1 files changed, 87 insertions, 8 deletions

diff --git a/contrib/ntp/libntp/socktohost.c b/contrib/ntp/libntp/socktohost.c
index 7aafdc7..c61e571 100644
--- a/contrib/ntp/libntp/socktohost.c
+++ b/contrib/ntp/libntp/socktohost.c
@@ -1,9 +1,14 @@
 /*
  * socktoa - return a numeric host name from a sockaddr_storage structure
  */
+#include <config.h>
 #include <sys/types.h>
+#ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
+#endif
+#ifdef HAVE_NETINET_IN_H
 #include <netinet/in.h>
+#endif
 
 #include <arpa/inet.h>
 
@@ -13,19 +18,93 @@
 #include "lib_strbuf.h"
 #include "ntp_stdlib.h"
 #include "ntp.h"
+#include "ntp_debug.h"
 
 
-char *
+const char *
 socktohost(
-	struct sockaddr_storage* sock
+	const sockaddr_u *sock
 	)
 {
-	register char *buffer;
+	const char		svc[] = "ntp";
+	char *			pbuf;
+	char *			pliar;
+	int			gni_flags;
+	struct addrinfo		hints;
+	struct addrinfo *	alist;
+	struct addrinfo *	ai;
+	sockaddr_u		addr;
+	size_t			octets;
+	int			a_info;
 
-	LIB_GETBUF(buffer);
-	if (getnameinfo((struct sockaddr *)sock, SOCKLEN(sock), buffer,
-	    LIB_BUFLENGTH /* NI_MAXHOST*/, NULL, 0, 0))
-		return stoa(sock);
+	/* reverse the address to purported DNS name */
+	LIB_GETBUF(pbuf);
+	gni_flags = NI_DGRAM | NI_NAMEREQD;
+	if (getnameinfo(&sock->sa, SOCKLEN(sock), pbuf, LIB_BUFLENGTH,
+			NULL, 0, gni_flags))
+		return stoa(sock);	/* use address */
 
-  	return buffer;
+	TRACE(1, ("%s reversed to %s\n", stoa(sock), pbuf));
+
+	/*
+	 * Resolve the reversed name and make sure the reversed address
+	 * is among the results.
+	 */
+	ZERO(hints);
+	hints.ai_family = AF(sock);
+	hints.ai_protocol = IPPROTO_UDP;
+	hints.ai_socktype = SOCK_DGRAM;
+	hints.ai_flags = 0;
+	alist = NULL;
+
+	a_info = getaddrinfo(pbuf, svc, &hints, &alist);
+	if (a_info == EAI_NONAME
+#ifdef EAI_NODATA
+	    || a_info == EAI_NODATA
+#endif
+	   ) {
+		hints.ai_flags = AI_CANONNAME;
+#ifdef AI_ADDRCONFIG
+		hints.ai_flags |= AI_ADDRCONFIG;
+#endif
+		a_info = getaddrinfo(pbuf, svc, &hints, &alist);	
+	}
+#ifdef AI_ADDRCONFIG
+	/* Some older implementations don't like AI_ADDRCONFIG. */
+	if (a_info == EAI_BADFLAGS) {
+		hints.ai_flags &= ~AI_ADDRCONFIG;
+		a_info = getaddrinfo(pbuf, svc, &hints, &alist);	
+	}
+#endif
+	if (a_info)
+		goto forward_fail;
+
+	NTP_INSIST(alist != NULL);
+
+	for (ai = alist; ai != NULL; ai = ai->ai_next) {
+		/*
+		 * Make a convenience sockaddr_u copy from ai->ai_addr
+		 * because casting from sockaddr * to sockaddr_u * is
+		 * risking alignment problems on platforms where
+		 * sockaddr_u has stricter alignment than sockaddr,
+		 * such as sparc.
+		 */
+		ZERO_SOCK(&addr);
+		octets = min(sizeof(addr), ai->ai_addrlen);
+		memcpy(&addr, ai->ai_addr, octets);
+		if (SOCK_EQ(sock, &addr))
+			break;
+	}
+	freeaddrinfo(alist);
+
+	if (ai != NULL)
+		return pbuf;	/* forward check passed */
+
+    forward_fail:
+	TRACE(1, ("%s forward check lookup fail: %s\n", pbuf,
+		  gai_strerror(a_info)));
+	LIB_GETBUF(pliar);
+	snprintf(pliar, LIB_BUFLENGTH, "%s (%s)", stoa(sock), pbuf);
+
+	return pliar;
 }