission queue when SACKs arrive. */
+static void tcp_sacktag_write_queue(struct sock *sk, struct tcp_sack_block *sp, int nsacks)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	int i = nsacks;
+
+	while(i--) {
+		struct sk_buff *skb = skb_peek(&sk->write_queue);
+		__u32 start_seq = ntohl(sp->start_seq);
+		__u32 end_seq = ntohl(sp->end_seq);
+		int fack_count = 0;
+
+		while((skb != NULL) &&
+		      (skb != tp->send_head) &&
+		      (skb != (struct sk_buff *)&sk->write_queue)) {
+			/* The retransmission queue is always in order, so
+			 * we can short-circuit the walk early.
+			 */
+			if(after(TCP_SKB_CB(skb)->seq, end_seq))
+				break;
+
+			/* We play conservative, we don't allow SACKS to partially
+			 * tag a sequence space.
+			 */
+			fack_count++;
+			if(!after(start_seq, TCP_SKB_CB(skb)->seq) &&
+			   !before(end_seq, TCP_SKB_CB(skb)->end_seq)) {
+				/* If this was a retransmitted frame, account for it. */
+				if((TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) &&
+				   tp->retrans_out)
+					tp->retrans_out--;
+				TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
+
+				/* RULE: All new SACKs will either decrease retrans_out
+				 *       or advance fackets_out.
+				 */
+				if(fack_count > tp->fackets_out)
+					tp->fackets_out = fack_count;
+			}
+			skb = skb->next;
+		}
+		sp++; /* Move on to the next SACK block. */
+	}
+}
+
+/* Look for tcp options. Normally only called on SYN and SYNACK packets.
+ * But, this can also be called on packets in the established flow when
+ * the fast version below fails.
+ */
+void tcp_parse_options(struct sock *sk, struct tcphdr *th, struct tcp_opt *tp, int no_fancy)
+{
+	unsigned char *ptr;
+	int length=(th->doff*4)-sizeof(struct tcphdr);
+	int saw_mss = 0;
+
+	ptr = (unsigned char *)(th + 1);
+	tp->saw_tstamp = 0;
+
+	while(length>0) {
+	  	int opcode=*ptr++;
+		int opsize;
+
+		switch (opcode) {
+			case TCPOPT_EOL:
+				return;
+			case TCPOPT_NOP:	/* Ref: RFC 793 section 3.1 */
+				length--;
+				continue;
+			default:
+				opsize=*ptr++;
+				if (opsize < 2) /* "silly options" */
+					return;
+				if (opsize > length)
+					break;	/* don't parse partial options */
+	  			switch(opcode) {
+				case TCPOPT_MSS:
+					if(opsize==TCPOLEN_MSS && th->syn) {
+						u16 in_mss = ntohs(*(__u16 *)ptr);
+						if (in_mss == 0)
+							in_mss = 536;
+						if (tp->mss_clamp > in_mss)
+							tp->mss_clamp = in_mss;
+						saw_mss = 1;
+					}
+					break;
+				case TCPOPT_WINDOW:
+					if(opsize==TCPOLEN_WINDOW && th->syn)
+						if (!no_fancy && sysctl_tcp_window_scaling) {
+							tp->wscale_ok = 1;
+							tp->snd_wscale = *(__u8 *)ptr;
+							if(tp->snd_wscale > 14) {
+								if(net_ratelimit())
+									printk("tcp_parse_options: Illegal window "
+									       "scaling value %d >14 received.",
+									       tp->snd_wscale);
+								tp->snd_wscale = 14;
+							}
+						}
+					break;
+				case TCPOPT_TIMESTAMP:
+					if(opsize==TCPOLEN_TIMESTAMP) {
+						if (sysctl_tcp_timestamps && !no_fancy) {
+							tp->tstamp_ok = 1;
+							tp->saw_tstamp = 1;
+							tp->rcv_tsval = ntohl(*(__u32 *)ptr);
+							tp->rcv_tsecr = ntohl(*(__u32 *)(ptr+4));
+						}
+					}
+					break;
+				case TCPOPT_SACK_PERM:
+					if(opsize==TCPOLEN_SACK_PERM && th->syn) {
+						if (sysctl_tcp_sack && !no_fancy) {
+							tp->sack_ok = 1;
+							tp->num_sacks = 0;
+						}
+					}
+					break;
+
+				case TCPOPT_SACK:
+					if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
+					   sysctl_tcp_sack && (sk != NULL) && !th->syn) {
+						int sack_bytes = opsize - TCPOLEN_SACK_BASE;
+
+						if(!(sack_bytes % TCPOLEN_SACK_PERBLOCK)) {
+							int num_sacks = sack_bytes >> 3;
+							struct tcp_sack_block *sackp;
+
+							sackp = (struct tcp_sack_block *)ptr;
+							tcp_sacktag_write_queue(sk, sackp, num_sacks);
+						}
+					}
+	  			};
+	  			ptr+=opsize-2;
+	  			length-=opsize;
+	  	};
+	}
+	if(th->syn && saw_mss == 0)
+		tp->mss_clamp = 536;
+}
+
+/* Fast parse options. This hopes to only see timestamps.
+ * If it is wrong it falls back on tcp_parse_options().
+ */
+static __inline__ int tcp_fast_parse_options(struct sock *sk, struct tcphdr *th, struct tcp_opt *tp)
+{
+	/* If we didn't send out any options ignore them all. */
+	if (tp->tcp_header_len == sizeof(struct tcphdr))
+		return 0;
+	if (th->doff == sizeof(struct tcphdr)>>2) {
+		tp->saw_tstamp = 0;
+		return 0;
+	} else if (th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
+		__u32 *ptr = (__u32 *)(th + 1);
+		if (*ptr == __constant_ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
+					     | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
+			tp->saw_tstamp = 1;
+			tp->rcv_tsval = ntohl(*++ptr);
+			tp->rcv_tsecr = ntohl(*++ptr);
+			return 1;
+		}
+	}
+	tcp_parse_options(sk, th, tp, 0);
+	return 1;
+}
+
+#define FLAG_DATA		0x01 /* Incoming frame contained data.		*/
+#define FLAG_WIN_UPDATE		0x02 /* Incoming ACK was a window update.	*/
+#define FLAG_DATA_ACKED		0x04 /* This ACK acknowledged new data.		*/
+#define FLAG_RETRANS_DATA_ACKED	0x08 /* "" "" some of which was retransmitted.	*/
+
+static __inline__ void clear_fast_retransmit(struct tcp_opt *tp)
+{
+	if (tp->dup_acks > 3)
+		tp->snd_cwnd = (tp->snd_ssthresh);
+
+	tp->dup_acks = 0;
+}
+
+/* NOTE: This code assumes that tp->dup_acks gets cleared when a
+ * retransmit timer fires.
+ */
+static void tcp_fast_retrans(struct sock *sk, u32 ack, int not_dup)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+
+	/* Note: If not_dup is set this implies we got a
+	 * data carrying packet or a window update.
+	 * This carries no new information about possible
+	 * lost packets, so we have to ignore it for the purposes
+	 * of counting duplicate acks. Ideally this does not imply we
+	 * should stop our fast retransmit phase, more acks may come
+	 * later without data to help us. Unfortunately this would make
+	 * the code below much more complex. For now if I see such
+	 * a packet I clear the fast retransmit phase.
+	 */
+	if (ack == tp->snd_una && tp->packets_out && (not_dup == 0)) {
+		/* This is the standard reno style fast retransmit branch. */
+
+                /* 1. When the third duplicate ack is received, set ssthresh 
+                 * to one half the current congestion window, but no less 
+                 * than two segments. Retransmit the missing segment.
+                 */
+		if (tp->high_seq == 0 || after(ack, tp->high_seq)) {
+			tp->dup_acks++;
+			if ((tp->fackets_out > 3) || (tp->dup_acks == 3)) {
+                                tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
+                                tp->snd_cwnd = (tp->snd_ssthresh + 3);
+				tp->high_seq = tp->snd_nxt;
+				if(!tp->fackets_out)
+					tcp_retransmit_skb(sk,
+							   skb_peek(&sk->write_queue));
+				else
+					tcp_fack_retransmit(sk);
+                                tcp_reset_xmit_timer(sk, TIME_RETRANS, tp->rto);
+			}
+		} else if (++tp->dup_acks > 3) {
+			/* 2. Each time another duplicate ACK arrives, increment 
+			 * cwnd by the segment size. [...] Transmit a packet...
+			 *
+			 * Packet transmission will be done on normal flow processing
+			 * since we're not in "retransmit mode".  We do not use
+			 * duplicate ACKs to artificially inflate the congestion
+			 * window when doing FACK.
+			 */
+			if(!tp->fackets_out) {
+				tp->snd_cwnd++;
+			} else {
+				/* Fill any further holes which may have
+				 * appeared.
+				 *
+				 * We may want to change this to run every
+				 * further multiple-of-3 dup ack increments,
+				 * to be more robust against out-of-order
+				 * packet delivery.  -DaveM
+				 */
+				tcp_fack_retransmit(sk);
+			}
+		}
+	} else if (tp->high_seq != 0) {
+		/* In this branch we deal with clearing the Floyd style
+		 * block on duplicate fast retransmits, and if requested
+		 * we do Hoe style secondary fast retransmits.
+		 */
+		if (!before(ack, tp->high_seq) || (not_dup & FLAG_DATA) != 0) {
+			/* Once we have acked all the packets up to high_seq
+			 * we are done this fast retransmit phase.
+			 * Alternatively data arrived. In this case we
+			 * Have to abort the fast retransmit attempt.
+			 * Note that we do want to accept a window
+			 * update since this is expected with Hoe's algorithm.
