Merge "Only look up A records if the system has IPv4." into gingerbread

getaddrinfo only asks DNS for IPv6 addresses if the system
has IPv6 connectivity, but always asks for IPv4 addresses.
Don't ask for IPv4 addresses if there is no IPv4
connectivity.

Change-Id: Iefe9fcb006fabe60b4b11dd4653a7c4a406506f4

libc/include/netinet/in6.h

@@ -60,6 +60,10 @@
 #define IN6_IS_ADDR_SITELOCAL(a)	\
 	(((a)->s6_addr[0] == 0xfe) && (((a)->s6_addr[1] & 0xc0) == 0xc0))
 
+/* RFC 4193. */
+#define IN6_IS_ADDR_ULA(a)	\
+	(((a)->s6_addr[0] & 0xfe) == 0xfc)
+
 #define IN6_IS_ADDR_MULTICAST(a)	\
 	(((__const uint8_t *) (a))[0] == 0xff)
 

libc/netbsd/net/getaddrinfo.c

@@ -340,35 +340,55 @@ str2number(const char *p)
 		return -1;
 }
 
-/* Determine whether IPv6 connectivity is available. */
+/*
+ * Connect a UDP socket to a given unicast address. This will cause no network
+ * traffic, but will fail fast if the system has no or limited reachability to
+ * the destination (e.g., no IPv4 address, no IPv6 default route, ...).
+ */
 static int
-_have_ipv6() {
-	/*
-	 * Connect a UDP socket to an global unicast IPv6 address. This will
-	 * cause no network traffic, but will fail fast if the system has no or
-	 * limited IPv6 connectivity (e.g., only a link-local address).
-	 */
-	static const struct sockaddr_in6 sin6_test = {
-		/* family, port, flow label */
-		AF_INET6, 0, 0,
-		/* 2000:: */
-		{{{ 0x20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }}},
-		/* scope ID */
-		0};
-        sockaddr_union addr_test;
-        addr_test.in6 = sin6_test;
-	int s = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+_test_connect(int pf, struct sockaddr *addr, size_t addrlen) {
+	int s = socket(pf, SOCK_DGRAM, IPPROTO_UDP);
 	if (s < 0)
 		return 0;
 	int ret;
 	do {
-		ret = connect(s, &addr_test.generic, sizeof(addr_test.in6));
+		ret = connect(s, addr, addrlen);
 	} while (ret < 0 && errno == EINTR);
-	int have_ipv6 = (ret == 0);
+	int success = (ret == 0);
 	do {
 		ret = close(s);
 	} while (ret < 0 && errno == EINTR);
-	return have_ipv6;
+	return success;
+}
+
+/*
+ * The following functions determine whether IPv4 or IPv6 connectivity is
+ * available in order to implement AI_ADDRCONFIG.
+ *
+ * Strictly speaking, AI_ADDRCONFIG should not look at whether connectivity is
+ * available, but whether addresses of the specified family are "configured
+ * on the local system". However, bionic doesn't currently support getifaddrs,
+ * so checking for connectivity is the next best thing.
+ */
+static int
+_have_ipv6() {
+	static const struct sockaddr_in6 sin6_test = {
+		.sin6_family = AF_INET6,
+		.sin6_addr.s6_addr = {  // 2000::
+			0x20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+		};
+        sockaddr_union addr = { .in6 = sin6_test };
+	return _test_connect(PF_INET6, &addr.generic, sizeof(addr.in6));
+}
+
+static int
+_have_ipv4() {
+	static const struct sockaddr_in sin_test = {
+		.sin_family = AF_INET,
+		.sin_addr.s_addr = __constant_htonl(0x08080808L)  // 8.8.8.8
+	};
+        sockaddr_union addr = { .in = sin_test };
+        return _test_connect(PF_INET, &addr.generic, sizeof(addr.in));
 }
 
 int
@@ -1299,11 +1319,13 @@ _get_scope(const struct sockaddr *addr)
 		if (IN_LOOPBACK(na) ||                          /* 127.0.0.0/8 */
 		    (na & 0xffff0000) == 0xa9fe0000) {          /* 169.254.0.0/16 */
 			return IPV6_ADDR_SCOPE_LINKLOCAL;
-		} else if ((na & 0xff000000) == 0x0a000000 ||   /* 10.0.0.0/8 */
-			   (na & 0xfff00000) == 0xac100000 ||   /* 172.16.0.0/12 */
-			   (na & 0xffff0000) == 0xc0a80000) {   /* 192.168.0.0/16 */
-			return IPV6_ADDR_SCOPE_SITELOCAL;
 		} else {
+			/*
+			 * According to draft-ietf-6man-rfc3484-revise-01 section 2.3,
+			 * it is best not to treat the private IPv4 ranges
+			 * (10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16) as being
+			 * in a special scope, so we don't.
+			 */
 			return IPV6_ADDR_SCOPE_GLOBAL;
 		}
 	} else {
@@ -1325,9 +1347,13 @@ _get_scope(const struct sockaddr *addr)
 #define IN6_IS_ADDR_6TO4(a)	 \
 	(((a)->s6_addr[0] == 0x20) && ((a)->s6_addr[1] == 0x02))
 
