Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1739 insertions, 0 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
new file mode 100644
index 00000000000..13c14cb6dee
--- /dev/null
+++ b/net/ipv4/tcp_output.c
@@ -0,0 +1,1739 @@
+/*
+ * 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_output.c,v 1.146 2002/02/01 22:01:04 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	:	Retransmit queue handled by TCP.
+ *				:	Fragmentation on mtu decrease
+ *				:	Segment collapse on retransmit
+ *				:	AF independence
+ *
+ *		Linus Torvalds	:	send_delayed_ack
+ *		David S. Miller	:	Charge memory using the right skb
+ *					during syn/ack processing.
+ *		David S. Miller :	Output engine completely rewritten.
+ *		Andrea Arcangeli:	SYNACK carry ts_recent in tsecr.
+ *		Cacophonix Gaul :	draft-minshall-nagle-01
+ *		J Hadi Salim	:	ECN support
+ *
+ */
+
+#include <net/tcp.h>
+
+#include <linux/compiler.h>
+#include <linux/module.h>
+#include <linux/smp_lock.h>
+
+/* People can turn this off for buggy TCP's found in printers etc. */
+int sysctl_tcp_retrans_collapse = 1;
+
+/* This limits the percentage of the congestion window which we
+ * will allow a single TSO frame to consume.  Building TSO frames
+ * which are too large can cause TCP streams to be bursty.
+ */
+int sysctl_tcp_tso_win_divisor = 8;
+
+static inline void update_send_head(struct sock *sk, struct tcp_sock *tp,
+				    struct sk_buff *skb)
+{
+	sk->sk_send_head = skb->next;
+	if (sk->sk_send_head == (struct sk_buff *)&sk->sk_write_queue)
+		sk->sk_send_head = NULL;
+	tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
+	tcp_packets_out_inc(sk, tp, skb);
+}
+
+/* SND.NXT, if window was not shrunk.
+ * If window has been shrunk, what should we make? It is not clear at all.
+ * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
+ * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
+ * invalid. OK, let's make this for now:
+ */
+static inline __u32 tcp_acceptable_seq(struct sock *sk, struct tcp_sock *tp)
+{
+	if (!before(tp->snd_una+tp->snd_wnd, tp->snd_nxt))
+		return tp->snd_nxt;
+	else
+		return tp->snd_una+tp->snd_wnd;
+}
+
+/* Calculate mss to advertise in SYN segment.
+ * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
+ *
+ * 1. It is independent of path mtu.
+ * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
+ * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
+ *    attached devices, because some buggy hosts are confused by
+ *    large MSS.
+ * 4. We do not make 3, we advertise MSS, calculated from first
+ *    hop device mtu, but allow to raise it to ip_rt_min_advmss.
+ *    This may be overridden via information stored in routing table.
+ * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
+ *    probably even Jumbo".
+ */
+static __u16 tcp_advertise_mss(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct dst_entry *dst = __sk_dst_get(sk);
+	int mss = tp->advmss;
+
+	if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) {
+		mss = dst_metric(dst, RTAX_ADVMSS);
+		tp->advmss = mss;
+	}
+
+	return (__u16)mss;
+}
+
+/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
+ * This is the first part of cwnd validation mechanism. */
+static void tcp_cwnd_restart(struct tcp_sock *tp, struct dst_entry *dst)
+{
+	s32 delta = tcp_time_stamp - tp->lsndtime;
+	u32 restart_cwnd = tcp_init_cwnd(tp, dst);
+	u32 cwnd = tp->snd_cwnd;
+
+	if (tcp_is_vegas(tp)) 
+		tcp_vegas_enable(tp);
+
+	tp->snd_ssthresh = tcp_current_ssthresh(tp);
+	restart_cwnd = min(restart_cwnd, cwnd);
+
+	while ((delta -= tp->rto) > 0 && cwnd > restart_cwnd)
+		cwnd >>= 1;
+	tp->snd_cwnd = max(cwnd, restart_cwnd);
+	tp->snd_cwnd_stamp = tcp_time_stamp;
+	tp->snd_cwnd_used = 0;
+}
+
+static inline void tcp_event_data_sent(struct tcp_sock *tp,
+				       struct sk_buff *skb, struct sock *sk)
+{
+	u32 now = tcp_time_stamp;
+
+	if (!tp->packets_out && (s32)(now - tp->lsndtime) > tp->rto)
+		tcp_cwnd_restart(tp, __sk_dst_get(sk));
+
+	tp->lsndtime = now;
+
+	/* If it is a reply for ato after last received
+	 * packet, enter pingpong mode.
