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Date:      Sat, 21 Jun 2025 17:33:40 +0000
From:      bugzilla-noreply@freebsd.org
To:        net@FreeBSD.org
Subject:   [Bug 287229] IP reassembly issue in FreeBSD 14.1
Message-ID:  <bug-287229-7501-hzUtfTtkFS@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-287229-7501@https.bugs.freebsd.org/bugzilla/>
References:  <bug-287229-7501@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D287229

--- Comment #36 from Gleb Smirnoff <glebius@FreeBSD.org> ---
On Sat Jun 21 08:55:37  2025 UTC, lucas.aubard@irisa.fr wrote:
> How can I disable this feature to test if it indeed provokes the observed
> reassembly inconsistencies ?

Option #1: you can recompile kernel with patched sys/netinet/ip_reass.c.
Change the line

        V_ipq_hashseed =3D arc4random();

to something non-random, e.g.:

        V_ipq_hashseed =3D 0;

Option #2: at runtime, before running any of your experiments run kernel
debugger in the write mode:

# kgdb -w

Now it depends if your kernel is compiled with VIMAGE or without. If
compiled without VIMAGE, then it is easy:

(kgbd) set ipq_hashseed =3D 0

If compiled without VIMAGE, then more complicated:

(kgdb) set *(uint32_t *)(vnet0->vnet_data_base +
(uintptr_t)&vnet_entry_ipq_hashseed) =3D 0

--=20
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