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Sun, 14 Jun 2026 06:19:25 -0700 (PDT) Received: from [192.168.88.32] ([150.228.25.72]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4606f26f3dcsm23933729f8f.13.2026.06.14.06.19.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 14 Jun 2026 06:19:25 -0700 (PDT) Message-ID: <617cfbfe-0b42-4ce8-a283-5c99da26bb10@redhat.com> Date: Sun, 14 Jun 2026 15:19:23 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v7 08/11] udp: Set length in UDP header to 0 for big GSO packets To: Alice Mikityanska , Daniel Borkmann , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Xin Long , Willem de Bruijn , Willem de Bruijn , David Ahern , Nikolay Aleksandrov Cc: Shuah Khan , Stanislav Fomichev , Andrew Lunn , Simon Horman , Florian Westphal , netdev@vger.kernel.org, Alice Mikityanska References: <20260611192955.604661-1-alice.kernel@fastmail.im> <20260611192955.604661-9-alice.kernel@fastmail.im> From: Paolo Abeni Content-Language: en-US In-Reply-To: <20260611192955.604661-9-alice.kernel@fastmail.im> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/11/26 9:29 PM, Alice Mikityanska wrote: > diff --git a/net/ipv6/ip6_udp_tunnel.c b/net/ipv6/ip6_udp_tunnel.c > index dcff7fb16ff6..32525a051a6f 100644 > --- a/net/ipv6/ip6_udp_tunnel.c > +++ b/net/ipv6/ip6_udp_tunnel.c > @@ -93,7 +93,7 @@ void udp_tunnel6_xmit_skb(struct dst_entry *dst, struct sock *sk, > uh->dest = dst_port; > uh->source = src_port; > > - udp_set_len_short(uh, skb->len); > + udp_set_len(uh, skb->len); Both Sashikos noted the above breaks GSO csum, as the following udp_set_csum() will use skb->len to compute the csum partial. I think it would be useful to consolidate udp_set_len() and udp_set_csum() in a single helper - say udp_set_csum_len(): void udp_set_csum_len(bool nocheck, struct sk_buff *skb, __be32 saddr, __be32 daddr, int len) { struct udphdr *uh = udp_hdr(skb); uh->len = htons(len); if (nocheck) { uh->check = 0; } else if (skb_is_gso(skb)) { uh->len = len < GRO_LEGACY_MAX_SIZE ? htons(len) : 0; uh->check = ~udp_v4_check(len, saddr, daddr, 0); } else if (skb->ip_summed == CHECKSUM_PARTIAL) { uh->check = 0; uh->check = udp_v4_check(len, saddr, daddr, // ... so that csum and len are always consistent, the 'set' logic is symmetric with udp_get_len(), and no duplicate checks are needed. /P