[Bug 239380] sys.netpfil.pf.forward.{v4,v6} and sys.netpfil.pf.set_tos.v4 fail on i386

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=239380

--- Comment #18 from Bjoern A. Zeeb <bz at FreeBSD.org> ---
(In reply to Bjoern A. Zeeb from comment #17)

As a follow-up.

The problem for the test cases was as follows (at least for the IPv6 ones).

To resolve the neighbour's address, scapy sends a NS.
The kernel of the destination/next hop replies with a NA.
Scapy receives the packets but due to the wrong offsets within the bpf header
the frame sizes are all way off and way too large.
As a result there is no result packet to the internal AsyncSniffer and neither
the original packet nor the NA reply is seen.
With the failed address resolution scapy uses a broadcast Ethernet destination
MAC address on the ethernet packets.  FreeBSD will mark this packet with
M_BCAST as a result and higher up in the kernel certain functions will check
for that and get an invalid result (or not accept the packet, or not trigger
and ICMPv6 reply).
With that the expected reply packet from the test cases are missing and the
sniffer there will not see any further packets and either timeout or checks
will fail and with that the test times out or fails.

Hope that explains some of this.

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