diff options
Diffstat (limited to 'net/ipv4/tcp_timer.c')
-rw-r--r-- | net/ipv4/tcp_timer.c | 841 |
1 files changed, 841 insertions, 0 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c new file mode 100644 index 0000000000..984ab4a042 --- /dev/null +++ b/net/ipv4/tcp_timer.c @@ -0,0 +1,841 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * 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). + * + * 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 <linux/gfp.h> +#include <net/tcp.h> + +static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + u32 elapsed, start_ts, user_timeout; + s32 remaining; + + start_ts = tcp_sk(sk)->retrans_stamp; + user_timeout = READ_ONCE(icsk->icsk_user_timeout); + if (!user_timeout) + return icsk->icsk_rto; + elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts; + remaining = user_timeout - elapsed; + if (remaining <= 0) + return 1; /* user timeout has passed; fire ASAP */ + + return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining)); +} + +u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + u32 remaining, user_timeout; + s32 elapsed; + + user_timeout = READ_ONCE(icsk->icsk_user_timeout); + if (!user_timeout || !icsk->icsk_probes_tstamp) + return when; + + elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp; + if (unlikely(elapsed < 0)) + elapsed = 0; + remaining = msecs_to_jiffies(user_timeout) - elapsed; + remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN); + + return min_t(u32, remaining, when); +} + +/** + * tcp_write_err() - close socket and save error info + * @sk: The socket the error has appeared on. + * + * Returns: Nothing (void) + */ + +static void tcp_write_err(struct sock *sk) +{ + WRITE_ONCE(sk->sk_err, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT); + sk_error_report(sk); + + tcp_write_queue_purge(sk); + tcp_done(sk); + __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); +} + +/** + * tcp_out_of_resources() - Close socket if out of resources + * @sk: pointer to current socket + * @do_reset: send a last packet with reset flag + * + * 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. + * + * Also close if our net namespace is exiting; in that case there is no + * hope of ever communicating again since all netns interfaces are already + * down (or about to be down), and we need to release our dst references, + * which have been moved to the netns loopback interface, so the namespace + * can finish exiting. This condition is only possible if we are a kernel + * socket, as those do not hold references to the namespace. + * + * 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. + * 3. If our net namespace is exiting. + */ +static int tcp_out_of_resources(struct sock *sk, bool do_reset) +{ + struct tcp_sock *tp = tcp_sk(sk); + int shift = 0; + + /* If peer does not open window for long time, or did not transmit + * anything for long time, penalize it. */ + if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset) + shift++; + + /* If some dubious ICMP arrived, penalize even more. */ + if (READ_ONCE(sk->sk_err_soft)) + shift++; + + if (tcp_check_oom(sk, shift)) { + /* Catch exceptional cases, when connection requires reset. + * 1. Last segment was sent recently. */ + if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN || + /* 2. Window is closed. */ + (!tp->snd_wnd && !tp->packets_out)) + do_reset = true; + if (do_reset) + tcp_send_active_reset(sk, GFP_ATOMIC); + tcp_done(sk); + __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY); + return 1; + } + + if (!check_net(sock_net(sk))) { + /* Not possible to send reset; just close */ + tcp_done(sk); + return 1; + } + + return 0; +} + +/** + * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket + * @sk: Pointer to the current socket. + * @alive: bool, socket alive state + */ +static int tcp_orphan_retries(struct sock *sk, bool alive) +{ + int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */ + + /* We know from an ICMP that something is wrong. */ + if (READ_ONCE(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; +} + +static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) +{ + const struct net *net = sock_net(sk); + int mss; + + /* Black hole detection */ + if (!READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing)) + return; + + if (!icsk->icsk_mtup.enabled) { + icsk->icsk_mtup.enabled = 1; + icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; + } else { + mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; + mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss); + mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_mtu_probe_floor)); + mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss)); + icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); + } + tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); +} + +static unsigned int tcp_model_timeout(struct sock *sk, + unsigned int boundary, + unsigned int rto_base) +{ + unsigned int linear_backoff_thresh, timeout; + + linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base); + if (boundary <= linear_backoff_thresh) + timeout = ((2 << boundary) - 1) * rto_base; + else + timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + + (boundary - linear_backoff_thresh) * TCP_RTO_MAX; + return jiffies_to_msecs(timeout); +} +/** + * retransmits_timed_out() - returns true if this connection has timed out + * @sk: The current socket + * @boundary: max number of retransmissions + * @timeout: A custom timeout value. + * If set to 0 the default timeout is calculated and used. + * Using TCP_RTO_MIN and the number of unsuccessful retransmits. + * + * The default "timeout" value this function can calculate and use + * is equivalent to the timeout of a TCP Connection + * after "boundary" unsuccessful, exponentially backed-off + * retransmissions with an initial RTO of TCP_RTO_MIN. + */ +static bool retransmits_timed_out(struct sock *sk, + unsigned int boundary, + unsigned int timeout) +{ + unsigned int start_ts; + + if (!inet_csk(sk)->icsk_retransmits) + return false; + + start_ts = tcp_sk(sk)->retrans_stamp; + if (likely(timeout == 0)) { + unsigned int rto_base = TCP_RTO_MIN; + + if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) + rto_base = tcp_timeout_init(sk); + timeout = tcp_model_timeout(sk, boundary, rto_base); + } + + return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0; +} + +/* 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); + struct net *net = sock_net(sk); + bool expired = false, do_reset; + int retry_until, max_retransmits; + + if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { + if (icsk->icsk_retransmits) + __dst_negative_advice(sk); + /* Paired with WRITE_ONCE() in tcp_sock_set_syncnt() */ + retry_until = READ_ONCE(icsk->icsk_syn_retries) ? : + READ_ONCE(net->ipv4.sysctl_tcp_syn_retries); + + max_retransmits = retry_until; + if (sk->sk_state == TCP_SYN_SENT) + max_retransmits += READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts); + + expired = icsk->icsk_retransmits >= max_retransmits; + } else { + if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1), 0)) { + /* Black hole detection */ + tcp_mtu_probing(icsk, sk); + + __dst_negative_advice(sk); + } + + retry_until = READ_ONCE(net->ipv4.sysctl_tcp_retries2); + if (sock_flag(sk, SOCK_DEAD)) { + const bool alive = icsk->icsk_rto < TCP_RTO_MAX; + + retry_until = tcp_orphan_retries(sk, alive); + do_reset = alive || + !retransmits_timed_out(sk, retry_until, 0); + + if (tcp_out_of_resources(sk, do_reset)) + return 1; + } + } + if (!expired) + expired = retransmits_timed_out(sk, retry_until, + READ_ONCE(icsk->icsk_user_timeout)); + tcp_fastopen_active_detect_blackhole(sk, expired); + + if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG)) + tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB, + icsk->icsk_retransmits, + icsk->icsk_rto, (int)expired); + + if (expired) { + /* Has it gone just too far? */ + tcp_write_err(sk); + return 1; + } + + if (sk_rethink_txhash(sk)) { + tp->timeout_rehash++; + __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH); + } + + return 0; +} + +/* Called with BH disabled */ +void tcp_delack_timer_handler(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + + if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) + return; + + /* Handling the sack compression case */ + if (tp->compressed_ack) { + tcp_mstamp_refresh(tp); + tcp_sack_compress_send_ack(sk); + return; + } + + if (!