linux-kernel - Re: [PATCH v2 1/2] ip_tunnel: fix ip tunnel lookup in collect

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Date:   Mon, 19 Jun 2017 11:08:15 -0700
From:   Pravin Shelar <pshelar@....org>
To:     严海双 <yanhaishuang@...s.chinamobile.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        linux-kernel@...r.kernel.org, Pravin B Shelar <pshelar@...ira.com>
Subject: Re: [PATCH v2 1/2] ip_tunnel: fix ip tunnel lookup in collect_md mode

On Mon, Jun 19, 2017 at 6:13 AM, 严海双 <yanhaishuang@...s.chinamobile.com> wrote:
>
>
>> On 19 Jun 2017, at 1:43 PM, Pravin Shelar <pshelar@....org> wrote:
>>
>> On Fri, Jun 16, 2017 at 8:27 PM, Haishuang Yan
>> <yanhaishuang@...s.chinamobile.com> wrote:
>>> In collect_md mode, if the tun dev is down, it still can call
>>> ip_tunnel_rcv to receive on packets, and the rx statistics increase
>>> improperly.
>>>
>>> Fixes: 2e15ea390e6f ("ip_gre: Add support to collect tunnel metadata.")
>>> Cc: Pravin B Shelar <pshelar@...ira.com>
>>> Signed-off-by: Haishuang Yan <yanhaishuang@...s.chinamobile.com>
>>>
>>> ---
>>> Change since v2:
>>>  * Fix wrong recipient addresss
>>> ---
>>> net/ipv4/ip_tunnel.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
>>> index 0f1d876..a3caba1 100644
>>> --- a/net/ipv4/ip_tunnel.c
>>> +++ b/net/ipv4/ip_tunnel.c
>>> @@ -176,7 +176,7 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn,
>>>                return cand;
>>>
>>>        t = rcu_dereference(itn->collect_md_tun);
>>> -       if (t)
>>> +       if (t && (t->dev->flags & IFF_UP))
>>>                return t;
>>>
>> It would be nice if we could increment drop count if tunnel device is not up.
>>
> Hi Pravin
>
> I think it’s not necessary, for example as gre tunnel, if ipgre_rcv fails, it would trigger send an icmp unreachable
> message:
>
>         if (ipgre_rcv(skb, &tpi, hdr_len) == PACKET_RCVD)
>                 return 0;
>
>         icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
>
> Since the tunnel device didn’t touch the packets, so increase drop statistics is not necessary.
>
icmp err packets are not reliable on all networks. device stats are
much more convenient during debugging connectivity issues.