Linux-2.6.12-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!
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
new file mode 100644
index 0000000..13c14cb
--- /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 we can. */
+ if(!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) &&
+ (skb->len < (cur_mss >> 1)) &&
+ (skb->next != sk->sk_send_head) &&
+ (skb->next != (struct sk_buff *)&sk->sk_write_queue) &&
+ (skb_shinfo(skb)->nr_frags == 0 && skb_shinfo(skb->next)->nr_frags == 0) &&
+ (tcp_skb_pcount(skb) == 1 && tcp_skb_pcount(skb->next) == 1) &&
+ (sysctl_tcp_retrans_collapse != 0))
+ tcp_retrans_try_collapse(sk, skb, cur_mss);
+
+ if(tp->af_specific->rebuild_header(sk))
+ return -EHOSTUNREACH; /* Routing failure or similar. */
+
+ /* Some Solaris stacks overoptimize and ignore the FIN on a
+ * retransmit when old data is attached. So strip it off
+ * since it is cheap to do so and saves bytes on the network.
+ */
+ if(skb->len > 0 &&
+ (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) &&
+ tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) {
+ if (!pskb_trim(skb, 0)) {
+ TCP_SKB_CB(skb)->seq = TCP_SKB_CB(skb)->end_seq - 1;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
+ skb->ip_summed = CHECKSUM_NONE;
+ skb->csum = 0;
+ }
+ }
+
+ /* Make a copy, if the first transmission SKB clone we made
+ * is still in somebody's hands, else make a clone.
+ */
+ TCP_SKB_CB(skb)->when = tcp_time_stamp;
+ tcp_tso_set_push(skb);
+
+ err = tcp_transmit_skb(sk, (skb_cloned(skb) ?
+ pskb_copy(skb, GFP_ATOMIC):
+ skb_clone(skb, GFP_ATOMIC)));
+
+ if (err == 0) {
+ /* Update global TCP statistics. */
+ TCP_INC_STATS(TCP_MIB_RETRANSSEGS);
+
+ tp->total_retrans++;
+
+#if FASTRETRANS_DEBUG > 0
+ if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
+ if (net_ratelimit())
+ printk(KERN_DEBUG "retrans_out leaked.\n");
+ }
+#endif
+ TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
+ tp->retrans_out += tcp_skb_pcount(skb);
+
+ /* Save stamp of the first retransmit. */
+ if (!tp->retrans_stamp)
+ tp->retrans_stamp = TCP_SKB_CB(skb)->when;
+
+ tp->undo_retrans++;
+
+ /* snd_nxt is stored to detect loss of retransmitted segment,
+ * see tcp_input.c tcp_sacktag_write_queue().
+ */
+ TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
+ }
+ return err;
+}
+
+/* This gets called after a retransmit timeout, and the initially
+ * retransmitted data is acknowledged. It tries to continue
+ * resending the rest of the retransmit queue, until either
+ * we've sent it all or the congestion window limit is reached.
+ * If doing SACK, the first ACK which comes back for a timeout
+ * based retransmit packet might feed us FACK information again.
+ * If so, we use it to avoid unnecessarily retransmissions.
+ */
+void tcp_xmit_retransmit_queue(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+ int packet_cnt = tp->lost_out;
+
+ /* First pass: retransmit lost packets. */
+ if (packet_cnt) {
+ sk_stream_for_retrans_queue(skb, sk) {
+ __u8 sacked = TCP_SKB_CB(skb)->sacked;
+
+ /* Assume this retransmit will generate
+ * only one packet for congestion window
+ * calculation purposes. This works because
+ * tcp_retransmit_skb() will chop up the
+ * packet to be MSS sized and all the
+ * packet counting works out.
