From: Nick Hudson <nhudson@akamai.com>
To: bpf@vger.kernel.org, netdev@vger.kernel.org,
Willem de Bruijn <willemb@google.com>,
Martin KaFai Lau <martin.lau@linux.dev>
Cc: Nick Hudson <nhudson@akamai.com>,
Max Tottenham <mtottenh@akamai.com>,
Anna Glasgall <aglasgal@akamai.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH bpf-next v4 5/6] bpf: clear decap tunnel GSO state in skb_adjust_room
Date: Thu, 16 Apr 2026 08:55:13 +0100 [thread overview]
Message-ID: <20260416075514.927101-6-nhudson@akamai.com> (raw)
In-Reply-To: <20260416075514.927101-1-nhudson@akamai.com>
On shrink in bpf_skb_adjust_room(), clear tunnel-specific GSO flags
according to the decapsulation flags:
- BPF_F_ADJ_ROOM_DECAP_L4_UDP clears SKB_GSO_UDP_TUNNEL{,_CSUM}
- BPF_F_ADJ_ROOM_DECAP_L4_GRE clears SKB_GSO_GRE{,_CSUM}
- BPF_F_ADJ_ROOM_DECAP_IPXIP4 clears SKB_GSO_IPXIP4
- BPF_F_ADJ_ROOM_DECAP_IPXIP6 clears SKB_GSO_IPXIP6
When all tunnel-related GSO bits are cleared, also clear
skb->encapsulation.
Handle the ESP inside a UDP tunnel case where encapsulation should remain
set.
If UDP decap is performed, clear encap_hdr_csum and remcsum_offload.
Co-developed-by: Max Tottenham <mtottenh@akamai.com>
Signed-off-by: Max Tottenham <mtottenh@akamai.com>
Co-developed-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Nick Hudson <nhudson@akamai.com>
---
net/core/filter.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/net/core/filter.c b/net/core/filter.c
index 7f8d43420afb..e113ae2f3f14 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3667,6 +3667,44 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff,
if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO))
skb_increase_gso_size(shinfo, len_diff);
+ /* Selective GSO flag clearing based on decap type.
+ * Only clear the flags for the tunnel layer being removed.
+ */
+ if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_UDP) &&
+ (shinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
+ SKB_GSO_UDP_TUNNEL_CSUM)))
+ shinfo->gso_type &= ~(SKB_GSO_UDP_TUNNEL |
+ SKB_GSO_UDP_TUNNEL_CSUM);
+ if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_GRE) &&
+ (shinfo->gso_type & (SKB_GSO_GRE | SKB_GSO_GRE_CSUM)))
+ shinfo->gso_type &= ~(SKB_GSO_GRE |
+ SKB_GSO_GRE_CSUM);
+ if ((flags & BPF_F_ADJ_ROOM_DECAP_IPXIP4) &&
+ (shinfo->gso_type & SKB_GSO_IPXIP4))
+ shinfo->gso_type &= ~SKB_GSO_IPXIP4;
+ if ((flags & BPF_F_ADJ_ROOM_DECAP_IPXIP6) &&
+ (shinfo->gso_type & SKB_GSO_IPXIP6))
+ shinfo->gso_type &= ~SKB_GSO_IPXIP6;
+
+ /* Clear encapsulation flag only when no tunnel GSO flags remain */
+ if (flags & (BPF_F_ADJ_ROOM_DECAP_L4_MASK |
+ BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)) {
+ if (!(shinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
+ SKB_GSO_UDP_TUNNEL_CSUM |
+ SKB_GSO_GRE |
+ SKB_GSO_GRE_CSUM |
+ SKB_GSO_IPXIP4 |
+ SKB_GSO_IPXIP6 |
+ SKB_GSO_ESP)))
+ if (skb->encapsulation)
+ skb->encapsulation = 0;
+
+ if (flags & BPF_F_ADJ_ROOM_DECAP_L4_UDP) {
+ skb->encap_hdr_csum = 0;
+ skb->remcsum_offload = 0;
+ }
+ }
+
/* Header must be checked, and gso_segs recomputed. */
shinfo->gso_type |= SKB_GSO_DODGY;
shinfo->gso_segs = 0;
--
2.34.1
next prev parent reply other threads:[~2026-04-16 7:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-16 7:55 [PATCH bpf-next v4 0/6] bpf: decap flags and GSO state updates Nick Hudson
2026-04-16 7:55 ` [PATCH bpf-next v4 1/6] bpf: name the enum for BPF_FUNC_skb_adjust_room flags Nick Hudson
2026-04-16 7:55 ` [PATCH bpf-next v4 2/6] bpf: refactor masks for ADJ_ROOM flags and encap validation Nick Hudson
2026-04-16 7:55 ` [PATCH bpf-next v4 3/6] bpf: add BPF_F_ADJ_ROOM_DECAP_* flags for tunnel decapsulation Nick Hudson
2026-04-16 7:55 ` [PATCH bpf-next v4 4/6] bpf: allow new DECAP flags and add guard rails Nick Hudson
2026-04-16 7:55 ` Nick Hudson [this message]
2026-04-16 8:34 ` [PATCH bpf-next v4 5/6] bpf: clear decap tunnel GSO state in skb_adjust_room bot+bpf-ci
2026-04-16 12:32 ` Willem de Bruijn
2026-04-17 12:27 ` Hudson, Nick
2026-04-16 7:55 ` [PATCH bpf-next v4 6/6] selftests/bpf: tc_tunnel validate decap GSO state Nick Hudson
2026-04-16 12:33 ` Willem de Bruijn
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260416075514.927101-6-nhudson@akamai.com \
--to=nhudson@akamai.com \
--cc=aglasgal@akamai.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=eddyz87@gmail.com \
--cc=edumazet@google.com \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=martin.lau@linux.dev \
--cc=memxor@gmail.com \
--cc=mtottenh@akamai.com \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=willemb@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox