Subject: Re: [PATCH v2 net] ip6_gre: use skb_vlan_inet_prepare() instead of pskb_inet_may_pull()

From: Florian Westphal <[email-masked]>
Date: Wed, 7 Jan 2026 09:46:53 +0100

Eric Dumazet <[email-masked]> wrote:
> On Tue, Jan 6, 2026 at 6:56 PM Jakub Kicinski <[email-masked]> wrote:
> >
> > On Tue,  6 Jan 2026 14:45:29 +0000 Eric Dumazet wrote:
> > > v2: invert the conditions (Jakub)
> >
> > Thanks! Much better now, but still failing
> > tools/testing/selftests/net/gre_gso.sh
> >
> > TAP version 13
> > 1..1
> > # timeout set to 3600
> > # selftests: net: gre_gso.sh
> > # 2.16 [+2.16]     TEST: GREv6/v4 - copy file w/ TSO                                   [ OK ]
> > # 3.16 [+1.01] 2026/01/06 10:32:57 socat[20546] W exiting on signal 15
> > # 3.17 [+0.01] 2026/01/06 10:32:57 socat[20546] W exiting on signal 15
> > # 3.17 [+0.00]     TEST: GREv6/v4 - copy file w/ GSO                                   [FAIL]
> > # 3.18 [+0.01] 2026/01/06 10:32:57 socat[20533] W exiting on signal 15
> > # 3.19 [+0.00]     TEST: GREv6/v6 - copy file w/ TSO                                   [ OK ]
> > # 4.19 [+1.00] 2026/01/06 10:32:59 socat[20559] W exiting on signal 15
> > # 4.19 [+0.01]     TEST: GREv6/v6 - copy file w/ GSO                                   [FAIL]
> > # 4.20 [+0.01] 2026/01/06 10:32:59 socat[20549] W exiting on signal 15
> > # 4.22 [+0.02] 2026/01/06 10:32:59 socat[20560] W exiting on signal 15
> > # 4.23 [+0.01]
> > # 4.23 [+0.00] Tests passed:   2
> > # 4.23 [+0.00] Tests failed:   2
> > not ok 1 selftests: net: gre_gso.sh # exit=1
> >
> > https://netdev-ctrl.bots.linux.dev/logs/vmksft/net/results/461862/65-gre-gso-sh/stdout
> 
> For some reason I am unable to run this test from a virtme-ng instance.
> 
> I guess I wlll not make a new version of this patch, maybe Florian can
> take over.

Its failing because nhoff is moved by 14 bytes, test passes after doing:

-       if (skb_vlan_inet_prepare(skb, false))
+       if (skb_vlan_inet_prepare(skb, true))