Re: [PATCH] sctp: set association state to established in dupcook_a handler

On 01/23/2013 08:46 AM, Neil Horman wrote:

On Wed, Jan 23, 2013 at 03:38:40PM +0800, xufengzhang.main@gmail.com wrote:

quoted

From: Xufeng Zhang <redacted>

While sctp handling a duplicate COOKIE-ECHO and the action is
'Association restart', sctp_sf_do_dupcook_a() will processing
the unexpected COOKIE-ECHO for peer restart, but it does not set
the association state to SCTP_STATE_ESTABLISHED, so the association
could stuck in SCTP_STATE_SHUTDOWN_PENDING state forever.
This violates the sctp specification:
   RFC 4960 5.2.4. Handle a COOKIE ECHO when a TCB Exists
   Action
   A) In this case, the peer may have restarted. .....
      After this, the endpoint shall enter the ESTABLISHED state.

Fix this problem by adding a SCTP_CMD_NEW_STATE cmd to the command
list so as to set the restart association to SCTP_STATE_ESTABLISHED
state properly.

Signed-off-by: Xufeng Zhang <redacted>
---
  net/sctp/sm_statefuns.c |    2 ++
  1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 618ec7e..528f1c8 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c

@@ -1779,6 +1779,8 @@ static sctp_disposition_t sctp_sf_do_dupcook_a(struct net *net,

  	/* Update the content of current association. */
  	sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_ASSOC, SCTP_ASOC(new_asoc));
+	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
+			SCTP_STATE(SCTP_STATE_ESTABLISHED));
  	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
  	sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));
  	return SCTP_DISPOSITION_CONSUME;
--

1.7.0.2

Looks reasonable to me, thanks

nit: The RFC indicate the association should enter the ESTABLISHED state after
preforming all other actions, so it seems that the state change should occur
after the ULP event is sent

I have a slight concern here that if we change state last, then any data 
that may have been bundled with COOKIE-ACK as part of CMD_REPLY will get 
the SACK_IMMEDIATE flag set since we are still in the SHUTDOWN_PENDING 
state.

I would be more correct (and would match sctp_sf_do_5_1D_ce) to
do it in this order:
   UPDATE_ASSOC  - resets all the congestion/association variables
   EVENT_UP  - send RESTART to USER
   NEW_STATE  - set ESTABLISHED state (as per spec)
   REPLY	- Send cookie-ack along with any pending data.

-vlad

Neil