Unlock IPv6 sysctl net.inet6.ip6.forwarding from net lock.

Use atomic operations to read ip6_forwarding while processing packets
in the network stack.
To make clear where actually the router property is needed, use the
i_am_router variable based on ip6_forwarding.  It already existed
in nd6_nbr.  Move i_am_router setting up the call stack until all
users are independent.
The forwarding decisions in pf_test, pf_refragment6, ip6_input do
also not interfere.
Use a new array ipv6ctl_vars_unlocked to make transition of all the
integer sysctls easier.  Adapt IPv4 to the new style.

OK mvs@

12 files changed, 62 insertions, 42 deletions

diff --git a/sys/net/if.c b/sys/net/if.c
index 46e4e8c95f5..e0a9db5144a 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if.c,v 1.719 2024/06/20 19:25:42 bluhm Exp $	*/
+/*	$OpenBSD: if.c,v 1.720 2024/07/14 18:53:39 bluhm Exp $	*/
 /*	$NetBSD: if.c,v 1.35 1996/05/07 05:26:04 thorpej Exp $	*/
 
 /*
@@ -3353,6 +3353,7 @@ ifnewlladdr(struct ifnet *ifp)
 {
 #ifdef INET6
 	struct ifaddr *ifa;
+	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
 #endif
 	struct ifreq ifrq;
 	short up;
@@ -3378,7 +3379,7 @@ ifnewlladdr(struct ifnet *ifp)
 	 * Update the link-local address.  Don't do it if we're
 	 * a router to avoid confusing hosts on the network.
 	 */
-	if (ip6_forwarding == 0) {
+	if (!i_am_router) {
 		ifa = &in6ifa_ifpforlinklocal(ifp, 0)->ia_ifa;
 		if (ifa) {
 			in6_purgeaddr(ifa);
diff --git a/sys/net/pf.c b/sys/net/pf.c
index fb278db3b14..378bafc2190 100644
--- a/sys/net/pf.c
+++ b/sys/net/pf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pf.c,v 1.1202 2024/07/12 09:25:27 bluhm Exp $ */
+/*	$OpenBSD: pf.c,v 1.1203 2024/07/14 18:53:39 bluhm Exp $ */
 
 /*
  * Copyright (c) 2001 Daniel Hartmeier
@@ -7988,7 +7988,7 @@ done:
 			if (pd.dir == PF_IN) {
 				int flags = IPV6_REDIRECT;
 
-				switch (ip6_forwarding) {
+				switch (atomic_load_int(&ip6_forwarding)) {
 				case 2:
 					SET(flags, IPV6_FORWARDING_IPSEC);
 					/* FALLTHROUGH */
diff --git a/sys/net/pf_norm.c b/sys/net/pf_norm.c
index 4178fe785a1..2bfad7873de 100644
--- a/sys/net/pf_norm.c
+++ b/sys/net/pf_norm.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pf_norm.c,v 1.232 2024/07/04 12:50:08 bluhm Exp $ */
+/*	$OpenBSD: pf_norm.c,v 1.233 2024/07/14 18:53:39 bluhm Exp $ */
 
 /*
  * Copyright 2001 Niels Provos <provos@citi.umich.edu>
@@ -1013,7 +1013,7 @@ pf_refragment6(struct mbuf **m0, struct m_tag *mtag, struct sockaddr_in6 *dst,
 		if (ifp == NULL) {
 			int flags = 0;
 
-			switch (ip6_forwarding) {
+			switch (atomic_load_int(&ip6_forwarding)) {
 			case 2:
 				SET(flags, IPV6_FORWARDING_IPSEC);
 				/* FALLTHROUGH */
diff --git a/sys/netinet/ip_carp.c b/sys/netinet/ip_carp.c
index c6e882f0b90..26139316c66 100644
--- a/sys/netinet/ip_carp.c
+++ b/sys/netinet/ip_carp.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ip_carp.c,v 1.362 2024/06/20 19:25:42 bluhm Exp $	*/
+/*	$OpenBSD: ip_carp.c,v 1.363 2024/07/14 18:53:39 bluhm Exp $	*/
 
 /*
  * Copyright (c) 2002 Michael Shalayeff. All rights reserved.
@@ -1287,9 +1287,10 @@ carp_send_na(struct carp_softc *sc)
 	struct ifaddr *ifa;
 	struct in6_addr *in6;
 	static struct in6_addr mcast = IN6ADDR_LINKLOCAL_ALLNODES_INIT;
+	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
 	int flags = ND_NA_FLAG_OVERRIDE;
 
-	if (ip6_forwarding != 0)
+	if (i_am_router)
 		flags |= ND_NA_FLAG_ROUTER;
 
