Try fallback on IPv4 ANYADDR when IPv6 ANYADDR fails

https://bugs.php.net/bug.php?id=74166
A host system with no/limited IPv6 support will fail at binding
the IPv6 ANYADDR address (::) as the address family is unsupported.

Deal with this by handling failure to implicitly bind to ::
as a soft failure, falling back to 0.0.0.0.

If binding to :: failed for some other reason (e.g. port in use)
then binding to 0.0.0.0 will likely fail as well, but we'll
get appropriate warnings for that.

sapi/fpm/fpm/fpm_sockets.c

@@ -246,64 +246,92 @@ enum fpm_address_domain fpm_sockets_domain_from_address(char *address) /* {{{ */
 }
 /* }}} */
 
-static int fpm_socket_af_inet_listening_socket(struct fpm_worker_pool_s *wp) /* {{{ */
+static int fpm_socket_af_inet_socket_by_addr(struct fpm_worker_pool_s *wp, const char *addr, const char *port) /* {{{ */
 {
 	struct addrinfo hints, *servinfo, *p;
+	char tmpbuf[INET6_ADDRSTRLEN];
+	int status;
+	int sock = -1;
+
+	memset(&hints, 0, sizeof hints);
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+
+	if ((status = getaddrinfo(addr, port, &hints, &servinfo)) != 0) {
+		zlog(ZLOG_ERROR, "getaddrinfo: %s\n", gai_strerror(status));
+		return -1;
+	}
+
+	for (p = servinfo; p != NULL; p = p->ai_next) {
+		inet_ntop(p->ai_family, fpm_get_in_addr(p->ai_addr), tmpbuf, INET6_ADDRSTRLEN);
+		if (sock < 0) {
+			if ((sock = fpm_sockets_get_listening_socket(wp, p->ai_addr, p->ai_addrlen)) != -1) {
+				zlog(ZLOG_DEBUG, "Found address for %s, socket opened on %s", addr, tmpbuf);
+			}
+		} else {
+			zlog(ZLOG_WARNING, "Found multiple addresses for %s, %s ignored", addr, tmpbuf);
+		}
+	}
+
+	freeaddrinfo(servinfo);
+
+	return sock;
+}
+/* }}} */
+
+static int fpm_socket_af_inet_listening_socket(struct fpm_worker_pool_s *wp) /* {{{ */
+{
 	char *dup_address = strdup(wp->config->listen_address);
 	char *port_str = strrchr(dup_address, ':');
 	char *addr = NULL;
-	char tmpbuf[INET6_ADDRSTRLEN];
 	int addr_len;
 	int port = 0;
 	int sock = -1;
-	int status;
 
 	if (port_str) { /* this is host:port pair */
 		*port_str++ = '\0';
 		port = atoi(port_str);
 		addr = dup_address;
+
+		/* strip brackets from address for getaddrinfo */
+		addr_len = strlen(addr);
+		if (addr[0] == '[' && addr[addr_len - 1] == ']') {
+			addr[addr_len - 1] = '\0';
+			addr++;
+		}
+
 	} else if (strlen(dup_address) == strspn(dup_address, "0123456789")) { /* this is port */
 		port = atoi(dup_address);
 		port_str = dup_address;
-		/* IPv6 catch-all + IPv4-mapped */
-		addr = "::";
 	}
 
 	if (port == 0) {
 		zlog(ZLOG_ERROR, "invalid port value '%s'", port_str);
 		return -1;
 	}
 
