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Date: Wed, 17 Mar 2010 17:56:38 +0200 From: Timo Teräs <timo.teras@....fi> To: Herbert Xu <herbert@...dor.apana.org.au> CC: netdev@...r.kernel.org Subject: Re: [PATCH] xfrm: cache bundle lookup results in flow cache Herbert Xu wrote: > On Wed, Mar 17, 2010 at 04:16:21PM +0200, Timo Teräs wrote: >> The problem is if I have multipoint gre1 and policy that says >> "encrypt all gre in transport mode". >> >> Thus for each public address, I get one bundle. But the >> xfrm_lookup() is called for each packet because ipgre_tunnel_xmit() >> calls ip_route_output_key() on per-packet basis. >> >> For my use-case it makes a huge difference. > > But if your traffic switches between those tunnels on each packet, > we're back to square one, right? Not to my understanding. Why would it change? >> Then we cannot maintain policy use time. But if it's not a >> requirement, we could drop the policy from cache. > > I don't see why we can't maintain the policy use time if we did > this, all you need is a back-pointer from the top xfrm_dst. Sure. >> Also. With this and your recent flowi patch, I'm seeing pmtu >> issues. Seems like xfrm_bundle_ok uses the original dst which >> resulted in the creation of the bundle. Somehow that dst >> does not get updated with pmtu... but the new dst used in >> next xfrm_lookup for same target does have proper mtu. >> I'm debugging right now why this is happening. Any ideas? > > The dynamic MTU is always maintained in a normal dst object in > the IPv4 routing cache. Each xfrm_dst points to such a dst > through xdst->route. > > If you were looking at the xfrm_dst's own MTU then that may well > cause problems. I figured the root cause. The original dst gets expired rt_genid goes old. But xfrm_dst does not notice that so it won't create a new bundle. xfrm_bundle_ok calls dst_check, but dst->obsolete = 0, and ipv4_dst_check is a no-op anyway. Somehow the rtable object should be able to tell back to xfrm that the dst is not good anymore. Any ideas? - Timo -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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