Re: [PATCH net] sctp: fix addip_serial increment on ASCONF_ACK allocation failure

[Jakub Kicinski <kuba@kernel.org>]

On Thu, 23 Jul 2026 15:18:18 +0800 luoqing wrote:
> From: Qing Luo <luoqing@kylinos.cn>
> 
> In sctp_process_asconf(), when sctp_make_asconf_ack() fails to allocate
> the ASCONF_ACK chunk due to memory pressure, the code jumps to the
> done label where asoc->peer.addip_serial is unconditionally incremented.
> 
> This leaves the peer's ASCONF (serial N) unacknowledged while the local
> endpoint now expects serial N+1. When the peer retransmits serial N, it
> falls into the serial < addip_serial + 1 branch ,
> which attempts to look up a cached ACK for serial N. No cached ACK
> exists since the allocation failed, so the retransmission is silently
> discarded. The peer eventually times out and ABORTs the association.
> 
> Move the addip_serial increment inside the if (asconf_ack) block so that
> the serial number is only advanced when the ASCONF_ACK is successfully
> created and cached. This way, on allocation failure, the serial number
> is unchanged and the peer's retransmitted ASCONF will be correctly
> re-processed.
> 
> Fixes: 1da177e4c3f4 (Linux-2.6.12-rc2)

nit: missing quotation marks around the subject
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