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Mon, 15 Sep 2025 04:41:09 -0700 (PDT) From: Richard Gobert To: netdev@vger.kernel.org, pabeni@redhat.com, ecree.xilinx@gmail.com, willemdebruijn.kernel@gmail.com Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, horms@kernel.org, corbet@lwn.net, saeedm@nvidia.com, tariqt@nvidia.com, mbloch@nvidia.com, leon@kernel.org, dsahern@kernel.org, ncardwell@google.com, kuniyu@google.com, shuah@kernel.org, sdf@fomichev.me, aleksander.lobakin@intel.com, florian.fainelli@broadcom.com, alexander.duyck@gmail.com, linux-kernel@vger.kernel.org, linux-net-drivers@amd.com, Richard Gobert Subject: [PATCH net-next v5 4/5] net: gro: remove unnecessary df checks Date: Mon, 15 Sep 2025 13:39:32 +0200 Message-Id: <20250915113933.3293-5-richardbgobert@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250915113933.3293-1-richardbgobert@gmail.com> References: <20250915113933.3293-1-richardbgobert@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, packets with fixed IDs will be merged only if their don't-fragment bit is set. This restriction is unnecessary since packets without the don't-fragment bit will be forwarded as-is even if they were merged together. If packets are merged together and then fragmented, they will first be re-split into segments before being further fragmented, so the behavior is identical whether or not the packets were first merged together. Clean up the code by removing the unnecessary don't-fragment checks. Signed-off-by: Richard Gobert --- include/net/gro.h | 5 ++--- net/ipv4/af_inet.c | 3 --- tools/testing/selftests/net/gro.c | 9 ++++----- 3 files changed, 6 insertions(+), 11 deletions(-) diff --git a/include/net/gro.h b/include/net/gro.h index 6aa563eec3d0..f14b7e88dbef 100644 --- a/include/net/gro.h +++ b/include/net/gro.h @@ -448,17 +448,16 @@ static inline int inet_gro_flush(const struct iphdr *= iph, const struct iphdr *ip const u32 id2 =3D ntohl(*(__be32 *)&iph2->id); const u16 ipid_offset =3D (id >> 16) - (id2 >> 16); const u16 count =3D NAPI_GRO_CB(p)->count; - const u32 df =3D id & IP_DF; =20 /* All fields must match except length and checksum. */ - if ((iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | (df ^ (id2 & IP_DF)= )) + if ((iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | ((id ^ id2) & IP_DF= )) return true; =20 /* When we receive our second frame we can make a decision on if we * continue this flow as an atomic flow with a fixed ID or if we use * an incrementing ID. */ - if (count =3D=3D 1 && df && !ipid_offset) + if (count =3D=3D 1 && !ipid_offset) NAPI_GRO_CB(p)->ip_fixedid |=3D 1 << inner; =20 return ipid_offset ^ (count * !(NAPI_GRO_CB(p)->ip_fixedid & (1 << inner)= )); diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index fc7a6955fa0a..c0542d9187e2 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -1393,10 +1393,7 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb, =20 segs =3D ERR_PTR(-EPROTONOSUPPORT); =20 - /* fixed ID is invalid if DF bit is not set */ fixedid =3D !!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCP_FIXEDID << encap)= ); - if (fixedid && !(ip_hdr(skb)->frag_off & htons(IP_DF))) - goto out; =20 if (!skb->encapsulation || encap) udpfrag =3D !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP); diff --git a/tools/testing/selftests/net/gro.c b/tools/testing/selftests/ne= t/gro.c index d5824eadea10..3d4a82a2607c 100644 --- a/tools/testing/selftests/net/gro.c +++ b/tools/testing/selftests/net/gro.c @@ -670,7 +670,7 @@ static void send_flush_id_case(int fd, struct sockaddr_= ll *daddr, int tcase) iph2->id =3D htons(9); break; =20 - case 3: /* DF=3D0, Fixed - should not coalesce */ + case 3: /* DF=3D0, Fixed - should coalesce */ iph1->frag_off &=3D ~htons(IP_DF); iph1->id =3D htons(8); =20 @@ -1188,10 +1188,9 @@ static void gro_receiver(void) correct_payload[0] =3D PAYLOAD_LEN * 2; check_recv_pkts(rxfd, correct_payload, 1); =20 - printf("DF=3D0, Fixed - should not coalesce: "); - correct_payload[0] =3D PAYLOAD_LEN; - correct_payload[1] =3D PAYLOAD_LEN; - check_recv_pkts(rxfd, correct_payload, 2); + printf("DF=3D0, Fixed - should coalesce: "); + correct_payload[0] =3D PAYLOAD_LEN * 2; + check_recv_pkts(rxfd, correct_payload, 1); =20 printf("DF=3D1, 2 Incrementing and one fixed - should coalesce only fir= st 2 packets: "); correct_payload[0] =3D PAYLOAD_LEN * 2; --=20 2.36.1