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![David S. Miller](/assets/img/avatar_default.png)
Otherwise we beat heavily on the global tcp_memory atomics when all of the sockets in the system are slowly sending perioding packet clumps. Noticed and suggested by Eric Dumazet. Signed-off-by: David S. Miller <davem@davemloft.net>
529 lines
14 KiB
C
529 lines
14 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Implementation of the Transmission Control Protocol(TCP).
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*
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* Version: $Id: tcp_timer.c,v 1.88 2002/02/01 22:01:04 davem Exp $
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*
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* Authors: Ross Biro
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* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
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* Mark Evans, <evansmp@uhura.aston.ac.uk>
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* Corey Minyard <wf-rch!minyard@relay.EU.net>
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* Florian La Roche, <flla@stud.uni-sb.de>
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* Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
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* Linus Torvalds, <torvalds@cs.helsinki.fi>
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* Alan Cox, <gw4pts@gw4pts.ampr.org>
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* Matthew Dillon, <dillon@apollo.west.oic.com>
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* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
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* Jorge Cwik, <jorge@laser.satlink.net>
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*/
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#include <linux/module.h>
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#include <net/tcp.h>
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int sysctl_tcp_syn_retries __read_mostly = TCP_SYN_RETRIES;
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int sysctl_tcp_synack_retries __read_mostly = TCP_SYNACK_RETRIES;
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int sysctl_tcp_keepalive_time __read_mostly = TCP_KEEPALIVE_TIME;
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int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES;
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int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL;
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int sysctl_tcp_retries1 __read_mostly = TCP_RETR1;
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int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
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int sysctl_tcp_orphan_retries __read_mostly;
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static void tcp_write_timer(unsigned long);
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static void tcp_delack_timer(unsigned long);
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static void tcp_keepalive_timer (unsigned long data);
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void tcp_init_xmit_timers(struct sock *sk)
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{
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inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
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&tcp_keepalive_timer);
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}
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EXPORT_SYMBOL(tcp_init_xmit_timers);
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static void tcp_write_err(struct sock *sk)
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{
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sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
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sk->sk_error_report(sk);
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tcp_done(sk);
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NET_INC_STATS_BH(LINUX_MIB_TCPABORTONTIMEOUT);
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}
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/* Do not allow orphaned sockets to eat all our resources.
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* This is direct violation of TCP specs, but it is required
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* to prevent DoS attacks. It is called when a retransmission timeout
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* or zero probe timeout occurs on orphaned socket.
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*
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* Criteria is still not confirmed experimentally and may change.
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* We kill the socket, if:
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* 1. If number of orphaned sockets exceeds an administratively configured
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* limit.
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* 2. If we have strong memory pressure.
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*/
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static int tcp_out_of_resources(struct sock *sk, int do_reset)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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int orphans = atomic_read(&tcp_orphan_count);
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/* If peer does not open window for long time, or did not transmit
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* anything for long time, penalize it. */
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if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
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orphans <<= 1;
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/* If some dubious ICMP arrived, penalize even more. */
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if (sk->sk_err_soft)
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orphans <<= 1;
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if (tcp_too_many_orphans(sk, orphans)) {
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if (net_ratelimit())
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printk(KERN_INFO "Out of socket memory\n");
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/* Catch exceptional cases, when connection requires reset.
