linux-kernel - Re: [PATCH] sctp: set association state to established in dupcook

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Message-ID: <51AEA8B6.9090609@windriver.com>
Date:	Wed, 5 Jun 2013 10:55:50 +0800
From:	Xufeng Zhang <xufeng.zhang@...driver.com>
To:	<gregkh@...uxfoundation.org>, <davem@...emloft.net>
CC:	Xufeng Zhang <xufeng.zhang@...driver.com>,
	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>,
	<nhorman@...driver.com>, <vyasevich@...il.com>
Subject: Re: [PATCH] sctp: set association state to established in dupcook_a
 handler

On 06/03/2013 03:52 PM, Xufeng Zhang wrote:
> 3.4-stable review patch.  If anyone has any objections, please let me know.
>    
Sorry Greg, David -- I did not fully understand all the details
of the stable kernel process earlier.

I have since checked the networking stable queue here:

http://patchwork.ozlabs.org/bundle/davem/stable/?state=*

to confirm this upstream commit 9839ff0d has not yet been queued.

It can be applied to kernel versions<3.0, 3.4>, and is
present in mainline for 3.8+ kernels.

I think it makes sense to queue for stable because it
fixes the SCTP association can get stuck in SCTP_STATE_SHUTDOWN_PENDING
state forever in the below test case:
1). Set SCTP parameters on A (slow detection of link failure):
net.sctp.association_max_retrans = 5
net.sctp.path_max_retrans = 5
net.sctp.hb_interval = 30000
2). Set SCTP parameters on B (fast detection of link failure):
net.sctp.association_max_retrans = 2
net.sctp.path_max_retrans = 2
net.sctp.hb_interval = 1000
3). Start sctp_darn on both sides:
A(interactive):
sctp_darn -H 192.168.100.10 -P 256 -h 192.168.100.100 -p 256 -I -s
B:
sctp_darn -H 192.168.100.100 -P 256 -h 192.168.100.10 -p 256 -l&
4). Send data on A to establish the SCTP association:
snd=5
5). Block SCTP traffic on B (simulates a network failure):
iptables -t filter -I INPUT 1 -p sctp --dport 256 -j DROP
iptables -t filter -I OUTPUT 1 -p sctp --dport 256 -j DROP
Then quickly send data on A and then shutdown (A goes into SHUTDOWN_PENDING state):
snd=5
snd=5
shutdown
6). Wait for link to drop on B (Recieved SCTP_COMM_LOST), and quickly kill the listener,
open the firewall for SCTP, then start an SCTP sender:
kill $PID
iptables -t filter -D INPUT 1
iptables -t filter -D OUTPUT 1
sctp_darn -H 192.168.100.100 -P 256 -h 192.168.100.10 -p 256 -s
Press<Enter>  to send data to trigger sending INIT to A, the SHUTDOWN on A will failed and
the association on A remains in SHUTDOWN_PENDING (5) state indefinitely.

However if David doesn't think it is worth bothering with for
net stable, then that is of course fine too.

Thanks,
Xufeng

> ------------------
>
>
> From: Xufeng Zhang<xufeng.zhang@...driver.com>
>
> [ Upstream commit 9839ff0dead906e85e4d17490aeff87a5859a157 ]
>
> 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.
>
> To resolve this problem, adding a SCTP_CMD_NEW_STATE cmd to the
> command list before SCTP_CMD_REPLY cmd, this will set the restart
> association to SCTP_STATE_ESTABLISHED state properly and also avoid
> I-bit being set in the DATA chunk header when COOKIE_ACK is bundled
> with DATA chunks.
>
> Signed-off-by: Xufeng Zhang<xufeng.zhang@...driver.com>
> Acked-by: Neil Horman<nhorman@...driver.com>
> Acked-by: Vlad Yasevich<vyasevich@...il.com>
> Signed-off-by: David S. Miller<davem@...emloft.net>
> ---
>   net/sctp/sm_statefuns.c |    4 +++-
>   1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> index cb1c430..ab08f65 100644
> --- a/net/sctp/sm_statefuns.c
> +++ b/net/sctp/sm_statefuns.c
> @@ -1747,8 +1747,10 @@ static sctp_disposition_t sctp_sf_do_dupcook_a(const struct sctp_endpoint *ep,
>
>   	/* 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_REPLY, SCTP_CHUNK(repl));
>   	sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));
> +	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));
>   	return SCTP_DISPOSITION_CONSUME;
>
>   nomem_ev:
>    

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