From: Vitaliy Makkoveev <mvs@openbsd.org>
Subject: Unlock ICMPV6CTL_ERRPPSLIMIT case of icmp6_sysctl()
To: Alexander Bluhm <bluhm@openbsd.org>, tech@openbsd.org
Date: Thu, 23 Oct 2025 23:56:36 +0300

The last one of locked `icmpv6ctl_vars'.

`icmp6errppslim' is the integer loaded once within icmp6_ratelimit()
which is accessed from two paths. The first one, icmp6_do_error() is
always the end of the error path. The usage of the second one, the
icmp6_redirect_output() is similar to already unlocked `ip6_forwarding',
except that icmp6_ratelimit() called only once. So we don't need to
cache `icmp6errppslim' anywhere.

Since icmp6_sysctl() became mp-safe, unlock it.

ok?

Index: sys/netinet6/icmp6.c
===================================================================
RCS file: /cvs/src/sys/netinet6/icmp6.c,v
retrieving revision 1.279
diff -u -p -r1.279 icmp6.c
--- sys/netinet6/icmp6.c	16 Sep 2025 09:19:43 -0000	1.279
+++ sys/netinet6/icmp6.c	23 Oct 2025 20:35:03 -0000
@@ -1693,7 +1693,7 @@ icmp6_ratelimit(const struct in6_addr *d
 {
 	/* PPS limit */
 	if (!ppsratecheck(&icmp6errppslim_last, &icmp6errpps_count,
-	    icmp6errppslim))
+	    atomic_load_int(&icmp6errppslim)))
 		return 1;	/* The packet is subject to rate limit */
 	return 0;		/* okay to send */
 }
@@ -1776,15 +1776,12 @@ icmp6_mtudisc_timeout(struct rtentry *rt
 }
 
 #ifndef SMALL_KERNEL
-const struct sysctl_bounded_args icmpv6ctl_vars_unlocked[] = {
+const struct sysctl_bounded_args icmpv6ctl_vars[] = {
 	{ ICMPV6CTL_ND6_DELAY, &nd6_delay, 0, INT_MAX },
 	{ ICMPV6CTL_ND6_UMAXTRIES, &nd6_umaxtries, 0, INT_MAX },
 	{ ICMPV6CTL_ND6_MMAXTRIES, &nd6_mmaxtries, 0, INT_MAX },
 	{ ICMPV6CTL_MTUDISC_HIWAT, &icmp6_mtudisc_hiwat, 0, INT_MAX },
 	{ ICMPV6CTL_MTUDISC_LOWAT, &icmp6_mtudisc_lowat, 0, INT_MAX },
-};
-
-const struct sysctl_bounded_args icmpv6ctl_vars[] = {
 	{ ICMPV6CTL_ERRPPSLIMIT, &icmp6errppslim, -1, 1000 },
 };
 
@@ -1805,12 +1802,6 @@ icmp6_sysctl_icmp6stat(void *oldp, size_
 	return (ret);
 }
 
-/*
- * Temporary, should be replaced with sysctl_lock after icmp6_sysctl()
- * unlocking.
- */
-struct rwlock icmp6_sysctl_lock = RWLOCK_INITIALIZER("icmp6rwl"); 
-
 int
 icmp6_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
     void *newp, size_t newlen)
@@ -1829,11 +1820,11 @@ icmp6_sysctl(int *name, u_int namelen, v
 		error = sysctl_int_bounded(oldp, oldlenp, newp, newlen,
 		    &newval, 0, INT_MAX);
 		if (error == 0 && oldval != newval) {
-			rw_enter_write(&icmp6_sysctl_lock);
+			rw_enter_write(&sysctl_lock);
 			atomic_store_int(&icmp6_redirtimeout, newval);
 			rt_timer_queue_change(&icmp6_redirect_timeout_q,
 			    newval);
-			rw_exit_write(&icmp6_sysctl_lock);
+			rw_exit_write(&sysctl_lock);
 		}
 
 		return (error);
@@ -1847,22 +1838,10 @@ icmp6_sysctl(int *name, u_int namelen, v
 		    atomic_load_int(&ln_hold_total));
 		break;
 
-	case ICMPV6CTL_ND6_DELAY:
-	case ICMPV6CTL_ND6_UMAXTRIES:
-	case ICMPV6CTL_ND6_MMAXTRIES:
-	case ICMPV6CTL_MTUDISC_HIWAT:
-	case ICMPV6CTL_MTUDISC_LOWAT:
-		error = sysctl_bounded_arr(icmpv6ctl_vars_unlocked,
-		    nitems(icmpv6ctl_vars_unlocked), name, namelen,
-		    oldp, oldlenp, newp, newlen);
-		break;
-
 	default:
-		NET_LOCK();
 		error = sysctl_bounded_arr(icmpv6ctl_vars,
 		    nitems(icmpv6ctl_vars), name, namelen, oldp, oldlenp, newp,
 		    newlen);
-		NET_UNLOCK();
 		break;
 	}
 
Index: sys/netinet6/in6_proto.c
===================================================================
RCS file: /cvs/src/sys/netinet6/in6_proto.c,v
retrieving revision 1.152
diff -u -p -r1.152 in6_proto.c
--- sys/netinet6/in6_proto.c	16 Sep 2025 09:19:16 -0000	1.152
+++ sys/netinet6/in6_proto.c	23 Oct 2025 20:35:03 -0000
@@ -169,7 +169,7 @@ const struct protosw inet6sw[] = {
   .pr_type	= SOCK_RAW,
   .pr_domain	= &inet6domain,
   .pr_protocol	= IPPROTO_ICMPV6,
-  .pr_flags	= PR_ATOMIC|PR_ADDR,
+  .pr_flags	= PR_ATOMIC|PR_ADDR|PR_MPSYSCTL,
   .pr_input	= icmp6_input,
   .pr_ctlinput	= rip6_ctlinput,
   .pr_ctloutput	= rip6_ctloutput,
@@ -376,5 +376,5 @@ u_long	rip6_recvspace = RIPV6RCVQ;
 
 /* ICMPV6 parameters */
 int	icmp6_redirtimeout = 10 * 60;	/* 10 minutes */
-int	icmp6errppslim = 100;		/* 100pps */
+int	icmp6errppslim = 100;		/* [a] 100pps */
 int	ip6_mtudisc_timeout = IPMTUDISCTIMEOUT;	/* [a] */