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kernel-fxtec-pro1x/net/ipv4/tcp_output.c
Stephen Hemminger 6a438bbe68 [TCP]: speed up SACK processing 
Use "hints" to speed up the SACK processing. Various forms 
of this have been used by TCP developers (Web100, STCP, BIC)
to avoid the 2x linear search of outstanding segments.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2005-11-10 17:14:59 -08:00

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/*
* 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
* 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 = 3;
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 sock *sk, struct dst_entry *dst)
{
struct tcp_sock *tp = tcp_sk(sk);
s32 delta = tcp_time_stamp - tp->lsndtime;
u32 restart_cwnd = tcp_init_cwnd(tp, dst);
u32 cwnd = tp->snd_cwnd;
tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
tp->snd_ssthresh = tcp_current_ssthresh(sk);
restart_cwnd = min(restart_cwnd, cwnd);
while ((delta -= inet_csk(sk)->icsk_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)
{
struct inet_connection_sock *icsk = inet_csk(sk);
const u32 now = tcp_time_stamp;
if (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)
tcp_cwnd_restart(sk, __sk_dst_get(sk));
tp->lsndtime = now;
/* If it is a reply for ato after last received
* packet, enter pingpong mode.
*/
if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
icsk->icsk_ack.pingpong = 1;
}
static __inline__ void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
{
tcp_dec_quickack_mode(sk, pkts);
inet_csk_clear_xmit_timer(sk, ICSK_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 RFC2414. 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) {
const struct inet_connection_sock *icsk = inet_csk(sk);
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
/* If congestion control is doing timestamping */
if (icsk->icsk_ca_ops->rtt_sample)
__net_timestamp(skb);
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 (tcp_packets_in_flight(tp) == 0)
tcp_ca_event(sk, CA_EVENT_TX_START);
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, tcp_skb_pcount(skb));
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(sk);
/* 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 void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
{
if (skb->len <= mss_now ||
!(sk->sk_route_caps & NETIF_F_TSO)) {
/* 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_now - 1);
factor /= mss_now;
skb_shinfo(skb)->tso_segs = factor;
skb_shinfo(skb)->tso_size = mss_now;
}
}
/* 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.
*/
int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss_now)
{
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *buff;
int nsize, old_factor;
u16 flags;
BUG_ON(len > skb->len);
clear_all_retrans_hints(tp);
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;
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;
buff->tstamp = skb->tstamp;
old_factor = tcp_skb_pcount(skb);
/* Fix up tso_factor for both original and new SKB. */
tcp_set_skb_tso_segs(sk, skb, mss_now);
tcp_set_skb_tso_segs(sk, buff, mss_now);
/* If this packet has been sent out already, we must
* adjust the various packet counters.
*/
if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
int diff = old_factor - tcp_skb_pcount(skb) -
tcp_skb_pcount(buff);
tp->packets_out -= diff;
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
tp->sacked_out -= diff;
if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
tp->retrans_out -= diff;
if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
tp->lost_out -= diff;
tp->left_out -= diff;
}
if (diff > 0) {
/* Adjust Reno SACK estimate. */
if (!tp->rx_opt.sack_ok) {
tp->sacked_out -= diff;
if ((int)tp->sacked_out < 0)
tp->sacked_out = 0;
tcp_sync_left_out(tp);
}
tp->fackets_out -= diff;
if ((int)tp->fackets_out < 0)
tp->fackets_out = 0;
}
}
/* Link BUFF into the send queue. */
skb_header_release(buff);
__skb_append(skb, buff, &sk->sk_write_queue);
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(sk, skb, tcp_current_mss(sk, 1));
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 minimum 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 = 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_allowed)
{
struct tcp_sock *tp = tcp_sk(sk);
struct dst_entry *dst = __sk_dst_get(sk);
