From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sat, 16 Apr 2005 15:20:36 -0700 Subject: Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip! --- net/ipv4/tcp_timer.c | 656 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 656 insertions(+) create mode 100644 net/ipv4/tcp_timer.c (limited to 'net/ipv4/tcp_timer.c') diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c new file mode 100644 index 00000000000..85b279f1e93 --- /dev/null +++ b/net/ipv4/tcp_timer.c @@ -0,0 +1,656 @@ +/* + * 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, + * Mark Evans, + * Corey Minyard + * Florian La Roche, + * Charles Hedrick, + * Linus Torvalds, + * Alan Cox, + * Matthew Dillon, + * Arnt Gulbrandsen, + * Jorge Cwik, + */ + +#include +#include + +int sysctl_tcp_syn_retries = TCP_SYN_RETRIES; +int sysctl_tcp_synack_retries = TCP_SYNACK_RETRIES; +int sysctl_tcp_keepalive_time = TCP_KEEPALIVE_TIME; +int sysctl_tcp_keepalive_probes = TCP_KEEPALIVE_PROBES; +int sysctl_tcp_keepalive_intvl = TCP_KEEPALIVE_INTVL; +int sysctl_tcp_retries1 = TCP_RETR1; +int sysctl_tcp_retries2 = TCP_RETR2; +int sysctl_tcp_orphan_retries; + +static void tcp_write_timer(unsigned long); +static void tcp_delack_timer(unsigned long); +static void tcp_keepalive_timer (unsigned long data); + +#ifdef TCP_DEBUG +const char tcp_timer_bug_msg[] = KERN_DEBUG "tcpbug: unknown timer value\n"; +EXPORT_SYMBOL(tcp_timer_bug_msg); +#endif + +/* + * Using different timers for retransmit, delayed acks and probes + * We may wish use just one timer maintaining a list of expire jiffies + * to optimize. + */ + +void tcp_init_xmit_timers(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + init_timer(&tp->retransmit_timer); + tp->retransmit_timer.function=&tcp_write_timer; + tp->retransmit_timer.data = (unsigned long) sk; + tp->pending = 0; + + init_timer(&tp->delack_timer); + tp->delack_timer.function=&tcp_delack_timer; + tp->delack_timer.data = (unsigned long) sk; + tp->ack.pending = 0; + + init_timer(&sk->sk_timer); + sk->sk_timer.function = &tcp_keepalive_timer; + sk->sk_timer.data = (unsigned long)sk; +} + +void tcp_clear_xmit_timers(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tp->pending = 0; + sk_stop_timer(sk, &tp->retransmit_timer); + + tp->ack.pending = 0; + tp->ack.blocked = 0; + sk_stop_timer(sk, &tp->delack_timer); + + sk_stop_timer(sk, &sk->sk_timer); +} + +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. + * + * Criterium 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 (orphans >= sysctl_tcp_max_orphans || + (sk->sk_wmem_queued > SOCK_MIN_SNDBUF && + atomic_read(&tcp_memory_allocated) > sysctl_tcp_mem[2])) { + 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 tcp_sock *tp = tcp_sk(sk); + int retry_until; + + if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { + if (tp->retransmits) + dst_negative_advice(&sk->sk_dst_cache); + retry_until = tp->syn_retries ? : sysctl_tcp_syn_retries; + } else { + if (tp->retransmits >= sysctl_tcp_retries1) { + /* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu black + hole detection. :-( + + It is place to make it. It is not made. I do not want + to make it. It is disguisting. It does not work in any + case. Let me to cite the same draft, which requires for + us to implement this: + + "The one security concern raised by this memo is that ICMP black holes + are often caused by over-zealous security administrators who block + all ICMP messages. It is vitally important that those who design and + deploy security systems understand the impact of strict filtering on + upper-layer protocols. The safest web site in the world is worthless + if most TCP implementations cannot transfer data from it. It would + be far nicer to have all of the black holes fixed rather than fixing + all of the TCP implementations." + + Golden words :-). + */ + + dst_negative_advice(&sk->sk_dst_cache); + } + + retry_until = sysctl_tcp_retries2; + if (sock_flag(sk, SOCK_DEAD)) { + int alive = (tp->rto < TCP_RTO_MAX); + + retry_until = tcp_orphan_retries(sk, alive); + + if (tcp_out_of_resources(sk, alive || tp->retransmits < retry_until)) + return 1; + } + } + + if (tp->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); + + bh_lock_sock(sk); + if (sock_owned_by_user(sk)) { + /* Try again later. */ + tp->ack.blocked = 1; + NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOCKED); + sk_reset_timer(sk, &tp->delack_timer, jiffies + TCP_DELACK_MIN); + goto out_unlock; + } + + sk_stream_mem_reclaim(sk); + + if (sk->sk_state == TCP_CLOSE || !