carp: fix global demotion counter to VRRP advertisementsHEADmain

When net.inet.carp.preempt=1 and a physical interface goes down, the global
V_carp_demotion counter is incremented. For CARP this was already reflected in
outgoing advertisements via DEMOTE_ADVSKEW(), but VRRP sent the raw
sc_vrrp_prio unchanged, so demotion had no effect.

Add DEMOTE_VRRP_PRIO(), a macro analogous to DEMOTE_ADVSKEW():
It subtracts V_carp_demotion from the configured priority and clamps the result
to [0, 254]. Priority 0 is VRRPv3's "resign" signal and causes backups to
preempt immediately. Priority 255 (IP address owner) is never demoted.

Reviewed by:	kp
Approved by:	kp
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D55558

0 files changed, 0 insertions, 0 deletions