SACK is sent to wrong IP address

SACK is sent to wrong IP address

[B N Srikant-A21035]

Hi,
 
We have multihomed server (IP1, IP2) and single home client (IP3).
Initially client has established association with multi homed server.
Later the server has restarted and sent INIT. The IP1 is temporarily
inactive and IP2 is active. 
So INIT is sent from IP2 and client has sent INIT ACK back to IP2. The
Cookie and Cookie ack are also exchanged on new address.
 
But when data was sent from server (IP2) to client the client is sending
SACK to IP1 instead IP2.
As per the RFC the SACK should be sent to the address from where data is
coming. 
 
Is there any fix for this ? Or any suggestion to fix it is helpful.
 
thanks
Srikant
 
 
 
 

Re: SACK is sent to wrong IP address

[Vlad Yasevich]

On 10/06/2010 01:48 PM, B N Srikant-A21035 wrote:
> Hi,
>
> We have multihomed server (IP1, IP2) and single home client (IP3).
> Initially client has established association with multi homed server.
> Later the server has restarted and sent INIT. The IP1 is temporarily
> inactive and IP2 is active.
> So INIT is sent from IP2 and client has sent INIT ACK back to IP2. The
> Cookie and Cookie ack are also exchanged on new address.
>
> But when data was sent from server (IP2) to client the client is sending
> SACK to IP1 instead IP2.
> As per the RFC the SACK should be sent to the address from where data is
> coming.
>
> Is there any fix for this ? Or any suggestion to fix it is helpful.
>
> thanks
> Srikant
>
>

Hi Srikant

This looks like a bug during the restart procedure.

When the association is restarted, the concept of primary transport may have changed, but
that is not accounted for during the restart procedure.  When the association restarts,
the we need to check if we need to change the primary transport and perform the change
if required.

-vlad

>
>
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RE: SACK is sent to wrong IP address

[B N Srikant-A21035]

Vlad,

Thanks for the reply. Do you suggest any code changes ? 

Rgds
Srikant 

-----Original Message-----
From: linux-sctp-owner@vger.kernel.org
[mailto:linux-sctp-owner@vger.kernel.org] On Behalf Of Vlad Yasevich
Sent: Thursday, October 07, 2010 12:23 AM
To: B N Srikant-A21035
Cc: linux-sctp@vger.kernel.org
Subject: Re: SACK is sent to wrong IP address

On 10/06/2010 01:48 PM, B N Srikant-A21035 wrote:
> Hi,
>
> We have multihomed server (IP1, IP2) and single home client (IP3).
> Initially client has established association with multi homed server.
> Later the server has restarted and sent INIT. The IP1 is temporarily 
> inactive and IP2 is active.
> So INIT is sent from IP2 and client has sent INIT ACK back to IP2. The

> Cookie and Cookie ack are also exchanged on new address.
>
> But when data was sent from server (IP2) to client the client is 
> sending SACK to IP1 instead IP2.
> As per the RFC the SACK should be sent to the address from where data 
> is coming.
>
> Is there any fix for this ? Or any suggestion to fix it is helpful.
>
> thanks
> Srikant
>
>

Hi Srikant

This looks like a bug during the restart procedure.

When the association is restarted, the concept of primary transport may
have changed, but that is not accounted for during the restart
procedure.  When the association restarts, the we need to check if we
need to change the primary transport and perform the change if required.

-vlad

>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-sctp" 
> in the body of a message to majordomo@vger.kernel.org More majordomo 
> info at  http://vger.kernel.org/majordomo-info.html
>

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