/* * 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_timer.c,v 1.88 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> */ #include <linux/module.h> #include <net/tcp.h> int sysctl_tcp_syn_retries __read_mostly = TCP_SYN_RETRIES; int sysctl_tcp_synack_retries __read_mostly = TCP_SYNACK_RETRIES; int sysctl_tcp_keepalive_time __read_mostly = TCP_KEEPALIVE_TIME; int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES; int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL; int sysctl_tcp_retries1 __read_mostly = TCP_RETR1; int sysctl_tcp_retries2 __read_mostly = TCP_RETR2; int sysctl_tcp_orphan_retries __read_mostly; static void tcp_write_timer(unsigned long); static void tcp_delack_timer(unsigned long); static void tcp_keepalive_timer (unsigned long data); void tcp_init_xmit_timers(struct sock *sk) { inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, &tcp_keepalive_timer); } EXPORT_SYMBOL(tcp_init_xmit_timers); static void tcp_write_err(struct sock *sk) { sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT; sk->sk_error_report(sk); tcp_done(sk); NET_INC_STATS_BH(LINUX_MIB_TCPABORTONTIMEOUT); } /* Do not allow orphaned sockets to eat all our resources. * This is direct violation of TCP specs, but it is required * to prevent DoS attacks. It is called when a retransmission timeout * or zero probe timeout occurs on orphaned socket. * * Criteria is still not confirmed experimentally and may change. * We kill the socket, if: * 1. If number of orphaned sockets exceeds an administratively configured * limit. * 2. If we have strong memory pressure. */ static int tcp_out_of_resources(struct sock *sk, int do_reset) { struct tcp_sock *tp = tcp_sk(sk); int orphans = atomic_read(&tcp_orphan_count); /* If peer does not open window for long time, or did not transmit * anything for long time, penalize it. */ if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset) orphans <<= 1; /* If some dubious ICMP arrived, penalize even more. */ if (sk->sk_err_soft) orphans <<= 1; if (tcp_too_many_orphans(sk, orphans)) { if (net_ratelimit()) printk(KERN_INFO "Out of socket memory\n"); /* Catch exceptional cases, when connection requires reset. * 1. Last segment was sent recently. */ if ((s32)(tcp_time_stamp - tp->lsndtime) <= TCP_TIMEWAIT_LEN || /* 2. Window is closed. */ (!tp->snd_wnd && !tp->packets_out)) do_reset = 1; if (do_reset) tcp_send_active_reset(sk, GFP_ATOMIC); tcp_done(sk); NET_INC_STATS_BH(LINUX_MIB_TCPABORTONMEMORY); return 1; } return 0; } /* Calculate maximal number or retries on an orphaned socket. */ static int tcp_orphan_retries(struct sock *sk, int alive) { int retries = sysctl_tcp_orphan_retries; /* May be zero. */ /* We know from an ICMP that something is wrong. */ if (sk->sk_err_soft && !alive) retries = 0; /* However, if socket sent something recently, select some safe * number of retries. 8 corresponds to >100 seconds with minimal * RTO of 200msec. */ if (retries == 0 && alive) retries = 8; return retries; } /* A write timeout has occurred. Process the after effects. */ static int tcp_write_timeout(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); int retry_until; int mss; if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { if (icsk->icsk_retransmits) dst_negative_advice(&sk->sk_dst_cache); retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries; } else { if (icsk->icsk_retransmits >= sysctl_tcp_retries1) { /* Black hole detection */ if (sysctl_tcp_mtu_probing) { if (!icsk->icsk_mtup.enabled) { icsk->icsk_mtup.enabled = 1; tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); } else { mss = min(sysctl_tcp_base_mss, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)/2); mss = max(mss, 68 - tp->tcp_header_len); icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); } } dst_negative_advice(&sk->sk_dst_cache); } retry_until = sysctl_tcp_retries2; if (sock_flag(sk, SOCK_DEAD)) { const int alive = (icsk->icsk_rto < TCP_RTO_MAX); retry_until = tcp_orphan_retries(sk, alive); if (tcp_out_of_resources(sk, alive || icsk->icsk_retransmits < retry_until)) return 1; } } if (icsk->icsk_retransmits >= retry_until) { /* Has it gone just too far? */ tcp_write_err(sk); return 1; } return 0; } static void tcp_delack_timer(unsigned long data) { struct sock *sk = (struct sock*)data; struct tcp_sock *tp = tcp_sk(sk); struct inet_connection_sock *icsk = inet_csk(sk); bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later. */ icsk->icsk_ack.blocked = 1; NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOCKED); sk_reset_timer(sk, &icsk->icsk_delack_timer, jiffies + TCP_DELACK_MIN); goto out_unlock; } sk_stream_mem_reclaim(sk); if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) goto out; if (time_after(icsk->icsk_ack.timeout, jiffies)) { sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); goto out; } icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; if (!skb_queue_empty(&tp->ucopy.prequeue)) { struct sk_buff *skb; NET_INC_STATS_BH(LINUX_MIB_TCPSCHEDULERFAILED); while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) sk->sk_backlog_rcv(sk, skb); tp->ucopy.memory = 0; } if (inet_csk_ack_scheduled(sk)) { if (!icsk->icsk_ack.pingpong) { /* Delayed ACK missed: inflate ATO. */ icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto); } else { /* Delayed ACK missed: leave pingpong mode and * deflate ATO. */ icsk->icsk_ack.pingpong = 0; icsk->icsk_ack.ato = TCP_ATO_MIN; } tcp_send_ack(sk); NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKS); } TCP_CHECK_TIMER(sk); out: if (tcp_memory_pressure) sk_stream_mem_reclaim(sk); out_unlock: bh_unlock_sock(sk); sock_put(sk); } static void tcp_probe_timer(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); int