+	 */
+	if ((u32)(now - tp->ack.lrcvtime) < tp->ack.ato)
+		tp->ack.pingpong = 1;
+}
+
+static __inline__ void tcp_event_ack_sent(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	tcp_dec_quickack_mode(tp);
+	tcp_clear_xmit_timer(sk, TCP_TIME_DACK);
+}
+
+/* Determine a window scaling and initial window to offer.
+ * Based on the assumption that the given amount of space
+ * will be offered. Store the results in the tp structure.
+ * NOTE: for smooth operation initial space offering should
+ * be a multiple of mss if possible. We assume here that mss >= 1.
+ * This MUST be enforced by all callers.
+ */
+void tcp_select_initial_window(int __space, __u32 mss,
+			       __u32 *rcv_wnd, __u32 *window_clamp,
+			       int wscale_ok, __u8 *rcv_wscale)
+{
+	unsigned int space = (__space < 0 ? 0 : __space);
+
+	/* If no clamp set the clamp to the max possible scaled window */
+	if (*window_clamp == 0)
+		(*window_clamp) = (65535 << 14);
+	space = min(*window_clamp, space);
+
+	/* Quantize space offering to a multiple of mss if possible. */
+	if (space > mss)
+		space = (space / mss) * mss;
+
+	/* NOTE: offering an initial window larger than 32767
+	 * will break some buggy TCP stacks. We try to be nice.
+	 * If we are not window scaling, then this truncates
+	 * our initial window offering to 32k. There should also
+	 * be a sysctl option to stop being nice.
+	 */
+	(*rcv_wnd) = min(space, MAX_TCP_WINDOW);
+	(*rcv_wscale) = 0;
+	if (wscale_ok) {
+		/* Set window scaling on max possible window
+		 * See RFC1323 for an explanation of the limit to 14 
+		 */
+		space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
+		while (space > 65535 && (*rcv_wscale) < 14) {
+			space >>= 1;
+			(*rcv_wscale)++;
+		}
+	}
+
+	/* Set initial window to value enough for senders,
+	 * following RFC1414. Senders, not following this RFC,
+	 * will be satisfied with 2.
+	 */
+	if (mss > (1<<*rcv_wscale)) {
+		int init_cwnd = 4;
+		if (mss > 1460*3)
+			init_cwnd = 2;
+		else if (mss > 1460)
+			init_cwnd = 3;
+		if (*rcv_wnd > init_cwnd*mss)
+			*rcv_wnd = init_cwnd*mss;
+	}
+
+	/* Set the clamp no higher than max representable value */
+	(*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
+}
+
+/* Chose a new window to advertise, update state in tcp_sock for the
+ * socket, and return result with RFC1323 scaling applied.  The return
+ * value can be stuffed directly into th->window for an outgoing
+ * frame.
+ */
+static __inline__ u16 tcp_select_window(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	u32 cur_win = tcp_receive_window(tp);
+	u32 new_win = __tcp_select_window(sk);
+
+	/* Never shrink the offered window */
+	if(new_win < cur_win) {
+		/* Danger Will Robinson!
+		 * Don't update rcv_wup/rcv_wnd here or else
+		 * we will not be able to advertise a zero
+		 * window in time.  --DaveM
+		 *
+		 * Relax Will Robinson.
+		 */
+		new_win = cur_win;
+	}
+	tp->rcv_wnd = new_win;
+	tp->rcv_wup = tp->rcv_nxt;
+
+	/* Make sure we do not exceed the maximum possible
+	 * scaled window.
+	 */
+	if (!tp->rx_opt.rcv_wscale)
+		new_win = min(new_win, MAX_TCP_WINDOW);
+	else
+		new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
+
+	/* RFC1323 scaling applied */
+	new_win >>= tp->rx_opt.rcv_wscale;
+
+	/* If we advertise zero window, disable fast path. */
+	if (new_win == 0)
+		tp->pred_flags = 0;
+
+	return new_win;
+}
+
+
+/* This routine actually transmits TCP packets queued in by
+ * tcp_do_sendmsg().  This is used by both the initial
+ * transmission and possible later retransmissions.
+ * All SKB's seen here are completely headerless.  It is our
+ * job to build the TCP header, and pass the packet down to
+ * IP so it can do the same plus pass the packet off to the
+ * device.
+ *
+ * We are working here with either a clone of the original
+ * SKB, or a fresh unique copy made by the retransmit engine.
