linux-kernel - [PATCH] selftests/bpf: Validate UDP length in cls

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Message-ID: <20250602174309.31315-1-suchitkarunakaran@gmail.com>
Date: Mon,  2 Jun 2025 23:13:09 +0530
From: Suchit <suchitkarunakaran@...il.com>
To: andrii@...nel.org,
	eddyz87@...il.com,
	bpf@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	mykolal@...com,
	ast@...nel.org,
	daniel@...earbox.net
Cc: martin.lau@...ux.dev,
	song@...nel.org,
	yonghong.song@...ux.dev,
	john.fastabend@...il.com,
	kpsingh@...nel.org,
	sdf@...ichev.me,
	haoluo@...gle.com,
	jolsa@...nel.org,
	shuah@...nel.org,
	Suchit <suchitkarunakaran@...il.com>
Subject: [PATCH] selftests/bpf: Validate UDP length in cls_redirect test

Add validation step to ensure that the UDP payload is
long enough to contain the expected GUE and UNIGUE encapsulation
headers

Signed-off-by: Suchit <suchitkarunakaran@...il.com>
---
 tools/testing/selftests/bpf/progs/test_cls_redirect.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/progs/test_cls_redirect.c b/tools/testing/selftests/bpf/progs/test_cls_redirect.c
index f344c6835e84..c1d2eaee2e77 100644
--- a/tools/testing/selftests/bpf/progs/test_cls_redirect.c
+++ b/tools/testing/selftests/bpf/progs/test_cls_redirect.c
@@ -978,7 +978,14 @@ int cls_redirect(struct __sk_buff *skb)
 		return TC_ACT_OK;
 	}
 
-	/* TODO Check UDP length? */
+	uint16_t udp_len = bpf_ntohs(encap->udp.len);
+	uint16_t min_encap_len = sizeof(encap->udp) + sizeof(encap->gue) + sizeof(encap->unigue);
+
+	if (udp_len < min_encap_len) {
+		metrics->errors_total_malformed_encapsulation++;
+		return TC_ACT_SHOT;
+	}

 	if (encap->udp.dest != ENCAPSULATION_PORT) {
 		return TC_ACT_OK;
 	}
-- 
2.49.0