 	TAILQ_FOREACH(ifa, &sc->sc_if.if_addrlist, ifa_list) {
diff --git a/sys/netinet/ip_icmp.c b/sys/netinet/ip_icmp.c
index baaa9a210fd..5c5ccde138a 100644
--- a/sys/netinet/ip_icmp.c
+++ b/sys/netinet/ip_icmp.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ip_icmp.c,v 1.195 2024/07/12 09:25:27 bluhm Exp $	*/
+/*	$OpenBSD: ip_icmp.c,v 1.196 2024/07/14 18:53:39 bluhm Exp $	*/
 /*	$NetBSD: ip_icmp.c,v 1.19 1996/02/13 23:42:22 christos Exp $	*/
 
 /*
@@ -588,9 +588,9 @@ reflect:
 		struct sockaddr_in sgw;
 		struct sockaddr_in ssrc;
 		struct rtentry *newrt = NULL;
+		int i_am_router = (atomic_load_int(&ip_forwarding) != 0);
 
-		if (icmp_rediraccept == 0 ||
-		    atomic_load_int(&ip_forwarding) != 0)
+		if (icmp_rediraccept == 0 || i_am_router)
 			goto freeit;
 		if (code > 3)
 			goto badcode;
diff --git a/sys/netinet/ip_input.c b/sys/netinet/ip_input.c
index 8797a26b025..1d68e0f6161 100644
--- a/sys/netinet/ip_input.c
+++ b/sys/netinet/ip_input.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ip_input.c,v 1.398 2024/07/12 09:25:27 bluhm Exp $	*/
+/*	$OpenBSD: ip_input.c,v 1.399 2024/07/14 18:53:39 bluhm Exp $	*/
 /*	$NetBSD: ip_input.c,v 1.30 1996/03/16 23:53:58 christos Exp $	*/
 
 /*
@@ -111,6 +111,10 @@ LIST_HEAD(, ipq) ipq;
 int	ip_maxqueue = 300;
 int	ip_frags = 0;
 
+const struct sysctl_bounded_args ipctl_vars_unlocked[] = {
+	{ IPCTL_FORWARDING, &ip_forwarding, 0, 2 },
+};
+
 const struct sysctl_bounded_args ipctl_vars[] = {
 #ifdef MROUTING
 	{ IPCTL_MRTPROTO, &ip_mrtproto, SYSCTL_INT_READONLY },
@@ -1799,8 +1803,9 @@ ip_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp, void *newp,
 		NET_UNLOCK();
 		return (error);
 	case IPCTL_FORWARDING:
-		return (sysctl_int_bounded(oldp, oldlenp, newp, newlen,
-		    &ip_forwarding, 0, 2));
+		return (sysctl_bounded_arr(
+		    ipctl_vars_unlocked, nitems(ipctl_vars_unlocked),
+		    name, namelen, oldp, oldlenp, newp, newlen));
 	default:
 		NET_LOCK();
 		error = sysctl_bounded_arr(ipctl_vars, nitems(ipctl_vars),
diff --git a/sys/netinet6/icmp6.c b/sys/netinet6/icmp6.c
index 2a8950d0a66..04ad1b3e023 100644
--- a/sys/netinet6/icmp6.c
+++ b/sys/netinet6/icmp6.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: icmp6.c,v 1.253 2024/06/20 19:25:42 bluhm Exp $	*/
+/*	$OpenBSD: icmp6.c,v 1.254 2024/07/14 18:53:39 bluhm Exp $	*/
 /*	$KAME: icmp6.c,v 1.217 2001/06/20 15:03:29 jinmei Exp $	*/
 
 /*
@@ -1228,6 +1228,7 @@ icmp6_redirect_input(struct mbuf *m, int off)
 	char *lladdr = NULL;
 	int lladdrlen = 0;
 	struct rtentry *rt = NULL;
+	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
 	int is_router;
 	int is_onlink;
 	struct in6_addr src6 = ip6->ip6_src;
@@ -1241,7 +1242,7 @@ icmp6_redirect_input(struct mbuf *m, int off)
 		return;
 
 	/* if we are router, we don't update route by icmp6 redirect */
-	if (ip6_forwarding != 0)
+	if (i_am_router)
 		goto freeit;
 	if (!(ifp->if_xflags & IFXF_AUTOCONF6))
 		goto freeit;
@@ -1366,7 +1367,7 @@ icmp6_redirect_input(struct mbuf *m, int off)
 
