Bug 199996

Initial state:
 1) lagg/lacp is organized between FreeBSD at one side and some network switch at another side (Cisco, Extreme Networks, Dell/Force10, ...)
 2) lagg/lacp is running and state is UP at both sides. For example and for  simplification, there is only one physical link in lagg. At FreeBSD side:
 laggport: ix1 flags=1c<ACTIVE,COLLECTING,DISTRIBUTING>

 In case if there is some unidirectional failure occured, and lacp packets are passed only in one direction and doesn't pass in another direction, we expect that LACP protocol will remove such link from lagg interface.
This is true if lacp packets doesn't pass from FreeBSD to some network switch. Then  lacp timeout is occured at switch side  and link is removed from agregat. (OK)
laggport: ix1 flags=0<>

This is not true if lacp packets doesn't pass from network switch to FreeBSD. At the same time lacp packets are transmitted from FreeBSD to network switch, so there is no any lacp timeout occured at switch side. (BUG?) 
laggport: ix1 flags=1c<ACTIVE,COLLECTING,DISTRIBUTING>

How to reproduce: For example, to filter with layer2 acl or something like that egress LACP packets at switch side.
At the same time, tcpdump at FreeBSD shows that incoming LACP packets is gone, only outgoing are present. 
lagg/lacp still UP.

P.S. The same behaviour regardless of net.link.lagg.0.lacp.lacp_strict_mode state.