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From: shengyong <shengyong1@huawei•com>
To: <davem@davemloft•net>
Cc: <netdev@vger•kernel.org>, <yangyingling@huawei•com>,
	<steffen.klassert@secunet•com>, <hannes@redhat•com>
Subject: Question: should local address be expired when updating PMTU?
Date: Mon, 2 Feb 2015 16:20:24 +0800	[thread overview]
Message-ID: <54CF3348.40207@huawei.com> (raw)

Hi, David Miller
Since commit 81aded246 (ipv6: Handle PMTU in ICMP error handlers), the entries
in neigh table may get expired. But in the situation:

          Host only
    PC <------------> Virtual Machine

a packet is sent from PC to VM, and the packet looks like:
-----------------------------------
| IPv6 (src=PC-addr, dst=VM-addr) |
|---------------------------------|
|     ICMPv6 (Packet Too Big)     |
|---------------------------------|
| IPv6 (src=VM-addr, dst=VM-addr) |
|---------------------------------|
| ICMPv6 (Neighbor Advertisement) |
-----------------------------------

Then the local addr on VM will be updated with an expire value. After the
lifetime of the local addr is expired, the VM is unreachable from PC.

	# ip -6 route list table local
	local fe80::1 dev lo  metric 0 *expire 596*

I find that the current code seems not check whether the entry is a local one
when doing PMTU update. And if the following code is added, the situation could
be avoided.

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index b2614b2..b80317a 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1136,6 +1136,9 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
 {
        struct rt6_info *rt6 = (struct rt6_info*)dst;

+       if (rt6->rt6i_flags & RTF_LOCAL)
+               return;
+
        dst_confirm(dst);
        if (mtu < dst_mtu(dst) && rt6->rt6i_dst.plen == 128) {
                struct net *net = dev_net(dst->dev);

So is this modification correct? Or how can we avoid such expiring?

thx & BR,
Sheng

next             reply	other threads:[~2015-02-02  8:21 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-02  8:20 shengyong [this message]
2015-02-02 21:31 ` Question: should local address be expired when updating PMTU? David Miller
2015-02-03  0:52 ` Alex Gartrell
2015-02-03  1:28   ` shengyong
2015-02-03  2:10   ` Calvin Owens
2015-02-03  3:21     ` shengyong
2015-02-03  9:28 ` Steffen Klassert
2015-02-03 10:54   ` shengyong
2015-02-03 12:01     ` Steffen Klassert
2015-02-04  1:59       ` shengyong
2015-02-05  7:21         ` Steffen Klassert
2015-02-27  2:37           ` shengyong
2015-02-27 10:32             ` Steffen Klassert
2015-03-30 10:32             ` Steffen Klassert
2015-03-30 10:33               ` [PATCH RFC 1/3] ipv6: Fix after pmtu events dissapearing host routes Steffen Klassert
2015-03-30 11:15                 ` Sheng Yong
2015-03-30 18:24                 ` Martin Lau
2015-04-01  8:09                   ` Steffen Klassert
2015-03-30 10:33               ` [PATCH RFC 2/3] ipv6: Extend the route lookups to low priority metrics Steffen Klassert
2015-03-30 10:34               ` [PATCH RFC 3/3] ipv6: Don't update pmtu on uncached routes Steffen Klassert
2015-03-30 11:13               ` Question: should local address be expired when updating PMTU? Sheng Yong

find likely ancestor, descendant, or conflicting patches for this message:
( dfblob:b2614b2 dfblob:b80317a )
 OR (
bs:"Question: should local address be expired when updating PMTU?" )
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