From nobody Fri Jun 10 22:18:09 2022 X-Original-To: net@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 54EE483AE7C for ; Fri, 10 Jun 2022 22:18:10 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4LKb2B15R4z3kSY for ; Fri, 10 Jun 2022 22:18:10 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2610:1c1:1:606c::50:1d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 01EF520EF7 for ; Fri, 10 Jun 2022 22:18:10 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.5]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id 25AMI9sx012782 for ; Fri, 10 Jun 2022 22:18:09 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 25AMI9vk012781 for net@FreeBSD.org; Fri, 10 Jun 2022 22:18:09 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: net@FreeBSD.org Subject: [Bug 260393] [tcp] Page Fault tcp_output/tcp_input Date: Fri, 10 Jun 2022 22:18:09 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 13.0-STABLE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: rscheff@freebsd.org X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: net@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: cc Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated List-Id: Networking and TCP/IP with FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-net List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-net@freebsd.org MIME-Version: 1.0 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1654899490; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=07HCCyehmb9Dwas80WssMdiVBqcu9YPxafRXGgfiLw4=; b=yjL8TJGMA8YxkfK/13JDNpPm5VEm1o6FeoXv619HYe5FZqWfMbT5iHecJJWt1U94ktlapy pSm0aOXaAIr/fPEd99FY7SC+sq57BrXEU2V+kIgN5Yjq4eLqyMf4Rxj5JeaqLBLB2pOpIP bkXIQihtMHqpxfIIeIUNW95C8rGzFYxOGx+KL1sp2uNxjIdMcaFDovZy9CjxtCoCsjzIeH 2292bBYx97gIvqWA+QkCd4ceNjwF7AXFry4uCHlvz09Lna5i/ydO83g2wtWq29OGGKD5Tp R4mD07oQybtjxShBLayN8wrce0+WsXtSJxKNekRo2gZPOE19TRBIC4S/ZBMFfg== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1654899490; a=rsa-sha256; cv=none; b=Vg41htSM2P6kHKRiZMhTWiaYluQRmmw2g59FLksFoibwYD8dPFTc8SvIXGCdkWc5NYlitr rOEFZAkOWxOhOv7qJFIgLlZ8V9NZDkiPIbuzb1wWxp3Gx/V5qTk0zbd6I1WH42nS+ILnPJ nN8ycjfTqR6UDhRp8Ea73Zt98OQEu/oTTwwP2pvJVyMxazLh5pO+JusZ5MJ1LYIosb0T+v FYSHFpoPtMs/NoJ37s2o8T7wTmW9ek2zk6qNmsDvsY1NK+B6CJHinEg2zv2y/5e5NUBbd0 aQ4QKZf1q9db6Dz8p9EymX0QxP7I59FE2vXnWW73EAjMWTneSWoAHoILuYy+EQ== ARC-Authentication-Results: i=1; mx1.freebsd.org; none X-ThisMailContainsUnwantedMimeParts: N https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D260393 Richard Scheffenegger changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |rscheff@freebsd.org --- Comment #93 from Richard Scheffenegger --- The current thinking is, that SACK rescue retransmissions (in FBSD13 this is gated by net.inet.tcp.rfc6675_pipe=3D1) very rarely creates an entry, which apparently is beyond the valid data range.=20 While under most common circumstances, a final FIN bit in the sequence spac= e is taken care of, it seems that there may be some double-counting for the FIN = bit. In most of the inspected cores, we found: TCP state: LAST_ACK (FIN received and also FIN sent) SACK loss recovery triggered A cumulative ACK before all outstanding data was received The remote cliet "disappears" for a significant amount of time (7 to 12 retransmission timeouts), but may re-appear again just prior. snd_max consistently 2 counts above the last data, instead of the expected 1 (for the FIN bit). However, it is still unclear under what circumstances this double-counting happens, possibly when the persist timer triggers, and a few other conditio= ns are also fulfilled - maybe a race condition between normal packet processing and a timer firing. In short: disabling rfc6675 enhanced SACK features (more correct pipeline accounting, rescue retransmissions) should address the cause of the panic, while not addressing the root cause of when/why there is the double-account= ing of the FIN bit... Would you be willing to run an intrumented kernel, which either panics (full core dump), or spews out various state, when inconsistencies are detected in this space - while ignoring/addressing them "on the fly" without panicing? --=20 You are receiving this mail because: You are the assignee for the bug.=