[Bug 283380] FreeBSD accepts and processes IPv4 packets destined to non-local MAC addresses instead of dropping them

From: <bugzilla-noreply_at_freebsd.org>
Date: Wed, 18 Dec 2024 03:44:31 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=283380

Zhenlei Huang <zlei@FreeBSD.org> changed:

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

--- Comment #3 from Zhenlei Huang <zlei@FreeBSD.org> ---
(In reply to Joerg Goltermann from comment #0)
> the system accepts and forwards IP packets to non-local MAC addresses which can be
> seen on a tcpdump eg tcpdump -netttti vtnet2 host 146.185.xx.yy

You may want to turn on the tcpdump(1) option `--no-promiscuous-mode`. By
default tcpdump(1) will put the interface into promiscuous mode, i.e., the
interface will see all traffic.

You can also check if the interface is put into promiscuous mode by
ifconfig(8).
```
$ ifconfig cxl0 | grep PROMISC
cxl0: flags=8902<BROADCAST,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
```

You're welcomed to report back if the issue persists.

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