 	/* RFC 2461 8.3 */
 	nd6_cache_lladdr(ifp, &redtgt6, lladdr, lladdrlen, ND_REDIRECT,
-			 is_onlink ? ND_REDIRECT_ONLINK : ND_REDIRECT_ROUTER);
+	    is_onlink ? ND_REDIRECT_ONLINK : ND_REDIRECT_ROUTER, i_am_router);
 
 	if (!is_onlink) {	/* better router case.  perform rtredirect. */
 		/* perform rtredirect */
@@ -1438,11 +1439,12 @@ icmp6_redirect_output(struct mbuf *m0, struct rtentry *rt)
 	size_t maxlen;
 	u_char *p;
 	struct sockaddr_in6 src_sa;
+	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
 
 	icmp6_errcount(ND_REDIRECT, 0);
 
 	/* if we are not router, we don't send icmp6 redirect */
-	if (ip6_forwarding == 0)
+	if (!i_am_router)
 		goto fail;
 
 	/* sanity check */
diff --git a/sys/netinet6/ip6_input.c b/sys/netinet6/ip6_input.c
index 6952cf632f9..4ab7d8c4578 100644
--- a/sys/netinet6/ip6_input.c
+++ b/sys/netinet6/ip6_input.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ip6_input.c,v 1.264 2024/07/04 12:50:08 bluhm Exp $	*/
+/*	$OpenBSD: ip6_input.c,v 1.265 2024/07/14 18:53:39 bluhm Exp $	*/
 /*	$KAME: ip6_input.c,v 1.188 2001/03/29 05:34:31 itojun Exp $	*/
 
 /*
@@ -416,7 +416,7 @@ ip6_input_if(struct mbuf **mp, int *offp, int nxt, int af, struct ifnet *ifp)
 		SET(flags, IPV6_REDIRECT);
 #endif
 
-	switch (ip6_forwarding) {
+	switch (atomic_load_int(&ip6_forwarding)) {
 	case 2:
 		SET(flags, IPV6_FORWARDING_IPSEC);
 		/* FALLTHROUGH */
@@ -1443,12 +1443,15 @@ const u_char inet6ctlerrmap[PRC_NCMDS] = {
 extern int ip6_mrtproto;
 #endif
 
+const struct sysctl_bounded_args ipv6ctl_vars_unlocked[] = {
+	{ IPV6CTL_FORWARDING, &ip6_forwarding, 0, 2 },
+};
+
 const struct sysctl_bounded_args ipv6ctl_vars[] = {
 	{ IPV6CTL_DAD_PENDING, &ip6_dad_pending, SYSCTL_INT_READONLY },
 #ifdef MROUTING
 	{ IPV6CTL_MRTPROTO, &ip6_mrtproto, SYSCTL_INT_READONLY },
 #endif
-	{ IPV6CTL_FORWARDING, &ip6_forwarding, 0, 2 },
 	{ IPV6CTL_SENDREDIRECTS, &ip6_sendredirects, 0, 1 },
 	{ IPV6CTL_DEFHLIM, &ip6_defhlim, 0, 255 },
 	{ IPV6CTL_MAXFRAGPACKETS, &ip6_maxfragpackets, 0, 1000 },
@@ -1568,6 +1571,10 @@ ip6_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
 			atomic_inc_long(&rtgeneration);
 		NET_UNLOCK();
 		return (error);
+	case IPV6CTL_FORWARDING:
+		return (sysctl_bounded_arr(
+		    ipv6ctl_vars_unlocked, nitems(ipv6ctl_vars_unlocked),
+		    name, namelen, oldp, oldlenp, newp, newlen));
 	default:
 		NET_LOCK();
 		error = sysctl_bounded_arr(ipv6ctl_vars, nitems(ipv6ctl_vars),
diff --git a/sys/netinet6/nd6.c b/sys/netinet6/nd6.c
index 28bc1b91d50..fce85be1a2c 100644
--- a/sys/netinet6/nd6.c
+++ b/sys/netinet6/nd6.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: nd6.c,v 1.281 2024/06/20 19:25:42 bluhm Exp $	*/
+/*	$OpenBSD: nd6.c,v 1.282 2024/07/14 18:53:39 bluhm Exp $	*/
 /*	$KAME: nd6.c,v 1.280 2002/06/08 19:52:07 itojun Exp $	*/
 
 /*
@@ -107,8 +107,8 @@ void nd6_slowtimo(void *);
 void nd6_expire(void *);
 void nd6_expire_timer(void *);
 void nd6_invalidate(struct rtentry *);
-void nd6_free(struct rtentry *);
-int nd6_llinfo_timer(struct rtentry *);
+void nd6_free(struct rtentry *, int);
+int nd6_llinfo_timer(struct rtentry *, int);
 
 struct timeout nd6_timer_to;
 struct timeout nd6_slowtimo_ch;
@@ -264,6 +264,7 @@ nd6_timer(void *unused)
 {
 	struct llinfo_nd6 *ln, *nln;
 	time_t uptime, expire;
+	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
 	int secs;
 