u32 mss_now;
u16 xmit_size_goal;
int doing_tso = 0;
mss_now = tp->mss_cache;
if (large_allowed &&
(sk->sk_route_caps & NETIF_F_TSO) &&
!tp->urg_mode)
doing_tso = 1;
if (dst) {
u32 mtu = dst_mtu(dst);
if (mtu != tp->pmtu_cookie)
mss_now = tcp_sync_mss(sk, mtu);
}
if (tp->rx_opt.eff_sacks)
mss_now -= (TCPOLEN_SACK_BASE_ALIGNED +
(tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK));
xmit_size_goal = mss_now;
if (doing_tso) {
xmit_size_goal = 65535 -
tp->af_specific->net_header_len -
tp->ext_header_len - tp->tcp_header_len;
if (tp->max_window &&
(xmit_size_goal > (tp->max_window >> 1)))
xmit_size_goal = max((tp->max_window >> 1),
68U - tp->tcp_header_len);
xmit_size_goal -= (xmit_size_goal % mss_now);
}
tp->xmit_size_goal = xmit_size_goal;
return mss_now;
}
/* Congestion window validation. (RFC2861) */
static inline void tcp_cwnd_validate(struct sock *sk, struct tcp_sock *tp)
{
__u32 packets_out = tp->packets_out;
if (packets_out >= tp->snd_cwnd) {
/* Network is feed fully. */
tp->snd_cwnd_used = 0;
tp->snd_cwnd_stamp = tcp_time_stamp;
} else {
/* Network starves. */
if (tp->packets_out > tp->snd_cwnd_used)
tp->snd_cwnd_used = tp->packets_out;
if ((s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
tcp_cwnd_application_limited(sk);
}
}
static unsigned int tcp_window_allows(struct tcp_sock *tp, struct sk_buff *skb, unsigned int mss_now, unsigned int cwnd)
{
u32 window, cwnd_len;
window = (tp->snd_una + tp->snd_wnd - TCP_SKB_CB(skb)->seq);
cwnd_len = mss_now * cwnd;
return min(window, cwnd_len);
}
/* Can at least one segment of SKB be sent right now, according to the
* congestion window rules? If so, return how many segments are allowed.
*/
static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, struct sk_buff *skb)
{
u32 in_flight, cwnd;
/* Don't be strict about the congestion window for the final FIN. */
if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)
return 1;
in_flight = tcp_packets_in_flight(tp);
cwnd = tp->snd_cwnd;
if (in_flight < cwnd)
return (cwnd - in_flight);
return 0;
}
/* This must be invoked the first time we consider transmitting
* SKB onto the wire.
*/
static inline int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
{
int tso_segs = tcp_skb_pcount(skb);
if (!tso_segs ||
(tso_segs > 1 &&
skb_shinfo(skb)->tso_size != mss_now)) {
tcp_set_skb_tso_segs(sk, skb, mss_now);
tso_segs = tcp_skb_pcount(skb);
}
return tso_segs;
}
static inline int tcp_minshall_check(const struct tcp_sock *tp)
{
return after(tp->snd_sml,tp->snd_una) &&
!after(tp->snd_sml, tp->snd_nxt);
}
/* Return 0, if packet can be sent now without violation Nagle's rules:
* 1. It is full sized.
* 2. Or it contains FIN. (already checked by caller)
* 3. Or TCP_NODELAY was set.
* 4. Or TCP_CORK is not set, and all sent packets are ACKed.
* With Minshall's modification: all sent small packets are ACKed.
*/
static inline int tcp_nagle_check(const struct tcp_sock *tp,
const struct sk_buff *skb,
unsigned mss_now, int nonagle)
{
return (skb->len < mss_now &&
((nonagle&TCP_NAGLE_CORK) ||
(!nonagle &&
tp->packets_out &&
tcp_minshall_check(tp))));
}
/* Return non-zero if the Nagle test allows this packet to be
* sent now.
*/
static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb,
unsigned int cur_mss, int nonagle)
{
/* Nagle rule does not apply to frames, which sit in the middle of the
* write_queue (they have no chances to get new data).
*
* This is implemented in the callers, where they modify the 'nonagle'
* argument based upon the location of SKB in the send queue.
*/
if (nonagle & TCP_NAGLE_PUSH)
return 1;
/* Don't use the nagle rule for urgent data (or for the final FIN). */
if (tp->urg_mode ||
(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN))
return 1;
if (!tcp_nagle_check(tp, skb, cur_mss, nonagle))
return 1;
return 0;
}
/* Does at least the first segment of SKB fit into the send window? */
static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb, unsigned int cur_mss)
{
u32 end_seq = TCP_SKB_CB(skb)->end_seq;
if (skb->len > cur_mss)
end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
return !after(end_seq, tp->snd_una + tp->snd_wnd);
}
/* This checks if the data bearing packet SKB (usually sk->sk_send_head)
* should be put on the wire right now. If so, it returns the number of
* packets allowed by the congestion window.