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* 1. Last segment was sent recently. */
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if ((s32)(tcp_time_stamp - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
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/* 2. Window is closed. */
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(!tp->snd_wnd && !tp->packets_out))
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do_reset = 1;
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if (do_reset)
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tcp_send_active_reset(sk, GFP_ATOMIC);
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tcp_done(sk);
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NET_INC_STATS_BH(LINUX_MIB_TCPABORTONMEMORY);
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return 1;
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}
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return 0;
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}
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/* Calculate maximal number or retries on an orphaned socket. */
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static int tcp_orphan_retries(struct sock *sk, int alive)
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{
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int retries = sysctl_tcp_orphan_retries; /* May be zero. */
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/* We know from an ICMP that something is wrong. */
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if (sk->sk_err_soft && !alive)
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retries = 0;
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/* However, if socket sent something recently, select some safe
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* number of retries. 8 corresponds to >100 seconds with minimal
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* RTO of 200msec. */
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if (retries == 0 && alive)
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retries = 8;
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return retries;
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}
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static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
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{
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/* Black hole detection */
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if (sysctl_tcp_mtu_probing) {
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if (!icsk->icsk_mtup.enabled) {
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icsk->icsk_mtup.enabled = 1;
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tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
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} else {
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struct tcp_sock *tp = tcp_sk(sk);
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int mss;
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mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
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mss = min(sysctl_tcp_base_mss, mss);
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mss = max(mss, 68 - tp->tcp_header_len);
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icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
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tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
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}
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}
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}
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/* A write timeout has occurred. Process the after effects. */
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static int tcp_write_timeout(struct sock *sk)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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int retry_until;
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if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
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if (icsk->icsk_retransmits)
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dst_negative_advice(&sk->sk_dst_cache);
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retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
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} else {
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if (icsk->icsk_retransmits >= sysctl_tcp_retries1) {
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/* Black hole detection */
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tcp_mtu_probing(icsk, sk);
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dst_negative_advice(&sk->sk_dst_cache);
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}
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retry_until = sysctl_tcp_retries2;
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if (sock_flag(sk, SOCK_DEAD)) {
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const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
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retry_until = tcp_orphan_retries(sk, alive);
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if (tcp_out_of_resources(sk, alive || icsk->icsk_retransmits < retry_until))
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return 1;
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}
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}
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if (icsk->icsk_retransmits >= retry_until) {
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/* Has it gone just too far? */
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tcp_write_err(sk);
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return 1;
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}
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return 0;
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}
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static void tcp_delack_timer(unsigned long data)
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{
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struct sock *sk = (struct sock*)data;
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struct tcp_sock *tp = tcp_sk(sk);
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struct inet_connection_sock *icsk = inet_csk(sk);
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bh_lock_sock(sk);
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if (sock_owned_by_user(sk)) {
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/* Try again later. */
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icsk->icsk_ack.blocked = 1;
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NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOCKED);
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sk_reset_timer(sk, &icsk->icsk_delack_timer, jiffies + TCP_DELACK_MIN);
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goto out_unlock;
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}
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sk_mem_reclaim_partial(sk);
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if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
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goto out;
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if (time_after(icsk->icsk_ack.timeout, jiffies)) {
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sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
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goto out;
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}
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icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
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if (!skb_queue_empty(&tp->ucopy.prequeue)) {
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struct sk_buff *skb;
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NET_INC_STATS_BH(LINUX_MIB_TCPSCHEDULERFAILED);
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while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
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sk->sk_backlog_rcv(sk, skb);
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tp->ucopy.memory = 0;
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}
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if (inet_csk_ack_scheduled(sk)) {
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if (!icsk->icsk_ack.pingpong) {
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/* Delayed ACK missed: inflate ATO. */
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icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
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} else {
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/* Delayed ACK missed: leave pingpong mode and
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* deflate ATO.
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*/
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icsk->icsk_ack.pingpong = 0;
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icsk->icsk_ack.ato = TCP_ATO_MIN;
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}
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tcp_send_ack(sk);
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NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKS);
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}
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TCP_CHECK_TIMER(sk);
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out:
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if (tcp_memory_pressure)
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sk_mem_reclaim(sk);
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out_unlock:
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bh_unlock_sock(sk);
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sock_put(sk);
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}
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static void tcp_probe_timer(struct sock *sk)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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struct tcp_sock *tp = tcp_sk(sk);
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int max_probes;
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if (tp->packets_out || !tcp_send_head(sk)) {
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icsk->icsk_probes_out = 0;
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return;
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}
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/* *WARNING* RFC 1122 forbids this
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*
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* It doesn't AFAIK, because we kill the retransmit timer -AK
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*
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* FIXME: We ought not to do it, Solaris 2.5 actually has fixing
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* this behaviour in Solaris down as a bug fix. [AC]
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*
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* Let me to explain. icsk_probes_out is zeroed by incoming ACKs
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* even if they advertise zero window. Hence, connection is killed only
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* if we received no ACKs for normal connection timeout. It is not killed
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* only because window stays zero for some time, window may be zero
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* until armageddon and even later. We are in full accordance
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* with RFCs, only probe timer combines both retransmission timeout
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* and probe timeout in one bottle. --ANK
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*/
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max_probes = sysctl_tcp_retries2;
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if (sock_flag(sk, SOCK_DEAD)) {
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const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
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max_probes = tcp_orphan_retries(sk, alive);
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if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes))
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return;
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}
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if (icsk->icsk_probes_out > max_probes) {
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tcp_write_err(sk);
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} else {
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/* Only send another probe if we didn't close things up. */
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tcp_send_probe0(sk);
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}
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}
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/*
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* The TCP retransmit timer.