 	NET_LOCK();
@@ -276,7 +277,7 @@ nd6_timer(void *unused)
 		struct rtentry *rt = ln->ln_rt;
 
 		if (rt->rt_expire && rt->rt_expire <= uptime)
-			if (nd6_llinfo_timer(rt))
+			if (nd6_llinfo_timer(rt, i_am_router))
 				continue;
 
 		if (rt->rt_expire && rt->rt_expire < expire)
@@ -300,7 +301,7 @@ nd6_timer(void *unused)
  * Returns 1 if `rt' should no longer be used, 0 otherwise.
  */
 int
-nd6_llinfo_timer(struct rtentry *rt)
+nd6_llinfo_timer(struct rtentry *rt, int i_am_router)
 {
 	struct llinfo_nd6 *ln = (struct llinfo_nd6 *)rt->rt_llinfo;
 	struct sockaddr_in6 *dst = satosin6(rt_key(rt));
@@ -346,7 +347,7 @@ nd6_llinfo_timer(struct rtentry *rt)
 			} else
 				atomic_sub_int(&ln_hold_total, len);
 
-			nd6_free(rt);
+			nd6_free(rt, i_am_router);
 			ln = NULL;
 		}
 		break;
@@ -362,7 +363,7 @@ nd6_llinfo_timer(struct rtentry *rt)
 	case ND6_LLINFO_PURGE:
 		/* Garbage Collection(RFC 2461 5.3) */
 		if (!ND6_LLINFO_PERMANENT(ln)) {
-			nd6_free(rt);
+			nd6_free(rt, i_am_router);
 			ln = NULL;
 		}
 		break;
@@ -383,7 +384,7 @@ nd6_llinfo_timer(struct rtentry *rt)
 			nd6_ns_output(ifp, &dst->sin6_addr, &dst->sin6_addr,
 			    &ln->ln_saddr6, 0);
 		} else {
-			nd6_free(rt);
+			nd6_free(rt, i_am_router);
 			ln = NULL;
 		}
 		break;
@@ -477,6 +478,7 @@ void
 nd6_purge(struct ifnet *ifp)
 {
 	struct llinfo_nd6 *ln, *nln;
+	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
 
 	NET_ASSERT_LOCKED_EXCLUSIVE();
 
@@ -492,7 +494,7 @@ nd6_purge(struct ifnet *ifp)
 		    rt->rt_gateway->sa_family == AF_LINK) {
 			sdl = satosdl(rt->rt_gateway);
 			if (sdl->sdl_index == ifp->if_index)
-				nd6_free(rt);
+				nd6_free(rt, i_am_router);
 		}
 	}
 }
@@ -661,7 +663,7 @@ nd6_invalidate(struct rtentry *rt)
  * Free an nd6 llinfo entry.
  */
 void
-nd6_free(struct rtentry *rt)
+nd6_free(struct rtentry *rt, int i_am_router)
 {
 	struct llinfo_nd6 *ln = (struct llinfo_nd6 *)rt->rt_llinfo;
 	struct in6_addr in6 = satosin6(rt_key(rt))->sin6_addr;
@@ -671,7 +673,7 @@ nd6_free(struct rtentry *rt)
 
 	ifp = if_get(rt->rt_ifidx);
 
-	if (ip6_forwarding == 0) {
+	if (!i_am_router) {
 		if (ln->ln_router) {
 			/*
 			 * rt6_flush must be called whether or not the neighbor
@@ -1031,7 +1033,7 @@ nd6_ioctl(u_long cmd, caddr_t data, struct ifnet *ifp)
  */
 void
 nd6_cache_lladdr(struct ifnet *ifp, const struct in6_addr *from, char *lladdr,
-    int lladdrlen, int type, int code)
+    int lladdrlen, int type, int code, int i_am_router)
 {
 	struct rtentry *rt;
 	struct llinfo_nd6 *ln;
@@ -1080,7 +1082,7 @@ nd6_cache_lladdr(struct ifnet *ifp, const struct in6_addr *from, char *lladdr,
 		return;
 	if ((rt->rt_flags & (RTF_GATEWAY | RTF_LLINFO)) != RTF_LLINFO) {
 fail:
-		nd6_free(rt);
+		nd6_free(rt, i_am_router);
 		rtfree(rt);
 		return;
 	}
diff --git a/sys/netinet6/nd6.h b/sys/netinet6/nd6.h
index 293ccbfb671..b65fad00977 100644
--- a/sys/netinet6/nd6.h
+++ b/sys/netinet6/nd6.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: nd6.h,v 1.99 2023/05/04 06:56:56 bluhm Exp $	*/
+/*	$OpenBSD: nd6.h,v 1.100 2024/07/14 18:53:39 bluhm Exp $	*/
 /*	$KAME: nd6.h,v 1.95 2002/06/08 11:31:06 itojun Exp $	*/
 
