Date: Mon, 08 Dec 2025 16:28:35 +0000 From: bugzilla-noreply@freebsd.org To: net@FreeBSD.org Subject: [Bug 291420] [epair] Bad UDP packet checksum with epair(4) and txcsum enabled Message-ID: <bug-291420-7501-nSypKcDS5a@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-291420-7501@https.bugs.freebsd.org/bugzilla/> References: <bug-291420-7501@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=291420 --- Comment #10 from Michael Tuexen <tuexen@freebsd.org> --- I am pretty sure that https://cgit.freebsd.org/src/commit/sys/net/if_epair.c?h=stable/14&id=503bf058cd0adfe3d5e66340b13d32b4516390cb results in the problem you are experiencing. If you disable txcsum on the epair interface, the problem goes away. I just want to understand the root cause of the problem. If I understand your data correctly, then the problem goes away if you set forced_udpcsum to 1. I think the problem should be limited to UDP, because bge devices announce TXCSUM support, but only do this for TCP, whereas the implicit assumption by the rest of the system is that TCP and UDP is supported. Setting forced_udpcsum to 1 enforces support for UDP. The default is forced_udpcsum = 0, since Broadcom NICs don't compute the UDP always correctly (I am not sure if this is currently fixed). We try to reproduce it in my lab, but we need to test it on a system with a Broadcom NIC. Once it is clear, we will work on a solution. As a workaround you can just disable txcsum for the epair interface. -- You are receiving this mail because: You are the assignee for the bug.help
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