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[176.103.220.4]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4391dfc87desm43046085e9.25.2025.02.06.22.51.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Feb 2025 22:51:17 -0800 (PST) Date: Fri, 7 Feb 2025 07:51:15 +0100 From: Stefano Brivio To: David Gibson Subject: Re: migrate/bidirectional debugging Message-ID: <20250207075115.78b6e1da@elisabeth> In-Reply-To: References: Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: qpkmVtmHWYdob996U6S7yCBXHI0XfkrvJOp3aEJflc8_1738911081 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Message-ID-Hash: TCIJQ53VKYQ2TNOSKUWEIIQT5BYBO27N X-Message-ID-Hash: TCIJQ53VKYQ2TNOSKUWEIIQT5BYBO27N X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Fri, 7 Feb 2025 17:26:35 +1100 David Gibson wrote: > It kind of seemed like we were sendmsg()ing "and from guest 2" and it > was bouncing straight back to our socket, instead of being delivered > to the outer pasta. Oops. diff --git a/tcp.c b/tcp.c index 0f05011..b7f5169 100644 --- a/tcp.c +++ b/tcp.c @@ -2796,6 +2796,12 @@ static int tcp_flow_repair_queues(int s, =09=09debug("Read socket %i receive queue: %zi bytes", s, rc); =09} =20 +=09v =3D TCP_NO_QUEUE; +=09if (setsockopt(s, SOL_TCP, TCP_REPAIR_QUEUE, &v, sizeof(v))) { +=09=09err_perror("Setting TCP_NO_QUEUE on socket %i", s); +=09=09return -errno; +=09} + =09return 0; } =20 otherwise, I guess, there's a time window in which we might be writing that message to our queue instead of writing it on the socket, even with repair mode off. The write might be pending or something. With this, the stray packet is gone. I spotted this case now: $ tshark -r test/test_logs/passt_2.pcap=20 1 0.000000 88.198.0.164 =E2=86=92 169.254.1.1 TCP 71 58150 =E2=86=92= 10006 [PSH, ACK] Seq=3D1 Ack=3D1 Win=3D1024 Len=3D17 2 0.000031 88.198.0.164 =E2=86=92 169.254.1.1 TCP 54 58150 =E2=86=92= 10006 [FIN, ACK] Seq=3D18 Ack=3D1 Win=3D1024 Len=3D0 3 0.000059 169.254.1.1 =E2=86=92 88.198.0.164 TCP 54 10006 =E2=86=92= 58150 [RST, ACK] Seq=3D1 Ack=3D1 Win=3D256 Len=3D0 4 0.026443 169.254.1.1 =E2=86=92 88.198.0.164 TCP 74 48150 =E2=86=92= 10001 [PSH, ACK] Seq=3D1 Ack=3D1 Win=3D256 Len=3D20 5 0.026538 88.198.0.164 =E2=86=92 169.254.1.1 TCP 54 10001 =E2=86=92= 48150 [ACK] Seq=3D1 Ack=3D21 Win=3D1023 Len=3D0 6 0.026557 169.254.1.1 =E2=86=92 88.198.0.164 TCP 54 48150 =E2=86=92= 10001 [FIN, ACK] Seq=3D21 Ack=3D1 Win=3D256 Len=3D0 7 0.026656 88.198.0.164 =E2=86=92 169.254.1.1 TCP 54 10001 =E2=86=92= 48150 [FIN, ACK] Seq=3D1 Ack=3D22 Win=3D1024 Len=3D0 8 0.026675 169.254.1.1 =E2=86=92 88.198.0.164 TCP 54 48150 =E2=86=92= 10001 [ACK] Seq=3D22 Ack=3D2 Win=3D256 Len=3D0 9 318.959707 fe80::1 =E2=86=92 ff02::1 ICMPv6 158 Router Adve= rtisement from 9a:55:9a:55:9a:55 That RST we send as frame #3 looks unwarranted. I wonder if we get packets from the target guest before we have a chance to set up flows. --=20 Stefano