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Message-ID: <540DF9E0.5030701@redhat.com> Date: Mon, 08 Sep 2014 14:48:00 -0400 From: Vlad Yasevich <vyasevic@...hat.com> To: Eric Dumazet <eric.dumazet@...il.com>, David Miller <davem@...emloft.net> CC: nicolas.dichtel@...nd.com, therbert@...gle.com, alexander.h.duyck@...el.com, netdev@...r.kernel.org Subject: Re: [PATCH net] ipv6: refresh rt6i_genid in ip6_pol_route() On 09/08/2014 01:07 AM, Eric Dumazet wrote: > On Sun, 2014-09-07 at 21:59 -0700, David Miller wrote: >> From: Eric Dumazet <eric.dumazet@...il.com> >> Date: Sun, 07 Sep 2014 21:43:54 -0700 >> >>> On Sun, 2014-09-07 at 21:27 -0700, David Miller wrote: >>>> From: Eric Dumazet <eric.dumazet@...il.com> >>>> Date: Sun, 07 Sep 2014 21:18:25 -0700 >>>> >>>>> On Sun, 2014-09-07 at 15:54 -0700, David Miller wrote: >>>>> >>>>>> This might be broken. >>>>>> >>>>>> We are dealing here with persistent entries in the ipv6 routine trie. >>>>>> >>>>>> If you just bump the genid on the next person to look it up, other >>>>>> sockets and cached entities might not have validated the route yet, >>>>>> and now will falsely see the route as valid. We have to ensure that >>>>>> they too drop this route and perform a relookup. >>>>> >>>>> I am confused, I thought it was the role of the cookie. >>>>> >>>>> (Ie socket has to store its own cookie to be able to validate a route) >>>>> >>>>> Before 6f3118b571b8 patch, how was this done anyway ? >>>>> >>>>> If persistent routes cannot refresh the genid, then they are useless ? >>>> >>>> I just speak about the genid aspect. >>>> >>>> I understand that cookie (via node->fn_sernum) invalidates the path >>>> in the fib_trie, but the genid protects against other circumstances >>>> (matching IPSEC rule, f.e.) >>>> >>>> You have to make sure all other sockets did a full route lookup >>>> (including IPSEC) before you can safely adjust the genid. >>>> >>>> I could be wrong, recheck my analysis please :-) >>> >>> So this whole genid protection can not work, unless we make sure a >>> socket cannot share a route with another socket. >>> >>> This means we have to clone all routes. >> >> I'm willing to revert the change in question if you think that's the >> sanest way forward. >> >> The bug fix for more obscure use cases (IPSEC) if pointless if it >> breaks more common things (TCP input route caching). > > Lets wait for Nicolas and/or Hannes input, they might have some ideas... > > So, looking at the differences between ipv4 and ipv6, it looks like ipv4 genid is only bumped by xfrm, while ipv6 one is bumped every time __ipv6_ifa_notify() is called which happens in a lot of palaces... So, my guess is that ipv4 genid doesn't really grow on non-xfrm configured systems, while ipv6 one can grow very fast. Probably why we don't see it with ipv4 and do with ipv6. -vlad > > -- > 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 > -- 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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