在 2015/2/3 8:52, Alex Gartrell 写道:
> Hello Shengyong,
>
>> 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?
>
>
> FWIW, we encountered this problem with IPVS tunneling. Here's a patch done by Calvin (cc'ed) that fixes my attempted fix for this. We're not particularly proud of this...
>
> At a high level, I don't think the RTF_LOCAL check was sufficient, but I didn't investigate deeply enough and hopefully Calvin can say why.
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index f14d49b..c607a42 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -1159,18 +1159,18 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
> }
> dst_metric_set(dst, RTAX_MTU, mtu);
>
> - /* FACEBOOK HACK: We need to not expire local non-expiring
> - * routes so that we don't accidentally start blackholing
> - * ipvs traffic when we happen to use it locally for
> - * healthchecking (see ip_vs_xmit.c --
> - * __ip_vs_get_out_rt_v6 invokes update_pmtu if the rt is
> - * associated with a socket)
> - * Alex Gartrell <agartrell@xxxxxx>
> + /*
> + * FACEBOOK HACK: Only expire routes that aren't destined for
> + * the loopback interface.
> + *
> + * This prevents the strange route coalescing that happens when
> + * you add an address to the loopback that had a route that had
> + * been used when the address didn't exist from getting expired
> + * and causing packet loss in shiv.
> */
> - if (!(rt6->rt6i_flags & RTF_LOCAL) ||
> - (rt6->rt6i_flags & (RTF_EXPIRES | RTF_CACHE)))
> - rt6_update_expires(
> - rt6, net->ipv6.sysctl.ip6_rt_mtu_expires);
> + if (!(dst->dev->flags & IFF_LOOPBACK))
> + rt6_update_expires(rt6,
> + net->ipv6.sysctl.ip6_rt_mtu_expires);
> }
> }
Thanks, your approach can also solve the problem I met. I just a bit confuse that
is this kind of packets (like I sent in the first mail) normal? and if they are
abnormal, I think we'd better drop them before update rt6i_flags.
thx,
Sheng
>
>
> Cheers,
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