(tp->ack.pending & TCP_ACK_TIMER)) + goto out; + + if (time_after(tp->ack.timeout, jiffies)) { + sk_reset_timer(sk, &tp->delack_timer, tp->ack.timeout); + goto out; + } + tp->ack.pending &= ~TCP_ACK_TIMER; + + if (skb_queue_len(&tp->ucopy.prequeue)) { + struct sk_buff *skb; + + NET_ADD_STATS_BH(LINUX_MIB_TCPSCHEDULERFAILED, + skb_queue_len(&tp->ucopy.prequeue)); + + while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) + sk->sk_backlog_rcv(sk, skb); + + tp->ucopy.memory = 0; + } + + if (tcp_ack_scheduled(tp)) { + if (!tp->ack.pingpong) { + /* Delayed ACK missed: inflate ATO. */ + tp->ack.ato = min(tp->ack.ato << 1, tp->rto); + } else { + /* Delayed ACK missed: leave pingpong mode and + * deflate ATO. + */ + tp->ack.pingpong = 0; + tp->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 tcp_sock *tp = tcp_sk(sk); + int max_probes; + + if (tp->packets_out || !sk->sk_send_head) { + tp->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. 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)) { + int alive = ((tp->rto<backoff) < TCP_RTO_MAX); + + max_probes = tcp_orphan_retries(sk, alive); + + if (tcp_out_of_resources(sk, alive || tp->probes_out <= max_probes)) + return; + } + + if (tp->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); + + if (!tp->packets_out) + goto out; + + BUG_TRAP(!skb_queue_empty(&sk->sk_write_queue)); + + 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 (net_ratelimit()) { + struct inet_sock *inet = inet_sk(sk); + printk(KERN_DEBUG "TCP: Treason uncloaked! Peer %u.%u.%u.%u:%u/%u shrinks window %u:%u. Repaired.\n", + NIPQUAD(inet->daddr), htons(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, skb_peek(&sk->sk_write_queue)); + __sk_dst_reset(sk); + goto out_reset_timer; + } + + if (tcp_write_timeout(sk)) + goto out; + + if (tp->retransmits == 0) { + if (tp->ca_state == TCP_CA_Disorder || tp->ca_state == TCP_CA_Recovery) { + if (tp->rx_opt.sack_ok) { + if (tp->ca_state == TCP_CA_Recovery) + NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERYFAIL); + else + NET_INC_STATS_BH(LINUX_MIB_TCPSACKFAILURES); + } else { + if (tp->ca_state == TCP_CA_Recovery) + NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERYFAIL); + else + NET_INC_STATS_BH(LINUX_MIB_TCPRENOFAILURES); + } + } else if (tp->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, skb_peek(&sk->sk_write_queue)) > 0) { + /* Retransmission failed because of local congestion, + * do not backoff. + */ + if (!tp->retransmits) + tp->retransmits=1; + tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, + min(tp->rto, TCP_RESOURCE_PROBE_INTERVAL)); + 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! + */ + tp->backoff++; + tp->retransmits++; + +out_reset_timer: + tp->rto = min(tp->rto << 1, TCP_RTO_MAX); + tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); + if (tp->retransmits > sysctl_tcp_retries1) + __sk_dst_reset(sk); + +out:; +} + +static void tcp_write_timer(unsigned long data) +{ + struct sock *sk = (struct sock*)data; + struct tcp_sock *tp = tcp_sk(sk); + int event; + + bh_lock_sock(sk); + if (sock_owned_by_user(sk)) { + /* Try again later */ + sk_reset_timer(sk, &tp->retransmit_timer, jiffies + (HZ / 20)); + goto out_unlock; + } + + if (sk->sk_state == TCP_CLOSE || !tp->pending) + goto out; + + if (time_after(tp->timeout, jiffies)) { + sk_reset_timer(sk, &tp->retransmit_timer, tp->timeout); + goto out; + } + + event = tp->pending; + tp->pending = 0; + + switch (event) { + case TCP_TIME_RETRANS: + tcp_retransmit_timer(sk); + break; + case TCP_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) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_listen_opt *lopt = tp->listen_opt; + int max_retries = tp->syn_retries ? : sysctl_tcp_synack_retries; + int thresh = max_retries; + unsigned long now = jiffies; + struct open_request **reqp, *req; + int i, budget; + + if (lopt == NULL || lopt->qlen == 0) + return; + + /* Normally all the openreqs are young and become mature + * (i.e. converted to established socket) for first timeout. + * If synack was not acknowledged for 3 seconds, it means + * one of the following things: synack was lost, ack was lost, + * rtt is high or nobody planned to ack (i.e. synflood). + * When server is a bit loaded, queue is populated with old + * open requests, reducing effective size of queue. + * When server is well loaded, queue size reduces to zero + * after several minutes of work. It is not synflood, + * it is normal operation. The solution is pruning + * too old entries overriding normal timeout, when + * situation becomes dangerous. + * + * Essentially, we reserve half of room for young + * embrions; and abort old ones without pity, if old + * ones are about to clog our table. + */ + if (lopt->qlen>>(lopt->max_qlen_log-1)) { + int young = (lopt->qlen_young<<1); + + while (thresh > 2) { + if (lopt->qlen < young) + break; + thresh--; + young <<= 1; + } + } + + if (tp->defer_accept) + max_retries = tp->defer_accept; + + budget = 2*(TCP_SYNQ_HSIZE/(TCP_TIMEOUT_INIT/TCP_SYNQ_INTERVAL)); + i = lopt->clock_hand; + + do { + reqp=&lopt->syn_table[i]; + while ((req = *reqp) != NULL) { + if (time_after_eq(now, req->expires)) { + if ((req->retrans < thresh || + (req->acked && req->retrans < max_retries)) + && !req->class->rtx_syn_ack(sk, req, NULL)) { + unsigned long timeo; + + if (req->retrans++ == 0) + lopt->qlen_young--; + timeo = min((TCP_TIMEOUT_INIT << req->retrans), + TCP_RTO_MAX); + req->expires = now + timeo; + reqp = &req->dl_next; + continue; + } + + /* Drop this request */ + write_lock(&tp->syn_wait_lock); + *reqp = req->dl_next; + write_unlock(&tp->syn_wait_lock); + lopt->qlen--; + if (req->retrans == 0) + lopt->qlen_young--; + tcp_openreq_free(req); + continue; + } + reqp = &req->dl_next; + } + + i = (i+1)&(TCP_SYNQ_HSIZE-1); + + } while (--budget > 0); + + lopt->clock_hand = i; + + if (lopt->qlen) + tcp_reset_keepalive_timer(sk, TCP_SYNQ_INTERVAL); +} + +void tcp_delete_keepalive_timer (struct sock *sk) +{ + sk_stop_timer(sk, &sk->sk_timer); +} + +void tcp_reset_keepalive_timer (struct sock *sk, unsigned long len) +{ + sk_reset_timer(sk, &sk->sk_timer, jiffies + len); +} + +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)) + tcp_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); + else if (!val) + tcp_delete_keepalive_timer(sk); +} + + +static void tcp_keepalive_timer (unsigned long data) +{ + struct sock *sk = (struct sock *) data; + 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. */ + tcp_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) { + int tmo = tcp_fin_time(tp) - 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 || sk->sk_send_head) + goto resched; + + elapsed = tcp_time_stamp - tp->rcv_tstamp; + + if (elapsed >= keepalive_time_when(tp)) { + if ((!tp->keepalive_probes && tp->probes_out >= sysctl_tcp_keepalive_probes) || + (tp->keepalive_probes && tp->probes_out >= tp->keepalive_probes)) { + tcp_send_active_reset(sk, GFP_ATOMIC); + tcp_write_err(sk); + goto out; + } + if (tcp_write_wakeup(sk) <= 0) { + tp->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: + tcp_reset_keepalive_timer (sk, elapsed); + goto out; + +death: + tcp_done(sk); + +out: + bh_unlock_sock(sk); + sock_put(sk); +} + +EXPORT_SYMBOL(tcp_clear_xmit_timers); +EXPORT_SYMBOL(tcp_delete_keepalive_timer); +EXPORT_SYMBOL(tcp_init_xmit_timers); +EXPORT_SYMBOL(tcp_reset_keepalive_timer); -- cgit v1.2.3