*/
static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb,
unsigned int cur_mss, int nonagle)
{
struct tcp_sock *tp = tcp_sk(sk);
unsigned int cwnd_quota;
tcp_init_tso_segs(sk, skb, cur_mss);
if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
return 0;
cwnd_quota = tcp_cwnd_test(tp, skb);
if (cwnd_quota &&
!tcp_snd_wnd_test(tp, skb, cur_mss))
cwnd_quota = 0;
return cwnd_quota;
}
static inline int tcp_skb_is_last(const struct sock *sk,
const struct sk_buff *skb)
{
return skb->next == (struct sk_buff *)&sk->sk_write_queue;
}
int tcp_may_send_now(struct sock *sk, struct tcp_sock *tp)
{
struct sk_buff *skb = sk->sk_send_head;
return (skb &&
tcp_snd_test(sk, skb, tcp_current_mss(sk, 1),
(tcp_skb_is_last(sk, skb) ?
TCP_NAGLE_PUSH :
tp->nonagle)));
}
/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
* which is put after SKB on the list. It is very much like
* tcp_fragment() except that it may make several kinds of assumptions
* in order to speed up the splitting operation. In particular, we
* know that all the data is in scatter-gather pages, and that the
* packet has never been sent out before (and thus is not cloned).
*/
static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, unsigned int mss_now)
{
struct sk_buff *buff;
int nlen = skb->len - len;
u16 flags;
/* All of a TSO frame must be composed of paged data. */
if (skb->len != skb->data_len)
return tcp_fragment(sk, skb, len, mss_now);
buff = sk_stream_alloc_pskb(sk, 0, 0, GFP_ATOMIC);
if (unlikely(buff == NULL))
return -ENOMEM;
buff->truesize = nlen;
skb->truesize -= nlen;
/* 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;
/* This packet was never sent out yet, so no SACK bits. */
TCP_SKB_CB(buff)->sacked = 0;
buff->ip_summed = skb->ip_summed = CHECKSUM_HW;
skb_split(skb, buff, len);
/* Fix up tso_factor for both original and new SKB. */
tcp_set_skb_tso_segs(sk, skb, mss_now);
tcp_set_skb_tso_segs(sk, buff, mss_now);
/* Link BUFF into the send queue. */
skb_header_release(buff);
__skb_append(skb, buff, &sk->sk_write_queue);
return 0;
}
/* Try to defer sending, if possible, in order to minimize the amount
* of TSO splitting we do. View it as a kind of TSO Nagle test.
*
* This algorithm is from John Heffner.
*/
static int tcp_tso_should_defer(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
u32 send_win, cong_win, limit, in_flight;
if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)
return 0;
if (icsk->icsk_ca_state != TCP_CA_Open)
return 0;
in_flight = tcp_packets_in_flight(tp);
BUG_ON(tcp_skb_pcount(skb) <= 1 ||
(tp->snd_cwnd <= in_flight));
send_win = (tp->snd_una + tp->snd_wnd) - TCP_SKB_CB(skb)->seq;
/* From in_flight test above, we know that cwnd > in_flight. */
cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
limit = min(send_win, cong_win);
if (sysctl_tcp_tso_win_divisor) {
u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
/* If at least some fraction of a window is available,
* just use it.
*/
chunk /= sysctl_tcp_tso_win_divisor;
if (limit >= chunk)
return 0;
} else {
/* Different approach, try not to defer past a single
* ACK. Receiver should ACK every other full sized
* frame, so if we have space for more than 3 frames
* then send now.
*/
if (limit > tcp_max_burst(tp) * tp->mss_cache)
return 0;
}
/* Ok, it looks like it is advisable to defer. */
return 1;
}
/* 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.
