git: 9f71153aec0c - main - carp: fix global demotion counter to VRRP advertisements
- Go to: [ bottom of page ] [ top of archives ] [ this month ]
Date: Thu, 05 Mar 2026 11:12:51 UTC
The branch main has been updated by olivier:
URL: https://cgit.FreeBSD.org/src/commit/?id=9f71153aec0cb455cd49af6d4ca7e4c16fd45d7a
commit 9f71153aec0cb455cd49af6d4ca7e4c16fd45d7a
Author: Olivier Cochard <olivier@FreeBSD.org>
AuthorDate: 2026-03-05 11:02:20 +0000
Commit: Olivier Cochard <olivier@FreeBSD.org>
CommitDate: 2026-03-05 11:02:20 +0000
carp: fix global demotion counter to VRRP advertisements
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
---
sys/netinet/ip_carp.c | 17 ++++++++++---
tests/sys/netinet/carp.sh | 61 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 75 insertions(+), 3 deletions(-)
diff --git a/sys/netinet/ip_carp.c b/sys/netinet/ip_carp.c
index d33ac4e9a154..3fedbda6b57f 100644
--- a/sys/netinet/ip_carp.c
+++ b/sys/netinet/ip_carp.c
@@ -331,6 +331,17 @@ SYSCTL_VNET_PCPUSTAT(_net_inet_carp, OID_AUTO, stats, struct carpstats,
(((sc)->sc_advskew + V_carp_demotion < 0) ? \
0 : ((sc)->sc_advskew + V_carp_demotion)))
+/*
+ * VRRPv3 priority is the inverse of CARP advskew: higher is better.
+ * Subtract the global demotion counter and clamp to [0, 254].
+ * Priority 255 (IP address owner) is never demoted.
+ */
+#define DEMOTE_VRRP_PRIO(sc) \
+ ((sc)->sc_vrrp_prio == 255 ? 255 : \
+ (((int)(sc)->sc_vrrp_prio - V_carp_demotion < 0) ? 0 : \
+ (((int)(sc)->sc_vrrp_prio - V_carp_demotion > 254) ? 254 : \
+ (int)(sc)->sc_vrrp_prio - V_carp_demotion)))
+
static void carp_input_c(struct mbuf *, struct carp_header *, sa_family_t, int);
static void vrrp_input_c(struct mbuf *, int, sa_family_t, int, int, uint16_t);
static struct carp_softc
@@ -1009,7 +1020,7 @@ vrrp_input_c(struct mbuf *m, int off, sa_family_t af, int ttl,
* Same if the peer has a higher priority than us.
*/
if (ntohs(vh->vrrp_max_adver_int) < sc->sc_vrrp_adv_inter ||
- vh->vrrp_priority > sc->sc_vrrp_prio) {
+ vh->vrrp_priority > DEMOTE_VRRP_PRIO(sc)) {
callout_stop(&sc->sc_ad_tmo);
carp_set_state(sc, BACKUP,
"more frequent advertisement received");
@@ -1023,7 +1034,7 @@ vrrp_input_c(struct mbuf *m, int off, sa_family_t af, int ttl,
* and this one claims to be slower, treat him as down.
*/
if (V_carp_preempt && (ntohs(vh->vrrp_max_adver_int) > sc->sc_vrrp_adv_inter
- || vh->vrrp_priority < sc->sc_vrrp_prio)) {
+ || vh->vrrp_priority < DEMOTE_VRRP_PRIO(sc))) {
carp_master_down_locked(sc,
"preempting a slower master");
break;
@@ -1359,7 +1370,7 @@ vrrp_send_ad_locked(struct carp_softc *sc)
.vrrp_version = CARP_VERSION_VRRPv3,
.vrrp_type = VRRP_TYPE_ADVERTISEMENT,
.vrrp_vrtid = sc->sc_vhid,
- .vrrp_priority = sc->sc_vrrp_prio,
+ .vrrp_priority = DEMOTE_VRRP_PRIO(sc),
.vrrp_count_addr = 0,
.vrrp_max_adver_int = htons(sc->sc_vrrp_adv_inter),
.vrrp_checksum = 0,
diff --git a/tests/sys/netinet/carp.sh b/tests/sys/netinet/carp.sh
index 90ed9d6f9baf..e0ef2fd97583 100755
--- a/tests/sys/netinet/carp.sh
+++ b/tests/sys/netinet/carp.sh
@@ -497,6 +497,66 @@ negative_demotion_cleanup()
vnet_cleanup
}
+atf_test_case "vrrp_preempt" "cleanup"
+vrrp_preempt_head()
+{
+ atf_set descr 'Test VRRP preemption'
+ atf_set require.user root
+}
+
+vrrp_preempt_body()
+{
+ carp_init
+
+ epair1=$(vnet_mkepair)
+ epair2=$(vnet_mkepair)
+
+ vnet_mkjail one ${epair1}a ${epair2}a
+ jexec one sysctl net.inet.carp.preempt=1
+ jexec one ifconfig ${epair1}a 192.0.2.1/24 up
+ jexec one ifconfig ${epair1}a add vhid 1 carpver 3 192.0.2.254/24 \
+ vrrpprio 10 pass foobar1
+ jexec one ifconfig ${epair2}a 192.0.3.1/24 up
+ jexec one ifconfig ${epair2}a add vhid 2 carpver 3 192.0.3.254/24 \
+ vrrpprio 10 pass foobar2
+
+ vnet_mkjail two ${epair1}b ${epair2}b
+ jexec two sysctl net.inet.carp.preempt=1
+ jexec two ifconfig ${epair1}b 192.0.2.2/24 up
+ jexec two ifconfig ${epair2}b 192.0.3.2/24 up
+ jexec two ifconfig ${epair1}b add vhid 1 carpver 3 192.0.2.254/24 \
+ vrrpprio 1 pass foobar1
+ jexec two ifconfig ${epair2}b add vhid 2 carpver 3 192.0.3.254/24 \
+ vrrpprio 1 pass foobar2
+
+ # Allow things to settle
+ wait_for_carp one ${epair1}a two ${epair1}b
+ wait_for_carp one ${epair2}a two ${epair2}b
+
+ # Bring down one interface; preemption should demote the second interface too
+ jexec one ifconfig ${epair1}a down
+ sleep 3
+
+ if is_master one ${epair2}a
+ then
+ atf_fail "preemption did not affect the second interface"
+ fi
+
+ # Bring interface back up; one should reclaim master
+ jexec one ifconfig ${epair1}a up
+ sleep 3
+
+ if ! is_master one ${epair2}a
+ then
+ atf_fail "Priority router did not take its master role back"
+ fi
+}
+
+vrrp_preempt_cleanup()
+{
+ vnet_cleanup
+}
+
atf_test_case "nd6_ns_source_mac" "cleanup"
@@ -596,5 +656,6 @@ atf_init_test_cases()
atf_add_test_case "unicast_ll_v6"
atf_add_test_case "negative_demotion"
atf_add_test_case "nd6_ns_source_mac"
+ atf_add_test_case "vrrp_preempt"
atf_add_test_case "switch"
}