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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , osmocom-net-gprs@lists.osmocom.org, netdev@vger.kernel.org, Zhixing Chen Subject: [PATCH net v3] gtp: parse extension headers before reading inner protocol Date: Wed, 8 Jul 2026 12:22:44 +0800 Message-Id: <20260708042244.120898-1-running910@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit GTPv1-U packets may carry a chain of extension headers before the inner IP packet. The receive path already parses and skips these extension headers, but it currently reads the inner protocol before doing so. As a result, the first extension header byte is interpreted as the inner IP version. Packets with extension headers are then dropped before PDP lookup. Parse the extension header chain before calling gtp_inner_proto(), so the inner protocol is read from the actual inner IP header. Fixes: c75fc0b9e5be ("gtp: identify tunnel via GTP device + GTP version + TEID + family") Signed-off-by: Zhixing Chen --- Changes in v3: - Refetch the GTP header after pskb_may_pull() before checking the extension-header flag. Changes in v2: - Add missing Fixes tag. v2: https://lore.kernel.org/netdev/20260703093708.18141-1-running910@gmail.com/T/ v1: https://lore.kernel.org/netdev/20260703084244.59077-1-running910@gmail.com/T/ --- drivers/net/gtp.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index a60ef32b35b8..c0e38878af51 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -826,13 +826,17 @@ static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb) if (!pskb_may_pull(skb, hdrlen)) return -1; + gtp1 = (struct gtp1_header *)(skb->data + sizeof(struct udphdr)); + + if (gtp1->flags & GTP1_F_EXTHDR && + gtp_parse_exthdrs(skb, &hdrlen) < 0) + return -1; + if (gtp_inner_proto(skb, hdrlen, &inner_proto) < 0) { netdev_dbg(gtp->dev, "GTP packet does not encapsulate an IP packet\n"); return -1; } - gtp1 = (struct gtp1_header *)(skb->data + sizeof(struct udphdr)); - pctx = gtp1_pdp_find(gtp, ntohl(gtp1->tid), gtp_proto_to_family(inner_proto)); if (!pctx) { @@ -840,10 +844,6 @@ static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb) return 1; } - if (gtp1->flags & GTP1_F_EXTHDR && - gtp_parse_exthdrs(skb, &hdrlen) < 0) - return -1; - return gtp_rx(pctx, skb, hdrlen, gtp->role, inner_proto); } -- 2.34.1