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Thu, 27 Nov 2025 01:14:28 -0800 (PST) Received: from localhost ([104.28.225.185]) by smtp.gmail.com with ESMTPSA id 00721157ae682-78ad0d3f5bbsm3796167b3.7.2025.11.27.01.14.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Nov 2025 01:14:27 -0800 (PST) From: Mariusz Klimek To: netdev@vger.kernel.org Cc: Mariusz Klimek Subject: [PATCH net-next 1/3] net: gso: do not include jumbogram HBH header in seglen calculation Date: Thu, 27 Nov 2025 10:13:23 +0100 Message-ID: <20251127091325.7248-2-maklimek97@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251127091325.7248-1-maklimek97@gmail.com> References: <20251127091325.7248-1-maklimek97@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This patch fixes an issue in skb_gso_network_seglen where the calculated segment length includes the HBH headers of BIG TCP jumbograms despite these headers being removed before segmentation. These headers are added by GRO or by ip6_xmit for BIG TCP packets and are later removed by GSO. This bug causes MTU validation of BIG TCP jumbograms to fail. Signed-off-by: Mariusz Klimek --- net/core/gso.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/core/gso.c b/net/core/gso.c index bcd156372f4d..251a49181031 100644 --- a/net/core/gso.c +++ b/net/core/gso.c @@ -180,6 +180,10 @@ static unsigned int skb_gso_network_seglen(const struct sk_buff *skb) unsigned int hdr_len = skb_transport_header(skb) - skb_network_header(skb); + /* Jumbogram HBH header is removed upon segmentation. */ + if (skb->protocol == htons(ETH_P_IPV6) && skb->len > IPV6_MAXPLEN) + hdr_len -= sizeof(struct hop_jumbo_hdr); + return hdr_len + skb_gso_transport_seglen(skb); } -- 2.47.3