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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 18 Mar 2016 15:09:39 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Wei Wang <tracywwnj@...il.com>
Cc:	Wei Wang <weiwan@...gle.com>, Martin KaFai Lau <kafai@...com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH] ipv6: Fix the pmtu path for connected UDP socket

On Fri, Mar 18, 2016 at 2:26 PM, Wei Wang <tracywwnj@...il.com> wrote:
> I don't think ip6_sk_update_pmtu() is a good place to put it as all it
> does is to call ip6_update_pmtu(). And ip6_update_pmtu() does the
> route lookup and call __ip6_rt_update_pmtu.
> We can put it in ip6_update_pmtu(). But that still means we need to
> pass sk to ip6_update_pmtu() and I don't think it makes any difference
> compared to the current fix.
>

Well, your patch touches all the callers of ip6_update_pmtu() , if you just
fix ip6_sk_update_pmtu() as I suggested, you only need to change one
function, ideally. And the ipv4 code is there, although I am not sure, it
looks like we can just mimic the logic here:

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index ed44663..b88c2ff 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1417,8 +1417,28 @@ EXPORT_SYMBOL_GPL(ip6_update_pmtu);

 void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, __be32 mtu)
 {
-       ip6_update_pmtu(skb, sock_net(sk), mtu,
-                       sk->sk_bound_dev_if, sk->sk_mark);
+       const struct ipv6hdr *iph = (struct ipv6hdr *) skb->data;
+       struct net *net = sock_net(sk);
+       struct dst_entry *dst;
+       struct flowi6 fl6;
+
+       bh_lock_sock(sk);
+
+       memset(&fl6, 0, sizeof(fl6));
+       fl6.flowi6_oif = sk->sk_bound_dev_if;
+       fl6.flowi6_mark = sk->sk_mark ? : IP6_REPLY_MARK(net, skb->mark);
+       fl6.daddr = iph->daddr;
+       fl6.saddr = iph->saddr;
+       fl6.flowlabel = ip6_flowinfo(iph);
+
+       dst = ip6_route_output(net, NULL, &fl6);
+       if (!dst->error)
+               __ip6_rt_update_pmtu(dst, NULL, iph, ntohl(mtu));
+
+       sk_dst_set(sk, &rt->dst);
+       bh_unlock_sock(sk);
+
+       dst_release(dst);
 }


Please don't judge me on the code, it could still miss a lot of things,
but it can show my idea...