+			 */
+			clear_fast_retransmit(tp);
+
+			/* After we have cleared up to high_seq we can
+			 * clear the Floyd style block.
+			 */
+			if (!before(ack, tp->high_seq)) {
+				tp->high_seq = 0;
+				tp->fackets_out = 0;
+			}
+		} else if (tp->dup_acks >= 3) {
+			if (!tp->fackets_out) {
+				/* Hoe Style. We didn't ack the whole
+				 * window. Take this as a cue that
+				 * another packet was lost and retransmit it.
+				 * Don't muck with the congestion window here.
+				 * Note that we have to be careful not to
+				 * act if this was a window update and it
+				 * didn't ack new data, since this does
+				 * not indicate a packet left the system.
+				 * We can test this by just checking
+				 * if ack changed from snd_una, since
+				 * the only way to get here without advancing
+				 * from snd_una is if this was a window update.
+				 */
+				if (ack != tp->snd_una && before(ack, tp->high_seq)) {
+                                	tcp_retransmit_skb(sk,
+							   skb_peek(&sk->write_queue));
+                                	tcp_reset_xmit_timer(sk, TIME_RETRANS, tp->rto);
+				}
+			} else {
+				/* FACK style, fill any remaining holes in
+				 * receiver's queue.
+				 */
+				tcp_fack_retransmit(sk);
+			}
+		}
+	}
+}
+
+/* This is Jacobson's slow start and congestion avoidance. 
+ * SIGCOMM '88, p. 328.
+ */
+static __inline__ void tcp_cong_avoid(struct tcp_opt *tp)
+{
+        if (tp->snd_cwnd <= tp->snd_ssthresh) {
+                /* In "safe" area, increase. */
+                tp->snd_cwnd++;
+	} else {
+                /* In dangerous area, increase slowly.
+		 * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
+		 */
+		if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
+			tp->snd_cwnd++;
+			tp->snd_cwnd_cnt=0;
+		} else
+			tp->snd_cwnd_cnt++;
+        }       
+}
+
+/* Remove acknowledged frames from the retransmission queue. */
+static int tcp_clean_rtx_queue(struct sock *sk, __u32 ack,
+			       __u32 *seq, __u32 *seq_rtt)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	struct sk_buff *skb;
+	__u32 now = tcp_time_stamp;
+	int acked = 0;
+
+	/* If we are retransmitting, and this ACK clears up to
+	 * the retransmit head, or further, then clear our state.
+	 */
+	if (tp->retrans_head != NULL &&
+	    !before(ack, TCP_SKB_CB(tp->retrans_head)->end_seq))
+		tp->retrans_head = NULL;
+
+	while((skb=skb_peek(&sk->write_queue)) && (skb != tp->send_head)) {
+		struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 
+		__u8 sacked = scb->sacked;
+		
+		/* If our packet is before the ack sequence we can
+		 * discard it as it's confirmed to have arrived at
+		 * the other end.
+		 */
+		if (after(scb->end_seq, ack))
+			break;
+
+		/* Initial outgoing SYN's get put onto the write_queue
+		 * just like anything else we transmit.  It is not
+		 * true data, and if we misinform our callers that
+		 * this ACK acks real data, we will erroneously exit
+		 * connection startup slow start one packet too
+		 * quickly.  This is severely frowned upon behavior.
+		 */
+		if((sacked & TCPCB_SACKED_RETRANS) && tp->retrans_out)
+			tp->retrans_out--;
+		if(!(scb->flags & TCPCB_FLAG_SYN)) {
+			acked |= FLAG_DATA_ACKED;
+			if(sacked & TCPCB_SACKED_RETRANS)
+				acked |= FLAG_RETRANS_DATA_ACKED;
+			if(tp->fackets_out)
+				tp->fackets_out--;
+		} else {
+			/* This is pure paranoia. */
+			tp->retrans_head = NULL;
+		}		
+		tp->packets_out--;
+		*seq = scb->seq;
+		*seq_rtt = now - scb->when;
+		__skb_unlink(skb, skb->list);
+		kfree_skb(skb);
+	}
+	return acked;
+}
+
+static void tcp_ack_probe(struct sock *sk, __u32 ack)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	
+	/* Our probe was answered. */
+	tp->probes_out = 0;
+	
+	/* Was it a usable window open? */
+
+	/* should always be non-null */
+	if (tp->send_head != NULL &&
+	    !before (ack + tp->snd_wnd, TCP_SKB_CB(tp->send_head)->end_seq)) {
+		tp->backoff = 0;
+		tp->pending = 0;
+		tcp_clear_xmit_timer(sk, TIME_PROBE0);
+	} else {
+		tcp_reset_xmit_timer(sk, TIME_PROBE0,
+				     min(tp->rto << tp->backoff, 120*HZ));
+	}
+}
+ 
+/* Should we open up the congestion window? */
+static __inline__ int should_advance_cwnd(struct tcp_opt *tp, int flag)
+{
+	/* Data must have been acked. */
+	if ((flag & FLAG_DATA_ACKED) == 0)
+		return 0;
+
+	/* Some of the data acked was retransmitted somehow? */
+	if ((flag & FLAG_RETRANS_DATA_ACKED) != 0) {
+		/* We advance in all cases except during
+		 * non-FACK fast retransmit/recovery.
+		 */
+		if (tp->fackets_out != 0 ||
+		    tp->retransmits != 0)
+			return 1;
+
+		/* Non-FACK fast retransmit does it's own
+		 * congestion window management, don't get
+		 * in the way.
+		 */
+		return 0;
+	}
+
+	/* New non-retransmitted data acked, always advance.  */
+	return 1;
+}
+
+/* Read draft-ietf-tcplw-high-performance before mucking
+ * with this code. (Superceeds RFC1323)
+ */
+static void tcp_ack_saw_tstamp(struct sock *sk, struct tcp_opt *tp,
+			       u32 seq, u32 ack, int flag)
+{
+	__u32 seq_rtt;
+
+	/* RTTM Rule: A TSecr value received in a segment is used to
+	 * update the averaged RTT measurement only if the segment
+	 * acknowledges some new data, i.e., only if it advances the
+	 * left edge of the send window.
+	 *
+	 * See draft-ietf-tcplw-high-performance-00, section 3.3.
+	 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
+	 */
+	if (!(flag & FLAG_DATA_ACKED))
+		return;
+
+	seq_rtt = tcp_time_stamp - tp->rcv_tsecr;
+	tcp_rtt_estimator(tp, seq_rtt);
+	if (tp->retransmits) {
+		if (tp->packets_out == 0) {
+			tp->retransmits = 0;
+			tp->fackets_out = 0;
+			tp->retrans_out = 0;
+			tp->backoff = 0;
+			tcp_set_rto(tp);
+		} else {
+			/* Still retransmitting, use backoff */
+			tcp_set_rto(tp);
+			tp->rto = tp->rto << tp->backoff;
+		}
+	} else {
+		tcp_set_rto(tp);
+	}
+
+	tcp_bound_rto(tp);
+}
+
+static __inline__ void tcp_ack_packets_out(struct sock *sk, struct tcp_opt *tp)
+{
+	struct sk_buff *skb = skb_peek(&sk->write_queue);
+
+	/* Some data was ACK'd, if still retransmitting (due to a
+	 * timeout), resend more of the retransmit queue.  The
+	 * congestion window is handled properly by that code.
+	 */
+	if (tp->retransmits) {
+		tcp_xmit_retransmit_queue(sk);
+		tcp_reset_xmit_timer(sk, TIME_RETRANS, tp->rto);
+	} else {
+		__u32 when = tp->rto - (tcp_time_stamp - TCP_SKB_CB(skb)->when);
+		if ((__s32)when < 0)
+			when = 1;
+		tcp_reset_xmit_timer(sk, TIME_RETRANS, when);
+	}
+}
+
+/* This routine deals with incoming acks, but not outgoing ones. */
+static int tcp_ack(struct sock *sk, struct tcphdr *th, 
+		   u32 ack_seq, u32 ack, int len)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	int flag = 0;
+	u32 seq = 0;
+	u32 seq_rtt = 0;
+
+	if(sk->zapped)
+		return(1);	/* Dead, can't ack any more so why bother */
+
+	if (tp->pending == TIME_KEEPOPEN)
+	  	tp->probes_out = 0;
+
+	tp->rcv_tstamp = tcp_time_stamp;
+
+	/* If the ack is newer than sent or older than previous acks
+	 * then we can probably ignore it.
+	 */
+	if (after(ack, tp->snd_nxt) || before(ack, tp->snd_una))
+		goto uninteresting_ack;
+
+	/* If there is data set flag 1 */
+	if (len != th->doff*4) {
+		flag |= FLAG_DATA;
+		tcp_delack_estimator(tp);
+	}
+
+	/* Update our send window. */
+
+	/* This is the window update code as per RFC 793
+	 * snd_wl{1,2} are used to prevent unordered
+	 * segments from shrinking the window 
+	 */
+	if (before(tp->snd_wl1, ack_seq) ||
+	    (tp->snd_wl1 == ack_seq && !after(tp->snd_wl2, ack))) {
+		u32 nwin = ntohs(th->window) << tp->snd_wscale;
+
+		if ((tp->snd_wl2 != ack) || (nwin > tp->snd_wnd)) {
+			flag |= FLAG_WIN_UPDATE;
+			tp->snd_wnd = nwin;
+
+			tp->snd_wl1 = ack_seq;
+			tp->snd_wl2 = ack;
+
+			if (nwin > tp->max_window)
+				tp->max_window = nwin;
+		}
+	}
+
+	/* We passed data and got it acked, remove any soft error
+	 * log. Something worked...