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*/
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static void tcp_retransmit_timer(struct sock *sk)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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struct inet_connection_sock *icsk = inet_csk(sk);
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if (!tp->packets_out)
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goto out;
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BUG_TRAP(!tcp_write_queue_empty(sk));
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if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
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!((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
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/* Receiver dastardly shrinks window. Our retransmits
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* become zero probes, but we should not timeout this
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* connection. If the socket is an orphan, time it out,
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* we cannot allow such beasts to hang infinitely.
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*/
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#ifdef TCP_DEBUG
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if (1) {
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struct inet_sock *inet = inet_sk(sk);
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LIMIT_NETDEBUG(KERN_DEBUG "TCP: Treason uncloaked! Peer %u.%u.%u.%u:%u/%u shrinks window %u:%u. Repaired.\n",
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NIPQUAD(inet->daddr), ntohs(inet->dport),
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inet->num, tp->snd_una, tp->snd_nxt);
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}
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#endif
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if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
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tcp_write_err(sk);
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goto out;
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}
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tcp_enter_loss(sk, 0);
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tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
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__sk_dst_reset(sk);
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goto out_reset_timer;
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}
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if (tcp_write_timeout(sk))
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goto out;
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if (icsk->icsk_retransmits == 0) {
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if (icsk->icsk_ca_state == TCP_CA_Disorder ||
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icsk->icsk_ca_state == TCP_CA_Recovery) {
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if (tcp_is_sack(tp)) {
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if (icsk->icsk_ca_state == TCP_CA_Recovery)
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NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERYFAIL);
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else
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NET_INC_STATS_BH(LINUX_MIB_TCPSACKFAILURES);
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} else {
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if (icsk->icsk_ca_state == TCP_CA_Recovery)
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NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERYFAIL);
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else
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NET_INC_STATS_BH(LINUX_MIB_TCPRENOFAILURES);
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}
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} else if (icsk->icsk_ca_state == TCP_CA_Loss) {
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NET_INC_STATS_BH(LINUX_MIB_TCPLOSSFAILURES);
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} else {
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NET_INC_STATS_BH(LINUX_MIB_TCPTIMEOUTS);
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}
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}
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if (tcp_use_frto(sk)) {
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tcp_enter_frto(sk);
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} else {
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tcp_enter_loss(sk, 0);
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}
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if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
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/* Retransmission failed because of local congestion,
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* do not backoff.
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*/
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if (!icsk->icsk_retransmits)
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icsk->icsk_retransmits = 1;
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inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
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min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
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TCP_RTO_MAX);
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goto out;
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}
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/* Increase the timeout each time we retransmit. Note that
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* we do not increase the rtt estimate. rto is initialized
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* from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
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* that doubling rto each time is the least we can get away with.
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* In KA9Q, Karn uses this for the first few times, and then
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* goes to quadratic. netBSD doubles, but only goes up to *64,
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* and clamps at 1 to 64 sec afterwards. Note that 120 sec is
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* defined in the protocol as the maximum possible RTT. I guess
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* we'll have to use something other than TCP to talk to the
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* University of Mars.
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*
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* PAWS allows us longer timeouts and large windows, so once
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* implemented ftp to mars will work nicely. We will have to fix
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* the 120 second clamps though!
