netdev - Re: [PATCH] ipv6: Fix the pmtu path for connected UDP socket

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Date:	Mon, 28 Mar 2016 16:44:00 -0700
From:	Martin KaFai Lau <kafai@...com>
To:	Cong Wang <xiyou.wangcong@...il.com>
CC:	Wei Wang <tracywwnj@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Wei Wang <weiwan@...gle.com>,
	David Miller <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH] ipv6: Fix the pmtu path for connected UDP socket

On Mon, Mar 28, 2016 at 03:39:42PM -0700, Cong Wang wrote:
> On Fri, Mar 25, 2016 at 5:16 PM, Martin KaFai Lau <kafai@...com> wrote:
> > On Fri, Mar 25, 2016 at 04:55:27PM -0700, Martin KaFai Lau wrote:
> >>  void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, __be32 mtu)
> >>  {
> >> +     struct dst_entry *odst;
> >> +
> >> +     odst = sk_dst_get(sk);
> >> +
> >>       ip6_update_pmtu(skb, sock_net(sk), mtu,
> >>                       sk->sk_bound_dev_if, sk->sk_mark);
> >> +
> >> +     if (odst && !odst->error &&
> >> +         !ip6_dst_check(odst, inet6_sk(sk)->dst_cookie)) {
> >> +             struct dst_entry *ndst;
> >> +             struct flowi6 fl6;
> >> +
> >> +             build_skb_flow_key(&fl6, skb, sock_net(sk),
> >> +                                sk->sk_bound_dev_if, sk->sk_mark);
> >> +             ndst = ip6_route_output(sock_net(sk), NULL, &fl6);
> >> +             if (!ndst->error)
> >> +                     ip6_dst_store(sk, ndst, NULL, NULL);
> > oops...missed:
> >                 else
> >                         dst_release(ndst);
>
>
> Can you send an updated patch for review? Since you have a test case
> while I didn't.
>
> Also,
>
> 2) Not sure if we need to update dst or dst->path here, I guess the later
> counts in xfrm case therefore more correct.
Thanks for pointing it out.  Calling ip6_dst_check is also not appropriate here.
odst->ops->check() should be used.  I need to take a closer look and may try
another approach.

Thanks
-- Martin