+ */
+static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb)
+{
+	if (skb != NULL) {
+		struct inet_sock *inet = inet_sk(sk);
+		struct tcp_sock *tp = tcp_sk(sk);
+		struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
+		int tcp_header_size = tp->tcp_header_len;
+		struct tcphdr *th;
+		int sysctl_flags;
+		int err;
+
+		BUG_ON(!tcp_skb_pcount(skb));
+
+#define SYSCTL_FLAG_TSTAMPS	0x1
+#define SYSCTL_FLAG_WSCALE	0x2
+#define SYSCTL_FLAG_SACK	0x4
+
+		sysctl_flags = 0;
+		if (tcb->flags & TCPCB_FLAG_SYN) {
+			tcp_header_size = sizeof(struct tcphdr) + TCPOLEN_MSS;
+			if(sysctl_tcp_timestamps) {
+				tcp_header_size += TCPOLEN_TSTAMP_ALIGNED;
+				sysctl_flags |= SYSCTL_FLAG_TSTAMPS;
+			}
+			if(sysctl_tcp_window_scaling) {
+				tcp_header_size += TCPOLEN_WSCALE_ALIGNED;
+				sysctl_flags |= SYSCTL_FLAG_WSCALE;
+			}
+			if(sysctl_tcp_sack) {
+				sysctl_flags |= SYSCTL_FLAG_SACK;
+				if(!(sysctl_flags & SYSCTL_FLAG_TSTAMPS))
+					tcp_header_size += TCPOLEN_SACKPERM_ALIGNED;
+			}
+		} else if (tp->rx_opt.eff_sacks) {
+			/* A SACK is 2 pad bytes, a 2 byte header, plus
+			 * 2 32-bit sequence numbers for each SACK block.
+			 */
+			tcp_header_size += (TCPOLEN_SACK_BASE_ALIGNED +
+					    (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK));
+		}
+		
+		/*
+		 * If the connection is idle and we are restarting,
+		 * then we don't want to do any Vegas calculations
+		 * until we get fresh RTT samples.  So when we
+		 * restart, we reset our Vegas state to a clean
+		 * slate. After we get acks for this flight of
+		 * packets, _then_ we can make Vegas calculations
+		 * again.
+		 */
+		if (tcp_is_vegas(tp) && tcp_packets_in_flight(tp) == 0)
+			tcp_vegas_enable(tp);
+
+		th = (struct tcphdr *) skb_push(skb, tcp_header_size);
+		skb->h.th = th;
+		skb_set_owner_w(skb, sk);
+
+		/* Build TCP header and checksum it. */
+		th->source		= inet->sport;
+		th->dest		= inet->dport;
+		th->seq			= htonl(tcb->seq);
+		th->ack_seq		= htonl(tp->rcv_nxt);
+		*(((__u16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) | tcb->flags);
+		if (tcb->flags & TCPCB_FLAG_SYN) {
+			/* RFC1323: The window in SYN & SYN/ACK segments
+			 * is never scaled.
+			 */
+			th->window	= htons(tp->rcv_wnd);
+		} else {
+			th->window	= htons(tcp_select_window(sk));
+		}
+		th->check		= 0;
+		th->urg_ptr		= 0;
+
+		if (tp->urg_mode &&
+		    between(tp->snd_up, tcb->seq+1, tcb->seq+0xFFFF)) {
+			th->urg_ptr		= htons(tp->snd_up-tcb->seq);
+			th->urg			= 1;
+		}
+
+		if (tcb->flags & TCPCB_FLAG_SYN) {
+			tcp_syn_build_options((__u32 *)(th + 1),
+					      tcp_advertise_mss(sk),
+					      (sysctl_flags & SYSCTL_FLAG_TSTAMPS),
+					      (sysctl_flags & SYSCTL_FLAG_SACK),
+					      (sysctl_flags & SYSCTL_FLAG_WSCALE),
+					      tp->rx_opt.rcv_wscale,
+					      tcb->when,
+		      			      tp->rx_opt.ts_recent);
+		} else {
+			tcp_build_and_update_options((__u32 *)(th + 1),
+						     tp, tcb->when);
+
+			TCP_ECN_send(sk, tp, skb, tcp_header_size);
+		}
+		tp->af_specific->send_check(sk, th, skb->len, skb);
+
+		if (tcb->flags & TCPCB_FLAG_ACK)
+			tcp_event_ack_sent(sk);
+
+		if (skb->len != tcp_header_size)
+			tcp_event_data_sent(tp, skb, sk);
+
+		TCP_INC_STATS(TCP_MIB_OUTSEGS);
+
+		err = tp->af_specific->queue_xmit(skb, 0);
+		if (err <= 0)
+			return err;
+
+		tcp_enter_cwr(tp);
+
+		/* NET_XMIT_CN is special. It does not guarantee,
+		 * that this packet is lost. It tells that device
+		 * is about to start to drop packets or already
+		 * drops some packets of the same priority and
+		 * invokes us to send less aggressively.
