From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [PATCH ipsec 1/3] ipv6: wire up skb->encapsulation Date: Sun, 18 Aug 2013 13:00:38 +0200 Message-ID: <20130818110038.GC7371@order.stressinduktion.org> References: <20130817175116.GA7001@order.stressinduktion.org> <20130817180738.GA24518@order.stressinduktion.org> <20130818042416.GK30709@verge.net.au> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: netdev@vger.kernel.org, steffen.klassert@secunet.com, yoshfuji@linux-ipv6.org, nicolas.dichtel@6wind.com To: Simon Horman Return-path: Received: from order.stressinduktion.org ([87.106.68.36]:58852 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754069Ab3HRLAo (ORCPT ); Sun, 18 Aug 2013 07:00:44 -0400 Content-Disposition: inline In-Reply-To: <20130818042416.GK30709@verge.net.au> Sender: netdev-owner@vger.kernel.org List-ID: On Sun, Aug 18, 2013 at 02:24:16PM +1000, Simon Horman wrote: > On Sat, Aug 17, 2013 at 08:07:38PM +0200, Hannes Frederic Sowa wrote: > > Hi Simon! > > > > On Sat, Aug 17, 2013 at 07:51:16PM +0200, Hannes Frederic Sowa wrote: > > > When pushing a new header before current one call skb_reset_inner_headers > > > to record the position of the inner headers in the various ipv6 tunnel > > > protocols. > > > > > > We later need this to correctly identify the addresses needed to send > > > back an error in the xfrm layer. > > > > > > This change is safe, because skb->protocol is always checked before > > > dereferencing data from the inner protocol. > > > > > > Cc: Steffen Klassert > > > Cc: YOSHIFUJI Hideaki > > > Cc: Nicolas Dichtel > > > Signed-off-by: Hannes Frederic Sowa > > > --- > > > > > > This patch is based on Steffen Klassert's ipsec tree. > > > > > > net/ipv6/ip6_gre.c | 5 +++++ > > > net/ipv6/ip6_tunnel.c | 6 ++++++ > > > net/ipv6/sit.c | 5 +++++ > > > 3 files changed, 16 insertions(+) > > > > > > diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c > > > index ecd6073..90747f1 100644 > > > --- a/net/ipv6/ip6_gre.c > > > +++ b/net/ipv6/ip6_gre.c > > > @@ -724,6 +724,11 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb, > > > ipv6_push_nfrag_opts(skb, &opt.ops, &proto, NULL); > > > } > > > > > > + if (likely(!skb->encapsulation)) { > > > + skb_reset_inner_headers(skb); > > > + skb->encapsulation = 1; > > > + } > > > + > > > > While doing these patches, I wondered how skb->inner_protocol will be > > used in future (you added it in 0d89d2035fe063461a5ddb609b2c12e7fb006e44 > > ("MPLS: Add limited GSO support")). Current use by tunnels seems safe to > > me, but I wondered how you would extend its use? > > Hi, > > I must confess that I'm not entirely sure that I understand the question. Sorry to be not clear enough. I try to present my envisioned use case for inner_protocol: I do think there may be some other corner cases when reporting back errors to a local socket when multiple tunnels+ipsecs are stacked into each other. The first encapsulation sets skb->inner_network_header, so that we can later extract the needed information for the error generation via inner_ip{v6,}_hdr. It would be handy here to use inner_protocol to mark the type of inner_network_header in advance (all this is because, even if we still have a reference to the local socket and know its af, it could also have emitted an IPv4 frame, so we have to jump to the ipv4 error handling path). Thanks, Hannes