From: Steffen Klassert <steffen.klassert@secunet•com>
To: Alexander Duyck <alexander.duyck@gmail•com>
Cc: David Miller <davem@davemloft•net>, NetDev <netdev@vger•kernel.org>
Subject: Re: Looking for a lost patch
Date: Mon, 18 May 2015 09:38:10 +0200 [thread overview]
Message-ID: <20150518073809.GD8928@secunet.com> (raw)
In-Reply-To: <55538E1F.2020505@gmail.com>
On Wed, May 13, 2015 at 10:47:11AM -0700, Alexander Duyck wrote:
> So I am in the process of trying to do some work on VTI6 and in the
> process of doing so I am trying to setup an IPv4 VTI tunnel and I
> have come across what appears to be a lost patch.
>
> So in commit a32452366b72 ("vti4: Don't count header length twice.")
> the following change was made:
>
> diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
> index 687ddef..cd62596 100644
> --- a/net/ipv4/ip_vti.c
> +++ b/net/ipv4/ip_vti.c
> @@ -349,7 +349,6 @@ static int vti_tunnel_init(struct net_device *dev)
> memcpy(dev->broadcast, &iph->daddr, 4);
>
> dev->type = ARPHRD_TUNNEL;
> - dev->hard_header_len = LL_MAX_HEADER + sizeof(struct iphdr);
> dev->mtu = ETH_DATA_LEN;
> dev->flags = IFF_NOARP;
> dev->iflink = 0;
>
> However in commit f895f0cfbb77 ("Merge branch 'master' of
> git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec") the
> change appears to have been undone as a result of a merge commit.
>
> I'm just wondering which is correct. Should the hard_header_len be
> set or unset in vti_tunnel_init? I ask because I have two kernels
> and one has the patch and one does not and I am seeing an MTU of
> 1332 for a VTI tunnel without, and 1480 for a VTI tunnel with.
A MTU of 1332 is definitively wrong. Actually I think a vti
tunnel can have a MTU of 1500 because xfrm cares to calculate
a PMTU based on the used states. The MTU of 1480 is because
the generic ip_tunnel_bind_dev() assumes that an ip tunnel
has always the overhead of an additional ip header. On IPsec
this header is included in the PMTU calculation.
next prev parent reply other threads:[~2015-05-18 7:38 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-13 17:47 Looking for a lost patch Alexander Duyck
2015-05-18 7:38 ` Steffen Klassert [this message]
2015-05-18 16:02 ` Alexander Duyck
2015-05-19 7:57 ` Steffen Klassert
2015-05-19 18:32 ` Alexander Duyck
2015-05-20 6:32 ` Steffen Klassert
2015-05-21 2:06 ` Alexander Duyck
2015-05-21 21:25 ` David Miller
2015-05-27 8:35 ` Steffen Klassert
2015-05-27 15:46 ` David Miller
2015-05-28 5:51 ` Steffen Klassert
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