(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) + return; + + if (time_after(icsk->icsk_ack.timeout, jiffies)) { + sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); + return; + } + icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; + + if (inet_csk_ack_scheduled(sk)) { + if (!inet_csk_in_pingpong_mode(sk)) { + /* 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. + */ + inet_csk_exit_pingpong_mode(sk); + icsk->icsk_ack.ato = TCP_ATO_MIN; + } + tcp_mstamp_refresh(tp); + tcp_send_ack(sk); + __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS); + } +} + + +/** + * tcp_delack_timer() - The TCP delayed ACK timeout handler + * @t: Pointer to the timer. (gets casted to struct sock *) + * + * This function gets (indirectly) called when the kernel timer for a TCP packet + * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work. + * + * Returns: Nothing (void) + */ +static void tcp_delack_timer(struct timer_list *t) +{ + struct inet_connection_sock *icsk = + from_timer(icsk, t, icsk_delack_timer); + struct sock *sk = &icsk->icsk_inet.sk; + + bh_lock_sock(sk); + if (!sock_owned_by_user(sk)) { + tcp_delack_timer_handler(sk); + } else { + __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); + /* deleguate our work to tcp_release_cb() */ + if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags)) + sock_hold(sk); + } + bh_unlock_sock(sk); + sock_put(sk); +} + +static void tcp_probe_timer(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct sk_buff *skb = tcp_send_head(sk); + struct tcp_sock *tp = tcp_sk(sk); + int max_probes; + + if (tp->packets_out || !skb) { + icsk->icsk_probes_out = 0; + icsk->icsk_probes_tstamp = 0; + return; + } + + /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as + * long as the receiver continues to respond probes. We support this by + * default and reset icsk_probes_out with incoming ACKs. But if the + * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we + * kill the socket when the retry count and the time exceeds the + * corresponding system limit. We also implement similar policy when + * we use RTO to probe window in tcp_retransmit_timer(). + */ + if (!icsk->icsk_probes_tstamp) { + icsk->icsk_probes_tstamp = tcp_jiffies32; + } else { + u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout); + + if (user_timeout && + (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >= + msecs_to_jiffies(user_timeout)) + goto abort; + } + max_probes = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retries2); + if (sock_flag(sk, SOCK_DEAD)) { + const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX; + + max_probes = tcp_orphan_retries(sk, alive); + if (!alive && icsk->icsk_backoff >= max_probes) + goto abort; + if (tcp_out_of_resources(sk, true)) + return; + } + + if (icsk->icsk_probes_out >= max_probes) { +abort: tcp_write_err(sk); + } else { + /* Only send another probe if we didn't close things up. */ + tcp_send_probe0(sk); + } +} + +/* + * Timer for Fast Open socket to retransmit SYNACK. Note that the + * sk here is the child socket, not the parent (listener) socket. + */ +static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + int max_retries; + + req->rsk_ops->syn_ack_timeout(req); + + /* Add one more retry for fastopen. + * Paired with WRITE_ONCE() in tcp_sock_set_syncnt() + */ + max_retries = READ_ONCE(icsk->icsk_syn_retries) ? : + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1; + + if (req->num_timeout >= max_retries) { + tcp_write_err(sk); + return; + } + /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */ + if (icsk->icsk_retransmits == 1) + tcp_enter_loss(sk); + /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error + * returned from rtx_syn_ack() to make it more persistent like + * regular retransmit because if the child socket has been accepted + * it's not good to give up too easily. + */ + inet_rtx_syn_ack(sk, req); + req->num_timeout++; + icsk->icsk_retransmits++; + if (!tp->retrans_stamp) + tp->retrans_stamp = tcp_time_stamp(tp); + inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + req->timeout << req->num_timeout, TCP_RTO_MAX); +} + +static bool tcp_rtx_probe0_timed_out(const struct sock *sk, + const struct sk_buff *skb) +{ + const struct tcp_sock *tp = tcp_sk(sk); + const int timeout = TCP_RTO_MAX * 2; + u32 rcv_delta, rtx_delta; + + rcv_delta = inet_csk(sk)->icsk_timeout - tp->rcv_tstamp; + if (rcv_delta <= timeout) + return