New ssh error I've not seen before: "message authentication code incorrect" after a time

From: Mark Millard via freebsd-arm <>
Date: Sat, 19 Jun 2021 20:41:30 UTC
In using macOS 10.13.6 (an older MacBook Pro) to ssh into:

# uname -apKU
FreeBSD CA72_16Gp_ZFS 13.0-RELEASE-p1 FreeBSD 13.0-RELEASE-p1 #1 releng/13.0-n244744-8023e729a521-dirty: Wed May 26 14:59:50 PDT 2021     root@CA72_16Gp_ZFS:/usr/obj/BUILDs/13_0R-CA72-nodbg-clang/usr/13_0R-src/arm64.aarch64/sys/GENERIC-NODBG-CA72  arm64 aarch64 1300139 1300139

multiple times at once, the session running top
eventually gets:

ssh_dispatch_run_fatal: Connection to 192.168.1.REPLACED port 22: message authentication code incorrect

seen in the macOS window for the ssh session. I do not find
any notices in dmesg -a or /var/log/messages reporting anything
that looks related. Generally it seems to have run for 3+
hours before failing.

Interestingly another session from the same macOS machine that
was sitting idle at a /bin/sh prompt continued to work. (It was
started about the same time.) So the amount of activity over
the connection may contribute to how long the connection is
likely to last.

The MACCHIATObin Double Shot is doing a poudriere bulk and
had devel/llvm10, lang/gcc11-devel, devel/llvm12, and
lang/gcc11 building in parallel, each allowed to use all
4 cores. So a load average of around 16 a fair amount of
the time. I'd not updated ports in some time, jumping
forward somewhat over 3000 commits. So the FreeBSD vintage
is more recent than last time I had a poudriere bulk going.

The macOS side of things have not changed in a long time
(2018-Jul). That includes the Ethernet cabling and switch
involved not having changed in recent times (over a year).

For reference, plugged into a USB2 port on the FreeBSD

ugen0.2: <Realtek USB 10/100/1000 LAN> at usbus0
ure0 on uhub2
ure0: <Realtek USB 10/100/1000 LAN, class 0/0, rev 2.10/30.00, addr 1> on usbus0
miibus0: <MII bus> on ure0
rgephy0: <RTL8251/8153 1000BASE-T media interface> PHY 0 on miibus0
rgephy0:  none, 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseT-FDX, 1000baseT-FDX-master, auto
ue0: <USB Ethernet> on ure0
. . .


ue0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
	inet 192.168.1.REPLACED netmask 0xffffff00 broadcast
	media: Ethernet autoselect (1000baseT <full-duplex>)
	status: active

The poudriere bulk was not stopped because it was running on the
serial console (that also got no messages beyond the normal
poudriere bulk output).

Mark Millard
marklmi at
( went
away in early 2018-Mar)