*/
static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
{
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *skb;
unsigned int tso_segs, sent_pkts;
int cwnd_quota;
/* 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 (unlikely(sk->sk_state == TCP_CLOSE))
return 0;
sent_pkts = 0;
while ((skb = sk->sk_send_head)) {
unsigned int limit;
tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
BUG_ON(!tso_segs);
cwnd_quota = tcp_cwnd_test(tp, skb);
if (!cwnd_quota)
break;
if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
break;
if (tso_segs == 1) {
if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
(tcp_skb_is_last(sk, skb) ?
nonagle : TCP_NAGLE_PUSH))))
break;
} else {
if (tcp_tso_should_defer(sk, tp, skb))
break;
}
limit = mss_now;
if (tso_segs > 1) {
limit = tcp_window_allows(tp, skb,
mss_now, cwnd_quota);
if (skb->len < limit) {
unsigned int trim = skb->len % mss_now;
if (trim)
limit = skb->len - trim;
}
}
if (skb->len > limit &&
unlikely(tso_fragment(sk, skb, limit, mss_now)))
break;
TCP_SKB_CB(skb)->when = tcp_time_stamp;
if (unlikely(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++;
}
if (likely(sent_pkts)) {
tcp_cwnd_validate(sk, tp);
return 0;
}
return !tp->packets_out && sk->sk_send_head;
}
/* Push out any pending frames which were held back due to
* TCP_CORK or attempt at coalescing tiny packets.
* The socket must be locked by the caller.
*/
void __tcp_push_pending_frames(struct sock *sk, struct tcp_sock *tp,
unsigned int cur_mss, int nonagle)
{
struct sk_buff *skb = sk->sk_send_head;
if (skb) {
if (tcp_write_xmit(sk, cur_mss, nonagle))
tcp_check_probe_timer(sk, tp);
}
}
/* 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 int mss_now)
{
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *skb = sk->sk_send_head;
unsigned int tso_segs, cwnd_quota;
BUG_ON(!skb || skb->len < mss_now);
tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH);
if (likely(cwnd_quota)) {
unsigned int limit;
BUG_ON(!tso_segs);
limit = mss_now;
if (tso_segs > 1) {
limit = tcp_window_allows(tp, skb,
mss_now, cwnd_quota);
if (skb->len < limit) {
unsigned int trim = skb->len % mss_now;
if (trim)
limit = skb->len - trim;
}
}
if (skb->len > limit &&
unlikely(tso_fragment(sk, skb, limit, mss_now)))
return;
/* Send it out now. */
TCP_SKB_CB(skb)->when = tcp_time_stamp;
if (likely(!tcp_transmit_skb(sk, skb_clone(skb, sk->sk_allocation)))) {
update_send_head(sk, tp, skb);
tcp_cwnd_validate(sk, tp);
return;
}
}
}
/* 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 inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
/* MSS for the peer's data. Previous versions 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 = icsk->icsk_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) {
icsk->icsk_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);
/* changing transmit queue under us so clear hints */
clear_all_retrans_hints(tp);
/* Ok. We will be able to collapse the packet. */
__skb_unlink(next_skb, &sk->sk_write_queue);
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)
{
const struct inet_connection_sock *icsk = inet_csk(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;
}
}
}
clear_all_retrans_hints(tp);
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 (icsk->icsk_ca_state != TCP_CA_Loss) {
tp->high_seq = tp->snd_nxt;
tp->snd_ssthresh = tcp_current_ssthresh(sk);
tp->prior_ssthresh = 0;
tp->undo_marker = 0;
tcp_set_ca_state(sk, 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: fragmentation, 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 (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) {
if (tcp_fragment(sk, skb, cur_mss, cur_mss))
return -ENOMEM; /* We'll try again later. */
}
/* 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;
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)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *skb;
int packet_cnt;
if (tp->retransmit_skb_hint) {
skb = tp->retransmit_skb_hint;
packet_cnt = tp->retransmit_cnt_hint;
}else{
skb = sk->sk_write_queue.next;
packet_cnt = 0;
}
/* First pass: retransmit lost packets. */
if (tp->lost_out) {
sk_stream_for_retrans_queue_from(skb, sk) {
__u8 sacked = TCP_SKB_CB(skb)->sacked;
/* we could do better than to assign each time */
tp->retransmit_skb_hint = skb;
tp->retransmit_cnt_hint = packet_cnt;
/* 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)) {
tp->retransmit_skb_hint = NULL;
return;
}
if (icsk->icsk_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))
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