+		 */
+		return err == NET_XMIT_CN ? 0 : err;
+	}
+	return -ENOBUFS;
+#undef SYSCTL_FLAG_TSTAMPS
+#undef SYSCTL_FLAG_WSCALE
+#undef SYSCTL_FLAG_SACK
+}
+
+
+/* This routine just queue's the buffer 
+ *
+ * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
+ * otherwise socket can stall.
+ */
+static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	/* Advance write_seq and place onto the write_queue. */
+	tp->write_seq = TCP_SKB_CB(skb)->end_seq;
+	skb_header_release(skb);
+	__skb_queue_tail(&sk->sk_write_queue, skb);
+	sk_charge_skb(sk, skb);
+
+	/* Queue it, remembering where we must start sending. */
+	if (sk->sk_send_head == NULL)
+		sk->sk_send_head = skb;
+}
+
+static inline void tcp_tso_set_push(struct sk_buff *skb)
+{
+	/* Force push to be on for any TSO frames to workaround
+	 * problems with busted implementations like Mac OS-X that
+	 * hold off socket receive wakeups until push is seen.
+	 */
+	if (tcp_skb_pcount(skb) > 1)
+		TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
+}
+
+/* Send _single_ skb sitting at the send head. This function requires
+ * true push pending frames to setup probe timer etc.
+ */
+void tcp_push_one(struct sock *sk, unsigned cur_mss)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *skb = sk->sk_send_head;
+
+	if (tcp_snd_test(tp, skb, cur_mss, TCP_NAGLE_PUSH)) {
+		/* Send it out now. */
+		TCP_SKB_CB(skb)->when = tcp_time_stamp;
+		tcp_tso_set_push(skb);
+		if (!tcp_transmit_skb(sk, skb_clone(skb, sk->sk_allocation))) {
+			sk->sk_send_head = NULL;
+			tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
+			tcp_packets_out_inc(sk, tp, skb);
+			return;
+		}
+	}
+}
+
+void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_std)
+{
+	if (skb->len <= mss_std) {
+		/* Avoid the costly divide in the normal
+		 * non-TSO case.
+		 */
+		skb_shinfo(skb)->tso_segs = 1;
+		skb_shinfo(skb)->tso_size = 0;
+	} else {
+		unsigned int factor;
+
+		factor = skb->len + (mss_std - 1);
+		factor /= mss_std;
+		skb_shinfo(skb)->tso_segs = factor;
+		skb_shinfo(skb)->tso_size = mss_std;
+	}
+}
+
+/* Function to create two new TCP segments.  Shrinks the given segment
+ * to the specified size and appends a new segment with the rest of the
+ * packet to the list.  This won't be called frequently, I hope. 
+ * Remember, these are still headerless SKBs at this point.
+ */
+static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *buff;
+	int nsize;
+	u16 flags;
+
+	nsize = skb_headlen(skb) - len;
+	if (nsize < 0)
+		nsize = 0;
+
+	if (skb_cloned(skb) &&
+	    skb_is_nonlinear(skb) &&
+	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+		return -ENOMEM;
+
+	/* Get a new skb... force flag on. */
+	buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
+	if (buff == NULL)
+		return -ENOMEM; /* We'll just try again later. */
+	sk_charge_skb(sk, buff);
+
+	/* Correct the sequence numbers. */
+	TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
+	TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
+	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
+
+	/* PSH and FIN should only be set in the second packet. */
+	flags = TCP_SKB_CB(skb)->flags;
+	TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
+	TCP_SKB_CB(buff)->flags = flags;
+	TCP_SKB_CB(buff)->sacked =
+		(TCP_SKB_CB(skb)->sacked &
+		 (TCPCB_LOST | TCPCB_EVER_RETRANS | TCPCB_AT_TAIL));
+	TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL;
+
+	if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_HW) {
+		/* Copy and checksum data tail into the new buffer. */
+		buff->csum = csum_partial_copy_nocheck(skb->data + len, skb_put(buff, nsize),
+						       nsize, 0);
+
+		skb_trim(skb, len);
+
+		skb->csum = csum_block_sub(skb->csum, buff->csum, len);
+	} else {
+		skb->ip_summed = CHECKSUM_HW;
+		skb_split(skb, buff, len);
+	}
+
+	buff->ip_summed = skb->ip_summed;
+
+	/* Looks stupid, but our code really uses when of
+	 * skbs, which it never sent before. --ANK
+	 */
+	TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
+
+	if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
+		tp->lost_out -= tcp_skb_pcount(skb);
+		tp->left_out -= tcp_skb_pcount(skb);
+	}
+
+	/* Fix up tso_factor for both original and new SKB.  */
+	tcp_set_skb_tso_segs(skb, tp->mss_cache_std);
+	tcp_set_skb_tso_segs(buff, tp->mss_cache_std);
+
+	if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
+		tp->lost_out += tcp_skb_pcount(skb);
+		tp->left_out += tcp_skb_pcount(skb);
+	}
+
+	if (TCP_SKB_CB(buff)->sacked&TCPCB_LOST) {
+		tp->lost_out += tcp_skb_pcount(buff);
+		tp->left_out += tcp_skb_pcount(buff);
+	}
+
+	/* Link BUFF into the send queue. */
+	__skb_append(skb, buff);
+
+	return 0;
+}
+
+/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
+ * eventually). The difference is that pulled data not copied, but
+ * immediately discarded.
