In case ntp cannot resolve a hostname on startup it will queue the entry

for resolving by a child process that, upon success, will add the entry
to the config of the running running parent process.

Unfortunately there are a couple of bugs with this, fixed in various
later versions of upstream in potentially different ways due to other
code changes:

1) Upon server [-46] <FQDN> the [-46] are used as FQDN for later resolving
   which does not work.  Make sure we always pass the name (or IP there).

2) The intermediate file to carry the information to the child process
   does not know about -4/-6 restrictions, so that a dual-stacked host
   could resolve to an IPv6 address but that might be unreachable (see
   r223626) leading to no working synchronization ignoring a IPv4 record.
   Thus alter the intermediate format to also pass the address family
   (AF_UNSPEC (default), AF_INET or AF_INET6) to the child process
   depending on -4 or -6.

3) Make the child process to parse the new intermediate file format and
   save the address family for getaddrinfo() hints flags.

4) Change child to always reload resolv.conf calling res_init() before
   trying to resolve names.  This will pick up resolv.conf changes or
   new resolv.confs should they have not existed or been empty or
   unusable on ntp startup.  This fix is more conditional in upstream
   versions but given FreeBSD has res_init there is no need for the
   configure logic as well.

Approved by:	roberto
Sponsored by:	Sandvine Incorporated
MFC after:	9 days

contrib/ntp/ntpd/ntp_config.c

@@ -414,7 +414,7 @@ enum gnn_type {
 static	int getnetnum P((const char *, struct sockaddr_storage *, int,
 			 enum gnn_type));
 static	void save_resolve P((char *, int, int, int, int, u_int, int,
-    keyid_t, u_char *));
+    keyid_t, u_char *, u_char));
 static	void do_resolve_internal P((void));
 static	void abort_resolve P((void));
 #if !defined(VMS) && !defined(SYS_WINNT)
@@ -870,9 +870,9 @@ getconfig(
 						stoa(&peeraddr));
 			    }
 			} else if (errflg == -1) {
-				save_resolve(tokens[1], hmode, peerversion,
+				save_resolve(tokens[istart - 1], hmode, peerversion,
 				    minpoll, maxpoll, peerflags, ttl,
-				    peerkey, peerkeystr);
+				    peerkey, peerkeystr, peeraddr.ss_family);
 			}
 			break;
 
@@ -2325,7 +2325,8 @@ save_resolve(
 	u_int flags,
 	int ttl,
 	keyid_t keyid,
-	u_char *keystr
+	u_char *keystr,
+	u_char peeraf
 	)
 {
 #ifndef SYS_VXWORKS
@@ -2365,11 +2366,11 @@ save_resolve(
 	}
 #endif
 
-	(void)fprintf(res_fp, "%s %d %d %d %d %d %d %u %s\n", name,
+	(void)fprintf(res_fp, "%s %u %d %d %d %d %d %d %u %s\n", name, peeraf,
 	    mode, version, minpoll, maxpoll, flags, ttl, keyid, keystr);
 #ifdef DEBUG
 	if (debug > 1)
-		printf("config: %s %d %d %d %d %x %d %u %s\n", name, mode,
+		printf("config: %s %u %d %d %d %d %x %d %u %s\n", name, peeraf, mode,
 		    version, minpoll, maxpoll, flags, ttl, keyid, keystr);
 #endif
 

contrib/ntp/ntpd/ntp_intres.c

@@ -29,6 +29,7 @@
 
 #include <stdio.h>
 #include <ctype.h>
+#include <resolv.h>
 #include <signal.h>
 
 /**/
@@ -111,15 +112,16 @@ static	int resolve_value;	/* next value of resolve timer */
  * is supposed to consist of entries in the following order
  */
 #define	TOK_HOSTNAME	0
-#define	TOK_HMODE	1
-#define	TOK_VERSION	2
-#define TOK_MINPOLL	3
-#define TOK_MAXPOLL	4
-#define	TOK_FLAGS	5
-#define TOK_TTL		6
-#define	TOK_KEYID	7
-#define TOK_KEYSTR	8
-#define	NUMTOK		9
+#define	TOK_PEERAF	1
+#define	TOK_HMODE	2
+#define	TOK_VERSION	3
+#define TOK_MINPOLL	4
+#define TOK_MAXPOLL	5
+#define	TOK_FLAGS	6
+#define TOK_TTL		7
+#define	TOK_KEYID	8
+#define TOK_KEYSTR	9
+#define	NUMTOK		10
 
