[PATCH net] seg6: fix seg6 lwtunnel output redirect for L2 reduced encap mode

[PATCH net] seg6: fix seg6 lwtunnel output redirect for L2 reduced encap mode

[Andrea Mayer]

When SEG6_IPTUN_MODE_L2ENCAP_RED (L2ENCAP_RED) was introduced, the
condition in seg6_build_state() that excludes L2 encap modes from
setting LWTUNNEL_STATE_OUTPUT_REDIRECT was not updated to account for
the new mode.
As a consequence, L2ENCAP_RED routes incorrectly trigger seg6_output()
on the output path, where the packet is silently dropped because
skb_mac_header_was_set() fails on L3 packets.

Extend the check to also exclude L2ENCAP_RED, consistent with L2ENCAP.

Fixes: 13f0296be8ec ("seg6: add support for SRv6 H.L2Encaps.Red behavior")
Cc: stable@vger.kernel.org
Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
---
 net/ipv6/seg6_iptunnel.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
index 97b50d9b1365..9b64343ebad6 100644
--- a/net/ipv6/seg6_iptunnel.c
+++ b/net/ipv6/seg6_iptunnel.c
@@ -746,7 +746,8 @@ static int seg6_build_state(struct net *net, struct nlattr *nla,
 	newts->type = LWTUNNEL_ENCAP_SEG6;
 	newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
 
-	if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP)
+	if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP &&
+	    tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP_RED)
 		newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
 
 	newts->headroom = seg6_lwt_headroom(tuninfo);
-- 
2.20.1

Re: [PATCH net] seg6: fix seg6 lwtunnel output redirect for L2 reduced encap mode

[Justin Iurman]

On 4/18/26 18:28, Andrea Mayer wrote:
> When SEG6_IPTUN_MODE_L2ENCAP_RED (L2ENCAP_RED) was introduced, the
> condition in seg6_build_state() that excludes L2 encap modes from
> setting LWTUNNEL_STATE_OUTPUT_REDIRECT was not updated to account for
> the new mode.
> As a consequence, L2ENCAP_RED routes incorrectly trigger seg6_output()
> on the output path, where the packet is silently dropped because
> skb_mac_header_was_set() fails on L3 packets.
> 
> Extend the check to also exclude L2ENCAP_RED, consistent with L2ENCAP.
> 
> Fixes: 13f0296be8ec ("seg6: add support for SRv6 H.L2Encaps.Red behavior")
> Cc: stable@vger.kernel.org
> Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
> ---
>   net/ipv6/seg6_iptunnel.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c
> index 97b50d9b1365..9b64343ebad6 100644
> --- a/net/ipv6/seg6_iptunnel.c
> +++ b/net/ipv6/seg6_iptunnel.c
> @@ -746,7 +746,8 @@ static int seg6_build_state(struct net *net, struct nlattr *nla,
>   	newts->type = LWTUNNEL_ENCAP_SEG6;
>   	newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
>   
> -	if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP)
> +	if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP &&
> +	    tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP_RED)
>   		newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
>   
>   	newts->headroom = seg6_lwt_headroom(tuninfo);

Reviewed-by: Justin Iurman <justin.iurman@gmail.com>

Re: [PATCH net] seg6: fix seg6 lwtunnel output redirect for L2 reduced encap mode

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Sat, 18 Apr 2026 18:28:38 +0200 you wrote:
> When SEG6_IPTUN_MODE_L2ENCAP_RED (L2ENCAP_RED) was introduced, the
> condition in seg6_build_state() that excludes L2 encap modes from
> setting LWTUNNEL_STATE_OUTPUT_REDIRECT was not updated to account for
> the new mode.
> As a consequence, L2ENCAP_RED routes incorrectly trigger seg6_output()
> on the output path, where the packet is silently dropped because
> skb_mac_header_was_set() fails on L3 packets.
> 
> [...]

Here is the summary with links:
  - [net] seg6: fix seg6 lwtunnel output redirect for L2 reduced encap mode
    https://git.kernel.org/netdev/net/c/ade67d5f5888

You are awesome, thank you!
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