+ */
+ if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
+ return;
+
+ if (sacked&TCPCB_LOST) {
+ if (!(sacked&(TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) {
+ if (tcp_retransmit_skb(sk, skb))
+ return;
+ if (tp->ca_state != TCP_CA_Loss)
+ NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS);
+ else
+ NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS);
+
+ if (skb ==
+ skb_peek(&sk->sk_write_queue))
+ tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
+ }
+
+ packet_cnt -= tcp_skb_pcount(skb);
+ if (packet_cnt <= 0)
+ break;
+ }
+ }
+ }
+
+ /* OK, demanded retransmission is finished. */
+
+ /* Forward retransmissions are possible only during Recovery. */
+ if (tp->ca_state != TCP_CA_Recovery)
+ return;
+
+ /* No forward retransmissions in Reno are possible. */
+ if (!tp->rx_opt.sack_ok)
+ return;
+
+ /* Yeah, we have to make difficult choice between forward transmission
+ * and retransmission... Both ways have their merits...
+ *
+ * For now we do not retransmit anything, while we have some new
+ * segments to send.
+ */
+
+ if (tcp_may_send_now(sk, tp))
+ return;
+
+ packet_cnt = 0;
+
+ sk_stream_for_retrans_queue(skb, sk) {
+ /* Similar to the retransmit loop above we
+ * can pretend that the retransmitted SKB
+ * we send out here will be composed of one
+ * real MSS sized packet because tcp_retransmit_skb()
+ * will fragment it if necessary.
+ */
+ if (++packet_cnt > tp->fackets_out)
+ break;
+
+ if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
+ break;
+
+ if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS)
+ continue;
+
+ /* Ok, retransmit it. */
+ if (tcp_retransmit_skb(sk, skb))
+ break;
+
+ if (skb == skb_peek(&sk->sk_write_queue))
+ tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
+
+ NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS);
+ }
+}
+
+
+/* Send a fin. The caller locks the socket for us. This cannot be
+ * allowed to fail queueing a FIN frame under any circumstances.
+ */
+void tcp_send_fin(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb = skb_peek_tail(&sk->sk_write_queue);
+ int mss_now;
+
+ /* Optimization, tack on the FIN if we have a queue of
+ * unsent frames. But be careful about outgoing SACKS
+ * and IP options.
+ */
+ mss_now = tcp_current_mss(sk, 1);
+
+ if (sk->sk_send_head != NULL) {
+ TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN;
+ TCP_SKB_CB(skb)->end_seq++;
+ tp->write_seq++;
+ } else {
+ /* Socket is locked, keep trying until memory is available. */
+ for (;;) {
+ skb = alloc_skb(MAX_TCP_HEADER, GFP_KERNEL);
+ if (skb)
+ break;
+ yield();
+ }
+
+ /* Reserve space for headers and prepare control bits. */
+ skb_reserve(skb, MAX_TCP_HEADER);
+ skb->csum = 0;
+ TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_FIN);
+ TCP_SKB_CB(skb)->sacked = 0;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
+
+ /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
+ TCP_SKB_CB(skb)->seq = tp->write_seq;
+ TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
+ tcp_queue_skb(sk, skb);
+ }
+ __tcp_push_pending_frames(sk, tp, mss_now, TCP_NAGLE_OFF);
+}
+
+/* We get here when a process closes a file descriptor (either due to
+ * an explicit close() or as a byproduct of exit()'ing) and there
+ * was unread data in the receive queue. This behavior is recommended
+ * by draft-ietf-tcpimpl-prob-03.txt section 3.10. -DaveM
+ */
+void tcp_send_active_reset(struct sock *sk, int priority)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+
+ /* NOTE: No TCP options attached and we never retransmit this. */
+ skb = alloc_skb(MAX_TCP_HEADER, priority);
+ if (!skb) {
+ NET_INC_STATS(LINUX_MIB_TCPABORTFAILED);
+ return;
+ }
+
+ /* Reserve space for headers and prepare control bits. */
+ skb_reserve(skb, MAX_TCP_HEADER);
+ skb->csum = 0;
+ TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_RST);
+ TCP_SKB_CB(skb)->sacked = 0;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
+
+ /* Send it off. */
+ TCP_SKB_CB(skb)->seq = tcp_acceptable_seq(sk, tp);
+ TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
+ TCP_SKB_CB(skb)->when = tcp_time_stamp;
+ if (tcp_transmit_skb(sk, skb))
+ NET_INC_STATS(LINUX_MIB_TCPABORTFAILED);
+}
+
+/* WARNING: This routine must only be called when we have already sent
+ * a SYN packet that crossed the incoming SYN that caused this routine
+ * to get called. If this assumption fails then the initial rcv_wnd
+ * and rcv_wscale values will not be correct.
