resolver: add function resolve_host_port()

Makefile.am

@@ -903,6 +903,7 @@ TESTS = $(C_TESTS)
 noinst_PROGRAMS = \
 	$(C_TESTS) \
 	test/read_conf \
+	test/run_resolver \
 	test/run_input \
 	test/dump_playlist \
 	test/run_decoder \
@@ -926,6 +927,11 @@ test_read_conf_LDADD = $(MPD_LIBS) \
 test_read_conf_SOURCES = test/read_conf.c \
 	src/conf.c src/tokenizer.c src/utils.c src/string_util.c
 
+test_run_resolver_LDADD = $(MPD_LIBS) \
+	$(GLIB_LIBS)
+test_run_resolver_SOURCES = test/run_resolver.c \
+	src/resolver.c
+
 test_run_input_CPPFLAGS = $(AM_CPPFLAGS) \
 	$(ARCHIVE_CFLAGS) \
 	$(INPUT_CFLAGS)

src/resolver.c

@@ -19,6 +19,7 @@
 
 #include "config.h"
 #include "resolver.h"
+#include "glib_compat.h"
 
 #ifndef G_OS_WIN32
 #include <sys/socket.h>
@@ -29,9 +30,7 @@
 #include <winsock.h>
 #endif /* G_OS_WIN32 */
 
-#ifdef HAVE_IPV6
 #include <string.h>
-#endif
 
 char *
 sockaddr_to_string(const struct sockaddr *sa, size_t length, GError **error)
@@ -81,3 +80,63 @@ sockaddr_to_string(const struct sockaddr *sa, size_t length, GError **error)
 
 	return g_strconcat(host, ":", serv, NULL);
 }
+
+struct addrinfo *
+resolve_host_port(const char *host_port, unsigned default_port,
+		  int flags, int socktype,
+		  GError **error_r)
+{
+	char *p = g_strdup(host_port);
+	const char *host = p, *port = NULL;
+
+	if (host_port[0] == '[') {
+		/* IPv6 needs enclosing square braces, to
+		   differentiate between IP colons and the port
+		   separator */
+
+		char *q = strchr(p + 1, ']');
+		if (q != NULL && q[1] == ':' && q[2] != 0) {
+			*q = 0;
+			++host;
+			port = q + 2;
+		}
+	}
+
+	if (port == NULL) {
+		/* port is after the colon, but only if it's the only
+		   colon (don't split IPv6 addresses) */
+
+		char *q = strchr(p, ':');
+		if (q != NULL && q[1] != 0 && strchr(q + 1, ':') == NULL) {
+			*q = 0;
+			port = q + 1;
+		}
+	}
+
+	char buffer[32];
+	if (port == NULL && default_port != 0) {
+		g_snprintf(buffer, sizeof(buffer), "%u", default_port);
+		port = buffer;
+	}
+
+	if ((flags & AI_PASSIVE) != 0 && strcmp(host, "*") == 0)
+		host = NULL;
+
+	const struct addrinfo hints = {
+		.ai_flags = flags,
+		.ai_family = AF_UNSPEC,
+		.ai_socktype = socktype,
+	};
+
+	struct addrinfo *ai;
+	int ret = getaddrinfo(host, port, &hints, &ai);
+	g_free(p);
+	if (ret != 0) {
+		g_set_error(error_r, resolver_quark(), ret,
+			    "Failed to look up '%s': %s",
+			    host_port, gai_strerror(ret));
+		return NULL;
+	}
+
+	return ai;
+}

src/resolver.h

@@ -23,6 +23,14 @@
 #include <glib.h>
 
 struct sockaddr;
+struct addrinfo;
+
+G_GNUC_CONST
+static inline GQuark
+resolver_quark(void)
+{
+	return g_quark_from_static_string("resolver");
+}
 
 /**
  * Converts the specified socket address into a string in the form
@@ -37,4 +45,19 @@ struct sockaddr;
 char *
 sockaddr_to_string(const struct sockaddr *sa, size_t length, GError **error);
 
+/**
+ * Resolve a specification in the form "host", "host:port",
+ * "[host]:port".  This is a convenience wrapper for getaddrinfo().
+ *
+ * @param default_port a default port number that will be used if none
+ * is given in the string (if applicable); pass 0 to go without a
+ * default
+ * @return an #addrinfo linked list that must be freed with
+ * freeaddrinfo(), or NULL on error
+ */
+struct addrinfo *
+resolve_host_port(const char *host_port, unsigned default_port,
+		  int flags, int socktype,
+		  GError **error_r);
+
 #endif

test/run_resolver.c

@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2003-2011 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "resolver.h"
+
+#ifdef WIN32
+#define WINVER 0x0501
+#include <ws2tcpip.h>
+#include <winsock.h>
+#else
+#include <sys/socket.h>
+#include <netdb.h>
+#endif
+
+#include <stdlib.h>
+
+int main(int argc, char **argv)
+{
+	if (argc != 2) {
+		g_printerr("Usage: run_resolver HOST\n");
+		return EXIT_FAILURE;
+	}
+
+	GError *error = NULL;
+	struct addrinfo *ai =
+		resolve_host_port(argv[1], 80, AI_PASSIVE, SOCK_STREAM,
+				  &error);
+	if (ai == NULL) {
+		g_printerr("%s\n", error->message);
+		g_error_free(error);
+		return EXIT_FAILURE;
+	}
+
+	for (const struct addrinfo *i = ai; i != NULL; i = i->ai_next) {
+		char *p = sockaddr_to_string(i->ai_addr, i->ai_addrlen,
+					     &error);
+		if (p == NULL) {
+			freeaddrinfo(ai);
+			g_printerr("%s\n", error->message);
+			g_error_free(error);
+			return EXIT_FAILURE;
+		}
+
+		g_print("%s\n", p);
+		g_free(p);
+	}
+
+	freeaddrinfo(ai);
+	return EXIT_SUCCESS;
+}