tcp: Add TCP_USER_TIMEOUT socket option.
This patch provides a "user timeout" support as described in RFC793. The
socket option is also needed for the the local half of RFC5482 "TCP User
Timeout Option".
TCP_USER_TIMEOUT is a TCP level socket option that takes an unsigned int,
when > 0, to specify the maximum amount of time in ms that transmitted
data may remain unacknowledged before TCP will forcefully close the
corresponding connection and return ETIMEDOUT to the application. If
0 is given, TCP will continue to use the system default.
Increasing the user timeouts allows a TCP connection to survive extended
periods without end-to-end connectivity. Decreasing the user timeouts
allows applications to "fail fast" if so desired. Otherwise it may take
upto 20 minutes with the current system defaults in a normal WAN
environment.
The socket option can be made during any state of a TCP connection, but
is only effective during the synchronized states of a connection
(ESTABLISHED, FIN-WAIT-1, FIN-WAIT-2, CLOSE-WAIT, CLOSING, or LAST-ACK).
Moreover, when used with the TCP keepalive (SO_KEEPALIVE) option,
TCP_USER_TIMEOUT will overtake keepalive to determine when to close a
connection due to keepalive failure.
The option does not change in anyway when TCP retransmits a packet, nor
when a keepalive probe will be sent.
This option, like many others, will be inherited by an acceptor from its
listener.
Signed-off-by: H.K. Jerry Chu <hkchu@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 808bb92..11569de 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -138,10 +138,10 @@
* retransmissions with an initial RTO of TCP_RTO_MIN.
*/
static bool retransmits_timed_out(struct sock *sk,
- unsigned int boundary)
+ unsigned int boundary,
+ unsigned int timeout)
{
- unsigned int timeout, linear_backoff_thresh;
- unsigned int start_ts;
+ unsigned int linear_backoff_thresh, start_ts;
if (!inet_csk(sk)->icsk_retransmits)
return false;
@@ -151,14 +151,15 @@
else
start_ts = tcp_sk(sk)->retrans_stamp;
- linear_backoff_thresh = ilog2(TCP_RTO_MAX/TCP_RTO_MIN);
+ if (likely(timeout == 0)) {
+ linear_backoff_thresh = ilog2(TCP_RTO_MAX/TCP_RTO_MIN);
- if (boundary <= linear_backoff_thresh)
- timeout = ((2 << boundary) - 1) * TCP_RTO_MIN;
- else
- timeout = ((2 << linear_backoff_thresh) - 1) * TCP_RTO_MIN +
- (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
-
+ if (boundary <= linear_backoff_thresh)
+ timeout = ((2 << boundary) - 1) * TCP_RTO_MIN;
+ else
+ timeout = ((2 << linear_backoff_thresh) - 1) * TCP_RTO_MIN +
+ (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
+ }
return (tcp_time_stamp - start_ts) >= timeout;
}
@@ -174,7 +175,7 @@
dst_negative_advice(sk);
retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
} else {
- if (retransmits_timed_out(sk, sysctl_tcp_retries1)) {
+ if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0)) {
/* Black hole detection */
tcp_mtu_probing(icsk, sk);
@@ -187,14 +188,16 @@
retry_until = tcp_orphan_retries(sk, alive);
do_reset = alive ||
- !retransmits_timed_out(sk, retry_until);
+ !retransmits_timed_out(sk, retry_until, 0);
if (tcp_out_of_resources(sk, do_reset))
return 1;
}
}
- if (retransmits_timed_out(sk, retry_until)) {
+ if (retransmits_timed_out(sk, retry_until,
+ (1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV) ? 0 :
+ icsk->icsk_user_timeout)) {
/* Has it gone just too far? */
tcp_write_err(sk);
return 1;
@@ -436,7 +439,7 @@
icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
}
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
- if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1))
+ if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1, 0))
__sk_dst_reset(sk);
out:;
@@ -556,7 +559,14 @@
elapsed = keepalive_time_elapsed(tp);
if (elapsed >= keepalive_time_when(tp)) {
- if (icsk->icsk_probes_out >= keepalive_probes(tp)) {
+ /* If the TCP_USER_TIMEOUT option is enabled, use that
+ * to determine when to timeout instead.
+ */
+ if ((icsk->icsk_user_timeout != 0 &&
+ elapsed >= 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;