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Date:      Thu, 19 Jun 2025 01:20:51 +0000
From:      bugzilla-noreply@freebsd.org
To:        net@FreeBSD.org
Subject:   [Bug 287229] IP reassembly issue in FreeBSD 14.1
Message-ID:  <bug-287229-7501-1mlJFU8ROe@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

Rodney W. Grimes <rgrimes@FreeBSD.org> changed:

           What    |Removed                     |Added
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                 CC|                            |rgrimes@FreeBSD.org

--- Comment #14 from Rodney W. Grimes <rgrimes@FreeBSD.org> ---
(In reply to Timo Voelker from comment #10)
The number of list entries (net.inet.ip.maxfragbucketsize) seems relevant h=
ere.
Out of the box, your FreeBSD VM has set maxfragbucketsize=3D1. This means i=
f the
FreeBSD VM must insert a new entry (i.e., when the first fragment of a pack=
et
has been received) in a bucket that already contains an entry, it removes t=
his
one first. In consequence, FreeBSD is probably unable to reassemble that pa=
cket
with the removed fragments.

So I believe the "relevant bug" here is that maxfrqgbucksize is allowed to =
go
to 1, there should be a clamp on the calculation to prevent this absurd val=
ue
that would lead to the behavior uncovered by artificially reducing kernel
memory space.  There are many values that we calculate based on tuning
parameters and those values should have reasonable clamps on them, if they =
lead
to bad behavior when they go to low or two high.

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