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[34.85.134.180]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-6503a9cabaesm573157d50.18.2026.04.01.17.28.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2026 17:28:46 -0700 (PDT) Date: Wed, 01 Apr 2026 20:28:46 -0400 From: Willem de Bruijn To: Jakub Kicinski , davem@davemloft.net Cc: netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, shuah@kernel.org, willemb@google.com, petrm@nvidia.com, anubhavsinggh@google.com, richardbgobert@gmail.com, linux-kselftest@vger.kernel.org, Jakub Kicinski Message-ID: In-Reply-To: <20260401182625.372605-7-kuba@kernel.org> References: <20260401182625.372605-1-kuba@kernel.org> <20260401182625.372605-7-kuba@kernel.org> Subject: Re: [PATCH net-next 6/6] selftests: drv-net: gro: add a test for bad IPv4 csum Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Jakub Kicinski wrote: > We have a test for coalescing with bad TCP checksum, let's also > test bad IPv4 header checksum. > > Signed-off-by: Jakub Kicinski > --- > tools/testing/selftests/net/lib/gro.c | 25 ++++++++++++++++++++++ > tools/testing/selftests/drivers/net/gro.py | 1 + > 2 files changed, 26 insertions(+) > > diff --git a/tools/testing/selftests/net/lib/gro.c b/tools/testing/selftests/net/lib/gro.c > index 762e88932ed2..a458cfbd11eb 100644 > --- a/tools/testing/selftests/net/lib/gro.c > +++ b/tools/testing/selftests/net/lib/gro.c > @@ -36,6 +36,7 @@ > * Packets with different (ECN, TTL, TOS) header, IP options or > * IP fragments shouldn't coalesce. > * - ip_ecn, ip_tos: shared between IPv4/IPv6 > + * - ip_csum: IPv4 only, bad IP header checksum > * - ip_ttl, ip_opt, ip_frag4: IPv4 only > * - ip_id_df*: IPv4 IP ID field coalescing tests > * - ip_frag6, ip_v6ext_*: IPv6 only > @@ -675,6 +676,21 @@ static void send_changed_checksum(int fd, struct sockaddr_ll *daddr) > write_packet(fd, buf, pkt_size, daddr); > } > > +/* Packets with incorrect IPv4 header checksum don't coalesce. */ > +static void send_changed_ip_checksum(int fd, struct sockaddr_ll *daddr) > +{ > + static char buf[MAX_HDR_LEN + PAYLOAD_LEN]; > + struct iphdr *iph = (struct iphdr *)(buf + ETH_HLEN); > + int pkt_size = total_hdr_len + PAYLOAD_LEN; > + > + create_packet(buf, 0, 0, PAYLOAD_LEN, 0); > + write_packet(fd, buf, pkt_size, daddr); > + > + create_packet(buf, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0); > + iph->check = iph->check - 1; > + write_packet(fd, buf, pkt_size, daddr); > +} > + > /* Packets with non-consecutive sequence number don't coalesce.*/ > static void send_changed_seq(int fd, struct sockaddr_ll *daddr) > { > @@ -1392,6 +1408,10 @@ static void gro_sender(void) > write_packet(txfd, fin_pkt, total_hdr_len, &daddr); > > /* ip sub-tests - IPv4 only */ > + } else if (strcmp(testname, "ip_csum") == 0) { > + send_changed_ip_checksum(txfd, &daddr); > + usleep(fin_delay_us); > + write_packet(txfd, fin_pkt, total_hdr_len, &daddr); > } else if (strcmp(testname, "ip_ttl") == 0) { > send_changed_ttl(txfd, &daddr); > write_packet(txfd, fin_pkt, total_hdr_len, &daddr); > @@ -1588,6 +1608,11 @@ static void gro_receiver(void) > check_recv_pkts(rxfd, correct_payload, 2); > > /* ip sub-tests - IPv4 only */ > + } else if (strcmp(testname, "ip_csum") == 0) { > + correct_payload[0] = PAYLOAD_LEN; > + correct_payload[1] = PAYLOAD_LEN; > + printf("bad ip checksum doesn't coalesce: "); > + check_recv_pkts(rxfd, correct_payload, 2); This verifies that a packet with bad csum does not coalesce to a valid packet. Perhaps too paranoid but, do you also want to test the reverse case? Can be a single test by adding another write_packet and observing all three separate packets.