netdev - Re: [PATCH net-next v2] ip_tunnel: allow to inherit from VLAN encapsulated IP frames

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Date:   Thu, 7 Jul 2022 09:44:06 +0200
From:   Matthias May <matthias.may@...termo.com>
To:     Eyal Birger <eyal.birger@...il.com>
CC:     <netdev@...r.kernel.org>, <davem@...emloft.net>,
        <yoshfuji@...ux-ipv6.org>, <dsahern@...nel.org>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2] ip_tunnel: allow to inherit from VLAN
 encapsulated IP frames

On 7/6/22 19:24, Eyal Birger wrote:
> 
> Hi,
> 
> On Wed, Jul 6, 2022 at 7:54 PM Matthias May <matthias.may@...termo.com <mailto:matthias.may@...termo.com>> wrote:
> 
>     The current code allows to inherit the TOS, TTL, DF from the payload
>     when skb->protocol is ETH_P_IP or ETH_P_IPV6.
>     However when the payload is VLAN encapsulated (e.g because the tunnel
>     is of type GRETAP), then this inheriting does not work, because the
>     visible skb->protocol is of type ETH_P_8021Q.
> 
>     Add a check on ETH_P_8021Q and subsequently check the payload protocol.
> 
>     Signed-off-by: Matthias May <matthias.may@...termo.com <mailto:matthias.may@...termo.com>>
>     ---
>     v1 -> v2:
>       - Add support for ETH_P_8021AD as suggested by Jakub Kicinski.
>     ---
>       net/ipv4/ip_tunnel.c | 22 ++++++++++++++--------
>       1 file changed, 14 insertions(+), 8 deletions(-)
> 
>     diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
>     index 94017a8c3994..bdcc0f1e83c8 100644
>     --- a/net/ipv4/ip_tunnel.c
>     +++ b/net/ipv4/ip_tunnel.c
>     @@ -648,6 +648,13 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
>              u8 tos, ttl;
>              __be32 dst;
>              __be16 df;
>     +       __be16 *payload_protocol;
>     +
>     +       if (skb->protocol == htons(ETH_P_8021Q) ||
>     +           skb->protocol == htons(ETH_P_8021AD))
>     +               payload_protocol = (__be16 *)(skb->head + skb->network_header - 2);
>     +       else
>     +               payload_protocol = &skb->protocol;
> 
> 
> Maybe it's better to use skb_protocol(skb, true) here instead of open
> coding the vlan parsing?
> 
> Eyal

Hi Eyal
I've looked into using skb_protocol(skb, true).
If skip_vlan is set to true, wouldn't it make sense to use vlan_get_protocol(skb) directly?

BR
Matthias

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