linux-kernel - Re: [PATCH] sctp: handle error of sctp_sf_heartbeat() in sctp_sf_do

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Message-ID: <CADvbK_dZVJktQexS+4y7XNJy8s3FPXz5w1duUe3R1OMwrkXp6g@mail.gmail.com>
Date: Wed, 12 Mar 2025 11:30:53 -0400
From: Xin Long <lucien.xin@...il.com>
To: Wentao Liang <vulab@...as.ac.cn>
Cc: marcelo.leitner@...il.com, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org, 
	linux-sctp@...r.kernel.org, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sctp: handle error of sctp_sf_heartbeat() in sctp_sf_do_asconf()

On Tue, Mar 11, 2025 at 11:22 PM Wentao Liang <vulab@...as.ac.cn> wrote:
>
> In sctp_sf_do_asconf(), SCTP_DISPOSITION_NOMEM error code returned
> from sctp_sf_heartbeat() represent a failure of sent HEARTBEAT. The
> return value of sctp_sf_heartbeat() needs to be checked and propagates
> to caller function.

Returning this error to the caller will only result in the packet
being discarded, without reverting any changes already made in
sctp_sf_do_asconf().

Moreover, this error is not fatal. Instead, it serves as an
optimization to confirm the new destination as quickly as possible,
as introduced in:

commit 6af29ccc223b0feb6fc6112281c3fa3cdb1afddf
Author: Michio Honda <micchie@....wide.ad.jp>
Date:   Thu Jun 16 17:14:34 2011 +0900

    sctp: Bundle HEAERTBEAT into ASCONF_ACK

Ignoring this error is entirely reasonable, especially considering
that running out of memory (nomem) is an unlikely scenario.

Thanks.

>
> Signed-off-by: Wentao Liang <vulab@...as.ac.cn>
> ---
>  net/sctp/sm_statefuns.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> index a0524ba8d787..89100546670a 100644
> --- a/net/sctp/sm_statefuns.c
> +++ b/net/sctp/sm_statefuns.c
> @@ -3973,8 +3973,10 @@ enum sctp_disposition sctp_sf_do_asconf(struct net *net,
>         asconf_ack->dest = chunk->source;
>         sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(asconf_ack));
>         if (asoc->new_transport) {
> -               sctp_sf_heartbeat(ep, asoc, type, asoc->new_transport, commands);
> -               ((struct sctp_association *)asoc)->new_transport = NULL;
> +               if (SCTP_DISPOSITION_NOMEM == sctp_sf_heartbeat(ep, asoc, type, asoc->new_transport, commands)) {
> +                       ((struct sctp_association *)asoc)->new_transport = NULL;
> +                       return SCTP_DISPOSITION_NOMEM;
> +               }
>         }
>
>         return SCTP_DISPOSITION_CONSUME;
> --
> 2.42.0.windows.2
>