| // 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; |
| s32 remaining; |
| |
| start_ts = tcp_sk(sk)->retrans_stamp; |
| if (!icsk->icsk_user_timeout) |
| return icsk->icsk_rto; |
| elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts; |
| remaining = icsk->icsk_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; |
| s32 elapsed; |
| |
| if (!icsk->icsk_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(icsk->icsk_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) |
| { |
| sk->sk_err = 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 (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 (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; |
| |
| if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { |
| if (icsk->icsk_retransmits) |
| __dst_negative_advice(sk); |
| retry_until = icsk->icsk_syn_retries ? : |
| READ_ONCE(net->ipv4.sysctl_tcp_syn_retries); |
| expired = icsk->icsk_retransmits >= retry_until; |
| } 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, |
| 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 if (icsk->icsk_user_timeout && |
| (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >= |
| msecs_to_jiffies(icsk->icsk_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 */ |
| max_retries = 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); |
| } |
| |
| |
| /** |
| * 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); |
| if (sk->sk_family == AF_INET) { |
| net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", |
| &inet->inet_daddr, |
| ntohs(inet->inet_dport), |
| inet->inet_num, |
| tp->snd_una, tp->snd_nxt); |
| } |
| #if IS_ENABLED(CONFIG_IPV6) |
| else if (sk->sk_family == AF_INET6) { |
| net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", |
| &sk->sk_v6_daddr, |
| ntohs(inet->inet_dport), |
| inet->inet_num, |
| tp->snd_una, tp->snd_nxt); |
| } |
| #endif |
| if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) { |
| 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 = min(__tcp_set_rto(tp), TCP_RTO_MAX); |
| } else { |
| /* Use normal (exponential) backoff */ |
| 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 (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)) { |
| /* If the TCP_USER_TIMEOUT option is enabled, use that |
| * to determine when to timeout instead. |
| */ |
| if ((icsk->icsk_user_timeout != 0 && |
| elapsed >= msecs_to_jiffies(icsk->icsk_user_timeout) && |
| icsk->icsk_probes_out > 0) || |
| (icsk->icsk_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; |
| } |