netdev - Re: [PATCH net-next 2/2] vxlan: fix getting tos value from DSCP field

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Date:   Mon, 3 Aug 2020 11:30:39 +0200
From:   Guillaume Nault <gnault@...hat.com>
To:     Hangbin Liu <liuhangbin@...il.com>
Cc:     netdev@...r.kernel.org, Petr Machata <pmachata@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        David Ahern <dsahern@...nel.org>,
        Eelco Chaudron <echaudro@...hat.com>
Subject: Re: [PATCH net-next 2/2] vxlan: fix getting tos value from DSCP field

On Mon, Aug 03, 2020 at 04:02:17PM +0800, Hangbin Liu wrote:
> In commit 71130f29979c ("vxlan: fix tos value before xmit") we strict
> the vxlan tos value before xmit. But as IP tos field has been obsoleted
> by RFC2474, and updated by RFC3168 later. We should use new DSCP field,
> or we will lost the first 3 bits value when xmit.
> 
Why sending this patch to net-next? Commit 71130f29979c ("vxlan: fix
tos value before xmit") broke setups where the high TOS bits were used.
This needs to be fixed in net (and probably pushed to -stable too).

> Fixes: 71130f29979c ("vxlan: fix tos value before xmit")
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> ---
>  drivers/net/vxlan.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
> index 77658425db8a..fe051ed0f6db 100644
> --- a/drivers/net/vxlan.c
> +++ b/drivers/net/vxlan.c
> @@ -2722,7 +2722,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
>  		ndst = &rt->dst;
>  		skb_tunnel_check_pmtu(skb, ndst, VXLAN_HEADROOM);
>  
> -		tos = ip_tunnel_ecn_encap(RT_TOS(tos), old_iph, skb);
> +		tos = ip_tunnel_ecn_encap(RT_DSCP(tos), old_iph, skb);
>  		ttl = ttl ? : ip4_dst_hoplimit(&rt->dst);
>  		err = vxlan_build_skb(skb, ndst, sizeof(struct iphdr),
>  				      vni, md, flags, udp_sum);
> @@ -2762,7 +2762,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
>  
>  		skb_tunnel_check_pmtu(skb, ndst, VXLAN6_HEADROOM);
>  
> -		tos = ip_tunnel_ecn_encap(RT_TOS(tos), old_iph, skb);
> +		tos = ip_tunnel_ecn_encap(RT_DSCP(tos), old_iph, skb);
>  		ttl = ttl ? : ip6_dst_hoplimit(ndst);
>  		skb_scrub_packet(skb, xnet);
>  		err = vxlan_build_skb(skb, ndst, sizeof(struct ipv6hdr),
> -- 
> 2.25.4
>