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*/
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icsk->icsk_backoff++;
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icsk->icsk_retransmits++;
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out_reset_timer:
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icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
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inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
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if (icsk->icsk_retransmits > sysctl_tcp_retries1)
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__sk_dst_reset(sk);
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out:;
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}
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static void tcp_write_timer(unsigned long data)
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{
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struct sock *sk = (struct sock*)data;
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struct inet_connection_sock *icsk = inet_csk(sk);
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int event;
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bh_lock_sock(sk);
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if (sock_owned_by_user(sk)) {
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/* Try again later */
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sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + (HZ / 20));
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goto out_unlock;
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}
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if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
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goto out;
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if (time_after(icsk->icsk_timeout, jiffies)) {
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sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
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goto out;
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}
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event = icsk->icsk_pending;
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icsk->icsk_pending = 0;
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switch (event) {
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case ICSK_TIME_RETRANS:
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tcp_retransmit_timer(sk);
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break;
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case ICSK_TIME_PROBE0:
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tcp_probe_timer(sk);
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break;
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}
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TCP_CHECK_TIMER(sk);
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out:
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sk_mem_reclaim(sk);
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out_unlock:
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bh_unlock_sock(sk);
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sock_put(sk);
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}
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/*
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* Timer for listening sockets
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*/
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static void tcp_synack_timer(struct sock *sk)
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{
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inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
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TCP_TIMEOUT_INIT, TCP_RTO_MAX);
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}
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void tcp_set_keepalive(struct sock *sk, int val)
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{
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if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
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return;
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if (val && !sock_flag(sk, SOCK_KEEPOPEN))
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inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
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else if (!val)
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inet_csk_delete_keepalive_timer(sk);
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}
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static void tcp_keepalive_timer (unsigned long data)
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{
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struct sock *sk = (struct sock *) data;
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struct inet_connection_sock *icsk = inet_csk(sk);
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struct tcp_sock *tp = tcp_sk(sk);
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__u32 elapsed;
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/* Only process if socket is not in use. */
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bh_lock_sock(sk);
|
|
if (sock_owned_by_user(sk)) {
|
|
/* Try again later. */
|
|
inet_csk_reset_keepalive_timer (sk, HZ/20);
|
|
goto out;
|
|
}
|
|
|
|
if (sk->sk_state == TCP_LISTEN) {
|
|
tcp_synack_timer(sk);
|
|
goto out;
|
|
}
|
|
|
|
if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
|
|
if (tp->linger2 >= 0) {
|
|
const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
|
|
|
|
if (tmo > 0) {
|
|
tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
|
|
goto out;
|
|
}
|
|
}
|
|
tcp_send_active_reset(sk, GFP_ATOMIC);
|
|
goto death;
|
|
}
|
|
|
|
if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
|
|
goto out;
|
|
|
|
elapsed = keepalive_time_when(tp);
|
|
|
|
/* It is alive without keepalive 8) */
|
|
if (tp->packets_out || tcp_send_head(sk))
|
|
goto resched;
|
|
|
|
elapsed = tcp_time_stamp - tp->rcv_tstamp;
|
|
|
|
if (elapsed >= keepalive_time_when(tp)) {
|
|
if ((!tp->keepalive_probes && icsk->icsk_probes_out >= sysctl_tcp_keepalive_probes) ||
|
|
(tp->keepalive_probes && icsk->icsk_probes_out >= tp->keepalive_probes)) {
|
|
tcp_send_active_reset(sk, GFP_ATOMIC);
|
|
tcp_write_err(sk);
|
|
goto out;
|
|
}
|
|
if (tcp_write_wakeup(sk) <= 0) {
|
|
icsk->icsk_probes_out++;
|
|
elapsed = keepalive_intvl_when(tp);
|
|
} else {
|
|
/* If keepalive was lost due to local congestion,
|
|
* try harder.
|
|
*/
|
|
elapsed = TCP_RESOURCE_PROBE_INTERVAL;
|
|
}
|
|
} else {
|
|
/* It is tp->rcv_tstamp + keepalive_time_when(tp) */
|
|
elapsed = keepalive_time_when(tp) - elapsed;
|
|
}
|
|
|
|
TCP_CHECK_TIMER(sk);
|
|
sk_mem_reclaim(sk);
|
|
|
|
resched:
|
|
inet_csk_reset_keepalive_timer (sk, elapsed);
|
|
goto out;
|
|
|
|
death:
|
|
tcp_done(sk);
|
|
|
|
out:
|
|
bh_unlock_sock(sk);
|
|
sock_put(sk);
|
|
}
|