inet_csk(sk)->icsk_rto,
TCP_RTO_MAX);
}
packet_cnt += tcp_skb_pcount(skb);
if (packet_cnt >= tp->lost_out)
break;
}
}
}
/* OK, demanded retransmission is finished. */
/* Forward retransmissions are possible only during Recovery. */
if (icsk->icsk_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;
if (tp->forward_skb_hint) {
skb = tp->forward_skb_hint;
packet_cnt = tp->forward_cnt_hint;
} else{
skb = sk->sk_write_queue.next;
packet_cnt = 0;
}
sk_stream_for_retrans_queue_from(skb, sk) {
tp->forward_cnt_hint = packet_cnt;
tp->forward_skb_hint = skb;
/* 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)) {
tp->forward_skb_hint = NULL;
break;
}
if (skb == skb_peek(&sk->sk_write_queue))
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
inet_csk(sk)->icsk_rto,
TCP_RTO_MAX);
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_fclone(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, gfp_t 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 request_sock *req)
{
struct inet_request_sock *ireq = inet_rsk(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 +
(ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) +
(ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) +
/* SACK_PERM is in the place of NOP NOP of TS */
((ireq->sack_ok && !ireq->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)
ireq->ecn_ok = 0;
TCP_ECN_make_synack(req, th);
th->source = inet_sk(sk)->sport;
th->dest = ireq->rmt_port;
TCP_SKB_CB(skb)->seq = tcp_rsk(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(tcp_rsk(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) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
&req->rcv_wnd,
&req->window_clamp,
ireq->wscale_ok,
&rcv_wscale);
ireq->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), ireq->tstamp_ok,
ireq->sack_ok, ireq->wscale_ok, ireq->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_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;
inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
inet_csk(sk)->icsk_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_fclone(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;
/* 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. */
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
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 inet_connection_sock *icsk = inet_csk(sk);
int ato = icsk->icsk_ack.ato;
unsigned long timeout;
if (ato > TCP_DELACK_MIN) {
const struct tcp_sock *tp = tcp_sk(sk);
int max_ato = HZ/2;
if (icsk->icsk_ack.pingpong || (icsk->icsk_ack.pending & ICSK_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 inet_csk(sk)->icsk_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 (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
/* If delack timer was blocked or is about to expire,
* send ACK now.
*/
if (icsk->icsk_ack.blocked ||
time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
tcp_send_ack(sk);
return;
}
if (!time_before(timeout, icsk->icsk_ack.timeout))
timeout = icsk->icsk_ack.timeout;
}
icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
icsk->icsk_ack.timeout = timeout;
sk_reset_timer(sk, &icsk->icsk_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) {
inet_csk_schedule_ack(sk);
inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
TCP_DELACK_MAX, TCP_RTO_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, mss))
return -1;
} else if (!tcp_skb_pcount(skb))
tcp_set_skb_tso_segs(sk, skb, mss);
TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
TCP_SKB_CB(skb)->when = tcp_time_stamp;
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 inet_connection_sock *icsk = inet_csk(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. */
icsk->icsk_probes_out = 0;
icsk->icsk_backoff = 0;
return;
}
if (err <= 0) {
if (icsk->icsk_backoff < sysctl_tcp_retries2)
icsk->icsk_backoff++;
icsk->icsk_probes_out++;
inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
TCP_RTO_MAX);
} else {
/* If packet was not sent due to local congestion,
* do not backoff and do not remember icsk_probes_out.
* Let local senders to fight for local resources.
*
* Use accumulated backoff yet.
*/
if (!icsk->icsk_probes_out)
icsk->icsk_probes_out = 1;
inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
min(icsk->icsk_rto << icsk->icsk_backoff,
TCP_RESOURCE_PROBE_INTERVAL),
TCP_RTO_MAX);
}
}
EXPORT_SYMBOL(tcp_connect);
EXPORT_SYMBOL(tcp_make_synack);
EXPORT_SYMBOL(tcp_simple_retransmit);
EXPORT_SYMBOL(tcp_sync_mss);
EXPORT_SYMBOL(sysctl_tcp_tso_win_divisor);
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