+	 */
+	sk->err_soft = 0;
+
+	/* If this ack opens up a zero window, clear backoff.  It was
+	 * being used to time the probes, and is probably far higher than
+	 * it needs to be for normal retransmission.
+	 */
+	if (tp->pending == TIME_PROBE0)
+		tcp_ack_probe(sk, ack);
+
+	/* See if we can take anything off of the retransmit queue. */
+	flag |= tcp_clean_rtx_queue(sk, ack, &seq, &seq_rtt);
+
+	/* We must do this here, before code below clears out important
+	 * state contained in tp->fackets_out and tp->retransmits.  -DaveM
+	 */
+	if (should_advance_cwnd(tp, flag))
+		tcp_cong_avoid(tp);
+
+	/* If we have a timestamp, we always do rtt estimates. */
+	if (tp->saw_tstamp) {
+		tcp_ack_saw_tstamp(sk, tp, seq, ack, flag);
+	} else {
+		/* If we were retransmiting don't count rtt estimate. */
+		if (tp->retransmits) {
+			if (tp->packets_out == 0) {
+				tp->retransmits = 0;
+				tp->fackets_out = 0;
+				tp->retrans_out = 0;
+			}
+		} else {
+			/* We don't have a timestamp. Can only use
+			 * packets that are not retransmitted to determine
+			 * rtt estimates. Also, we must not reset the
+			 * backoff for rto until we get a non-retransmitted
+			 * packet. This allows us to deal with a situation
+			 * where the network delay has increased suddenly.
+			 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
+			 */
+			if (flag & FLAG_DATA_ACKED) {
+				if(!(flag & FLAG_RETRANS_DATA_ACKED)) {
+					tp->backoff = 0;
+					tcp_rtt_estimator(tp, seq_rtt);
+					tcp_set_rto(tp);
+					tcp_bound_rto(tp);
+				}
+			}
+		}
+	}
+
+	if (tp->packets_out) {
+		if (flag & FLAG_DATA_ACKED)
+			tcp_ack_packets_out(sk, tp);
+	} else {
+		tcp_clear_xmit_timer(sk, TIME_RETRANS);
+	}
+
+	flag &= (FLAG_DATA | FLAG_WIN_UPDATE);
+	if ((ack == tp->snd_una	&& tp->packets_out && flag == 0) ||
+	    (tp->high_seq != 0)) {
+		tcp_fast_retrans(sk, ack, flag);
+	} else {
+		/* Clear any aborted fast retransmit starts. */
+		tp->dup_acks = 0;
+	}
+	/* It is not a brain fart, I thought a bit now. 8)
+	 *
+	 * Forward progress is indicated, if:
+	 *   1. the ack acknowledges new data.
+	 *   2. or the ack is duplicate, but it is caused by new segment
+	 *      arrival. This case is filtered by:
+	 *      - it contains no data, syn or fin.
+	 *      - it does not update window.
+	 *   3. or new SACK. It is difficult to check, so that we ignore it.
+	 *
+	 * Forward progress is also indicated by arrival new data,
+	 * which was caused by window open from our side. This case is more
+	 * difficult and it is made (alas, incorrectly) in tcp_data_queue().
+	 *                                              --ANK (990513)
+	 */
+	if (ack != tp->snd_una || (flag == 0 && !th->fin))
+		dst_confirm(sk->dst_cache);
+
+	/* Remember the highest ack received. */
+	tp->snd_una = ack;
+	return 1;
+
+uninteresting_ack:
+	SOCK_DEBUG(sk, "Ack ignored %u %u\n", ack, tp->snd_nxt);
+	return 0;
+}
+
+/* New-style handling of TIME_WAIT sockets. */
+extern void tcp_tw_schedule(struct tcp_tw_bucket *tw);
+extern void tcp_tw_reschedule(struct tcp_tw_bucket *tw);
+extern void tcp_tw_deschedule(struct tcp_tw_bucket *tw);
+
+void tcp_timewait_kill(struct tcp_tw_bucket *tw)
+{
+	struct tcp_bind_bucket *tb = tw->tb;
+
+	/* Disassociate with bind bucket. */
+	if(tw->bind_next)
+		tw->bind_next->bind_pprev = tw->bind_pprev;
+	*(tw->bind_pprev) = tw->bind_next;
+	if (tb->owners == NULL) {
+		if (tb->next)
+			tb->next->pprev = tb->pprev;
+		*(tb->pprev) = tb->next;
+		kmem_cache_free(tcp_bucket_cachep, tb);
+	}
+
+	/* Unlink from established hashes. */
+	if(tw->next)
+		tw->next->pprev = tw->pprev;
+	*tw->pprev = tw->next;
+
+	/* We decremented the prot->inuse count when we entered TIME_WAIT
+	 * and the sock from which this came was destroyed.
+	 */
+	tw->sklist_next->sklist_prev = tw->sklist_prev;
+	tw->sklist_prev->sklist_next = tw->sklist_next;
+
+	/* Ok, now free it up. */
+	kmem_cache_free(tcp_timewait_cachep, tw);
+}
+
+/* We come here as a special case from the AF specific TCP input processing,
+ * and the SKB has no owner.  Essentially handling this is very simple,
+ * we just keep silently eating rx'd packets, acking them if necessary,
+ * until none show up for the entire timeout period. 
+ *
+ * Return 0, TCP_TW_ACK, TCP_TW_RST
+ */
+enum tcp_tw_status 
+tcp_timewait_state_process(struct tcp_tw_bucket *tw, struct sk_buff *skb,
+			       struct tcphdr *th, unsigned len)
+{
+	/*	RFC 1122:
+	 *	"When a connection is [...] on TIME-WAIT state [...]
+	 *	[a TCP] MAY accept a new SYN from the remote TCP to
+	 *	reopen the connection directly, if it:
+	 *	
+	 *	(1)  assigns its initial sequence number for the new
+	 *	connection to be larger than the largest sequence
+	 *	number it used on the previous connection incarnation,
+	 *	and
+	 *
+	 *	(2)  returns to TIME-WAIT state if the SYN turns out 
+	 *	to be an old duplicate".
+	 */
+	if(th->syn && !th->rst && after(TCP_SKB_CB(skb)->seq, tw->rcv_nxt)) {
+		struct sock *sk;
+		struct tcp_func *af_specific = tw->af_specific;
+		__u32 isn;
+
+		isn = tw->snd_nxt + 128000;
+		if(isn == 0)
+			isn++;
+		tcp_tw_deschedule(tw);
+		tcp_timewait_kill(tw);
+		sk = af_specific->get_sock(skb, th);
+		if(sk == NULL ||
+		   !ipsec_sk_policy(sk,skb) ||
+		   atomic_read(&sk->sock_readers) != 0)
+			return 0;
+		skb_set_owner_r(skb, sk);
+		af_specific = sk->tp_pinfo.af_tcp.af_specific;
+		if(af_specific->conn_request(sk, skb, isn) < 0)
+			return TCP_TW_RST; /* Toss a reset back. */
+		return 0; /* Discard the frame. */
+	}
+
+	/* Check RST or SYN */
+	if(th->rst || th->syn) {
+		/* This is TIME_WAIT assasination, in two flavors.
+		 * Oh well... nobody has a sufficient solution to this
+		 * protocol bug yet.
+		 */
+		if(sysctl_tcp_rfc1337 == 0) {
+			tcp_tw_deschedule(tw);
+			tcp_timewait_kill(tw);
+		}
+		if(!th->rst)
+			return TCP_TW_RST; /* toss a reset back */
+		return 0;
+	} else {
+		/* In this case we must reset the TIMEWAIT timer. */
+		if(th->ack)
+			tcp_tw_reschedule(tw);
+	}
+	/* Ack old packets if necessary */ 
+	if (!after(TCP_SKB_CB(skb)->end_seq, tw->rcv_nxt) &&
+	    (th->doff * 4) > len)
+		return TCP_TW_ACK; 
+	return 0; 
+}
+
+/* Enter the time wait state.  This is always called from BH
+ * context.  Essentially we whip up a timewait bucket, copy the
+ * relevant info into it from the SK, and mess with hash chains
+ * and list linkage.
