[PATCHv2 nf] netfilter: set default timeout to 3 secs for sctp shutdown send and recv state

[PATCHv2 nf] netfilter: set default timeout to 3 secs for sctp shutdown send and recv state

[Xin Long]

In SCTP protocol, it is using the same timer (T2 timer) for SHUTDOWN and
SHUTDOWN_ACK retransmission. However in sctp conntrack the default timeout
value for SCTP_CONNTRACK_SHUTDOWN_ACK_SENT state is 3 secs while it's 300
msecs for SCTP_CONNTRACK_SHUTDOWN_SEND/RECV state.

As Paolo Valerio noticed, this might cause unwanted expiration of the ct
entry. In my test, with 1s tc netem delay set on the NAT path, after the
SHUTDOWN is sent, the sctp ct entry enters SCTP_CONNTRACK_SHUTDOWN_SEND
state. However, due to 300ms (too short) delay, when the SHUTDOWN_ACK is
sent back from the peer, the sctp ct entry has expired and been deleted,
and then the SHUTDOWN_ACK has to be dropped.

Also, it is confusing these two sysctl options always show 0 due to all
timeout values using sec as unit:

  net.netfilter.nf_conntrack_sctp_timeout_shutdown_recd = 0
  net.netfilter.nf_conntrack_sctp_timeout_shutdown_sent = 0

This patch fixes it by also using 3 secs for sctp shutdown send and recv
state in sctp conntrack, which is also RTO.initial value in SCTP protocol.

Note that the very short time value for SCTP_CONNTRACK_SHUTDOWN_SEND/RECV
was probably used for a rare scenario where SHUTDOWN is sent on 1st path
but SHUTDOWN_ACK is replied on 2nd path, then a new connection started
immediately on 1st path. So this patch also moves from SHUTDOWN_SEND/RECV
to CLOSE when receiving INIT in the ORIGINAL direction.

Fixes: 9fb9cbb1082d ("[NETFILTER]: Add nf_conntrack subsystem.")
Reported-by: Paolo Valerio <pvalerio@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
---
v1->v2:
- fix sysctl nf_conntrack_sctp_timeout_shutdown_sent default value
  described in nf_conntrack-sysctl.rst, as Sriram noticed.
---
 Documentation/networking/nf_conntrack-sysctl.rst | 4 ++--
 net/netfilter/nf_conntrack_proto_sctp.c          | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Documentation/networking/nf_conntrack-sysctl.rst b/Documentation/networking/nf_conntrack-sysctl.rst
index 8b1045c3b59e..c383a394c665 100644
--- a/Documentation/networking/nf_conntrack-sysctl.rst
+++ b/Documentation/networking/nf_conntrack-sysctl.rst
@@ -178,10 +178,10 @@ nf_conntrack_sctp_timeout_established - INTEGER (seconds)
 	Default is set to (hb_interval * path_max_retrans + rto_max)
 
 nf_conntrack_sctp_timeout_shutdown_sent - INTEGER (seconds)
-	default 0.3
+	default 3
 
 nf_conntrack_sctp_timeout_shutdown_recd - INTEGER (seconds)
-	default 0.3
+	default 3
 
 nf_conntrack_sctp_timeout_shutdown_ack_sent - INTEGER (seconds)
 	default 3
diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index 91eacc9b0b98..b6bcc8f2f46b 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -49,8 +49,8 @@ static const unsigned int sctp_timeouts[SCTP_CONNTRACK_MAX] = {
 	[SCTP_CONNTRACK_COOKIE_WAIT]		= 3 SECS,
 	[SCTP_CONNTRACK_COOKIE_ECHOED]		= 3 SECS,
 	[SCTP_CONNTRACK_ESTABLISHED]		= 210 SECS,
-	[SCTP_CONNTRACK_SHUTDOWN_SENT]		= 300 SECS / 1000,
-	[SCTP_CONNTRACK_SHUTDOWN_RECD]		= 300 SECS / 1000,
+	[SCTP_CONNTRACK_SHUTDOWN_SENT]		= 3 SECS,
+	[SCTP_CONNTRACK_SHUTDOWN_RECD]		= 3 SECS,
 	[SCTP_CONNTRACK_SHUTDOWN_ACK_SENT]	= 3 SECS,
 	[SCTP_CONNTRACK_HEARTBEAT_SENT]		= 30 SECS,
 };
@@ -105,7 +105,7 @@ static const u8 sctp_conntracks[2][11][SCTP_CONNTRACK_MAX] = {
 	{
 /*	ORIGINAL	*/
 /*                  sNO, sCL, sCW, sCE, sES, sSS, sSR, sSA, sHS */
-/* init         */ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sSA, sCW},
+/* init         */ {sCL, sCL, sCW, sCE, sES, sCL, sCL, sSA, sCW},
 /* init_ack     */ {sCL, sCL, sCW, sCE, sES, sSS, sSR, sSA, sCL},
 /* abort        */ {sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL},
 /* shutdown     */ {sCL, sCL, sCW, sCE, sSS, sSS, sSR, sSA, sCL},
-- 
2.39.1

Re: [PATCHv2 nf] netfilter: set default timeout to 3 secs for sctp shutdown send and recv state

[Marcelo Ricardo Leitner]

On Tue, Aug 15, 2023 at 02:08:47PM -0400, Xin Long wrote:
...
> Note that the very short time value for SCTP_CONNTRACK_SHUTDOWN_SEND/RECV
> was probably used for a rare scenario where SHUTDOWN is sent on 1st path
> but SHUTDOWN_ACK is replied on 2nd path, then a new connection started
> immediately on 1st path. So this patch also moves from SHUTDOWN_SEND/RECV
> to CLOSE when receiving INIT in the ORIGINAL direction.

Yeah.

> 
> Fixes: 9fb9cbb1082d ("[NETFILTER]: Add nf_conntrack subsystem.")
> Reported-by: Paolo Valerio <pvalerio@redhat.com>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>
> Reviewed-by: Simon Horman <horms@kernel.org>

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>