network flow offloading broken in 6.18.45+

network flow offloading broken in 6.18.45+

[Hauke Mehrtens]

Hi,

flow offloading is currently broken in Linux 6.18.45.

Since the backport of commit b5964aac51e0 ("netfilter: flowtable: 
consolidate xmit path") to Linux 6.18.45. This is happening in a router 
with traffic from wifi to the Ethernet device when mac80211 returns 
-EOPNOTSUPP.

Upstream fixed it in 871df5007eda ("netfilter: flowtable: bail out if 
forward path cannot be discovered") by not offloading the flow at all. 
backporting this change looks more complicated.

This cam up in a discussion in an OpenWrt PR:
https://github.com/openwrt/openwrt/pull/24800

An LLM suggested this change: 
https://github.com/openwrt/openwrt/pull/24800/changes/394d741e6e76ecd172dbbf1d9ba171e378211734

It seams to work, but I do not understand this part of the code god 
enough to judge if this is correct.

Hauke

Re: network flow offloading broken in 6.18.45+

[Pablo Neira Ayuso]

Hi Hauke,

On Wed, Sep 09, 2026 at 06:29:50PM +0200, Hauke Mehrtens wrote:
> Hi,
> 
> flow offloading is currently broken in Linux 6.18.45.
> 
> Since the backport of commit b5964aac51e0 ("netfilter: flowtable:
> consolidate xmit path") to Linux 6.18.45. This is happening in a router with
> traffic from wifi to the Ethernet device when mac80211 returns -EOPNOTSUPP.
> 
> Upstream fixed it in 871df5007eda ("netfilter: flowtable: bail out if
> forward path cannot be discovered") by not offloading the flow at all.
> backporting this change looks more complicated.
> 
> This cam up in a discussion in an OpenWrt PR:
> https://github.com/openwrt/openwrt/pull/24800
> 
> An LLM suggested this change: https://github.com/openwrt/openwrt/pull/24800/changes/394d741e6e76ecd172dbbf1d9ba171e378211734

Patch went away.

> It seams to work, but I do not understand this part of the code god enough
> to judge if this is correct.

Could you attach the patch to this email for review?

Thanks.

Re: network flow offloading broken in 6.18.45+

[Pablo Neira Ayuso]

On Mon, Sep 14, 2026 at 12:12:16AM +0200, Pablo Neira Ayuso wrote:
> Hi Hauke,
> 
> On Wed, Sep 09, 2026 at 06:29:50PM +0200, Hauke Mehrtens wrote:
> > Hi,
> > 
> > flow offloading is currently broken in Linux 6.18.45.
> > 
> > Since the backport of commit b5964aac51e0 ("netfilter: flowtable:
> > consolidate xmit path") to Linux 6.18.45. This is happening in a router with
> > traffic from wifi to the Ethernet device when mac80211 returns -EOPNOTSUPP.
> > 
> > Upstream fixed it in 871df5007eda ("netfilter: flowtable: bail out if
> > forward path cannot be discovered") by not offloading the flow at all.
> > backporting this change looks more complicated.
> > 
> > This cam up in a discussion in an OpenWrt PR:
> > https://github.com/openwrt/openwrt/pull/24800
> > 
> > An LLM suggested this change: https://github.com/openwrt/openwrt/pull/24800/changes/394d741e6e76ecd172dbbf1d9ba171e378211734
> 
> Patch went away.
> 
> > It seams to work, but I do not understand this part of the code god enough
> > to judge if this is correct.
> 
> Could you attach the patch to this email for review?

I've found it :)

https://github.com/openwrt/openwrt/commit/d2b53b8043e17087b877bfc2335cbba87dffb4e0