+ */
+int tcp_send_synack(struct sock *sk)
+{
+ struct sk_buff* skb;
+
+ skb = skb_peek(&sk->sk_write_queue);
+ if (skb == NULL || !(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_SYN)) {
+ printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n");
+ return -EFAULT;
+ }
+ if (!(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_ACK)) {
+ if (skb_cloned(skb)) {
+ struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
+ if (nskb == NULL)
+ return -ENOMEM;
+ __skb_unlink(skb, &sk->sk_write_queue);
+ skb_header_release(nskb);
+ __skb_queue_head(&sk->sk_write_queue, nskb);
+ sk_stream_free_skb(sk, skb);
+ sk_charge_skb(sk, nskb);
+ skb = nskb;
+ }
+
+ TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK;
+ TCP_ECN_send_synack(tcp_sk(sk), skb);
+ }
+ TCP_SKB_CB(skb)->when = tcp_time_stamp;
+ return tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC));
+}
+
+/*
+ * Prepare a SYN-ACK.
+ */
+struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
+ struct open_request *req)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct tcphdr *th;
+ int tcp_header_size;
+ struct sk_buff *skb;
+
+ skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC);
+ if (skb == NULL)
+ return NULL;
+
+ /* Reserve space for headers. */
+ skb_reserve(skb, MAX_TCP_HEADER);
+
+ skb->dst = dst_clone(dst);
+
+ tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS +
+ (req->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) +
+ (req->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) +
+ /* SACK_PERM is in the place of NOP NOP of TS */
+ ((req->sack_ok && !req->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0));
+ skb->h.th = th = (struct tcphdr *) skb_push(skb, tcp_header_size);
+
+ memset(th, 0, sizeof(struct tcphdr));
+ th->syn = 1;
+ th->ack = 1;
+ if (dst->dev->features&NETIF_F_TSO)
+ req->ecn_ok = 0;
+ TCP_ECN_make_synack(req, th);
+ th->source = inet_sk(sk)->sport;
+ th->dest = req->rmt_port;
+ TCP_SKB_CB(skb)->seq = req->snt_isn;
+ TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
+ TCP_SKB_CB(skb)->sacked = 0;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
+ th->seq = htonl(TCP_SKB_CB(skb)->seq);
+ th->ack_seq = htonl(req->rcv_isn + 1);
+ if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
+ __u8 rcv_wscale;
+ /* Set this up on the first call only */
+ req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
+ /* tcp_full_space because it is guaranteed to be the first packet */
+ tcp_select_initial_window(tcp_full_space(sk),
+ dst_metric(dst, RTAX_ADVMSS) - (req->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
+ &req->rcv_wnd,
+ &req->window_clamp,
+ req->wscale_ok,
+ &rcv_wscale);
+ req->rcv_wscale = rcv_wscale;
+ }
+
+ /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
+ th->window = htons(req->rcv_wnd);
+
+ TCP_SKB_CB(skb)->when = tcp_time_stamp;
+ tcp_syn_build_options((__u32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), req->tstamp_ok,
+ req->sack_ok, req->wscale_ok, req->rcv_wscale,
+ TCP_SKB_CB(skb)->when,
+ req->ts_recent);
+
+ skb->csum = 0;
+ th->doff = (tcp_header_size >> 2);
+ TCP_INC_STATS(TCP_MIB_OUTSEGS);
+ return skb;
+}
+
+/*
+ * Do all connect socket setups that can be done AF independent.