 #define	MAXLINESIZE	512
 
@@ -140,7 +142,7 @@ char *req_file;		/* name of the file with configuration info */
 static	void	checkparent	P((void));
 static	void	removeentry	P((struct conf_entry *));
 static	void	addentry	P((char *, int, int, int, int, u_int,
-				   int, keyid_t, char *));
+				   int, keyid_t, char *, u_char));
 static	int	findhostaddr	P((struct conf_entry *));
 static	void	openntp		P((void));
 static	int	request		P((struct conf_peer *));
@@ -397,7 +399,8 @@ addentry(
 	u_int flags,
 	int ttl,
 	keyid_t keyid,
-	char *keystr
+	char *keystr,
+	u_char peeraf
 	)
 {
 	register char *cp;
@@ -407,7 +410,7 @@ addentry(
 #ifdef DEBUG
 	if (debug > 1)
 		msyslog(LOG_INFO, 
-		    "intres: <%s> %d %d %d %d %x %d %x %s\n", name,
+		    "intres: <%s> %u %d %d %d %d %x %d %x %s\n", name, peeraf,
 		    mode, version, minpoll, maxpoll, flags, ttl, keyid,
 		    keystr);
 #endif
@@ -422,6 +425,7 @@ addentry(
 	ce->ce_peeraddr6 = in6addr_any;
 #endif
 	ANYSOCK(&ce->peer_store);
+	ce->peer_store.ss_family = peeraf;	/* Save AF for getaddrinfo hints. */
 	ce->ce_hmode = (u_char)mode;
 	ce->ce_version = (u_char)version;
 	ce->ce_minpoll = (u_char)minpoll;
@@ -482,7 +486,8 @@ findhostaddr(
 			entry->ce_name));
 
 		memset(&hints, 0, sizeof(hints));
-		hints.ai_family = AF_UNSPEC;
+		hints.ai_family = entry->peer_store.ss_family;
+		hints.ai_socktype = SOCK_DGRAM;
 		/*
 		 * If the IPv6 stack is not available look only for IPv4 addresses
 		 */
@@ -1051,6 +1056,13 @@ readconf(
 			}
 		}
 
+		if (intval[TOK_PEERAF] != AF_UNSPEC && intval[TOK_PEERAF] !=
+		    AF_INET && intval[TOK_PEERAF] != AF_INET6) {
+			msyslog(LOG_ERR, "invalid peer address family (%u) in "
+			    "file %s", intval[TOK_PEERAF], name);
+			exit(1);
+		}
+
 		if (intval[TOK_HMODE] != MODE_ACTIVE &&
 		    intval[TOK_HMODE] != MODE_CLIENT &&
 		    intval[TOK_HMODE] != MODE_BROADCAST) {
@@ -1107,7 +1119,7 @@ readconf(
 		addentry(token[TOK_HOSTNAME], (int)intval[TOK_HMODE],
 			 (int)intval[TOK_VERSION], (int)intval[TOK_MINPOLL],
 			 (int)intval[TOK_MAXPOLL], flags, (int)intval[TOK_TTL],
-			 intval[TOK_KEYID], token[TOK_KEYSTR]);
+			 intval[TOK_KEYID], token[TOK_KEYSTR], (u_char)intval[TOK_PEERAF]);
 	}
 }
 
@@ -1129,6 +1141,9 @@ doconfigure(
 			    dores ? "with" : "without" );
 #endif
 
+	if (dores)         /* Reload /etc/resolv.conf - bug 1226 */
+		res_init();
+
 	ce = confentries;
 	while (ce != NULL) {
 #ifdef DEBUG