Re: [PATCH net-next 06/15] ipv4: Merge ip_local_out and ip_local_out_sk

[Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>]

Le 07/10/2015 22:39, Eric W. Biederman a écrit :
> Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx> writes:
>
> > Le 06/10/2015 20:53, Eric W. Biederman a écrit :
> > > It is confusing and silly hiding a paramater so modify all of
> > > the callers to pass in the appropriate socket or skb->sk if
> > > no socket is known.
> > >
> > > Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> > > ---
> > [snip]
> > > @@ -456,7 +456,7 @@ packet_routed:
> > >         skb->priority = sk->sk_priority;
> > >         skb->mark = sk->sk_mark;
> > >
> > > -       res = ip_local_out(skb);
> > > +       res = ip_local_out(sk, skb);
> > As stated in the comment at the top of this function (ip_queue_xmit()), skb->sk
> > can be different from sk. See also commit b0270e91014d ("ipv4: add a sock
> > pointer to ip_queue_xmit()").
> > Not sure if this change is right.
> Good catch.  This change should not have been buried in this patch. It
> needs to be it's own separate bug fix.
>
> As I read the code we actually do want to pass sk not skb->sk into
> ip_local_out.  For all of the reasons that sk is potentially different
> from skb->sk already.
>
> The way I understand this is we have pushed an sk parameter through the
> output path so that sk_mc_loop(sk) can be called with the tunnel's
> socket not whatever is on skb->sk.  This allows for looking to see if
> local multicast loopback is configured on the tunnels socket not on the
> originating socket of the packet.
Ok, thank you for the explanation.
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