Restore a feature that was present in 5.x and 6.x, and was cleared in

7.x, 8.x and 9.x with pf(4) imports: pfsync(4) should suppress CARP
preemption, while it is running its bulk update.

However, reimplement the feature in more elegant manner, that is
partially inspired by newer OpenBSD:

- Rename term "suppression" to "demotion", to match with OpenBSD.
- Keep a global demotion factor, that can be raised by several
  conditions, for now these are:
  - interface goes down
  - carp(4) has problems with ip_output() or ip6_output()
  - pfsync performs bulk update
- Unlike in OpenBSD the demotion factor isn't a counter, but
  is actual value added to advskew. The adjustment values for
  particular error conditions are also configurable, and their
  defaults are maximum advskew value, so a single failure bumps
  demotion to maximum. This is for POLA compatibility, and should
  satisfy most users.
- Demotion factor is a writable sysctl, so user can do
  foot shooting, if he desires to.

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/net/if.c b/sys/net/if.c
index 437734354af3..50aa11ca1291 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -129,6 +129,7 @@ void	(*ng_ether_link_state_p)(struct ifnet *ifp, int state);
 void	(*lagg_linkstate_p)(struct ifnet *ifp, int state);
 /* These are external hooks for CARP. */
 void	(*carp_linkstate_p)(struct ifnet *ifp);
+void	(*carp_demote_adj_p)(int, char *);
 #if defined(INET) || defined(INET6)
 int	(*carp_forus_p)(struct ifnet *ifp, u_char *dhost);
 int	(*carp_output_p)(struct ifnet *ifp, struct mbuf *m,