From 61820d8298b67337208c8e1cbf490e4d04ac414e Mon Sep 17 00:00:00 2001
From: mav <mav@FreeBSD.org>
Date: Fri, 26 Apr 2019 22:18:22 +0000
Subject: [PATCH] MFC r333322: Keep CARP state as INIT when
 net.inet.carp.allow=0.

Currently when net.inet.carp.allow=0 CARP state remains as MASTER, which is
not very useful (if there are other masters -- it can lead to split brain,
if there are none -- it makes no sense).  Having it as INIT makes it clear
that carp packets are disabled.

Sponsored by:	iXsystems, Inc.
---
 share/man/man4/carp.4 |  6 ++++--
 sys/netinet/ip_carp.c | 39 +++++++++++++++++++++++++++++++++++----
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/share/man/man4/carp.4 b/share/man/man4/carp.4
index 877f6a76f1f..04307cb961e 100644
--- a/share/man/man4/carp.4
+++ b/share/man/man4/carp.4
@@ -93,9 +93,11 @@ Additionally, there are a number of global parameters which can be set using
 .Xr sysctl 8 :
 .Bl -tag -width ".Va net.inet.carp.ifdown_demotion_factor"
 .It Va net.inet.carp.allow
-Accept incoming
+Allow
 .Nm
-packets.
+operation.
+When disabled, virtual hosts remain in initial state, neither sending nor
+receiving announcements or traffic.
 Enabled by default.
 .It Va net.inet.carp.preempt
 Allow virtual hosts to preempt each other.
diff --git a/sys/netinet/ip_carp.c b/sys/netinet/ip_carp.c
index 9a9e609fe3a..6afdb8209f3 100644
--- a/sys/netinet/ip_carp.c
+++ b/sys/netinet/ip_carp.c
@@ -214,12 +214,14 @@ static VNET_DEFINE(int, carp_senderr_adj) = CARP_MAXSKEW;
 static VNET_DEFINE(int, carp_ifdown_adj) = CARP_MAXSKEW;
 #define	V_carp_ifdown_adj	VNET(carp_ifdown_adj)
 
+static int carp_allow_sysctl(SYSCTL_HANDLER_ARGS);
 static int carp_dscp_sysctl(SYSCTL_HANDLER_ARGS);
 static int carp_demote_adj_sysctl(SYSCTL_HANDLER_ARGS);
 
 SYSCTL_NODE(_net_inet, IPPROTO_CARP,	carp,	CTLFLAG_RW, 0,	"CARP");
-SYSCTL_INT(_net_inet_carp, OID_AUTO, allow, CTLFLAG_VNET | CTLFLAG_RW,
-    &VNET_NAME(carp_allow), 0, "Accept incoming CARP packets");
+SYSCTL_PROC(_net_inet_carp, OID_AUTO, allow,
+    CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW, 0, 0, carp_allow_sysctl, "I",
+    "Accept incoming CARP packets");
 SYSCTL_PROC(_net_inet_carp, OID_AUTO, dscp,
     CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW, 0, 0, carp_dscp_sysctl, "I",
     "DSCP value for carp packets");
@@ -1209,7 +1211,8 @@ carp_setrun(struct carp_softc *sc, sa_family_t af)
 
 	if ((sc->sc_carpdev->if_flags & IFF_UP) == 0 ||
 	    sc->sc_carpdev->if_link_state != LINK_STATE_UP ||
-	    (sc->sc_naddrs == 0 && sc->sc_naddrs6 == 0))
+	    (sc->sc_naddrs == 0 && sc->sc_naddrs6 == 0) ||
+	    !V_carp_allow)
 		return;
 
 	switch (sc->sc_state) {
@@ -1984,7 +1987,8 @@ carp_sc_state(struct carp_softc *sc)
 	CARP_LOCK_ASSERT(sc);
 
 	if (sc->sc_carpdev->if_link_state != LINK_STATE_UP ||
-	    !(sc->sc_carpdev->if_flags & IFF_UP)) {
+	    !(sc->sc_carpdev->if_flags & IFF_UP) ||
+	    !V_carp_allow) {
 		callout_stop(&sc->sc_ad_tmo);
 #ifdef INET
 		callout_stop(&sc->sc_md_tmo);
@@ -2014,6 +2018,33 @@ carp_demote_adj(int adj, char *reason)
 	taskqueue_enqueue(taskqueue_swi, &carp_sendall_task);
 }
 
+static int
+carp_allow_sysctl(SYSCTL_HANDLER_ARGS)
+{
+	int new, error;
+	struct carp_softc *sc;
+
+	new = V_carp_allow;
+	error = sysctl_handle_int(oidp, &new, 0, req);
+	if (error || !req->newptr)
+		return (error);
+
+	if (V_carp_allow != new) {
+		V_carp_allow = new;
+
+		mtx_lock(&carp_mtx);
+		LIST_FOREACH(sc, &carp_list, sc_next) {
+			CARP_LOCK(sc);
+			if (curvnet == sc->sc_carpdev->if_vnet)
+				carp_sc_state(sc);
+			CARP_UNLOCK(sc);
+		}
+		mtx_unlock(&carp_mtx);
+	}
+
+	return (0);
+}
+
 static int
 carp_dscp_sysctl(SYSCTL_HANDLER_ARGS)
 {
-- 
2.45.0