netdev - Re: [PATCH 1/3] netlink: fix NETLINK_RECV_NO_ENOBUFS in netlink_set

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Message-ID: <4BA22463.6050601@trash.net>
Date:	Thu, 18 Mar 2010 14:02:27 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Pablo Neira Ayuso <pablo@...filter.org>
CC:	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH 1/3] netlink: fix NETLINK_RECV_NO_ENOBUFS in netlink_set_err()

Pablo Neira Ayuso wrote:
> Patrick McHardy wrote:
>> Pablo Neira Ayuso wrote:
>>> Currently, ENOBUFS errors are reported to the socket via
>>> netlink_set_err() even if NETLINK_RECV_NO_ENOBUFS is set. However,
>>> that should not happen. This fixes this problem and it changes the
>>> prototype of netlink_set_err() to return the number of sockets whose
>>> error has been set. This allows to know if any error has been set.
>>> This return value is used in the next patch in these bugfix series.
>> But that only happens if we have a message allocate error, which is
>> a different situation than rcvqueue overrun, which I thought the
>> original patch was supposed to handle (disable netlink congestion
>> control).
> 
> Yes, allocation is a different situation but we still report ENOBUFS to
> user-space. I think that NETLINK_RECV_NO_ENOBUFS is there to a) disable
> ENOBUFS reports to user-space and b) disable Netlink congestion.
> 
>> Is there any problem with these errors?
> 
> Specifically in ctnetlink, if we fail to allocate a message in ctnetlink
> and NETLINK_RECV_NO_ENOBUFS is set, we still lose an event and that
> should not happen.

I assume you mean "not set"? Otherwise I fail to follow :)

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