+ */
+static __inline__ void tcp_tw_hashdance(struct sock *sk, struct tcp_tw_bucket *tw)
+{
+	struct sock **head, *sktw;
+
+	/* Step 1: Remove SK from established hash. */
+	if(sk->next)
+		sk->next->pprev = sk->pprev;
+	*sk->pprev = sk->next;
+	sk->pprev = NULL;
+	tcp_reg_zap(sk);
+
+	/* Step 2: Put TW into bind hash where SK was. */
+	tw->tb = (struct tcp_bind_bucket *)sk->prev;
+	if((tw->bind_next = sk->bind_next) != NULL)
+		sk->bind_next->bind_pprev = &tw->bind_next;
+	tw->bind_pprev = sk->bind_pprev;
+	*sk->bind_pprev = (struct sock *)tw;
+	sk->prev = NULL;
+
+	/* Step 3: Same for the protocol sklist. */
+	(tw->sklist_next = sk->sklist_next)->sklist_prev = (struct sock *)tw;
+	(tw->sklist_prev = sk->sklist_prev)->sklist_next = (struct sock *)tw;
+	sk->sklist_next = NULL;
+	sk->prot->inuse--;
+
+	/* Step 4: Hash TW into TIMEWAIT half of established hash table. */
+	head = &tcp_established_hash[sk->hashent + (TCP_HTABLE_SIZE/2)];
+	sktw = (struct sock *)tw;
+	if((sktw->next = *head) != NULL)
+		(*head)->pprev = &sktw->next;
+	*head = sktw;
+	sktw->pprev = head;
+}
+
+void tcp_time_wait(struct sock *sk)
+{
+	struct tcp_tw_bucket *tw;
+
+	tw = kmem_cache_alloc(tcp_timewait_cachep, SLAB_ATOMIC);
+	if(tw != NULL) {
+		/* Give us an identity. */
+		tw->daddr	= sk->daddr;
+		tw->rcv_saddr	= sk->rcv_saddr;
+		tw->bound_dev_if= sk->bound_dev_if;
+		tw->num		= sk->num;
+		tw->state	= TCP_TIME_WAIT;
+		tw->sport	= sk->sport;
+		tw->dport	= sk->dport;
+		tw->family	= sk->family;
+		tw->reuse	= sk->reuse;
+		tw->rcv_nxt	= sk->tp_pinfo.af_tcp.rcv_nxt;
+		tw->snd_nxt     = sk->tp_pinfo.af_tcp.snd_nxt;
+		tw->window	= tcp_select_window(sk);
+		tw->af_specific	= sk->tp_pinfo.af_tcp.af_specific;
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+		if(tw->family == PF_INET6) {
+			memcpy(&tw->v6_daddr,
+			       &sk->net_pinfo.af_inet6.daddr,
+			       sizeof(struct in6_addr));
+			memcpy(&tw->v6_rcv_saddr,
+			       &sk->net_pinfo.af_inet6.rcv_saddr,
+			       sizeof(struct in6_addr));
+		}
+#endif
+		/* Linkage updates. */
+		tcp_tw_hashdance(sk, tw);
+
+		/* Get the TIME_WAIT timeout firing. */
+		tcp_tw_schedule(tw);
+
+		/* CLOSE the SK. */
+		if(sk->state == TCP_ESTABLISHED)
+			tcp_statistics.TcpCurrEstab--;
+		sk->state = TCP_CLOSE;
+		net_reset_timer(sk, TIME_DONE,
+				min(sk->tp_pinfo.af_tcp.srtt * 2, TCP_DONE_TIME));
+	} else {
+		/* Sorry, we're out of memory, just CLOSE this
+		 * socket up.  We've got bigger problems than
+		 * non-graceful socket closings.
+		 */
+		tcp_set_state(sk, TCP_CLOSE);
+	}
+
+	/* Prevent rcvmsg/sndmsg calls, and wake people up. */
+	sk->shutdown = SHUTDOWN_MASK;
+	if(!sk->dead)
+		sk->state_change(sk);
+}
+
+/*
+ * 	Process the FIN bit. This now behaves as it is supposed to work
+ *	and the FIN takes effect when it is validly part of sequence
+ *	space. Not before when we get holes.
+ *
+ *	If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
+ *	(and thence onto LAST-ACK and finally, CLOSE, we never enter
+ *	TIME-WAIT)
+ *
+ *	If we are in FINWAIT-1, a received FIN indicates simultaneous
+ *	close and we go into CLOSING (and later onto TIME-WAIT)
+ *
+ *	If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
+ */
+ 
+static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
+{
+	sk->tp_pinfo.af_tcp.fin_seq = TCP_SKB_CB(skb)->end_seq;
+
+	tcp_send_ack(sk);
+
+	if (!sk->dead) {
+		sk->state_change(sk);
+		sock_wake_async(sk->socket, 1);
+	}
+
+	switch(sk->state) {
+		case TCP_SYN_RECV:
+		case TCP_ESTABLISHED:
+			/* Move to CLOSE_WAIT */
+			tcp_set_state(sk, TCP_CLOSE_WAIT);
+			if (th->rst)
+				sk->shutdown = SHUTDOWN_MASK;
+			break;
+
+		case TCP_CLOSE_WAIT:
+		case TCP_CLOSING:
+			/* Received a retransmission of the FIN, do
+			 * nothing.
+			 */
+			break;
+		case TCP_LAST_ACK:
+			/* RFC793: Remain in the LAST-ACK state. */
+			break;
+
+		case TCP_FIN_WAIT1:
+			/* This case occurs when a simultaneous close
+			 * happens, we must ack the received FIN and
+			 * enter the CLOSING state.
+			 *
+			 * This causes a WRITE timeout, which will either
+			 * move on to TIME_WAIT when we timeout, or resend
+			 * the FIN properly (maybe we get rid of that annoying
+			 * FIN lost hang). The TIME_WRITE code is already 
+			 * correct for handling this timeout.
+			 */
+			tcp_set_state(sk, TCP_CLOSING);
+			break;
+		case TCP_FIN_WAIT2:
+			/* Received a FIN -- send ACK and enter TIME_WAIT. */
+			tcp_time_wait(sk);
+			break;
+		default:
+			/* Only TCP_LISTEN and TCP_CLOSE are left, in these
+			 * cases we should never reach this piece of code.
+			 */
+			printk("tcp_fin: Impossible, sk->state=%d\n", sk->state);
+			break;
+	};
+}
+
+/* These routines update the SACK block as out-of-order packets arrive or
+ * in-order packets close up the sequence space.
+ */
+static void tcp_sack_maybe_coalesce(struct tcp_opt *tp, struct tcp_sack_block *sp)
+{
+	int this_sack, num_sacks = tp->num_sacks;
+	struct tcp_sack_block *swalk = &tp->selective_acks[0];
+
+	/* If more than one SACK block, see if the recent change to SP eats into
+	 * or hits the sequence space of other SACK blocks, if so coalesce.
+	 */
+	if(num_sacks != 1) {
+		for(this_sack = 0; this_sack < num_sacks; this_sack++, swalk++) {
+			if(swalk == sp)
+				continue;
+
+			/* First case, bottom of SP moves into top of the
+			 * sequence space of SWALK.
+			 */
+			if(between(sp->start_seq, swalk->start_seq, swalk->end_seq)) {
+				sp->start_seq = swalk->start_seq;
+				goto coalesce;
+			}
+			/* Second case, top of SP moves into bottom of the
+			 * sequence space of SWALK.
+			 */
+			if(between(sp->end_seq, swalk->start_seq, swalk->end_seq)) {
+				sp->end_seq = swalk->end_seq;
+				goto coalesce;
+			}
+		}
+	}
+	/* SP is the only SACK, or no coalescing cases found. */
+	return;
+
+coalesce:
+	/* Zap SWALK, by moving every further SACK up by one slot.
+	 * Decrease num_sacks.
+	 */
+	for(; this_sack < num_sacks-1; this_sack++, swalk++) {
+		struct tcp_sack_block *next = (swalk + 1);
+		swalk->start_seq = next->start_seq;
+		swalk->end_seq = next->end_seq;
+	}
+	tp->num_sacks--;
+}
+
+static __inline__ void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
+{
+	__u32 tmp;
+
+	tmp = sack1->start_seq;
+	sack1->start_seq = sack2->start_seq;
+	sack2->start_seq = tmp;
+
+	tmp = sack1->end_seq;
+	sack1->end_seq = sack2->end_seq;
+	sack2->end_seq = tmp;
+}
+
+static void tcp_sack_new_ofo_skb(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	struct tcp_sack_block *sp = &tp->selective_acks[0];
+	int cur_sacks = tp->num_sacks;
+
+	if (!cur_sacks)
+		goto new_sack;
+
+	/* Optimize for the common case, new ofo frames arrive
+	 * "in order". ;-)  This also satisfies the requirements
+	 * of RFC2018 about ordering of SACKs.
+	 */
+	if(sp->end_seq == TCP_SKB_CB(skb)->seq) {
+		sp->end_seq = TCP_SKB_CB(skb)->end_seq;
+		tcp_sack_maybe_coalesce(tp, sp);
+	} else if(sp->start_seq == TCP_SKB_CB(skb)->end_seq) {
+		/* Re-ordered arrival, in this case, can be optimized
+		 * as well.
+		 */
+		sp->start_seq = TCP_SKB_CB(skb)->seq;
+		tcp_sack_maybe_coalesce(tp, sp);
+	} else {
+		struct tcp_sack_block *swap = sp + 1;
+		int this_sack, max_sacks = (tp->tstamp_ok ? 3 : 4);
+
+		/* Oh well, we have to move things around.
+		 * Try to find a SACK we can tack this onto.
+		 */
+
+		for(this_sack = 1; this_sack < cur_sacks; this_sack++, swap++) {
+			if((swap->end_seq == TCP_SKB_CB(skb)->seq) ||
+			   (swap->start_seq == TCP_SKB_CB(skb)->end_seq)) {
+				if(swap->end_seq == TCP_SKB_CB(skb)->seq)
+					swap->end_seq = TCP_SKB_CB(skb)->end_seq;
+				else
+					swap->start_seq = TCP_SKB_CB(skb)->seq;
+				tcp_sack_swap(sp, swap);
+				tcp_sack_maybe_coalesce(tp, sp);
+				return;
+			}
+		}
+
+		/* Could not find an adjacent existing SACK, build a new one,
+		 * put it at the front, and shift everyone else down.  We
+		 * always know there is at least one SACK present already here.
+		 *
+		 * If the sack array is full, forget about the last one.
+		 */
+		if (cur_sacks >= max_sacks) {
+			cur_sacks--;
+			tp->num_sacks--;
+		}
+		while(cur_sacks >= 1) {
+			struct tcp_sack_block *this = &tp->selective_acks[cur_sacks];
+			struct tcp_sack_block *prev = (this - 1);
+			this->start_seq = prev->start_seq;
+			this->end_seq = prev->end_seq;
+			cur_sacks--;
+		}
+
+	new_sack:
+		/* Build the new head SACK, and we're done. */
+		sp->start_seq = TCP_SKB_CB(skb)->seq;
+		sp->end_seq = TCP_SKB_CB(skb)->end_seq;
+		tp->num_sacks++;
+	}
+}
+
+static void tcp_sack_remove_skb(struct tcp_opt *tp, struct sk_buff *skb)
+{
+	struct tcp_sack_block *sp = &tp->selective_acks[0];
+	int num_sacks = tp->num_sacks;
+	int this_sack;
+
+	/* This is an in order data segment _or_ an out-of-order SKB being
+	 * moved to the receive queue, so we know this removed SKB will eat
+	 * from the front of a SACK.
