netdev - Re: [PATCH v6 net-next 09/14] ip6_tun: Add infrastructure for doing encapsulation

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Date:	Mon, 16 May 2016 15:37:07 -0700
From:	Tom Herbert <tom@...bertland.com>
To:	Alexander Duyck <alexander.duyck@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>, Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v6 net-next 09/14] ip6_tun: Add infrastructure for doing encapsulation

On Mon, May 16, 2016 at 3:25 PM, Alexander Duyck
<alexander.duyck@...il.com> wrote:
> On Mon, May 16, 2016 at 2:33 PM, Tom Herbert <tom@...bertland.com> wrote:
>> Add encap_hlen and ip_tunnel_encap structure to ip6_tnl. Add functions
>> for getting encap hlen, setting up encap on a tunnel, performing
>> encapsulation operation.
>>
>> Signed-off-by: Tom Herbert <tom@...bertland.com>
>> ---
>>  include/net/ip6_tunnel.h  | 58 ++++++++++++++++++++++++++++++++
>>  net/ipv4/ip_tunnel_core.c |  5 +++
>>  net/ipv6/ip6_tunnel.c     | 85 ++++++++++++++++++++++++++++++++++++++++++-----
>>  3 files changed, 139 insertions(+), 9 deletions(-)
>>
>
> So it looks like you completely dropped the two spots that were
> updating mtu and max_headroom with the t->hlen.  I thought you needed
> to at least have a check that used t->encap_hlen here in order to
> avoid overflowing the buffer or exceeding skb_headroom, or am I
> missing something?
>
Sorry, you're probably right. max_headroom seems to be an absolute
value. mtu being calculated seems relative to what is in skbuff
already.

Tom

> - Alex