[PATCH v1 net] TCP_USER_TIMEOUT and tcp_keepalive should conform to RFC5482
flat view
STALE3357d
From: Rao Shoaib <hidden>
Date: 2017-08-07 18:16:44
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
Change from version 0: Rationale behind the change: The man page for tcp(7) states when used with the TCP keepalive (SO_KEEPALIVE) option, TCP_USER_TIMEOUT will override keepalive to determine when to close a connection due to keepalive failure. This is ambigious at best. user expectation is most likely that the connection will be reset after TCP_USER_TIMEOUT milliseconds of inactivity. The code however waits for the keepalive to kick-in (default 2hrs) and than after one failure resets the conenction. What is the rationale for that ? The same effect can be obtained by simply changing the value of tcp_keep_alive_probes. Since the TCP_USER_TIMEOUT option was added based on RFC 5482 we need to follow the RFC. Which states 4.2 TCP keep-Alives: Some TCP implementations, such as those in BSD systems, use a different abort policy for TCP keep-alives than for user data. Thus, the TCP keep-alive mechanism might abort a connection that would otherwise have survived the transient period without connectivity. Therefore, if a connection that enables keep-alives is also using the TCP User Timeout Option, then the keep-alive timer MUST be set to a value larger than that of the adopted USER TIMEOUT. This patch enforces the MUST and also dis-associates user timeout from keep alive. A man page patch will be submitted separately. Signed-off-by: Rao Shoaib <redacted> --- net/ipv4/tcp.c | 10 ++++++++-- net/ipv4/tcp_timer.c | 9 +-------- 2 files changed, 9 insertions(+), 10 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 71ce33d..f2af44d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c@@ -2628,7 +2628,9 @@ static int do_tcp_setsockopt(struct sock *sk, int level, break; case TCP_KEEPIDLE: - if (val < 1 || val > MAX_TCP_KEEPIDLE) + /* Per RFC5482 keepalive_time must be > user_timeout */ + if (val < 1 || val > MAX_TCP_KEEPIDLE || + ((val * HZ) <= icsk->icsk_user_timeout)) err = -EINVAL; else { tp->keepalive_time = val * HZ;
@@ -2724,8 +2726,12 @@ static int do_tcp_setsockopt(struct sock *sk, int level, case TCP_USER_TIMEOUT: /* Cap the max time in ms TCP will retry or probe the window * before giving up and aborting (ETIMEDOUT) a connection. + * Per RFC5482 TCP user timeout must be < keepalive_time. + * If the default value changes later -- all bets are off. */ - if (val < 0) + if (val < 0 || (tp->keepalive_time && + tp->keepalive_time <= msecs_to_jiffies(val)) || + net->ipv4.sysctl_tcp_keepalive_time <= msecs_to_jiffies(val)) err = -EINVAL; else icsk->icsk_user_timeout = msecs_to_jiffies(val);
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index c0feeee..d39fe60 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c@@ -664,14 +664,7 @@ static void tcp_keepalive_timer (unsigned long data) elapsed = keepalive_time_elapsed(tp); if (elapsed >= keepalive_time_when(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))) { + if (icsk->icsk_probes_out >= keepalive_probes(tp)) { tcp_send_active_reset(sk, GFP_ATOMIC); tcp_write_err(sk); goto out;
--
2.7.4