Re: [PATCH] netlink: fix append of whole original message on negative ack.

From: Evgeniy Polyakov
Date: Thu Oct 23 2008 - 16:55:59 EST


On Thu, Oct 23, 2008 at 01:45:13PM -0700, David Miller (davem@xxxxxxxxxxxxx) wrote:
> > Netlink can return an negative acknowledgement, which AFAICT should include an error code and the whole original message. This patch fixes the size argument given to the __nlmsg_put call. Without this patch only the original header was attached.
> > ---
> >
> > Can anyone explain to me why struct nlmsgerr contains an int error and the nlmsghdr struct. The comment in netlink_ack states that the whole message should be appended. Why not only include an int error in struct nlmsgerr and just append the original message?

Having header (even seq/pid only) is enough to find a message
for that userspace which cares. Looks like your patch can break
existing applications which are used to work with header only,
even if that was a mistake? Although application is supposed to
check the length, it still can expect only a header. I have to
note, that I do not know any such application though.

Evgeniy Polyakov
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