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Date:      Thu, 08 Jun 2017 22:13:57 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-virtualization@FreeBSD.org
Subject:   [Bug 219672] vmxnet3: with LRO enabled under FreeBSD 11 as a router,  outgoing speed of forwarded traffic becomes slower
Message-ID:  <bug-219672-27103-7fHIqxgCYZ@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-219672-27103@https.bugs.freebsd.org/bugzilla/>
References:  <bug-219672-27103@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D219672

--- Comment #3 from Mark Peek <mp@FreeBSD.org> ---
>From my testing this is not a bug and everything is working as designed. I =
am
seeing a large decrease in performance when LRO is turned on and using pfSe=
nse
as a gateway. This is due to the originating packets having the IP DF (don=
=E2=80=99t
fragment) flag set which then gets combined into larger packets via LRO. Wh=
en
this (larger) packet needs to be fragmented to match the other NIC the Free=
BSD
kernel sees the DF flag, drops the packet, and then sends back an ICMP
=E2=80=9Cunreachable - need to frag=E2=80=9D message to the sender. The rea=
son it works at all
is due to other traffic which disallows the LRO to occur and some packets g=
et
forwarded.

One test I did was turning LRO on and using scp to put a file onto the pfSe=
nse
appliance which resulted in good performance (not seeing the same drop in
performance). I would be interested if you 1) see good performance with LRO
turned on and scp a large file to the appliance and 2) see ICMP "need to fr=
ag"
with LRO turned on and scp to a machine on the remote side.

Since the pfSense appliance is being used as a gateway you should leave LRO
turned off.

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