false; + + rtx_delta = (u32)msecs_to_jiffies(tcp_time_stamp(tp) - + (tp->retrans_stamp ?: tcp_skb_timestamp(skb))); + + return rtx_delta > timeout; +} + +/** + * tcp_retransmit_timer() - The TCP retransmit timeout handler + * @sk: Pointer to the current socket. + * + * This function gets called when the kernel timer for a TCP packet + * of this socket expires. + * + * It handles retransmission, timer adjustment and other necessary measures. + * + * Returns: Nothing (void) + */ +void tcp_retransmit_timer(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct net *net = sock_net(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + struct request_sock *req; + struct sk_buff *skb; + + req = rcu_dereference_protected(tp->fastopen_rsk, + lockdep_sock_is_held(sk)); + if (req) { + WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && + sk->sk_state != TCP_FIN_WAIT1); + tcp_fastopen_synack_timer(sk, req); + /* Before we receive ACK to our SYN-ACK don't retransmit + * anything else (e.g., data or FIN segments). + */ + return; + } + + if (!tp->packets_out) + return; + + skb = tcp_rtx_queue_head(sk); + if (WARN_ON_ONCE(!skb)) + return; + + tp->tlp_high_seq = 0; + + 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. + */ + struct inet_sock *inet = inet_sk(sk); + u32 rtx_delta; + + rtx_delta = tcp_time_stamp(tp) - (tp->retrans_stamp ?: tcp_skb_timestamp(skb)); + if (sk->sk_family == AF_INET) { + net_dbg_ratelimited("Probing zero-window on %pI4:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n", + &inet->inet_daddr, ntohs(inet->inet_dport), + inet->inet_num, tp->snd_una, tp->snd_nxt, + jiffies_to_msecs(jiffies - tp->rcv_tstamp), + rtx_delta); + } +#if IS_ENABLED(CONFIG_IPV6) + else if (sk->sk_family == AF_INET6) { + net_dbg_ratelimited("Probing zero-window on %pI6:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n", + &sk->sk_v6_daddr, ntohs(inet->inet_dport), + inet->inet_num, tp->snd_una, tp->snd_nxt, + jiffies_to_msecs(jiffies - tp->rcv_tstamp), + rtx_delta); + } +#endif + if (tcp_rtx_probe0_timed_out(sk, skb)) { + tcp_write_err(sk); + goto out; + } + tcp_enter_loss(sk); + tcp_retransmit_skb(sk, skb, 1); + __sk_dst_reset(sk); + goto out_reset_timer; + } + + __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); + if (tcp_write_timeout(sk)) + goto out; + + if (icsk->icsk_retransmits == 0) { + int mib_idx = 0; + + if (icsk->icsk_ca_state == TCP_CA_Recovery) { + if (tcp_is_sack(tp)) + mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; + else + mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; + } else if (icsk->icsk_ca_state == TCP_CA_Loss) { + mib_idx = LINUX_MIB_TCPLOSSFAILURES; + } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || + tp->sacked_out) { + if (tcp_is_sack(tp)) + mib_idx = LINUX_MIB_TCPSACKFAILURES; + else + mib_idx = LINUX_MIB_TCPRENOFAILURES; + } + if (mib_idx) + __NET_INC_STATS(sock_net(sk), mib_idx); + } + + tcp_enter_loss(sk); + + icsk->icsk_retransmits++; + if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) { + /* Retransmission failed because of local congestion, + * Let senders fight for local resources conservatively. + */ + inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + 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++; + +out_reset_timer: + /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is + * used to reset timer, set to 0. Recalculate 'icsk_rto' as this + * might be increased if the stream oscillates between thin and thick, + * thus the old value might already be too high compared to the value + * set by 'tcp_set_rto' in tcp_input.c which resets the rto without + * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating + * exponential backoff behaviour to avoid continue hammering + * linear-timeout retransmissions into a black hole + */ + if (sk->sk_state == TCP_ESTABLISHED && + (tp->thin_lto || READ_ONCE(net->ipv4.sysctl_tcp_thin_linear_timeouts)) && + tcp_stream_is_thin(tp) && + icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { + icsk->icsk_backoff = 0; + icsk->icsk_rto = clamp(__tcp_set_rto(tp), + tcp_rto_min(sk), + TCP_RTO_MAX); + } else if (sk->sk_state != TCP_SYN_SENT || + icsk->icsk_backoff > + READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts)) { + /* Use normal (exponential) backoff unless linear timeouts are + * activated. + */ + icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); + } + inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX); + if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0)) + __sk_dst_reset(sk); + +out:; +} + +/* Called with bottom-half processing disabled. + Called by tcp_write_timer() */ +void tcp_write_timer_handler(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + int event; + + if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || + !icsk->icsk_pending) + return; + + if (time_after(icsk->icsk_timeout, jiffies)) { + sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); + return; + } + + tcp_mstamp_refresh(tcp_sk(sk)); + event = icsk->icsk_pending; + + switch (event) { + case ICSK_TIME_REO_TIMEOUT: + tcp_rack_reo_timeout(sk); + break; + case ICSK_TIME_LOSS_PROBE: + tcp_send_loss_probe(sk); + break; + case ICSK_TIME_RETRANS: + icsk->icsk_pending = 0; + tcp_retransmit_timer(sk); + break; + case ICSK_TIME_PROBE0: + icsk->icsk_pending = 0; + tcp_probe_timer(sk); + break; + } +} + +static void tcp_write_timer(struct timer_list *t) +{ + struct inet_connection_sock *icsk = + from_timer(icsk, t, icsk_retransmit_timer); + struct sock *sk = &icsk->icsk_inet.sk; + + bh_lock_sock(sk); + if (!sock_owned_by_user(sk)) { + tcp_write_timer_handler(sk); + } else { + /* delegate our work to tcp_release_cb() */ + if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags)) + sock_hold(sk); + } + bh_unlock_sock(sk); + sock_put(sk); +} + +void tcp_syn_ack_timeout(const struct request_sock *req) +{ + struct net *net = read_pnet(&inet_rsk(req)->ireq_net); + + __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS); +} +EXPORT_SYMBOL(tcp_syn_ack_timeout); + +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); +} +EXPORT_SYMBOL_GPL(tcp_set_keepalive); + + +static void tcp_keepalive_timer (struct timer_list *t) +{ + struct sock *sk = from_timer(sk, t, sk_timer); + 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) { + pr_err("Hmm... keepalive on a LISTEN ???\n"); + goto out; + } + + tcp_mstamp_refresh(tp); + if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { + if (READ_ONCE(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) || + ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT))) + goto out; + + elapsed = keepalive_time_when(tp); + + /* It is alive without keepalive 8) */ + if (tp->packets_out || !tcp_write_queue_empty(sk)) + goto resched; + + elapsed = keepalive_time_elapsed(tp); + + if (elapsed >= keepalive_time_when(tp)) { + u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout); + + /* If the TCP_USER_TIMEOUT option is enabled, use that + * to determine when to timeout instead. + */ + if ((user_timeout != 0 && + elapsed >= msecs_to_jiffies(user_timeout) && + icsk->icsk_probes_out > 0) || + (user_timeout == 0 && + icsk->icsk_probes_out >= keepalive_probes(tp))) { + tcp_send_active_reset(sk, GFP_ATOMIC); + tcp_write_err(sk); + goto out; + } + if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 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; + } + +resched: + inet_csk_reset_keepalive_timer (sk, elapsed); + goto out; + +death: + tcp_done(sk); + +out: + bh_unlock_sock(sk); + sock_put(sk); +} + +static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer) +{ + struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer); + struct sock *sk = (struct sock *)tp; + + bh_lock_sock(sk); + if (!sock_owned_by_user(sk)) { + if (tp->compressed_ack) { + /* Since we have to send one ack finally, + * subtract one from tp->compressed_ack to keep + * LINUX_MIB_TCPACKCOMPRESSED accurate. + */ + tp->compressed_ack--; + tcp_send_ack(sk); + } + } else { + if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, + &sk->sk_tsq_flags)) + sock_hold(sk); + } + bh_unlock_sock(sk); + + sock_put(sk); + + return HRTIMER_NORESTART; +} + +void tcp_init_xmit_timers(struct sock *sk) +{ + inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, + &tcp_keepalive_timer); + hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC, + HRTIMER_MODE_ABS_PINNED_SOFT); + tcp_sk(sk)->pacing_timer.function = tcp_pace_kick; + + hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC, + HRTIMER_MODE_REL_PINNED_SOFT); + tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick; +} |