 /*
@@ -134,7 +134,7 @@ void nd6_nud_hint(struct rtentry *);
 void nd6_rtrequest(struct ifnet *, int, struct rtentry *);
 int nd6_ioctl(u_long, caddr_t, struct ifnet *);
 void nd6_cache_lladdr(struct ifnet *, const struct in6_addr *, char *,
-    int, int, int);
+    int, int, int, int);
 int nd6_resolve(struct ifnet *, struct rtentry *, struct mbuf *,
 	 struct sockaddr *, u_char *);
 int nd6_need_cache(struct ifnet *);
diff --git a/sys/netinet6/nd6_nbr.c b/sys/netinet6/nd6_nbr.c
index b6747312d5b..2e491334501 100644
--- a/sys/netinet6/nd6_nbr.c
+++ b/sys/netinet6/nd6_nbr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: nd6_nbr.c,v 1.152 2024/06/20 19:25:42 bluhm Exp $	*/
+/*	$OpenBSD: nd6_nbr.c,v 1.153 2024/07/14 18:53:39 bluhm Exp $	*/
 /*	$KAME: nd6_nbr.c,v 1.61 2001/02/10 16:06:14 jinmei Exp $	*/
 
 /*
@@ -108,7 +108,7 @@ nd6_ns_input(struct mbuf *m, int off, int icmp6len)
 	struct ifaddr *ifa = NULL;
 	int lladdrlen = 0;
 	int anycast = 0, proxy = 0, tentative = 0;
-	int i_am_router = (ip6_forwarding != 0);
+	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
 	int tlladdr;
 	struct nd_opts ndopts;
 	struct sockaddr_dl *proxydl = NULL;
@@ -323,7 +323,7 @@ nd6_ns_input(struct mbuf *m, int off, int icmp6len)
 	}
 
 	nd6_cache_lladdr(ifp, &saddr6, lladdr, lladdrlen, ND_NEIGHBOR_SOLICIT,
-	    0);
+	    0, i_am_router);
 
 	nd6_na_output(ifp, &saddr6, &taddr6,
 	    ((anycast || proxy || !tlladdr) ? 0 : ND_NA_FLAG_OVERRIDE) |
@@ -559,7 +559,7 @@ nd6_na_input(struct mbuf *m, int off, int icmp6len)
 	int is_override;
 	char *lladdr = NULL;
 	int lladdrlen = 0;
-	int i_am_router = (ip6_forwarding != 0);
+	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
 	struct ifaddr *ifa;
 	struct in6_ifaddr *ifa6;
 	struct llinfo_nd6 *ln;
diff --git a/sys/netinet6/nd6_rtr.c b/sys/netinet6/nd6_rtr.c
index d68b7a8ef67..1d4ec431259 100644
--- a/sys/netinet6/nd6_rtr.c
+++ b/sys/netinet6/nd6_rtr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: nd6_rtr.c,v 1.170 2023/03/31 19:43:33 bluhm Exp $	*/
+/*	$OpenBSD: nd6_rtr.c,v 1.171 2024/07/14 18:53:39 bluhm Exp $	*/
 /*	$KAME: nd6_rtr.c,v 1.97 2001/02/07 11:09:13 itojun Exp $	*/
 
 /*
@@ -73,6 +73,7 @@ nd6_rtr_cache(struct mbuf *m, int off, int icmp6len, int icmp6_type)
 	struct in6_addr saddr6 = ip6->ip6_src;
 	char *lladdr = NULL;
 	int lladdrlen = 0;
+	int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
 	struct nd_opts ndopts;
 	char src[INET6_ADDRSTRLEN], dst[INET6_ADDRSTRLEN];
 
@@ -157,7 +158,8 @@ nd6_rtr_cache(struct mbuf *m, int off, int icmp6len, int icmp6_type)
 		goto bad;
 	}
 
-	nd6_cache_lladdr(ifp, &saddr6, lladdr, lladdrlen, icmp6_type, 0);
+	nd6_cache_lladdr(ifp, &saddr6, lladdr, lladdrlen, icmp6_type, 0,
+	    i_am_router);
 	if_put(ifp);
 
  freeit: