netdev - Re: Patch to fix 'ip' utility recvmsg with ancillary data

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Message-ID: <ed9a4beb-1984-42c2-5cca-3101d285baf7@6wind.com>
Date:   Thu, 15 Jul 2021 09:07:06 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     Lahav Daniel Schlesinger <lschlesinger@...venets.com>,
        David Ahern <dsahern@...il.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: Patch to fix 'ip' utility recvmsg with ancillary data

Le 14/07/2021 à 10:48, Lahav Daniel Schlesinger a écrit :
> Hi David, thanks for reviewing the patch!
> Here is the updated patch, I hope it's okay now:
> 
> ipmonitor: Fix recvmsg with ancillary data
> 
> A successful call to recvmsg() causes msg.msg_controllen to contain the length
> of the received ancillary data. However, the current code in the 'ip' utility
> doesn't reset this value after each recvmsg().
> 
> This means that if a call to recvmsg() doesn't have ancillary data, then
> 'msg.msg_controllen' will be set to 0, causing future recvmsg() which do
> contain ancillary data to get MSG_CTRUNC set in msg.msg_flags.
> 
> This fixes 'ip monitor' running with the all-nsid option - With this option the
> kernel passes the nsid as ancillary data. If while 'ip monitor' is running an
> even on the current netns is received, then no ancillary data will be sent,
> causing 'msg.msg_controllen' to be set to 0, which causes 'ip monitor' to
> indefinitely print "[nsid current]" instead of the real nsid.
> 
> Fixes: 449b824ad196 ("ipmonitor: allows to monitor in several netns")
> Cc: Nicolas Dichtel <nicolas.dichtel@...nd.com>
> Signed-off-by: Lahav Schlesinger <lschlesinger@...venets.com>
Acked-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>

[snip]

>> patch looks right. Can you send it as a formal patch with a commit log
>> message, Signed-off-by, etc. See  'git log' for expected format and
>> Documentation/process/submitting-patches.rst in the kernel tree. Make
The format is still unexpected. Please, consider using git send-email.


Regards,
Nicolas