+/* 6bone testing address area (3ffe::/16), deprecated in RFC 3701. */
+#define IN6_IS_ADDR_6BONE(a)      \
+	(((a)->s6_addr[0] == 0x3f) && ((a)->s6_addr[1] == 0xfe))
+
 /*
  * Get the label for a given IPv4/IPv6 address.
- * RFC 3484, section 2.1, plus Teredo added in with label 5.
+ * RFC 3484, section 2.1, plus changes from draft-ietf-6man-rfc3484-revise-01.
  */
 
 /*ARGSUSED*/
@@ -1335,19 +1361,27 @@ static int
 _get_label(const struct sockaddr *addr)
 {
 	if (addr->sa_family == AF_INET) {
-		return 4;
+		return 3;
 	} else if (addr->sa_family == AF_INET6) {
 		const struct sockaddr_in6 *addr6 = (const struct sockaddr_in6 *)addr;
 		if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr)) {
 			return 0;
-		} else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr)) {
+		} else if (IN6_IS_ADDR_ULA(&addr6->sin6_addr)) {
+			return 1;
+		} else if (IN6_IS_ADDR_V4MAPPED(&addr6->sin6_addr)) {
 			return 3;
+		} else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
+			return 4;
 		} else if (IN6_IS_ADDR_TEREDO(&addr6->sin6_addr)) {
 			return 5;
-		} else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
-			return 2;
+		} else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr)) {
+			return 10;
+		} else if (IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr)) {
+			return 11;
+		} else if (IN6_IS_ADDR_6BONE(&addr6->sin6_addr)) {
+			return 12;
 		} else {
-			return 1;
+			return 2;
 		}
 	} else {
 		/*
@@ -1360,7 +1394,7 @@ _get_label(const struct sockaddr *addr)
 
 /*
  * Get the precedence for a given IPv4/IPv6 address.
- * RFC 3484, section 2.1, plus Teredo added in with precedence 25.
+ * RFC 3484, section 2.1, plus changes from draft-ietf-6man-rfc3484-revise-01.
  */
 
 /*ARGSUSED*/
@@ -1368,22 +1402,28 @@ static int
 _get_precedence(const struct sockaddr *addr)
 {
 	if (addr->sa_family == AF_INET) {
-		return 10;
+		return 30;
 	} else if (addr->sa_family == AF_INET6) {
 		const struct sockaddr_in6 *addr6 = (const struct sockaddr_in6 *)addr;
 		if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr)) {
+			return 60;
+		} else if (IN6_IS_ADDR_ULA(&addr6->sin6_addr)) {
 			return 50;
-		} else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr)) {
+		} else if (IN6_IS_ADDR_V4MAPPED(&addr6->sin6_addr)) {
+			return 30;
+		} else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
 			return 20;
 		} else if (IN6_IS_ADDR_TEREDO(&addr6->sin6_addr)) {
-			return 25;
-		} else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
-			return 30;
+			return 10;
+		} else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr) ||
+		           IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr) ||
+		           IN6_IS_ADDR_6BONE(&addr6->sin6_addr)) {
+			return 1;
 		} else {
 			return 40;
 		}
 	} else {
-		return 5;
+		return 1;
 	}
 }
 
@@ -1667,17 +1707,27 @@ _dns_getaddrinfo(void *rv, void	*cb_data, va_list ap)
 		q.qclass = C_IN;
 		q.answer = buf->buf;
 		q.anslen = sizeof(buf->buf);
-		/* If AI_ADDRCONFIG, lookup IPv6 only if we have connectivity */
-		if (!(pai->ai_flags & AI_ADDRCONFIG) || _have_ipv6()) {
+		int query_ipv6 = 1, query_ipv4 = 1;
+		if (pai->ai_flags & AI_ADDRCONFIG) {
+			query_ipv6 = _have_ipv6();
+			query_ipv4 = _have_ipv4();
+		}
+		if (query_ipv6) {
 			q.qtype = T_AAAA;
-			q.next = &q2;
-			q2.name = name;
-			q2.qclass = C_IN;
-			q2.qtype = T_A;
-			q2.answer = buf2->buf;
-			q2.anslen = sizeof(buf2->buf);
-		} else {
+			if (query_ipv4) {
+				q.next = &q2;
+				q2.name = name;
+				q2.qclass = C_IN;
+				q2.qtype = T_A;
+				q2.answer = buf2->buf;
+				q2.anslen = sizeof(buf2->buf);
+			}
+		} else if (query_ipv4) {
 			q.qtype = T_A;
+		} else {
+			free(buf);
+			free(buf2);
+			return NS_NOTFOUND;
 		}
 		break;
 	case AF_INET: