Commit dca43c75 authored by Jerry Chu's avatar Jerry Chu Committed by David S. Miller
Browse files

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: default avatarH.K. Jerry Chu <hkchu@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 409456b1

include/linux/tcp.h

+1 −0
Original line number Diff line number Diff line
@@ -105,6 +105,7 @@ enum { 
#define TCP_COOKIE_TRANSACTIONS	15	/* TCP Cookie Transactions */

#define TCP_THIN_LINEAR_TIMEOUTS 16      /* Use linear timeouts for thin streams*/

#define TCP_THIN_DUPACK         17      /* Fast retrans. after 1 dupack */

#define TCP_USER_TIMEOUT	18	/* How long for loss retry before timeout */



/* for TCP_INFO socket option */

#define TCPI_OPT_TIMESTAMPS	1

include/net/inet_connection_sock.h

+1 −0
Original line number Diff line number Diff line
@@ -125,6 +125,7 @@ struct inet_connection_sock { 
		int		  probe_size;

	} icsk_mtup;

	u32			  icsk_ca_priv[16];

	u32			  icsk_user_timeout;

#define ICSK_CA_PRIV_SIZE	(16 * sizeof(u32))

};

net/ipv4/tcp.c

+10 −1
Original line number Diff line number Diff line
@@ -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;

	}

net/ipv4/tcp_timer.c

+25 −15
Original line number Diff line number Diff line
@@ -138,10 +138,10 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 
 * 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;
@@ -151,6 +151,7 @@ static bool retransmits_timed_out(struct sock *sk, 
	else

		start_ts = tcp_sk(sk)->retrans_stamp;



	if (likely(timeout == 0)) {

		linear_backoff_thresh = ilog2(TCP_RTO_MAX/TCP_RTO_MIN);



		if (boundary <= linear_backoff_thresh)
@@ -158,7 +159,7 @@ static bool retransmits_timed_out(struct sock *sk, 
		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 @@ static int tcp_write_timeout(struct sock *sk) 
			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 @@ static int tcp_write_timeout(struct sock *sk) 


			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 @@ out_reset_timer: 
		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 @@ static void tcp_keepalive_timer (unsigned long data) 
	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;

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