+ */
+static inline void tcp_connect_init(struct sock *sk)
+{
+ struct dst_entry *dst = __sk_dst_get(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ __u8 rcv_wscale;
+
+ /* We'll fix this up when we get a response from the other end.
+ * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
+ */
+ tp->tcp_header_len = sizeof(struct tcphdr) +
+ (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
+
+ /* If user gave his TCP_MAXSEG, record it to clamp */
+ if (tp->rx_opt.user_mss)
+ tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
+ tp->max_window = 0;
+ tcp_sync_mss(sk, dst_mtu(dst));
+
+ if (!tp->window_clamp)
+ tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
+ tp->advmss = dst_metric(dst, RTAX_ADVMSS);
+ tcp_initialize_rcv_mss(sk);
+ tcp_ca_init(tp);
+
+ tcp_select_initial_window(tcp_full_space(sk),
+ tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
+ &tp->rcv_wnd,
+ &tp->window_clamp,
+ sysctl_tcp_window_scaling,
+ &rcv_wscale);
+
+ tp->rx_opt.rcv_wscale = rcv_wscale;
+ tp->rcv_ssthresh = tp->rcv_wnd;
+
+ sk->sk_err = 0;
+ sock_reset_flag(sk, SOCK_DONE);
+ tp->snd_wnd = 0;
+ tcp_init_wl(tp, tp->write_seq, 0);
+ tp->snd_una = tp->write_seq;
+ tp->snd_sml = tp->write_seq;
+ tp->rcv_nxt = 0;
+ tp->rcv_wup = 0;
+ tp->copied_seq = 0;
+
+ tp->rto = TCP_TIMEOUT_INIT;
+ tp->retransmits = 0;
+ tcp_clear_retrans(tp);
+}
+
+/*
+ * Build a SYN and send it off.
+ */
+int tcp_connect(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *buff;
+
+ tcp_connect_init(sk);
+
+ buff = alloc_skb(MAX_TCP_HEADER + 15, sk->sk_allocation);
+ if (unlikely(buff == NULL))
+ return -ENOBUFS;
+
+ /* Reserve space for headers. */
+ skb_reserve(buff, MAX_TCP_HEADER);
+
+ TCP_SKB_CB(buff)->flags = TCPCB_FLAG_SYN;
+ TCP_ECN_send_syn(sk, tp, buff);
+ TCP_SKB_CB(buff)->sacked = 0;
+ skb_shinfo(buff)->tso_segs = 1;
+ skb_shinfo(buff)->tso_size = 0;
+ buff->csum = 0;
+ TCP_SKB_CB(buff)->seq = tp->write_seq++;
+ TCP_SKB_CB(buff)->end_seq = tp->write_seq;
+ tp->snd_nxt = tp->write_seq;
+ tp->pushed_seq = tp->write_seq;
+ tcp_ca_init(tp);
+
+ /* Send it off. */
+ TCP_SKB_CB(buff)->when = tcp_time_stamp;
+ tp->retrans_stamp = TCP_SKB_CB(buff)->when;
+ skb_header_release(buff);
+ __skb_queue_tail(&sk->sk_write_queue, buff);
+ sk_charge_skb(sk, buff);
+ tp->packets_out += tcp_skb_pcount(buff);
+ tcp_transmit_skb(sk, skb_clone(buff, GFP_KERNEL));
+ TCP_INC_STATS(TCP_MIB_ACTIVEOPENS);
+
+ /* Timer for repeating the SYN until an answer. */
+ tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
+ return 0;
+}
+
+/* Send out a delayed ack, the caller does the policy checking
+ * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
+ * for details.
