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.c b/net/ipv4/tcp.c
index 176e11a..cf32545 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2391,7 +2391,12 @@
err = tp->af_specific->md5_parse(sk, optval, optlen);
break;
#endif
-
+ case TCP_USER_TIMEOUT:
+ /* Cap the max timeout in ms TCP will retry/retrans
+ * before giving up and aborting (ETIMEDOUT) a connection.
+ */
+ icsk->icsk_user_timeout = msecs_to_jiffies(val);
+ break;
default:
err = -ENOPROTOOPT;
break;
@@ -2610,6 +2615,10 @@
case TCP_THIN_DUPACK:
val = tp->thin_dupack;
break;
+
+ case TCP_USER_TIMEOUT:
+ val = jiffies_to_msecs(icsk->icsk_user_timeout);
+ break;
default:
return -ENOPROTOOPT;
}