From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: Re: [RFC PATCH] sctp: Don't lookup dst if transport dst is still valid Date: Wed, 03 Jul 2013 09:48:29 -0400 Message-ID: <51D42BAD.4050808@gmail.com> References: <1372747174-23580-1-git-send-email-fan.du@windriver.com> <51D2E3C8.5050100@gmail.com> <20130702155545.GB324@hmsreliant.think-freely.org> <51D38ED4.1000000@windriver.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Neil Horman , nicolas.dichtel@6wind.com, davem@davemloft.net, netdev@vger.kernel.org To: Fan Du Return-path: Received: from mail-gh0-f182.google.com ([209.85.160.182]:33857 "EHLO mail-gh0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751193Ab3GCNsc (ORCPT ); Wed, 3 Jul 2013 09:48:32 -0400 Received: by mail-gh0-f182.google.com with SMTP id z15so41866ghb.13 for ; Wed, 03 Jul 2013 06:48:32 -0700 (PDT) In-Reply-To: <51D38ED4.1000000@windriver.com> Sender: netdev-owner@vger.kernel.org List-ID: On 07/02/2013 10:39 PM, Fan Du wrote: > > > On 2013=E5=B9=B407=E6=9C=8802=E6=97=A5 23:55, Neil Horman wrote: >> On Tue, Jul 02, 2013 at 10:29:28AM -0400, Vlad Yasevich wrote: >>> On 07/02/2013 02:39 AM, Fan Du wrote: >>>> When sctp sits on IPv6, sctp_transport_dst_check pass cookie as ZE= RO, >>>> as a result ip6_dst_check always fail out. This behaviour makes >>>> transport->dst useless, because every sctp_packet_transmit must lo= ok >>>> for valid dst(Is this what supposed to be?) >>>> >>>> One aggressive way is to call rt_genid_bump which invalid all dst = to >>>> make new dst for transport, apparently it also hurts others. >>>> I'm sure this may not be the best for all, so any commnets? >>>> >>>> Signed-off-by: Fan Du >>>> --- >>>> include/net/sctp/sctp.h | 18 ++++++++++++------ >>>> net/sctp/ipv6.c | 2 ++ >>>> 2 files changed, 14 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h >>>> index cd89510..f05af01 100644 >>>> --- a/include/net/sctp/sctp.h >>>> +++ b/include/net/sctp/sctp.h >>>> @@ -719,14 +719,20 @@ static inline void sctp_v4_map_v6(union >>>> sctp_addr *addr) >>>> addr->v6.sin6_addr.s6_addr32[2] =3D htonl(0x0000ffff); >>>> } >>>> >>>> -/* The cookie is always 0 since this is how it's used in the >>>> - * pmtu code. >>>> - */ >>>> +/* Set cookie with the right one for IPv6 and zero for others */ >>>> static inline struct dst_entry *sctp_transport_dst_check(struct >>>> sctp_transport *t) >>>> { >>>> - if (t->dst&& !dst_check(t->dst, 0)) { >>>> - dst_release(t->dst); >>>> - t->dst =3D NULL; >>>> + >>>> + if (t->dst) { >>>> + struct rt6_info *rt =3D (struct rt6_info *)t->dst; >>>> + u32 cookie =3D 0; >>>> + >>>> + if ((t->af_specific->sa_family =3D=3D AF_INET6)&& rt->rt= 6i_node) >>>> + cookie =3D rt->rt6i_node->fn_sernum; >>>> + if (!dst_check(t->dst, cookie)) { >>>> + dst_release(t->dst); >>>> + t->dst =3D NULL; >>>> + } >>>> } >>> >>> I think it would be better if we stored the dst_cookie in the >>> transport structure and initialized it at lookup time. If you do >>> that, then if the route table changes, we'd correctly detect it >>> without artificially bumping rt_genid (and hurting ipv4). >>> >> Agreed, thats how we do it for ipv4, IIRC > ^^^^ > Hello Neil > > I'm sorry I didn't find such things about IPv4. > > sctp_transport_dst_check > -> ipv4_dst_check > -> rt_is_expired > ^^^^^^^^^ > By "expired", currently we *do* check rt->rt_genid against net->rt_ge= nid, > and for IPv4, every adding/deleting an IPv4 address will bump > net->rt_genid, > (this does impact IPv6 dst checking as well) so when I delete an IPv4 > address, > ipv4_dst_check failed as expected to look for new dst, basically that= 's > what > I find after checking the code for IPv4 cookie things as mentioned ab= ove. > Am I missing something here? No, you are not missing anything. IPv4 doesn't use the cookie and=20 always seems to pass it as 0. Yes, ipv4 will bump the gen_id thus invalidating all routes (there has=20 been disagreement about it). IPv6 doesn't do that. In ipv6, when the=20 addresses are added or removed, routes are also added or removed and an= y=20 time the route is added it will have a new serial number. So, you don'= t=20 have to disturb ipv4 cache when ipv6 routing info changes. -vlad > > >> Neil >> >>> -vlad >>> >>>> >>>> return t->dst; >>>> diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c >>>> index 8ee553b..cfae77e 100644 >>>> --- a/net/sctp/ipv6.c >>>> +++ b/net/sctp/ipv6.c >>>> @@ -137,6 +137,8 @@ static int sctp_inet6addr_event(struct >>>> notifier_block *this, unsigned long ev, >>>> break; >>>> } >>>> >>>> + /* invalid all transport dst forcing to look up new dst */ >>>> + rt_genid_bump(net); >>>> return NOTIFY_DONE; >>>> } >>>> >>>> >>> >>> >> >