+	 */
+	for(this_sack = 0; this_sack < num_sacks; this_sack++, sp++) {
+		/* Check if the start of the sack is covered by skb. */
+		if(!before(sp->start_seq, TCP_SKB_CB(skb)->seq) &&
+		   before(sp->start_seq, TCP_SKB_CB(skb)->end_seq))
+			break;
+	}
+
+	/* This should only happen if so many SACKs get built that some get
+	 * pushed out before we get here, or we eat some in sequence packets
+	 * which are before the first SACK block.
+	 */
+	if(this_sack >= num_sacks)
+		return;
+
+	sp->start_seq = TCP_SKB_CB(skb)->end_seq;
+	if(!before(sp->start_seq, sp->end_seq)) {
+		/* Zap this SACK, by moving forward any other SACKS. */
+		for(this_sack += 1; this_sack < num_sacks; this_sack++, sp++) {
+			struct tcp_sack_block *next = (sp + 1);
+			sp->start_seq = next->start_seq;
+			sp->end_seq = next->end_seq;
+		}
+		tp->num_sacks--;
+	}
+}
+
+static void tcp_sack_extend(struct tcp_opt *tp, struct sk_buff *old_skb, struct sk_buff *new_skb)
+{
+	struct tcp_sack_block *sp = &tp->selective_acks[0];
+	int num_sacks = tp->num_sacks;
+	int this_sack;
+
+	for(this_sack = 0; this_sack < num_sacks; this_sack++, sp++) {
+		if(sp->end_seq == TCP_SKB_CB(old_skb)->end_seq)
+			break;
+	}
+	if(this_sack >= num_sacks)
+		return;
+	sp->end_seq = TCP_SKB_CB(new_skb)->end_seq;
+}
+
+/* This one checks to see if we can put data from the
+ * out_of_order queue into the receive_queue.
+ */
+static void tcp_ofo_queue(struct sock *sk)
+{
+	struct sk_buff *skb;
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+
+	while ((skb = skb_peek(&tp->out_of_order_queue))) {
+		if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
+			break;
+
+		if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
+			SOCK_DEBUG(sk, "ofo packet was already received \n");
+			__skb_unlink(skb, skb->list);
+			kfree_skb(skb);
+			continue;
+		}
+		SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
+			   tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
+			   TCP_SKB_CB(skb)->end_seq);
+
+		if(tp->sack_ok)
+			tcp_sack_remove_skb(tp, skb);
+		__skb_unlink(skb, skb->list);
+		__skb_queue_tail(&sk->receive_queue, skb);
+		tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+		if(skb->h.th->fin)
+			tcp_fin(skb, sk, skb->h.th);
+	}
+}
+
+static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
+{
+	struct sk_buff *skb1;
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+
+	/*  Queue data for delivery to the user.
+	 *  Packets in sequence go to the receive queue.
+	 *  Out of sequence packets to the out_of_order_queue.
+	 */
+	if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
+		/* Ok. In sequence. */
+	queue_and_out:
+		dst_confirm(sk->dst_cache);
+		__skb_queue_tail(&sk->receive_queue, skb);
+		tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+		if(skb->h.th->fin) {
+			tcp_fin(skb, sk, skb->h.th);
+		} else {
+			tcp_remember_ack(tp, skb->h.th, skb); 
+		}
+		/* This may have eaten into a SACK block. */
+		if(tp->sack_ok && tp->num_sacks)
+			tcp_sack_remove_skb(tp, skb);
+		tcp_ofo_queue(sk);
+
+		/* Turn on fast path. */ 
+		if (skb_queue_len(&tp->out_of_order_queue) == 0)
+			tp->pred_flags = htonl(((tp->tcp_header_len >> 2) << 28) |
+					       (0x10 << 16) |
+					       tp->snd_wnd);
+		return;
+	}
+	
+	/* An old packet, either a retransmit or some packet got lost. */
+	if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
+		/* A retransmit, 2nd most common case.  Force an imediate ack. */
+		SOCK_DEBUG(sk, "retransmit received: seq %X\n", TCP_SKB_CB(skb)->seq);
+		tcp_enter_quickack_mode(tp);
+		kfree_skb(skb);
+		return;
+	}
+
+	if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
+		/* Partial packet, seq < rcv_next < end_seq */
+		SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
+			   tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
+			   TCP_SKB_CB(skb)->end_seq);
+
+		goto queue_and_out;
+	}
+
+	/* Ok. This is an out_of_order segment, force an ack. */
+	tp->delayed_acks++;
+	tcp_enter_quickack_mode(tp);
+
+	/* Disable header prediction. */
+	tp->pred_flags = 0;
+
+	SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
+		   tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
+
+	if (skb_peek(&tp->out_of_order_queue) == NULL) {
+		/* Initial out of order segment, build 1 SACK. */
+		if(tp->sack_ok) {
+			tp->num_sacks = 1;
+			tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
+			tp->selective_acks[0].end_seq = TCP_SKB_CB(skb)->end_seq;
+		}
+		__skb_queue_head(&tp->out_of_order_queue,skb);
+	} else {
+		for(skb1=tp->out_of_order_queue.prev; ; skb1 = skb1->prev) {
+			/* Already there. */
+			if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb1)->seq) {
+				if (skb->len >= skb1->len) {
+					if(tp->sack_ok)
+						tcp_sack_extend(tp, skb1, skb);
+					__skb_append(skb1, skb);
+					__skb_unlink(skb1, skb1->list);
+					kfree_skb(skb1);
+				} else {
+					/* A duplicate, smaller than what is in the
+					 * out-of-order queue right now, toss it.
+					 */
+					kfree_skb(skb);
+				}
+				break;
+			}
+			
+			if (after(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb1)->seq)) {
+				__skb_append(skb1, skb);
+				if(tp->sack_ok)
+					tcp_sack_new_ofo_skb(sk, skb);
+				break;
+			}
+
+                        /* See if we've hit the start. If so insert. */
+			if (skb1 == skb_peek(&tp->out_of_order_queue)) {
+				__skb_queue_head(&tp->out_of_order_queue,skb);
+				if(tp->sack_ok)
+					tcp_sack_new_ofo_skb(sk, skb);
+				break;
+			}
+		}
+	}
+}
+
+
+/*
+ *	This routine handles the data.  If there is room in the buffer,
+ *	it will be have already been moved into it.  If there is no
+ *	room, then we will just have to discard the packet.
+ */
+
+static int tcp_data(struct sk_buff *skb, struct sock *sk, unsigned int len)
+{
+	struct tcphdr *th;
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+
+	th = skb->h.th;
+	skb_pull(skb, th->doff*4);
+	skb_trim(skb, len - (th->doff*4));
+
+        if (skb->len == 0 && !th->fin)
+		return(0);
+
+	/* 
+	 *	If our receive queue has grown past its limits shrink it.
+	 *	Make sure to do this before moving snd_nxt, otherwise
+	 *	data might be acked for that we don't have enough room.
+	 */
+	if (atomic_read(&sk->rmem_alloc) > sk->rcvbuf) { 
+		if (prune_queue(sk) < 0) { 
+			/* Still not enough room. That can happen when
+			 * skb->true_size differs significantly from skb->len.
+			 */
+			return 0;
+		}
+	}
+
+	tcp_data_queue(sk, skb);
+
+	if (before(tp->rcv_nxt, tp->copied_seq)) {
+		printk(KERN_DEBUG "*** tcp.c:tcp_data bug acked < copied\n");
+		tp->rcv_nxt = tp->copied_seq;
+	}
+
+	/* Above, tcp_data_queue() increments delayed_acks appropriately.
+	 * Now tell the user we may have some data.
+	 */
+	if (!sk->dead) {
+		sk->data_ready(sk,0);
+	}
+	return(1);
+}
+
+static void __tcp_data_snd_check(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+
+	if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una + tp->snd_wnd) &&
+	    tcp_packets_in_flight(tp) < tp->snd_cwnd) {
+		/* Put more data onto the wire. */
+		tcp_write_xmit(sk);
+	} else if (tp->packets_out == 0 && !tp->pending) {
+		/* Start probing the receivers window. */
+		tcp_reset_xmit_timer(sk, TIME_PROBE0, tp->rto);
+	}
+}
+
+static __inline__ void tcp_data_snd_check(struct sock *sk)
+{
+	struct sk_buff *skb = sk->tp_pinfo.af_tcp.send_head;
+
+	if (skb != NULL)
+		__tcp_data_snd_check(sk, skb); 
+}
+
+/* 
+ * Adapt the MSS value used to make delayed ack decision to the 
+ * real world. 
+ */ 
+static __inline__ void tcp_measure_rcv_mss(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	unsigned int len = skb->len, lss; 
+
+	if (len > tp->rcv_mss) 
+		tp->rcv_mss = len; 
+	lss = tp->last_seg_size; 
+	tp->last_seg_size = 0; 
+	if (len >= 536) {
+		if (len == lss) 
+			tp->rcv_mss = len; 
+		tp->last_seg_size = len; 
+	}
+}
+
+/*
+ * Check if sending an ack is needed.
+ */
+static __inline__ void __tcp_ack_snd_check(struct sock *sk)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+
+	/* This also takes care of updating the window.
