From 5d79fdffd3cd0533e3cd236beb58f2c2f1fc37a4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maciej=20=C5=BBenczykowski?= <maze@google.com>
Date: Mon, 2 Jun 2025 01:13:06 -0700
Subject: [PATCH] bpf/progs/offload.c: disable ipv6 offload for non-gso >pmtu
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Bug: 263884894
Bug: 419747540
Test: TreeHugger
Flag: EXEMPT mainline
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Idecc355084220ea5c53924c720c806adab153b5d
---
 bpf/progs/offload.c | 3 +++
 bpf/progs/offload.h | 1 +
 2 files changed, 4 insertions(+)

diff --git a/bpf/progs/offload.c b/bpf/progs/offload.c
index 1c64eb679c..3937ba634d 100644
--- a/bpf/progs/offload.c
+++ b/bpf/progs/offload.c
@@ -178,6 +178,9 @@ static inline __always_inline int do_forward6(struct __sk_buff* skb,
     uint64_t packets = 1;
     uint64_t L3_bytes = skb->len - l2_header_size;
     if (L3_bytes > v->pmtu) {
+        if (KVER_IS_AT_LEAST(kver, 5, 4, 0)) {
+            if (skb->gso_segs <= 1) TC_PUNT(ABOVE_IPV6_PMTU);
+        }
         const int tcp6_overhead = sizeof(struct ipv6hdr) + sizeof(struct tcphdr) + 12;
         const int mss = v->pmtu - tcp6_overhead;
         const uint64_t payload = L3_bytes - tcp6_overhead;
diff --git a/bpf/progs/offload.h b/bpf/progs/offload.h
index 4d6d3e41f6..870983ec7d 100644
--- a/bpf/progs/offload.h
+++ b/bpf/progs/offload.h
@@ -41,6 +41,7 @@
     ERR(BELOW_IPV4_MTU)       \
     ERR(ABOVE_IPV4_PMTU)      \
     ERR(BELOW_IPV6_MTU)       \
+    ERR(ABOVE_IPV6_PMTU)      \
     ERR(LIMIT_REACHED)        \
     ERR(CHANGE_HEAD_FAILED)   \
     ERR(TOO_SHORT)            \