+ */
+static unsigned char *__pskb_trim_head(struct sk_buff *skb, int len)
+{
+	int i, k, eat;
+
+	eat = len;
+	k = 0;
+	for (i=0; i<skb_shinfo(skb)->nr_frags; i++) {
+		if (skb_shinfo(skb)->frags[i].size <= eat) {
+			put_page(skb_shinfo(skb)->frags[i].page);
+			eat -= skb_shinfo(skb)->frags[i].size;
+		} else {
+			skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
+			if (eat) {
+				skb_shinfo(skb)->frags[k].page_offset += eat;
+				skb_shinfo(skb)->frags[k].size -= eat;
+				eat = 0;
+			}
+			k++;
+		}
+	}
+	skb_shinfo(skb)->nr_frags = k;
+
+	skb->tail = skb->data;
+	skb->data_len -= len;
+	skb->len = skb->data_len;
+	return skb->tail;
+}
+
+int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
+{
+	if (skb_cloned(skb) &&
+	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+		return -ENOMEM;
+
+	if (len <= skb_headlen(skb)) {
+		__skb_pull(skb, len);
+	} else {
+		if (__pskb_trim_head(skb, len-skb_headlen(skb)) == NULL)
+			return -ENOMEM;
+	}
+
+	TCP_SKB_CB(skb)->seq += len;
+	skb->ip_summed = CHECKSUM_HW;
+
+	skb->truesize	     -= len;
+	sk->sk_wmem_queued   -= len;
+	sk->sk_forward_alloc += len;
+	sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
+
+	/* Any change of skb->len requires recalculation of tso
+	 * factor and mss.
+	 */
+	if (tcp_skb_pcount(skb) > 1)
+		tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb));
+
+	return 0;
+}
+
+/* This function synchronize snd mss to current pmtu/exthdr set.
+
+   tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
+   for TCP options, but includes only bare TCP header.
+
+   tp->rx_opt.mss_clamp is mss negotiated at connection setup.
+   It is minumum of user_mss and mss received with SYN.
+   It also does not include TCP options.
+
+   tp->pmtu_cookie is last pmtu, seen by this function.
+
+   tp->mss_cache is current effective sending mss, including
+   all tcp options except for SACKs. It is evaluated,
+   taking into account current pmtu, but never exceeds
+   tp->rx_opt.mss_clamp.
+
+   NOTE1. rfc1122 clearly states that advertised MSS
+   DOES NOT include either tcp or ip options.
+
+   NOTE2. tp->pmtu_cookie and tp->mss_cache are READ ONLY outside
+   this function.			--ANK (980731)
+ */
+
+unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	int mss_now;
+
+	/* Calculate base mss without TCP options:
+	   It is MMS_S - sizeof(tcphdr) of rfc1122
+	 */
+	mss_now = pmtu - tp->af_specific->net_header_len - sizeof(struct tcphdr);
+
+	/* Clamp it (mss_clamp does not include tcp options) */
+	if (mss_now > tp->rx_opt.mss_clamp)
+		mss_now = tp->rx_opt.mss_clamp;
+
+	/* Now subtract optional transport overhead */
+	mss_now -= tp->ext_header_len;
+
+	/* Then reserve room for full set of TCP options and 8 bytes of data */
+	if (mss_now < 48)
+		mss_now = 48;
+
+	/* Now subtract TCP options size, not including SACKs */
+	mss_now -= tp->tcp_header_len - sizeof(struct tcphdr);
+
+	/* Bound mss with half of window */
+	if (tp->max_window && mss_now > (tp->max_window>>1))
+		mss_now = max((tp->max_window>>1), 68U - tp->tcp_header_len);
+
+	/* And store cached results */
+	tp->pmtu_cookie = pmtu;
+	tp->mss_cache = tp->mss_cache_std = mss_now;
+
+	return mss_now;
+}
+
+/* Compute the current effective MSS, taking SACKs and IP options,
+ * and even PMTU discovery events into account.
+ *
+ * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
+ * cannot be large. However, taking into account rare use of URG, this
+ * is not a big flaw.
+ */
+
+unsigned int tcp_current_mss(struct sock *sk, int large)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct dst_entry *dst = __sk_dst_get(sk);
+	unsigned int do_large, mss_now;
+
+	mss_now = tp->mss_cache_std;
+	if (dst) {
+		u32 mtu = dst_mtu(dst);
+		if (mtu != tp->pmtu_cookie)
+			mss_now = tcp_sync_mss(sk, mtu);
+	}
+
+	do_large = (large &&
+		    (sk->sk_route_caps & NETIF_F_TSO) &&
+		    !tp->urg_mode);
+
+	if (do_large) {
+		unsigned int large_mss, factor, limit;
+
+		large_mss = 65535 - tp->af_specific->net_header_len -
+			tp->ext_header_len - tp->tcp_header_len;
+
+		if (tp->max_window && large_mss > (tp->max_window>>1))
+			large_mss = max((tp->max_window>>1),
+					68U - tp->tcp_header_len);
+
+		factor = large_mss / mss_now;
+
+		/* Always keep large mss multiple of real mss, but
+		 * do not exceed 1/tso_win_divisor of the congestion window
+		 * so we can keep the ACK clock ticking and minimize
+		 * bursting.
+		 */
+		limit = tp->snd_cwnd;
+		if (sysctl_tcp_tso_win_divisor)
+			limit /= sysctl_tcp_tso_win_divisor;
+		limit = max(1U, limit);
+		if (factor > limit)
+			factor = limit;
+
+		tp->mss_cache = mss_now * factor;
+
+		mss_now = tp->mss_cache;
+	}
+
+	if (tp->rx_opt.eff_sacks)
+		mss_now -= (TCPOLEN_SACK_BASE_ALIGNED +
+			    (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK));
+	return mss_now;
+}
+
+/* This routine writes packets to the network.  It advances the
+ * send_head.  This happens as incoming acks open up the remote
+ * window for us.
+ *
+ * Returns 1, if no segments are in flight and we have queued segments, but
+ * cannot send anything now because of SWS or another problem.
+ */
+int tcp_write_xmit(struct sock *sk, int nonagle)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	unsigned int mss_now;
+
+	/* If we are closed, the bytes will have to remain here.
+	 * In time closedown will finish, we empty the write queue and all
+	 * will be happy.
+	 */
+	if (sk->sk_state != TCP_CLOSE) {
+		struct sk_buff *skb;
+		int sent_pkts = 0;
+
+		/* Account for SACKS, we may need to fragment due to this.
+		 * It is just like the real MSS changing on us midstream.
+		 * We also handle things correctly when the user adds some
+		 * IP options mid-stream.  Silly to do, but cover it.
+		 */
+		mss_now = tcp_current_mss(sk, 1);
+
+		while ((skb = sk->sk_send_head) &&
+		       tcp_snd_test(tp, skb, mss_now,
+			       	    tcp_skb_is_last(sk, skb) ? nonagle :
+				    			       TCP_NAGLE_PUSH)) {
+			if (skb->len > mss_now) {
+				if (tcp_fragment(sk, skb, mss_now))
+					break;
+			}
+
+			TCP_SKB_CB(skb)->when = tcp_time_stamp;
+			tcp_tso_set_push(skb);
+			if (tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC)))
+				break;
+
+			/* Advance the send_head.  This one is sent out.
+			 * This call will increment packets_out.
+			 */
+			update_send_head(sk, tp, skb);
+
+			tcp_minshall_update(tp, mss_now, skb);
+			sent_pkts = 1;
+		}
+
+		if (sent_pkts) {
+			tcp_cwnd_validate(sk, tp);
+			return 0;
+		}
+
+		return !tp->packets_out && sk->sk_send_head;
+	}
+	return 0;
+}
+
+/* This function returns the amount that we can raise the
+ * usable window based on the following constraints
+ *  
+ * 1. The window can never be shrunk once it is offered (RFC 793)
+ * 2. We limit memory per socket
+ *
+ * RFC 1122:
+ * "the suggested [SWS] avoidance algorithm for the receiver is to keep
+ *  RECV.NEXT + RCV.WIN fixed until:
+ *  RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
+ *
+ * i.e. don't raise the right edge of the window until you can raise
+ * it at least MSS bytes.
+ *
+ * Unfortunately, the recommended algorithm breaks header prediction,
+ * since header prediction assumes th->window stays fixed.
+ *
+ * Strictly speaking, keeping th->window fixed violates the receiver
+ * side SWS prevention criteria. The problem is that under this rule
+ * a stream of single byte packets will cause the right side of the
+ * window to always advance by a single byte.