+	 * This if statement needs to be simplified.
+	 *
+	 * Rules for delaying an ack:
+	 *      - delay time <= 0.5 HZ
+	 *      - we don't have a window update to send
+	 *      - must send at least every 2 full sized packets
+	 *	- must send an ACK if we have any out of order data
+	 *
+	 * With an extra heuristic to handle loss of packet
+	 * situations and also helping the sender leave slow
+	 * start in an expediant manner.
+	 */
+
+	    /* Two full frames received or... */
+	if (((tp->rcv_nxt - tp->rcv_wup) >= tp->rcv_mss * MAX_DELAY_ACK) ||
+	    /* We will update the window "significantly" or... */
+	    tcp_raise_window(sk) ||
+	    /* We entered "quick ACK" mode or... */
+	    tcp_in_quickack_mode(tp) ||
+	    /* We have out of order data */
+	    (skb_peek(&tp->out_of_order_queue) != NULL)) {
+		/* Then ack it now */
+		tcp_send_ack(sk);
+	} else {
+		/* Else, send delayed ack. */
+		tcp_send_delayed_ack(tp, HZ/2);
+	}
+}
+
+static __inline__ void tcp_ack_snd_check(struct sock *sk)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	if (tp->delayed_acks == 0) {
+		/* We sent a data segment already. */
+		return;
+	}
+	__tcp_ack_snd_check(sk);
+}
+
+
+/*
+ *	This routine is only called when we have urgent data
+ *	signalled. Its the 'slow' part of tcp_urg. It could be
+ *	moved inline now as tcp_urg is only called from one
+ *	place. We handle URGent data wrong. We have to - as
+ *	BSD still doesn't use the correction from RFC961.
+ *	For 1003.1g we should support a new option TCP_STDURG to permit
+ *	either form (or just set the sysctl tcp_stdurg).
+ */
+ 
+static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	u32 ptr = ntohs(th->urg_ptr);
+
+	if (ptr && !sysctl_tcp_stdurg)
+		ptr--;
+	ptr += ntohl(th->seq);
+
+	/* Ignore urgent data that we've already seen and read. */
+	if (after(tp->copied_seq, ptr))
+		return;
+
+	/* Do we already have a newer (or duplicate) urgent pointer? */
+	if (tp->urg_data && !after(ptr, tp->urg_seq))
+		return;
+
+	/* Tell the world about our new urgent pointer. */
+	if (sk->proc != 0) {
+		if (sk->proc > 0)
+			kill_proc(sk->proc, SIGURG, 1);
+		else
+			kill_pg(-sk->proc, SIGURG, 1);
+	}
+
+	/* We may be adding urgent data when the last byte read was
+	 * urgent. To do this requires some care. We cannot just ignore
+	 * tp->copied_seq since we would read the last urgent byte again
+	 * as data, nor can we alter copied_seq until this data arrives
+	 * or we break the sematics of SIOCATMARK (and thus sockatmark())
+	 */
+	if (tp->urg_seq == tp->copied_seq)
+		tp->copied_seq++;	/* Move the copied sequence on correctly */
+	tp->urg_data = URG_NOTYET;
+	tp->urg_seq = ptr;
+
+	/* Disable header prediction. */
+	tp->pred_flags = 0;
+}
+
+/* This is the 'fast' part of urgent handling. */
+static inline void tcp_urg(struct sock *sk, struct tcphdr *th, unsigned long len)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+
+	/* Check if we get a new urgent pointer - normally not. */
+	if (th->urg)
+		tcp_check_urg(sk,th);
+
+	/* Do we wait for any urgent data? - normally not... */
+	if (tp->urg_data == URG_NOTYET) {
+		u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff*4);
+
+		/* Is the urgent pointer pointing into this packet? */	 
+		if (ptr < len) {
+			tp->urg_data = URG_VALID | *(ptr + (unsigned char *) th);
+			if (!sk->dead)
+				sk->data_ready(sk,0);
+		}
+	}
+}
+
+/* Clean the out_of_order queue if we can, trying to get
+ * the socket within its memory limits again.
+ *
+ * Return less than zero if we should start dropping frames
+ * until the socket owning process reads some of the data
+ * to stabilize the situation.
+ */
+static int prune_queue(struct sock *sk)
+{
+	struct tcp_opt *tp = &sk->tp_pinfo.af_tcp; 
+	struct sk_buff * skb;
+
+	SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
+
+	net_statistics.PruneCalled++; 
+
+	/* First, purge the out_of_order queue. */
+	skb = __skb_dequeue_tail(&tp->out_of_order_queue);
+	if(skb != NULL) {
+		/* Free it all. */
+		do {	net_statistics.OfoPruned += skb->len; 
+			kfree_skb(skb);
+			skb = __skb_dequeue_tail(&tp->out_of_order_queue);
+		} while(skb != NULL);
+
+		/* Reset SACK state.  A conforming SACK implementation will
+		 * do the same at a timeout based retransmit.  When a connection
+		 * is in a sad state like this, we care only about integrity
+		 * of the connection not performance.
+		 */
+		if(tp->sack_ok)
+			tp->num_sacks = 0;
+	}
+	
+	/* If we are really being abused, tell the caller to silently
+	 * drop receive data on the floor.  It will get retransmitted
+	 * and hopefully then we'll have sufficient space.
+	 *
+	 * We used to try to purge the in-order packets too, but that
+	 * turns out to be deadly and fraught with races.  Consider:
+	 *
+	 * 1) If we acked the data, we absolutely cannot drop the
+	 *    packet.  This data would then never be retransmitted.
+	 * 2) It is possible, with a proper sequence of events involving
+	 *    delayed acks and backlog queue handling, to have the user
+	 *    read the data before it gets acked.  The previous code
+	 *    here got this wrong, and it lead to data corruption.
+	 * 3) Too much state changes happen when the FIN arrives, so once
+	 *    we've seen that we can't remove any in-order data safely.
+	 *
+	 * The net result is that removing in-order receive data is too
+	 * complex for anyones sanity.  So we don't do it anymore.  But
+	 * if we are really having our buffer space abused we stop accepting
+	 * new receive data.
+	 */
+	if(atomic_read(&sk->rmem_alloc) < (sk->rcvbuf << 1))
+		return 0;
+
+	/* Massive buffer overcommit. */
+	return -1;
+}
+
+/*
+ *	TCP receive function for the ESTABLISHED state. 
+ *
+ *	It is split into a fast path and a slow path. The fast path is 
+ * 	disabled when:
+ *	- A zero window was announced from us - zero window probing
+ *        is only handled properly in the slow path. 
+ *      - Out of order segments arrived.
+ *	- Urgent data is expected.
+ *	- There is no buffer space left
+ *	- Unexpected TCP flags/window values/header lengths are received
+ *	  (detected by checking the TCP header against pred_flags) 
+ *	- Data is sent in both directions. Fast path only supports pure senders
+ *	  or pure receivers (this means either the sequence number or the ack
+ *	  value must stay constant)
+ *
+ *	When these conditions are not satisfied it drops into a standard 
+ *	receive procedure patterned after RFC793 to handle all cases.
+ *	The first three cases are guaranteed by proper pred_flags setting,
+ *	the rest is checked inline. Fast processing is turned on in 
+ *	tcp_data_queue when everything is OK.
+ */
+int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
+			struct tcphdr *th, unsigned len)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	int queued;
+	u32 flg;
+
+	/*
+	 *	Header prediction.
+	 *	The code follows the one in the famous 
+	 *	"30 instruction TCP receive" Van Jacobson mail.
+	 *	
+	 *	Van's trick is to deposit buffers into socket queue 
+	 *	on a device interrupt, to call tcp_recv function
+	 *	on the receive process context and checksum and copy
+	 *	the buffer to user space. smart...
+	 *
+	 *	Our current scheme is not silly either but we take the 
+	 *	extra cost of the net_bh soft interrupt processing...
+	 *	We do checksum and copy also but from device to kernel.
+	 */
+
+	/*
+	 * RFC1323: H1. Apply PAWS check first.
+	 */
+	if (tcp_fast_parse_options(sk, th, tp)) {
+		if (tp->saw_tstamp) {
+			if (tcp_paws_discard(tp, th, len)) {
+				tcp_statistics.TcpInErrs++;
+				if (!th->rst) {
+					tcp_send_ack(sk);
+					goto discard;
+				}
+			}
+			tcp_replace_ts_recent(sk, tp,
+					      TCP_SKB_CB(skb)->seq,
+					      TCP_SKB_CB(skb)->end_seq);
+		}
+	}
+
+	flg = *(((u32 *)th) + 3) & ~htonl(0xFC8 << 16);
+
+	/*	pred_flags is 0xS?10 << 16 + snd_wnd
+	 *	if header_predition is to be made
+	 *	'S' will always be tp->tcp_header_len >> 2
+	 *	'?' will be 0 else it will be !0
+	 *	(when there are holes in the receive 
+	 *	 space for instance)
+	 *	PSH flag is ignored.
+         */
+
+	if (flg == tp->pred_flags && TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
+		if (len <= th->doff*4) {
+			/* Bulk data transfer: sender */
+			if (len == th->doff*4) {
+				tcp_ack(sk, th, TCP_SKB_CB(skb)->seq,
+					TCP_SKB_CB(skb)->ack_seq, len); 
+				kfree_skb(skb); 
+				tcp_data_snd_check(sk);
+				return 0;
+			} else { /* Header too small */
+				tcp_statistics.TcpInErrs++;
+				goto discard;
+			}
+		} else if (TCP_SKB_CB(skb)->ack_seq == tp->snd_una &&
+			   atomic_read(&sk->rmem_alloc) <= sk->rcvbuf) {
+			/* Bulk data transfer: receiver */
+			__skb_pull(skb,th->doff*4);
+
+			tcp_measure_rcv_mss(sk, skb); 
+
+			/* DO NOT notify forward progress here.