-	/* strip brackets from address for getaddrinfo */
-	addr_len = strlen(addr);
-	if (addr[0] == '[' && addr[addr_len - 1] == ']') {
-		addr[addr_len - 1] = '\0';
-		addr++;
-	}
+	if (addr) {
+		/* Bind a specific address */
+		sock = fpm_socket_af_inet_socket_by_addr(wp, addr, port_str);
+	} else {
+		/* Bind ANYADDR
+		 *
+		 * Try "::" first as that covers IPv6 ANYADDR and mapped IPv4 ANYADDR
+		 * silencing warnings since failure is an option
+		 *
+		 * If that fails (because AF_INET6 is unsupported) retry with 0.0.0.0
+		 */
+		int old_level = zlog_set_level(ZLOG_ALERT);
+		sock = fpm_socket_af_inet_socket_by_addr(wp, "::", port_str);
+		zlog_set_level(old_level);
 
-	memset(&hints, 0, sizeof hints);
-	hints.ai_family = AF_UNSPEC;
-	hints.ai_socktype = SOCK_STREAM;
-
-	if ((status = getaddrinfo(addr, port_str, &hints, &servinfo)) != 0) {
-		zlog(ZLOG_ERROR, "getaddrinfo: %s\n", gai_strerror(status));
-		free(dup_address);
-		return -1;
-	}
-
-	for (p = servinfo; p != NULL; p = p->ai_next) {
-		inet_ntop(p->ai_family, fpm_get_in_addr(p->ai_addr), tmpbuf, INET6_ADDRSTRLEN);
 		if (sock < 0) {
-			if ((sock = fpm_sockets_get_listening_socket(wp, p->ai_addr, p->ai_addrlen)) != -1) {
-				zlog(ZLOG_DEBUG, "Found address for %s, socket opened on %s", addr, tmpbuf);
-			}
-		} else {
-			zlog(ZLOG_WARNING, "Found multiple addresses for %s, %s ignored", addr, tmpbuf);
+			zlog(ZLOG_NOTICE, "Failed implicitly binding to ::, retrying with 0.0.0.0");
+			sock = fpm_socket_af_inet_socket_by_addr(wp, "0.0.0.0", port_str);
 		}
 	}
 
 	free(dup_address);
-	freeaddrinfo(servinfo);
 
 	return sock;
 }

sapi/fpm/tests/023.phpt

@@ -0,0 +1,57 @@
+--TEST--
+FPM: Test already bound address
+--SKIPIF--
+<?php include "skipif.inc"; ?>
+--FILE--
+<?php
+
+include "include.inc";
+
+$logfile = dirname(__FILE__).'/php-fpm.log.tmp';
+$port = 9000+PHP_INT_SIZE;
+
+$cfg = <<<EOT
+[global]
+log_level = debug
+error_log = $logfile
+[unconfined]
+listen = $port
+ping.path = /ping
+ping.response = pong
+pm = dynamic
+pm.max_children = 5
+pm.start_servers = 2
+pm.min_spare_servers = 1
+pm.max_spare_servers = 3
+EOT;
+
+// Occupy our port and let things fail
+$busy = stream_socket_server("tcp://[::]:$port");
+
+$fpm = run_fpm($cfg, $tail);
+if (is_resource($fpm)) {
+	/* Expect two specific lines of log output and show them
+	 * If we get any different number of those patterns, display whole log
+	 */
+	$out = $all = '';
+	$count = 0;
+	while (!feof($tail)) {
+		$line = fgets($tail);
+		$all .= $line;
+		if ((false !== strpos($line, 'retrying with 0.0.0.0')) ||
+		    (false !== strpos($line, 'unable to bind'))) {
+			$out .= $line;
+			++$count;
+		}
+	}
+	echo ($count == 2) ? $out : $all;
+}
+?>
+--EXPECTF--
+[%d-%s-%d %d:%d:%f] NOTICE: pid %d, fpm_socket_af_inet_listening_socket(), line %d: Failed implicitly binding to ::, retrying with 0.0.0.0
+[%d-%s-%d %d:%d:%f] ERROR: pid %d, fpm_sockets_new_listening_socket(), line %d: unable to bind listening socket for address '%d': %s
+--CLEAN--
+<?php
+    $logfile = dirname(__FILE__).'/php-fpm.log.tmp';
+    @unlink($logfile);
+?>