Fix hostname to be returned in an ICMPv6 NI Reply message defined

in RFC 4620, ICMPv6 Node Information Queries.  A vnet jail with an
IPv6 address sent a hostname of the host environment, not the
jail, even if another hostname was set to the jail.

This change can be tested by the following commands:

 # ifconfig epair0 create
 # jail -c -n j1 vnet host.hostname=vnetjail path=/ persist
 # ifconfig epair0b vnet j1
 # ifconfig epair0a inet6 -ifdisabled auto_linklocal up
 # jexec j1 ifconfig epair0b inet6 -ifdisabled auto_linklocal up
 # ping6 -w ff02::1%epair0a

Differential Revision:	https://reviews.freebsd.org/D20207
MFC after:	1 week

1 files changed, 19 insertions, 14 deletions

diff --git a/sys/netinet6/icmp6.c b/sys/netinet6/icmp6.c
index 2b2425b45aa8..4f0d465ac0ed 100644
--- a/sys/netinet6/icmp6.c
+++ b/sys/netinet6/icmp6.c
@@ -140,7 +140,7 @@ static int icmp6_rip6_input(struct mbuf **, int);
 static int icmp6_ratelimit(const struct in6_addr *, const int, const int);
 static const char *icmp6_redirect_diag(struct in6_addr *,
 	struct in6_addr *, struct in6_addr *);
-static struct mbuf *ni6_input(struct mbuf *, int);
+static struct mbuf *ni6_input(struct mbuf *, int, struct prison *);
 static struct mbuf *ni6_nametodns(const char *, int, int);
 static int ni6_dnsmatch(const char *, int, const char *, int);
 static int ni6_addrs(struct icmp6_nodeinfo *, struct mbuf *,
@@ -627,6 +627,7 @@ icmp6_input(struct mbuf **mp, int *offp, int proto)
 	case ICMP6_WRUREQUEST:	/* ICMP6_FQDN_QUERY */
 	    {
 		enum { WRU, FQDN } mode;
+		struct prison *pr;
 
 		if (!V_icmp6_nodeinfo)
 			break;
@@ -638,6 +639,14 @@ icmp6_input(struct mbuf **mp, int *offp, int proto)
 		else
 			goto badlen;
 
+		pr = NULL;
+		sx_slock(&allprison_lock);
+		TAILQ_FOREACH(pr, &allprison, pr_list)
+			if (pr->pr_vnet == ifp->if_vnet)
+				break; 
+		sx_sunlock(&allprison_lock);
+		if (pr == NULL)
+			pr = curthread->td_ucred->cr_prison;
 		if (mode == FQDN) {
 #ifndef PULLDOWN_TEST
 			IP6_EXTHDR_CHECK(m, off, sizeof(struct icmp6_nodeinfo),
@@ -645,11 +654,10 @@ icmp6_input(struct mbuf **mp, int *offp, int proto)
 #endif
 			n = m_copym(m, 0, M_COPYALL, M_NOWAIT);
 			if (n)
-				n = ni6_input(n, off);
+				n = ni6_input(n, off, pr);
 			/* XXX meaningless if n == NULL */
 			noff = sizeof(struct ip6_hdr);
 		} else {
-			struct prison *pr;
 			u_char *p;
 			int maxhlen, hlen;
 
@@ -683,13 +691,6 @@ icmp6_input(struct mbuf **mp, int *offp, int proto)
 				n = NULL;
 				break;
 			}
-			maxhlen = M_TRAILINGSPACE(n) -
-			    (sizeof(*nip6) + sizeof(*nicmp6) + 4);
-			pr = curthread->td_ucred->cr_prison;
-			mtx_lock(&pr->pr_mtx);
-			hlen = strlen(pr->pr_hostname);
-			if (maxhlen > hlen)
-				maxhlen = hlen;
 			/*
 			 * Copy IPv6 and ICMPv6 only.
 			 */
@@ -699,6 +700,13 @@ icmp6_input(struct mbuf **mp, int *offp, int proto)
 			bcopy(icmp6, nicmp6, sizeof(struct icmp6_hdr));
 			p = (u_char *)(nicmp6 + 1);
 			bzero(p, 4);
+
+			maxhlen = M_TRAILINGSPACE(n) -
+			    (sizeof(*nip6) + sizeof(*nicmp6) + 4);
+			mtx_lock(&pr->pr_mtx);
+			hlen = strlen(pr->pr_hostname);
+			if (maxhlen > hlen)
+				maxhlen = hlen;
 			/* meaningless TTL */
 			bcopy(pr->pr_hostname, p + 4, maxhlen);
 			mtx_unlock(&pr->pr_mtx);
@@ -1167,11 +1175,10 @@ icmp6_mtudisc_update(struct ip6ctlparam *ip6cp, int validated)
  *   with hostname changes by sethostname(3)
  */
 static struct mbuf *
-ni6_input(struct mbuf *m, int off)
+ni6_input(struct mbuf *m, int off, struct prison *pr)
 {
 	struct icmp6_nodeinfo *ni6, *nni6;
 	struct mbuf *n = NULL;
-	struct prison *pr;
 	u_int16_t qtype;
 	int subjlen;
 	int replylen = sizeof(struct ip6_hdr) + sizeof(struct icmp6_nodeinfo);
@@ -1323,7 +1330,6 @@ ni6_input(struct mbuf *m, int off)
 			 *   wildcard match, if gethostname(3) side has
 			 *   truncated hostname.
 			 */
-			pr = curthread->td_ucred->cr_prison;
 			mtx_lock(&pr->pr_mtx);
 			n = ni6_nametodns(pr->pr_hostname,
 			    strlen(pr->pr_hostname), 0);
@@ -1448,7 +1454,6 @@ ni6_input(struct mbuf *m, int off)
 		/*
 		 * XXX do we really have FQDN in hostname?
 		 */
-		pr = curthread->td_ucred->cr_prison;
 		mtx_lock(&pr->pr_mtx);
 		n->m_next = ni6_nametodns(pr->pr_hostname,
 		    strlen(pr->pr_hostname), oldfqdn);