+			 * It saves dozen of CPU instructions in fast path. --ANK
+			 */
+			__skb_queue_tail(&sk->receive_queue, skb);
+			tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+
+			/* FIN bit check is not done since if FIN is set in
+			 * this frame, the pred_flags won't match up. -DaveM
+			 */
+			sk->data_ready(sk, 0);
+			tcp_delack_estimator(tp);
+
+			tcp_remember_ack(tp, th, skb); 
+
+			__tcp_ack_snd_check(sk);
+			return 0;
+		}
+	}
+
+	/*
+	 *	Standard slow path.
+	 */
+
+	if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
+		/* RFC793, page 37: "In all states except SYN-SENT, all reset
+		 * (RST) segments are validated by checking their SEQ-fields."
+		 * And page 69: "If an incoming segment is not acceptable,
+		 * an acknowledgment should be sent in reply (unless the RST bit
+		 * is set, if so drop the segment and return)".
+		 */
+		if (th->rst)
+			goto discard;
+		if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
+			SOCK_DEBUG(sk, "seq:%d end:%d wup:%d wnd:%d\n",
+				   TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
+				   tp->rcv_wup, tp->rcv_wnd);
+		}
+		tcp_send_ack(sk);
+		goto discard;
+	}
+
+	if(th->syn && TCP_SKB_CB(skb)->seq != tp->syn_seq) {
+		SOCK_DEBUG(sk, "syn in established state\n");
+		tcp_statistics.TcpInErrs++;
+		tcp_reset(sk);
+		return 1;
+	}
+	
+	if(th->rst) {
+		tcp_reset(sk);
+		goto discard;
+	}
+
+	if(th->ack)
+		tcp_ack(sk, th, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->ack_seq, len);
+	
+	/* Process urgent data. */
+	tcp_urg(sk, th, len);
+
+	/* step 7: process the segment text */
+	queued = tcp_data(skb, sk, len);
+
+	/* This must be after tcp_data() does the skb_pull() to
+	 * remove the header size from skb->len.
+	 *
+	 * Dave!!! Phrase above (and all about rcv_mss) has 
+	 * nothing to do with reality. rcv_mss must measure TOTAL
+	 * size, including sacks, IP options etc. Hence, measure_rcv_mss
+	 * must occure before pulling etc, otherwise it will flap
+	 * like hell. Even putting it before tcp_data is wrong,
+	 * it should use skb->tail - skb->nh.raw instead.
+	 *					--ANK (980805)
+	 * 
+	 * BTW I broke it. Now all TCP options are handled equally
+	 * in mss_clamp calculations (i.e. ignored, rfc1122),
+	 * and mss_cache does include all of them (i.e. tstamps)
+	 * except for sacks, to calulate effective mss faster.
+	 * 					--ANK (980805)
+	 */
+	tcp_measure_rcv_mss(sk, skb); 
+
+	/* Be careful, tcp_data() may have put this into TIME_WAIT. */
+	if(sk->state != TCP_CLOSE) {
+		tcp_data_snd_check(sk);
+		tcp_ack_snd_check(sk);
+	}
+
+	if (!queued) {
+	discard:
+		kfree_skb(skb);
+	}
+
+	return 0;
+}
+
+/* 
+ *	Process an incoming SYN or SYN-ACK for SYN_RECV sockets represented
+ *	as an open_request. 
+ */
+
+struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, 
+			   struct open_request *req)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	u32 flg;
+
+	/*	assumption: the socket is not in use.
+	 *	as we checked the user count on tcp_rcv and we're
+	 *	running from a soft interrupt.
+	 */
+
+	/* Check for syn retransmission */
+	flg = *(((u32 *)skb->h.th) + 3);
+	
+	flg &= __constant_htonl(0x00170000);
+	/* Only SYN set? */
+	if (flg == __constant_htonl(0x00020000)) {
+		if (TCP_SKB_CB(skb)->seq == req->rcv_isn) {
+			/*	retransmited syn.
+			 */
+			req->class->rtx_syn_ack(sk, req); 
+			return NULL;
+		} else {
+			return sk; /* Pass new SYN to the listen socket. */
+		}
+	}
+
+	/* We know it's an ACK here */	
+	if (req->sk) {
+		/*	socket already created but not
+		 *	yet accepted()...
+		 */
+		sk = req->sk;
+	} else {
+		/* In theory the packet could be for a cookie, but
+		 * TIME_WAIT should guard us against this. 
+		 * XXX: Nevertheless check for cookies?
+		 * This sequence number check is done again later,
+		 * but we do it here to prevent syn flood attackers
+		 * from creating big SYN_RECV sockets.
+		 */ 
+		if (!between(TCP_SKB_CB(skb)->ack_seq, req->snt_isn, req->snt_isn+1) ||
+		    !between(TCP_SKB_CB(skb)->seq, req->rcv_isn, 
+			     req->rcv_isn+1+req->rcv_wnd)) {
+			req->class->send_reset(skb);
+			return NULL;
+		}
+	
+		sk = tp->af_specific->syn_recv_sock(sk, skb, req, NULL);
+		tcp_dec_slow_timer(TCP_SLT_SYNACK);
+		if (sk == NULL)
+			return NULL;
+		
+		req->expires = 0UL;
+		req->sk = sk;
+	}
+	skb_orphan(skb); 
+	skb_set_owner_r(skb, sk);
+	return sk; 
+}
+
+/*
+ *	This function implements the receiving procedure of RFC 793 for
+ *	all states except ESTABLISHED and TIME_WAIT. 
+ *	It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
+ *	address independent.
+ */
+	
+int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
+			  struct tcphdr *th, unsigned len)
+{
+	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+	int queued = 0;
+
+	switch (sk->state) {
+	case TCP_CLOSE:
+		/* When state == CLOSED, hash lookup always fails.
+		 *
+		 * But, there is a back door, the backlog queue.
+		 * If we have a sequence of packets in the backlog
+		 * during __release_sock() which have a sequence such
+		 * that:
+		 *	packet X	causes entry to TCP_CLOSE state
+		 *	...
+		 *	packet X + N	has FIN bit set
+		 *
+		 * We report a (luckily) harmless error in this case.
+		 * The issue is that backlog queue processing bypasses
+		 * any hash lookups (we know which socket packets are for).
+		 * The correct behavior here is what 2.0.x did, since
+		 * a TCP_CLOSE socket does not exist.  Drop the frame
+		 * and send a RST back to the other end.
+		 */
+		return 1;
+
+	case TCP_LISTEN:
+		/* These use the socket TOS.. 
+		 * might want to be the received TOS 
+		 */
+		if(th->ack)
+			return 1;
+		
+		if(th->syn) {
+			if(tp->af_specific->conn_request(sk, skb, 0) < 0)
+				return 1;
+
+			/* Now we have several options: In theory there is 
+			 * nothing else in the frame. KA9Q has an option to 
+			 * send data with the syn, BSD accepts data with the
+			 * syn up to the [to be] advertised window and 
+			 * Solaris 2.1 gives you a protocol error. For now 
+			 * we just ignore it, that fits the spec precisely 
+			 * and avoids incompatibilities. It would be nice in
+			 * future to drop through and process the data.
+			 *
+			 * Now that TTCP is starting to be used we ought to 
+			 * queue this data.
+			 * But, this leaves one open to an easy denial of
+		 	 * service attack, and SYN cookies can't defend
+			 * against this problem. So, we drop the data
+			 * in the interest of security over speed.
+			 */
+			goto discard;
+		}
+		
+		goto discard;
+		break;
+
+	case TCP_SYN_SENT:
+		/* SYN sent means we have to look for a suitable ack and 
+		 * either reset for bad matches or go to connected. 
+		 * The SYN_SENT case is unusual and should
+		 * not be in line code. [AC]
+		 */
+		if(th->ack) {
+			/* rfc793:
+			 * "If the state is SYN-SENT then
+			 *    first check the ACK bit
+			 *      If the ACK bit is set
+			 *	  If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
+			 *        a reset (unless the RST bit is set, if so drop
+			 *        the segment and return)"
+			 *
+			 *  I cite this place to emphasize one essential
+			 *  detail, this check is different of one
+			 *  in established state: SND.UNA <= SEG.ACK <= SND.NXT.
+			 *  SEG_ACK == SND.UNA == ISS is invalid in SYN-SENT,
+			 *  because we have no previous data sent before SYN.
+			 *                                        --ANK(990513)
+			 *
+			 *  We do not send data with SYN, so that RFC-correct
+			 *  test reduces to:
+			 */
+			if (sk->zapped ||
+			    TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
+				return 1;
+
+			/* Now ACK is acceptable.
+			 *
+			 * "If the RST bit is set
+			 *    If the ACK was acceptable then signal the user "error:
+			 *    connection reset", drop the segment, enter CLOSED state,
+			 *    delete TCB, and return."
+			 */
+
+			if (th->rst) {
+				tcp_reset(sk);
+				goto discard;
+			}
+
+			/* rfc793:
+			 *   "fifth, if neither of the SYN or RST bits is set then
+			 *    drop the segment and return."
+			 *
+			 *    See note below!
+			 *                                        --ANK(990513)
+		         */
+			
+			if (!th->syn)
+				goto discard;
+
+			/* rfc793:
+			 *   "If the SYN bit is on ...
+			 *    are acceptable then ...
+			 *    (our SYN has been ACKed), change the connection
+			 *    state to ESTABLISHED..."
