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

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

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

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

Neil

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

On 1/23/13, Vlad Yasevich [off-list ref] wrote:

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

quoted

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.

Yep, I agree with you, I'll send V2 patch based on your suggestion.
Thanks for your review!


Thanks,
Xufeng

-vlad

quoted

Neil

On 1/23/13, Neil Horman [off-list ref] 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

Good catch! I'll do what vlad suggested.
Thanks for your review!


Thanks,
Xufeng

Neil