+ */
+void tcp_send_delayed_ack(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int ato = tp->ack.ato;
+ unsigned long timeout;
+
+ if (ato > TCP_DELACK_MIN) {
+ int max_ato = HZ/2;
+
+ if (tp->ack.pingpong || (tp->ack.pending&TCP_ACK_PUSHED))
+ max_ato = TCP_DELACK_MAX;
+
+ /* Slow path, intersegment interval is "high". */
+
+ /* If some rtt estimate is known, use it to bound delayed ack.
+ * Do not use tp->rto here, use results of rtt measurements
+ * directly.
+ */
+ if (tp->srtt) {
+ int rtt = max(tp->srtt>>3, TCP_DELACK_MIN);
+
+ if (rtt < max_ato)
+ max_ato = rtt;
+ }
+
+ ato = min(ato, max_ato);
+ }
+
+ /* Stay within the limit we were given */
+ timeout = jiffies + ato;
+
+ /* Use new timeout only if there wasn't a older one earlier. */
+ if (tp->ack.pending&TCP_ACK_TIMER) {
+ /* If delack timer was blocked or is about to expire,
+ * send ACK now.
+ */
+ if (tp->ack.blocked || time_before_eq(tp->ack.timeout, jiffies+(ato>>2))) {
+ tcp_send_ack(sk);
+ return;
+ }
+
+ if (!time_before(timeout, tp->ack.timeout))
+ timeout = tp->ack.timeout;
+ }
+ tp->ack.pending |= TCP_ACK_SCHED|TCP_ACK_TIMER;
+ tp->ack.timeout = timeout;
+ sk_reset_timer(sk, &tp->delack_timer, timeout);
+}
+
+/* This routine sends an ack and also updates the window. */
+void tcp_send_ack(struct sock *sk)
+{
+ /* If we have been reset, we may not send again. */
+ if (sk->sk_state != TCP_CLOSE) {
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *buff;
+
+ /* We are not putting this on the write queue, so
+ * tcp_transmit_skb() will set the ownership to this
+ * sock.
+ */
+ buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
+ if (buff == NULL) {
+ tcp_schedule_ack(tp);
+ tp->ack.ato = TCP_ATO_MIN;
+ tcp_reset_xmit_timer(sk, TCP_TIME_DACK, TCP_DELACK_MAX);
+ return;
+ }
+
+ /* Reserve space for headers and prepare control bits. */
+ skb_reserve(buff, MAX_TCP_HEADER);
+ buff->csum = 0;
+ TCP_SKB_CB(buff)->flags = TCPCB_FLAG_ACK;
+ TCP_SKB_CB(buff)->sacked = 0;
+ skb_shinfo(buff)->tso_segs = 1;
+ skb_shinfo(buff)->tso_size = 0;
+
+ /* Send it off, this clears delayed acks for us. */
+ TCP_SKB_CB(buff)->seq = TCP_SKB_CB(buff)->end_seq = tcp_acceptable_seq(sk, tp);
+ TCP_SKB_CB(buff)->when = tcp_time_stamp;
+ tcp_transmit_skb(sk, buff);
+ }
+}
+
+/* This routine sends a packet with an out of date sequence
+ * number. It assumes the other end will try to ack it.
+ *
+ * Question: what should we make while urgent mode?
+ * 4.4BSD forces sending single byte of data. We cannot send
+ * out of window data, because we have SND.NXT==SND.MAX...
+ *
+ * Current solution: to send TWO zero-length segments in urgent mode:
+ * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
+ * out-of-date with SND.UNA-1 to probe window.
