netdev - Re: [PATCH net-next v6] vxlan: add support for flowlabel inherit

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Date: Tue, 24 Oct 2023 11:53:00 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Alce Lafranque <alce@...ranque.net>, "David S. Miller"
 <davem@...emloft.net>,  Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, David Ahern <dsahern@...nel.org>,  Ido Schimmel
 <idosch@...dia.com>, netdev@...r.kernel.org
Cc: Vincent Bernat <vincent@...nat.ch>
Subject: Re: [PATCH net-next v6] vxlan: add support for flowlabel inherit

On Sun, 2023-10-22 at 14:14 -0500, Alce Lafranque wrote:
> By default, VXLAN encapsulation over IPv6 sets the flow label to 0, with
> an option for a fixed value. This commits add the ability to inherit the
> flow label from the inner packet, like for other tunnel implementations.
> This enables devices using only L3 headers for ECMP to correctly balance
> VXLAN-encapsulated IPv6 packets.
> 
> ```
> $ ./ip/ip link add dummy1 type dummy
> $ ./ip/ip addr add 2001:db8::2/64 dev dummy1
> $ ./ip/ip link set up dev dummy1
> $ ./ip/ip link add vxlan1 type vxlan id 100 flowlabel inherit remote 2001:db8::1 local 2001:db8::2
> $ ./ip/ip link set up dev vxlan1
> $ ./ip/ip addr add 2001:db8:1::2/64 dev vxlan1
> $ ./ip/ip link set arp off dev vxlan1
> $ ping -q 2001:db8:1::1 &
> $ tshark -d udp.port==8472,vxlan -Vpni dummy1 -c1
> [...]
> Internet Protocol Version 6, Src: 2001:db8::2, Dst: 2001:db8::1
>     0110 .... = Version: 6
>     .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
>         .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
>         .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
>     .... 1011 0001 1010 1111 1011 = Flow Label: 0xb1afb
> [...]
> Virtual eXtensible Local Area Network
>     Flags: 0x0800, VXLAN Network ID (VNI)
>     Group Policy ID: 0
>     VXLAN Network Identifier (VNI): 100
> [...]
> Internet Protocol Version 6, Src: 2001:db8:1::2, Dst: 2001:db8:1::1
>     0110 .... = Version: 6
>     .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
>         .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
>         .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
>     .... 1011 0001 1010 1111 1011 = Flow Label: 0xb1afb
> ```
> 
> Signed-off-by: Alce Lafranque <alce@...ranque.net>
> Co-developed-by: Vincent Bernat <vincent@...nat.ch>
> Signed-off-by: Vincent Bernat <vincent@...nat.ch>
> Reviewed-by: Ido Schimmel <idosch@...dia.com>
> 
> ---
> v6:
>   - Rebase patch
> v5: https://lore.kernel.org/netdev/20231019180417.210523-1-alce@lafranque.net/
>   - Rollback policy label to fixed by default
> v4: https://lore.kernel.org/all/20231014132102.54051-1-alce@lafranque.net/
>   - Fix tabs
> v3: https://lore.kernel.org/all/20231014131320.51810-1-alce@lafranque.net/
>   - Adopt policy label inherit by default
>   - Set policy to label fixed when flowlabel is set
>   - Rename IFLA_VXLAN_LABEL_BEHAVIOR to IFLA_VXLAN_LABEL_POLICY
> v2: https://lore.kernel.org/all/20231007142624.739192-1-alce@lafranque.net/
>   - Use an enum instead of flag to define label behavior
> v1: https://lore.kernel.org/all/4444C5AE-FA5A-49A4-9700-7DD9D7916C0F.1@mail.lac-coloc.fr/
> ---
>  drivers/net/vxlan/vxlan_core.c | 23 ++++++++++++++++++++++-
>  include/net/ip_tunnels.h       | 11 +++++++++++
>  include/net/vxlan.h            | 33 +++++++++++++++++----------------
>  include/uapi/linux/if_link.h   |  8 ++++++++
>  4 files changed, 58 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
> index 6f7d45e3cfa2..341fd5eee9e1 100644
> --- a/drivers/net/vxlan/vxlan_core.c
> +++ b/drivers/net/vxlan/vxlan_core.c
> @@ -2443,7 +2443,17 @@ void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
>  			udp_sum = !(flags & VXLAN_F_UDP_ZERO_CSUM6_TX);
>  #if IS_ENABLED(CONFIG_IPV6)
>  		local_ip = vxlan->cfg.saddr;
> -		label = vxlan->cfg.label;
> +		switch (vxlan->cfg.label_policy) {
> +		case VXLAN_LABEL_FIXED:
> +			label = vxlan->cfg.label;
> +			break;
> +		case VXLAN_LABEL_INHERIT:
> +			label = ip_tunnel_get_flowlabel(old_iph, skb);
> +			break;
> +		default:
> +			DEBUG_NET_WARN_ON_ONCE(1);
> +			goto drop;
> +		}
>  #endif
>  	} else {
>  		if (!info) {

I'm sorry, this does not apply cleanly to net-next as this chunk
conflicts with commit 2aceb896ee18 ("vxlan: use generic function for
tunnel IPv6 route lookup"), please rebase and re-post, thanks!

Paolo