summaryrefslogtreecommitdiffstats
path: root/net/ipv4/tcp_timer.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--net/ipv4/tcp_timer.c819
1 files changed, 819 insertions, 0 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
new file mode 100644
index 000000000..44b49f7d1
--- /dev/null
+++ b/net/ipv4/tcp_timer.c
@@ -0,0 +1,819 @@
+// 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);
+}
+
+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);
+ 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_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 {
+ /* 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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-10-30 01:16:37 +0000