Re: [PATCH] sctp: don't compare hb_timer expire date before starting it
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: 2019-02-22 12:49:20
Also in:
linux-sctp
On Fri, Feb 22, 2019 at 09:45:26AM +0100, kwiecienmaciek@gmail.com wrote:
From: Maciej Kwiecien <redacted>
hb_timer might not start at all for a particular transport because its
start is conditional. In a result a node is not sending heartbeats.
Function sctp_transport_reset_hb_timer has two roles:
- initial start of hb_timer for a given transport,
- update expire date of hb_timer for a given transport.
The function is optimized to update timer's expire only if it is before
a new calculated one but this comparison is invalid for a timer which
has not yet started. Such a timer has expire == 0 and if a new expire
value is bigger than (MAX_JIFFIES / 2 + 2) then "time_before" macro will
fail and timer will not start resulting in no heartbeat packets send by
the node.
This was found when association was initialized within first 5 mins
after system boot due to jiffies init value which is near to MAX_JIFFIES.
Test kernel version: 4.9.154 (ARCH=arm)
hb_timer.expire = 0; //initialized, not started timer
new_expire = MAX_JIFFIES / 2 + 2; //or more
time_before(hb_timer.expire, new_expire) == false
Fixes: ba6f5e33bdbb ("sctp: avoid refreshing heartbeat timer too often")
Reported-by: Marcin Stojek <redacted>
Tested-by: Marcin Stojek <redacted>
Signed-off-by: Maciej Kwiecien <redacted>Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
quoted hunk ↗ jump to hunk
--- net/sctp/transport.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/net/sctp/transport.c b/net/sctp/transport.c index 033696e6f74f..ad158d311ffa 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c@@ -207,7 +207,8 @@ void sctp_transport_reset_hb_timer(struct sctp_transport *transport) /* When a data chunk is sent, reset the heartbeat interval. */ expires = jiffies + sctp_transport_timeout(transport); - if (time_before(transport->hb_timer.expires, expires) && + if ((time_before(transport->hb_timer.expires, expires) || + !timer_pending(&transport->hb_timer)) && !mod_timer(&transport->hb_timer, expires + prandom_u32_max(transport->rto))) sctp_transport_hold(transport);-- 2.14.1