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Mon, 08 Jun 2026 06:09:08 -0700 (PDT) Received: from localhost ([104.28.193.185]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-490c2d37edbsm300135675e9.2.2026.06.08.06.09.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Jun 2026 06:09:07 -0700 (PDT) From: Mariusz Klimek To: netdev@vger.kernel.org Cc: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, dsahern@kernel.org, idosch@nvidia.com, ncardwell@google.com, shuah@kernel.org, kuniyu@google.com, alice@isovalent.com, Mariusz Klimek Subject: [PATCH net-next 03/10] ipv6: add jumbo payload option to non-gso jumbograms Date: Mon, 8 Jun 2026 15:07:48 +0200 Message-ID: <20260608130755.5626-4-maklimek97@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260608130755.5626-1-maklimek97@gmail.com> References: <20260608130755.5626-1-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 path reintroduces code recently removed by Alice in commit 741d069aa488 ("net/ipv6: Drop HBH for BIG TCP on TX side") and commit 35f66ce90037 ("net/ipv6: Remove HBH helpers") that adds a hop-by-hop header containing a jumbo-payload option to packets larger than 65535 bytes. The hop-by-hop header is only added to jumbograms that aren't BIG TCP packets since BIG TCP packets no longer need to contain such hop-by-hop headers. This fixes sending jumbograms to a loopback device with MTU > 65535. Fixes: 741d069aa488 ("net/ipv6: Drop HBH for BIG TCP on TX side") Signed-off-by: Mariusz Klimek --- include/net/ipv6.h | 11 +++++++++++ net/ipv6/ip6_output.c | 22 ++++++++++++++++++++-- 2 files changed, 31 insertions(+), 2 deletions(-) diff --git a/include/net/ipv6.h b/include/net/ipv6.h index 1dec81faff28..d9e1fdca6934 100644 --- a/include/net/ipv6.h +++ b/include/net/ipv6.h @@ -152,6 +152,17 @@ struct frag_hdr { __be32 identification; }; +/* + * Jumbo payload option, as described in RFC 2675 2. + */ +struct hop_jumbo_hdr { + u8 nexthdr; + u8 hdrlen; + u8 tlv_type; /* IPV6_TLV_JUMBO, 0xC2 */ + u8 tlv_len; /* 4 */ + __be32 jumbo_payload_len; +}; + #define IP6_MF 0x0001 #define IP6_OFFSET 0xFFF8 diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 67c34fb281c6..405a9a0e65a4 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -293,6 +293,8 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, struct in6_addr *first_hop = &fl6->daddr; struct dst_entry *dst = skb_dst(skb); struct inet6_dev *idev = ip6_dst_idev(dst); + struct hop_jumbo_hdr *hop_jumbo; + int hoplen = sizeof(*hop_jumbo); struct net *net = sock_net(sk); unsigned int head_room; struct net_device *dev; @@ -305,7 +307,7 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, rcu_read_lock(); dev = dst_dev_rcu(dst); - head_room = sizeof(struct ipv6hdr) + LL_RESERVED_SPACE(dev); + head_room = sizeof(struct ipv6hdr) + hoplen + LL_RESERVED_SPACE(dev); if (opt) head_room += opt->opt_nflen + opt->opt_flen; @@ -331,8 +333,24 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, &fl6->saddr); } - if (unlikely(seg_len > IPV6_MAXPLEN)) + if (unlikely(seg_len > IPV6_MAXPLEN)) { + /* Only "real" jumbograms require a jumbo-payload option. + * BIG TCP packets just rely on skb->len. + */ + if (!skb_is_gso(skb)) { + hop_jumbo = __skb_push(skb, hoplen); + + hop_jumbo->nexthdr = proto; + hop_jumbo->hdrlen = 0; + hop_jumbo->tlv_type = IPV6_TLV_JUMBO; + hop_jumbo->tlv_len = 4; + hop_jumbo->jumbo_payload_len = htonl(seg_len + hoplen); + + proto = IPPROTO_HOPOPTS; + } + seg_len = 0; + } __skb_push(skb, sizeof(struct ipv6hdr)); skb_reset_network_header(skb); -- 2.47.3