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tcp: Add TCP_USER_TIMEOUT socket option.

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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>
This commit is contained in:
Jerry Chu
2010-08-27 19:13:28 +00:00
committed by David S. Miller
parent 409456b10f
commit dca43c75e7
4 changed files with 37 additions and 16 deletions
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11
net/ipv4/tcp.c
View File

@@ -2391,7 +2391,12 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
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 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
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;
}