// 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, <[email protected]>
* Mark Evans, <[email protected]>
* Corey Minyard <[email protected]>
* Florian La Roche, <[email protected]>
* Charles Hedrick, <[email protected]>
* Linus Torvalds, <[email protected]>
* Alan Cox, <[email protected]>
* Matthew Dillon, <[email protected]>
* Arnt Gulbrandsen, <[email protected]>
* Jorge Cwik, <[email protected]>
*/
#include <linux/module.h>
#include <linux/gfp.h>
#include <net/tcp.h>
#include <net/rstreason.h>
static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
const struct tcp_sock *tp = tcp_sk(sk);
u32 elapsed, user_timeout;
s32 remaining;
user_timeout = READ_ONCE(icsk->icsk_user_timeout);
if (!user_timeout)
return icsk->icsk_rto;
elapsed = tcp_time_stamp_ts(tp) - tp->retrans_stamp;
if (tp->tcp_usec_ts)
elapsed /= USEC_PER_MSEC;
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)
{
const 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)
{
tcp_done_with_error(sk, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT);
__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,
SK_RST_REASON_TCP_ABORT_ON_MEMORY);
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)
{
struct tcp_sock *tp = tcp_sk(sk);
unsigned int start_ts, delta;
if (!inet_csk(sk)->icsk_retransmits)
return false;
start_ts = tp->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);
}
if (tp->tcp_usec_ts) {
/* delta maybe off up to a jiffy due to timer granularity. */
delta = tp->tcp_mstamp - start_ts + jiffies_to_usecs(1);
return (s32)(delta - timeout * USEC_PER_MSEC) >= 0;
}
return (s32)(tcp_time_stamp_ts(tp) - 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);
mptcp_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_t(u32, 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);
}
}
static void tcp_update_rto_stats(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
if (!icsk->icsk_retransmits) {
tp->total_rto_recoveries++;
tp->rto_stamp = tcp_time_stamp_ms(tp);
}
icsk->icsk_retransmits++;
tp->total_rto++;
}
/*
* 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++;
tcp_update_rto_stats(sk);
if (!tp->retrans_stamp)
tp->retrans_stamp = tcp_time_stamp_ts(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,
u32 rtx_delta)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout);
const struct tcp_sock *tp = tcp_sk(sk);
int timeout = TCP_RTO_MAX * 2;
s32 rcv_delta;
if (user_timeout) {
/* If user application specified a TCP_USER_TIMEOUT,
* it does not want win 0 packets to 'reset the timer'
* while retransmits are not making progress.
*/
if (rtx_delta > user_timeout)
return true;
timeout = min_t(u32, timeout, msecs_to_jiffies(user_timeout));
}
/* Note: timer interrupt might have been delayed by at least one jiffy,
* and tp->rcv_tstamp might very well have been written recently.
* rcv_delta can thus be negative.
*/
rcv_delta = icsk->icsk_timeout - tp->rcv_tstamp;
if (rcv_delta <= timeout)
return false;
return msecs_to_jiffies(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;
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_ts(tp) - (tp->retrans_stamp ?:
tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb));
if (tp->tcp_usec_ts)
rtx_delta /= USEC_PER_MSEC;
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, rtx_delta)) {
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);
tcp_update_rto_stats(sk);
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!
*/
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 ||
tp->total_rto >
READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts)) {
/* Use normal (exponential) backoff unless linear timeouts are
* activated.
*/
icsk->icsk_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 (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, SK_RST_REASON_TCP_STATE);
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,
SK_RST_REASON_TCP_KEEPALIVE_TIMEOUT);
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;
}
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