+			 *
+			 * Do you see? SYN-less ACKs in SYN-SENT state are
+			 * completely ignored.
+			 *
+			 * The bug causing stalled SYN-SENT sockets
+			 * was here: tcp_ack advanced snd_una and canceled
+			 * retransmit timer, so that bare ACK received
+			 * in SYN-SENT state (even with invalid ack==ISS,
+			 * because tcp_ack check is too weak for SYN-SENT)
+			 * causes moving socket to invalid semi-SYN-SENT,
+			 * semi-ESTABLISHED state and connection hangs.
+			 *
+			 * There exist buggy stacks, which really send
+			 * such ACKs: f.e. 202.226.91.94 (okigate.oki.co.jp)
+			 * Actually, if this host did not try to get something
+			 * from ftp.inr.ac.ru I'd never find this bug 8)
+			 *
+			 *                                     --ANK (990514)
+			 */
+
+			tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
+			tcp_ack(sk,th, TCP_SKB_CB(skb)->seq,
+				TCP_SKB_CB(skb)->ack_seq, len);
+
+			/* Ok.. it's good. Set up sequence numbers and
+			 * move to established.
+			 */
+			tp->rcv_nxt = TCP_SKB_CB(skb)->seq+1;
+			tp->rcv_wup = TCP_SKB_CB(skb)->seq+1;
+
+			/* RFC1323: The window in SYN & SYN/ACK segments is
+			 * never scaled.
+			 */
+			tp->snd_wnd = htons(th->window);
+			tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
+			tp->snd_wl2 = TCP_SKB_CB(skb)->ack_seq;
+			tp->fin_seq = TCP_SKB_CB(skb)->seq;
+
+			tcp_set_state(sk, TCP_ESTABLISHED);
+			tcp_parse_options(sk, th, tp, 0);
+
+        		if (tp->wscale_ok == 0) {
+                		tp->snd_wscale = tp->rcv_wscale = 0;
+                		tp->window_clamp = min(tp->window_clamp,65535);
+        		}
+
+			if (tp->tstamp_ok) {
+				tp->tcp_header_len =
+					sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
+			} else
+				tp->tcp_header_len = sizeof(struct tcphdr);
+			if (tp->saw_tstamp) {
+				tp->ts_recent = tp->rcv_tsval;
+				tp->ts_recent_stamp = tcp_time_stamp;
+			}
+
+			/* Can't be earlier, doff would be wrong. */
+			tcp_send_ack(sk);
+
+			sk->dport = th->source;
+			tp->copied_seq = tp->rcv_nxt;
+
+			if(!sk->dead) {
+				sk->state_change(sk);
+				sock_wake_async(sk->socket, 0);
+			}
+		} else {
+			if(th->syn && !th->rst) {
+				/* The previous version of the code
+				 * checked for "connecting to self"
+				 * here. that check is done now in
+				 * tcp_connect.
+				 */
+				tcp_set_state(sk, TCP_SYN_RECV);
+				tcp_parse_options(sk, th, tp, 0);
+				if (tp->saw_tstamp) {
+					tp->ts_recent = tp->rcv_tsval;
+					tp->ts_recent_stamp = tcp_time_stamp;
+				}
+				
+				tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
+				tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
+
+				/* RFC1323: The window in SYN & SYN/ACK segments is
+				 * never scaled.
+				 */
+				tp->snd_wnd = htons(th->window);
+				tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
+				
+				tcp_send_synack(sk);
+			} else
+				break; 
+		}
+
+		/* tp->tcp_header_len and tp->mss_clamp
+		   probably changed, synchronize mss.
+		   */
+		tcp_sync_mss(sk, tp->pmtu_cookie);
+		tp->rcv_mss = tp->mss_cache;
+
+		if (sk->state == TCP_SYN_RECV)
+			goto discard;
+		
+		goto step6; 
+	}
+
+	/*   Parse the tcp_options present on this header.
+	 *   By this point we really only expect timestamps.
+	 *   Note that this really has to be here and not later for PAWS
+	 *   (RFC1323) to work.
+	 */
+	if (tcp_fast_parse_options(sk, th, tp)) {
+		/* NOTE: assumes saw_tstamp is never set if we didn't
+		 * negotiate the option. tcp_fast_parse_options() must
+		 * guarantee this.
+		 */
+		if (tp->saw_tstamp) {
+			if (tcp_paws_discard(tp, th, len)) {
+				tcp_statistics.TcpInErrs++;
+				if (!th->rst) {
+					tcp_send_ack(sk);
+					goto discard;
+				}
+			}
+			tcp_replace_ts_recent(sk, tp,
+					      TCP_SKB_CB(skb)->seq,
+					      TCP_SKB_CB(skb)->end_seq);
+		}
+	}
+
+	/* The silly FIN test here is necessary to see an advancing ACK in
+	 * retransmitted FIN frames properly.  Consider the following sequence:
+	 *
+	 *	host1 --> host2		FIN XSEQ:XSEQ(0) ack YSEQ
+	 *	host2 --> host1		FIN YSEQ:YSEQ(0) ack XSEQ
+	 *	host1 --> host2		XSEQ:XSEQ(0) ack YSEQ+1
+	 *	host2 --> host1		FIN YSEQ:YSEQ(0) ack XSEQ+1	(fails tcp_sequence test)
+	 *
+	 * At this point the connection will deadlock with host1 believing
+	 * that his FIN is never ACK'd, and thus it will retransmit it's FIN
+	 * forever.  The following fix is from Taral (taral@taral.net).
+	 */
+
+	/* step 1: check sequence number */
+	if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq) &&
+	    !(th->fin && TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt)) {
+		if (!th->rst) {
+			tcp_send_ack(sk);
+		}
+		goto discard;
+	}
+
+	/* step 2: check RST bit */
+	if(th->rst) {
+		tcp_reset(sk);
+		goto discard;
+	}
+
+	/* step 3: check security and precedence [ignored] */
+
+	/*	step 4:
+	 *
+	 *	Check for a SYN, and ensure it matches the SYN we were
+	 *	first sent. We have to handle the rather unusual (but valid)
+	 *	sequence that KA9Q derived products may generate of
+	 *
+	 *	SYN
+	 *				SYN|ACK Data
+	 *	ACK	(lost)
+	 *				SYN|ACK Data + More Data
+	 *	.. we must ACK not RST...
+	 *
+	 *	We keep syn_seq as the sequence space occupied by the 
+	 *	original syn. 
+	 */
+
+	if (th->syn && TCP_SKB_CB(skb)->seq != tp->syn_seq) {
+		tcp_reset(sk);
+		return 1;
+	}
+
+	/* step 5: check the ACK field */
+	if (th->ack) {
+		int acceptable = tcp_ack(sk, th, TCP_SKB_CB(skb)->seq,
+					 TCP_SKB_CB(skb)->ack_seq, len);
+		
+		switch(sk->state) {
+		case TCP_SYN_RECV:
+			if (acceptable) {
+				tcp_set_state(sk, TCP_ESTABLISHED);
+				sk->dport = th->source;
+				tp->copied_seq = tp->rcv_nxt;
+
+				if(!sk->dead)
+					sk->state_change(sk);		
+
+				tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
+				tp->snd_wnd = htons(th->window) << tp->snd_wscale;
+				tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
+				tp->snd_wl2 = TCP_SKB_CB(skb)->ack_seq;
+
+			} else {
+				SOCK_DEBUG(sk, "bad ack\n");
+				return 1;
+			}
+			break;
+
+		case TCP_FIN_WAIT1:
+			if (tp->snd_una == tp->write_seq) {
+				sk->shutdown |= SEND_SHUTDOWN;
+				tcp_set_state(sk, TCP_FIN_WAIT2);
+				if (!sk->dead)
+					sk->state_change(sk);
+				else
+					tcp_reset_msl_timer(sk, TIME_CLOSE, sysctl_tcp_fin_timeout);
+			}
+			break;
+
+		case TCP_CLOSING:	
+			if (tp->snd_una == tp->write_seq) {
+				tcp_time_wait(sk);
+				goto discard;
+			}
+			break;
+
+		case TCP_LAST_ACK:
+			if (tp->snd_una == tp->write_seq) {
+				sk->shutdown = SHUTDOWN_MASK;
+				tcp_set_state(sk,TCP_CLOSE);
+				if (!sk->dead)
+					sk->state_change(sk);
+				goto discard;
+			}
+			break;
+		}
+	} else
+		goto discard;
+
+step6:
+	/* step 6: check the URG bit */
+	tcp_urg(sk, th, len);
+
+	/* step 7: process the segment text */
+	switch (sk->state) {
+	case TCP_CLOSE_WAIT:
+	case TCP_CLOSING:
+		if (!before(TCP_SKB_CB(skb)->seq, tp->fin_seq))
+			break;
+	
+	case TCP_FIN_WAIT1:
+	case TCP_FIN_WAIT2:
+		/* RFC 793 says to queue data in these states,
+		 * RFC 1122 says we MUST send a reset. 
+		 * BSD 4.4 also does reset.
+		 */
+		if ((sk->shutdown & RCV_SHUTDOWN) && sk->dead) {
+			if (after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
+				tcp_reset(sk);
+				return 1;
+			}
+		}
+		
+	case TCP_ESTABLISHED: 
+		queued = tcp_data(skb, sk, len);
+
+		/* This must be after tcp_data() does the skb_pull() to
+		 * remove the header size from skb->len.
+		 */
+		tcp_measure_rcv_mss(sk, skb); 
+		break;
+	}
+
+	tcp_data_snd_check(sk);
+	tcp_ack_snd_check(sk);
+
+	if (!queued) { 
+discard:
+		kfree_skb(skb);
+	}
+	return 0;
+}