K 10
svn:author
V 2
kp
K 8
svn:date
V 27
2021-11-22T05:17:23.202833Z
K 7
svn:log
V 1067
carp: deal with negative net.inet.carp.demotion

Given nodes 1 and 2, where node 1 has an advskew of 0 and node 2 has an
advskew of 100, making them master and backup respectively.

If net.inet.carp.demotion is set to a negative value on node 1, node 2
might become master while node 1 still retains it master status. Wether
or not node 2 becomes master seems to depend on the nodes advskew and
what the demotion sysctl was set to on node 1.

The reason for node 2 becoming master seems to be that the calculated
advskew taking demotion into account is truncated to a single unsigned
byte when copied into the carp header for sending, and node 1 stays
master since it takes uses the whole non-truncated calculated advskew
when deciding wether to stay master.

PR:		259528
Reviewed by:	donner, glebius
MFC after:	3 weeks
Sponsored by:	Modirum MDPay
Differential Revision:	https://reviews.freebsd.org/D32759

(cherry picked from commit 1019354b54161c140d10a8203ff1e849c09c8010)

Git Hash:   1c16de99bd7ddddad9d5877ba0f91aa2a2f57eb3
Git Author: marius.halden@modirum.com
END