netdev - Re: [PATCH] xfrm: use gre key as flow upper protocol info

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Date:	Wed, 3 Nov 2010 14:35:41 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	Michał Mirosław <mirqus@...il.com>
Cc:	Timo Teräs <timo.teras@....fi>,
	netdev@...r.kernel.org, Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH] xfrm: use gre key as flow upper protocol info

2010/11/3 Michał Mirosław <mirqus@...il.com>:
> 2010/11/3 Timo Teräs <timo.teras@....fi>:
>> The GRE Key field is intended to be used for identifying an individual
>> traffic flow within a tunnel. It is useful to be able to have XFRM
>> policy selector matches to have different policies for different
>> GRE tunnels.
> [...]
>> diff --git a/net/ipv4/xfrm4_policy.c b/net/ipv4/xfrm4_policy.c
>> index 4464f3b..57af4bd 100644
>> --- a/net/ipv4/xfrm4_policy.c
>> +++ b/net/ipv4/xfrm4_policy.c
>> @@ -158,6 +159,20 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
>>                                fl->fl_ipsec_spi = htonl(ntohs(ipcomp_hdr[1]));
>>                        }
>>                        break;
>> +
>> +               case IPPROTO_GRE:
>> +                       if (pskb_may_pull(skb, xprth + 12 - skb->data)) {
>> +                               __be16 *greflags = (__be16 *)xprth;
>> +                               __be32 *gre_hdr = (__be32 *)xprth;
>> +
>> +                               if (greflags[0] & GRE_KEY) {
>> +                                       if (greflags[0] & GRE_CSUM)
>> +                                               gre_hdr++;
>> +                                       fl->fl_gre_key = gre_hdr[1];
>> +                               }
>> +                       }
>> +                       break;
>> +
>>                default:
>>                        fl->fl_ipsec_spi = 0;
>>                        break;
>
> I would expect that keyless tunnel would be separate from key 0 tunnel.

No key and key 0 are generally treated the same.  Both will match the
same tunnel when doing the lookup in the GRE receive path.
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