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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>
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/tcp.h
View File

@ -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

1
include/net/inet_connection_sock.h
View File

@ -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))
};

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;
}

40
net/ipv4/tcp_timer.c
View File

@ -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;
@ -151,14 +151,15 @@ static bool retransmits_timed_out(struct sock *sk,
else
start_ts = tcp_sk(sk)->retrans_stamp;
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 (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;
}
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;