+ * 
+ * Of course, if the sender implements sender side SWS prevention
+ * then this will not be a problem.
+ * 
+ * BSD seems to make the following compromise:
+ * 
+ *	If the free space is less than the 1/4 of the maximum
+ *	space available and the free space is less than 1/2 mss,
+ *	then set the window to 0.
+ *	[ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
+ *	Otherwise, just prevent the window from shrinking
+ *	and from being larger than the largest representable value.
+ *
+ * This prevents incremental opening of the window in the regime
+ * where TCP is limited by the speed of the reader side taking
+ * data out of the TCP receive queue. It does nothing about
+ * those cases where the window is constrained on the sender side
+ * because the pipeline is full.
+ *
+ * BSD also seems to "accidentally" limit itself to windows that are a
+ * multiple of MSS, at least until the free space gets quite small.
+ * This would appear to be a side effect of the mbuf implementation.
+ * Combining these two algorithms results in the observed behavior
+ * of having a fixed window size at almost all times.
+ *
+ * Below we obtain similar behavior by forcing the offered window to
+ * a multiple of the mss when it is feasible to do so.
+ *
+ * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
+ * Regular options like TIMESTAMP are taken into account.
+ */
+u32 __tcp_select_window(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	/* MSS for the peer's data.  Previous verions used mss_clamp
+	 * here.  I don't know if the value based on our guesses
+	 * of peer's MSS is better for the performance.  It's more correct
+	 * but may be worse for the performance because of rcv_mss
+	 * fluctuations.  --SAW  1998/11/1
+	 */
+	int mss = tp->ack.rcv_mss;
+	int free_space = tcp_space(sk);
+	int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk));
+	int window;
+
+	if (mss > full_space)
+		mss = full_space; 
+
+	if (free_space < full_space/2) {
+		tp->ack.quick = 0;
+
+		if (tcp_memory_pressure)
+			tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U*tp->advmss);
+
+		if (free_space < mss)
+			return 0;
+	}
+
+	if (free_space > tp->rcv_ssthresh)
+		free_space = tp->rcv_ssthresh;
+
+	/* Don't do rounding if we are using window scaling, since the
+	 * scaled window will not line up with the MSS boundary anyway.
+	 */
+	window = tp->rcv_wnd;
+	if (tp->rx_opt.rcv_wscale) {
+		window = free_space;
+
+		/* Advertise enough space so that it won't get scaled away.
+		 * Import case: prevent zero window announcement if
+		 * 1<<rcv_wscale > mss.
+		 */
+		if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
+			window = (((window >> tp->rx_opt.rcv_wscale) + 1)
+				  << tp->rx_opt.rcv_wscale);
+	} else {
+		/* Get the largest window that is a nice multiple of mss.
+		 * Window clamp already applied above.
+		 * If our current window offering is within 1 mss of the
+		 * free space we just keep it. This prevents the divide
+		 * and multiply from happening most of the time.
+		 * We also don't do any window rounding when the free space
+		 * is too small.
+		 */
+		if (window <= free_space - mss || window > free_space)
+			window = (free_space/mss)*mss;
+	}
+
+	return window;
+}
+
+/* Attempt to collapse two adjacent SKB's during retransmission. */
+static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int mss_now)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *next_skb = skb->next;
+
+	/* The first test we must make is that neither of these two
+	 * SKB's are still referenced by someone else.
+	 */
+	if (!skb_cloned(skb) && !skb_cloned(next_skb)) {
+		int skb_size = skb->len, next_skb_size = next_skb->len;
+		u16 flags = TCP_SKB_CB(skb)->flags;
+
+		/* Also punt if next skb has been SACK'd. */
+		if(TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED)
+			return;
+
+		/* Next skb is out of window. */
+		if (after(TCP_SKB_CB(next_skb)->end_seq, tp->snd_una+tp->snd_wnd))
+			return;
+
+		/* Punt if not enough space exists in the first SKB for
+		 * the data in the second, or the total combined payload
+		 * would exceed the MSS.
+		 */
+		if ((next_skb_size > skb_tailroom(skb)) ||
+		    ((skb_size + next_skb_size) > mss_now))
+			return;
+
+		BUG_ON(tcp_skb_pcount(skb) != 1 ||
+		       tcp_skb_pcount(next_skb) != 1);
+
+		/* Ok.  We will be able to collapse the packet. */
+		__skb_unlink(next_skb, next_skb->list);
+
+		memcpy(skb_put(skb, next_skb_size), next_skb->data, next_skb_size);
+
+		if (next_skb->ip_summed == CHECKSUM_HW)
+			skb->ip_summed = CHECKSUM_HW;
+
+		if (skb->ip_summed != CHECKSUM_HW)
+			skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
+
+		/* Update sequence range on original skb. */
+		TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
+
+		/* Merge over control information. */
+		flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */
+		TCP_SKB_CB(skb)->flags = flags;
+
+		/* All done, get rid of second SKB and account for it so
+		 * packet counting does not break.
