Subject: Re: [PATCH 1/3] netlink: fix NETLINK_RECV_NO_ENOBUFS in netlink_set_err()

From: Pablo Neira Ayuso <[email-masked]>
Date: Wed, 17 Mar 2010 17:17:25 +0100

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.