max_probes; if (tp->packets_out || !tcp_send_head(sk)) { icsk->icsk_probes_out = 0; return; } /* *WARNING* RFC 1122 forbids this * * It doesn't AFAIK, because we kill the retransmit timer -AK * * FIXME: We ought not to do it, Solaris 2.5 actually has fixing * this behaviour in Solaris down as a bug fix. [AC] * * Let me to explain. icsk_probes_out is zeroed by incoming ACKs * even if they advertise zero window. Hence, connection is killed only * if we received no ACKs for normal connection timeout. It is not killed * only because window stays zero for some time, window may be zero * until armageddon and even later. We are in full accordance * with RFCs, only probe timer combines both retransmission timeout * and probe timeout in one bottle. --ANK */ max_probes = sysctl_tcp_retries2; if (sock_flag(sk, SOCK_DEAD)) { const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX); max_probes = tcp_orphan_retries(sk, alive); if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes)) return; } if (icsk->icsk_probes_out > max_probes) { tcp_write_err(sk); } else { /* Only send another probe if we didn't close things up. */ tcp_send_probe0(sk); } } /* * The TCP retransmit timer. */ static void tcp_retransmit_timer(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); struct inet_connection_sock *icsk = inet_csk(sk); if (!tp->packets_out) goto out; BUG_TRAP(!tcp_write_queue_empty(sk)); if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { /* Receiver dastardly shrinks window. Our retransmits * become zero probes, but we should not timeout this * connection. If the socket is an orphan, time it out, * we cannot allow such beasts to hang infinitely. */ #ifdef TCP_DEBUG if (1) { struct inet_sock *inet = inet_sk(sk); LIMIT_NETDEBUG(KERN_DEBUG "TCP: Treason uncloaked! Peer %u.%u.%u.%u:%u/%u shrinks window %u:%u. Repaired.\n", NIPQUAD(inet->daddr), ntohs(inet->dport), inet->num, tp->snd_una, tp->snd_nxt); } #endif if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) { tcp_write_err(sk); goto out; } tcp_enter_loss(sk, 0); tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); __sk_dst_reset(sk); goto out_reset_timer; } if (tcp_write_timeout(sk)) goto out; if (icsk->icsk_retransmits == 0) { if (icsk->icsk_ca_state == TCP_CA_Disorder || icsk->icsk_ca_state == TCP_CA_Recovery) { if (tcp_is_sack(tp)) { if (icsk->icsk_ca_state == TCP_CA_Recovery) NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERYFAIL); else NET_INC_STATS_BH(LINUX_MIB_TCPSACKFAILURES); } else { if (icsk->icsk_ca_state == TCP_CA_Recovery) NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERYFAIL); else NET_INC_STATS_BH(LINUX_MIB_TCPRENOFAILURES); } } else if (icsk->icsk_ca_state == TCP_CA_Loss) { NET_INC_STATS_BH(LINUX_MIB_TCPLOSSFAILURES); } else { NET_INC_STATS_BH(LINUX_MIB_TCPTIMEOUTS); } } if (tcp_use_frto(sk)) { tcp_enter_frto(sk); } else { tcp_enter_loss(sk, 0); } if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) { /* Retransmission failed because of local congestion, * do not backoff. */ if (!icsk->icsk_retransmits) icsk->icsk_retransmits = 1; inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL), TCP_RTO_MAX); goto out; } /* Increase the timeout each time we retransmit. Note that * we do not increase the rtt estimate. rto is initialized * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests * that doubling rto each time is the least we can get away with. * In KA9Q, Karn uses this for the first few times, and then * goes to quadratic. netBSD doubles, but only goes up to *64, * and clamps at 1 to 64 sec afterwards. Note that 120 sec is * defined in the protocol as the maximum possible RTT. I guess * we'll have to use something other than TCP to talk to the * University of Mars. * * PAWS allows us longer timeouts and large windows, so once * implemented ftp to mars will work nicely. We will have to fix * the 120 second clamps though! */ icsk->icsk_backoff++; icsk->icsk_retransmits++; out_reset_timer: icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX); if (icsk->icsk_retransmits > sysctl_tcp_retries1) __sk_dst_reset(sk); out:; } static void tcp_write_timer(unsigned long data) { struct sock *sk = (struct sock*)data; struct inet_connection_sock *icsk = inet_csk(sk); int event; bh_lock_sock(sk); if (sock_owned_by_user(sk)) { /* Try again later */ sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + (HZ / 20)); goto out_unlock; } if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending) goto out; if (time_after(icsk->icsk_timeout, jiffies)) { sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); goto out; } event = icsk->icsk_pending; icsk->icsk_pending = 0; switch (event) { case ICSK_TIME_RETRANS: tcp_retransmit_timer(sk); break; case ICSK_TIME_PROBE0: tcp_probe_timer(sk); break; } TCP_CHECK_TIMER(sk); out: sk_stream_mem_reclaim(sk); out_unlock: bh_unlock_sock(sk); sock_put(sk); } /* * Timer for listening sockets */ static void tcp_synack_timer(struct sock *sk) { inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL, TCP_TIMEOUT_INIT, TCP_RTO_MAX); } void tcp_set_keepalive(struct sock *sk, int val) { if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) return; if (val && !sock_flag(sk, SOCK_KEEPOPEN)) inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); else if (!val) inet_csk_delete_keepalive_timer(sk); } static void tcp_keepalive_timer (unsigned long data) { struct sock *sk = (struct sock *) data; struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); __u32 elapsed; /* Only process if socket is not in use. */ 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_stream_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); }