+ */
+static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+
+ /* We don't queue it, tcp_transmit_skb() sets ownership. */
+ skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
+ if (skb == NULL)
+ return -1;
+
+ /* Reserve space for headers and set control bits. */
+ skb_reserve(skb, MAX_TCP_HEADER);
+ skb->csum = 0;
+ TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK;
+ TCP_SKB_CB(skb)->sacked = urgent;
+ skb_shinfo(skb)->tso_segs = 1;
+ skb_shinfo(skb)->tso_size = 0;
+
+ /* Use a previous sequence. This should cause the other
+ * end to send an ack. Don't queue or clone SKB, just
+ * send it.
+ */
+ TCP_SKB_CB(skb)->seq = urgent ? tp->snd_una : tp->snd_una - 1;
+ TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
+ TCP_SKB_CB(skb)->when = tcp_time_stamp;
+ return tcp_transmit_skb(sk, skb);
+}
+
+int tcp_write_wakeup(struct sock *sk)
+{
+ if (sk->sk_state != TCP_CLOSE) {
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+
+ if ((skb = sk->sk_send_head) != NULL &&
+ before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)) {
+ int err;
+ unsigned int mss = tcp_current_mss(sk, 0);
+ unsigned int seg_size = tp->snd_una+tp->snd_wnd-TCP_SKB_CB(skb)->seq;
+
+ if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
+ tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
+
+ /* We are probing the opening of a window
+ * but the window size is != 0
+ * must have been a result SWS avoidance ( sender )
+ */
+ if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
+ skb->len > mss) {
+ seg_size = min(seg_size, mss);
+ TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
+ if (tcp_fragment(sk, skb, seg_size))
+ return -1;
+ /* SWS override triggered forced fragmentation.
+ * Disable TSO, the connection is too sick. */
+ if (sk->sk_route_caps & NETIF_F_TSO) {
+ sock_set_flag(sk, SOCK_NO_LARGESEND);
+ sk->sk_route_caps &= ~NETIF_F_TSO;
+ tp->mss_cache = tp->mss_cache_std;
+ }
+ } else if (!tcp_skb_pcount(skb))
+ tcp_set_skb_tso_segs(skb, tp->mss_cache_std);
+
+ TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
+ TCP_SKB_CB(skb)->when = tcp_time_stamp;
+ tcp_tso_set_push(skb);
+ err = tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC));
+ if (!err) {
+ update_send_head(sk, tp, skb);
+ }
+ return err;
+ } else {
+ if (tp->urg_mode &&
+ between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF))
+ tcp_xmit_probe_skb(sk, TCPCB_URG);
+ return tcp_xmit_probe_skb(sk, 0);
+ }
+ }
+ return -1;
+}
+
+/* A window probe timeout has occurred. If window is not closed send
+ * a partial packet else a zero probe.
+ */
+void tcp_send_probe0(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int err;
+
+ err = tcp_write_wakeup(sk);
+
+ if (tp->packets_out || !sk->sk_send_head) {
+ /* Cancel probe timer, if it is not required. */
+ tp->probes_out = 0;
+ tp->backoff = 0;
+ return;
+ }
+
+ if (err <= 0) {
+ if (tp->backoff < sysctl_tcp_retries2)
+ tp->backoff++;
+ tp->probes_out++;
+ tcp_reset_xmit_timer (sk, TCP_TIME_PROBE0,
+ min(tp->rto << tp->backoff, TCP_RTO_MAX));
+ } else {
+ /* If packet was not sent due to local congestion,
+ * do not backoff and do not remember probes_out.
+ * Let local senders to fight for local resources.
+ *
+ * Use accumulated backoff yet.
+ */
+ if (!tp->probes_out)
+ tp->probes_out=1;
+ tcp_reset_xmit_timer (sk, TCP_TIME_PROBE0,
+ min(tp->rto << tp->backoff, TCP_RESOURCE_PROBE_INTERVAL));
+ }
+}
+
+EXPORT_SYMBOL(tcp_connect);
+EXPORT_SYMBOL(tcp_make_synack);
+EXPORT_SYMBOL(tcp_simple_retransmit);
+EXPORT_SYMBOL(tcp_sync_mss);