+		 */
+		TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked&(TCPCB_EVER_RETRANS|TCPCB_AT_TAIL);
+		if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS)
+			tp->retrans_out -= tcp_skb_pcount(next_skb);
+		if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST) {
+			tp->lost_out -= tcp_skb_pcount(next_skb);
+			tp->left_out -= tcp_skb_pcount(next_skb);
+		}
+		/* Reno case is special. Sigh... */
+		if (!tp->rx_opt.sack_ok && tp->sacked_out) {
+			tcp_dec_pcount_approx(&tp->sacked_out, next_skb);
+			tp->left_out -= tcp_skb_pcount(next_skb);
+		}
+
+		/* Not quite right: it can be > snd.fack, but
+		 * it is better to underestimate fackets.
+		 */
+		tcp_dec_pcount_approx(&tp->fackets_out, next_skb);
+		tcp_packets_out_dec(tp, next_skb);
+		sk_stream_free_skb(sk, next_skb);
+	}
+}
+
+/* Do a simple retransmit without using the backoff mechanisms in
+ * tcp_timer. This is used for path mtu discovery. 
+ * The socket is already locked here.
+ */ 
+void tcp_simple_retransmit(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *skb;
+	unsigned int mss = tcp_current_mss(sk, 0);
+	int lost = 0;
+
+	sk_stream_for_retrans_queue(skb, sk) {
+		if (skb->len > mss && 
+		    !(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
+			if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
+				TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
+				tp->retrans_out -= tcp_skb_pcount(skb);
+			}
+			if (!(TCP_SKB_CB(skb)->sacked&TCPCB_LOST)) {
+				TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+				tp->lost_out += tcp_skb_pcount(skb);
+				lost = 1;
+			}
+		}
+	}
+
+	if (!lost)
+		return;
+
+	tcp_sync_left_out(tp);
+
+ 	/* Don't muck with the congestion window here.
+	 * Reason is that we do not increase amount of _data_
+	 * in network, but units changed and effective
+	 * cwnd/ssthresh really reduced now.
+	 */
+	if (tp->ca_state != TCP_CA_Loss) {
+		tp->high_seq = tp->snd_nxt;
+		tp->snd_ssthresh = tcp_current_ssthresh(tp);
+		tp->prior_ssthresh = 0;
+		tp->undo_marker = 0;
+		tcp_set_ca_state(tp, TCP_CA_Loss);
+	}
+	tcp_xmit_retransmit_queue(sk);
+}
+
+/* This retransmits one SKB.  Policy decisions and retransmit queue
+ * state updates are done by the caller.  Returns non-zero if an
+ * error occurred which prevented the send.
+ */
+int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+ 	unsigned int cur_mss = tcp_current_mss(sk, 0);
+	int err;
+
+	/* Do not sent more than we queued. 1/4 is reserved for possible
+	 * copying overhead: frgagmentation, tunneling, mangling etc.
+	 */
+	if (atomic_read(&sk->sk_wmem_alloc) >
+	    min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
+		return -EAGAIN;
+
+	if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
+		if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
+			BUG();
+
+		if (sk->sk_route_caps & NETIF_F_TSO) {
+			sk->sk_route_caps &= ~NETIF_F_TSO;
+			sock_set_flag(sk, SOCK_NO_LARGESEND);
+			tp->mss_cache = tp->mss_cache_std;
+		}
+
+		if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
+			return -ENOMEM;
+	}
+
+	/* If receiver has shrunk his window, and skb is out of
+	 * new window, do not retransmit it. The exception is the
+	 * case, when window is shrunk to zero. In this case
+	 * our retransmit serves as a zero window probe.
+	 */
+	if (!before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)
+	    && TCP_SKB_CB(skb)->seq != tp->snd_una)
+		return -EAGAIN;
+
+	if (skb->len > cur_mss) {
+		int old_factor = tcp_skb_pcount(skb);
+		int new_factor;
+
+		if (tcp_fragment(sk, skb, cur_mss))
+			return -ENOMEM; /* We'll try again later. */
+
+		/* New SKB created, account for it. */
+		new_factor = tcp_skb_pcount(skb);
+		tp->packets_out -= old_factor - new_factor;
+		tp->packets_out += tcp_skb_pcount(skb->next);
+	}
+
+	/* Collapse two adjacent packets if worthwhile and