net/Resolver: replace with more advanced implementation

Makefile.am

@@ -594,7 +594,9 @@ libnet_a_SOURCES = \
 	src/net/Features.hxx \
 	src/net/Init.hxx \
 	src/net/ToString.cxx src/net/ToString.hxx \
+	src/net/HostParser.cxx src/net/HostParser.hxx \
 	src/net/Resolver.cxx src/net/Resolver.hxx \
+	src/net/AddressInfo.cxx src/net/AddressInfo.hxx \
 	src/net/StaticSocketAddress.cxx src/net/StaticSocketAddress.hxx \
 	src/net/AllocatedSocketAddress.cxx src/net/AllocatedSocketAddress.hxx \
 	src/net/IPv4Address.cxx src/net/IPv4Address.hxx \

src/event/ServerSocket.cxx

@@ -27,6 +27,7 @@
 #include "net/SocketError.hxx"
 #include "net/UniqueSocketDescriptor.hxx"
 #include "net/Resolver.hxx"
+#include "net/AddressInfo.hxx"
 #include "net/ToString.hxx"
 #include "event/SocketMonitor.hxx"
 #include "fs/AllocatedPath.hxx"
@@ -369,12 +370,9 @@ void
 ServerSocket::AddHost(const char *hostname, unsigned port)
 {
 #ifdef HAVE_TCP
-	struct addrinfo *ai = resolve_host_port(hostname, port,
-						AI_PASSIVE, SOCK_STREAM);
-	AtScopeExit(ai) { freeaddrinfo(ai); };
-
-	for (const struct addrinfo *i = ai; i != nullptr; i = i->ai_next)
-		AddAddress(SocketAddress(i->ai_addr, i->ai_addrlen));
+	for (const auto &i : Resolve(hostname, port,
+				     AI_PASSIVE, SOCK_STREAM))
+		AddAddress(i);
 
 	++next_serial;
 #else /* HAVE_TCP */

src/net/AddressInfo.cxx

+/*
+ * Copyright (C) 2016-2017 Max Kellermann <max.kellermann@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "AddressInfo.hxx"
+
+#include <assert.h>
+
+static constexpr int address_family_ranking[] = {
+#ifdef HAVE_UN
+	AF_LOCAL,
+#endif
+	AF_INET6,
+};
+
+static bool
+IsAddressFamilyBetter(int previous, int next)
+{
+	for (auto i : address_family_ranking) {
+		if (next == i)
+			return previous != i;
+		if (previous == i)
+			return false;
+	}
+
+	return false;
+}
+
+static bool
+IsBetter(const AddressInfo &previous, const AddressInfo &next)
+{
+	return IsAddressFamilyBetter(previous.GetFamily(),
+				     next.GetFamily());
+}
+
+static bool
+IsBetter(const AddressInfo *previous, const AddressInfo &next)
+{
+	return previous == nullptr || IsBetter(*previous, next);
+}
+
+const AddressInfo &
+AddressInfoList::GetBest() const
+{
+	assert(!empty());
+
+	const AddressInfo *best = nullptr;
+
+	for (const auto &i : *this)
+		if (IsBetter(best, i))
+			best = &i;
+
+	assert(best != nullptr);
+	return *best;
+}

src/net/AddressInfo.hxx

+/*
+ * Copyright (C) 2016-2017 Max Kellermann <max.kellermann@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef NET_ADDRESS_INFO_HXX
+#define NET_ADDRESS_INFO_HXX
+
+#include "SocketAddress.hxx"
+
+#include <algorithm>
+#include <utility>
+
+#ifdef _WIN32
+#include <ws2tcpip.h>
+#else
+#include <netdb.h>
+#endif
+
+class AddressInfo : addrinfo {
+	/* this class cannot be instantiated, it can only be cast from
+	   a struct addrinfo pointer */
+	AddressInfo() = delete;
+	~AddressInfo() = delete;
+
+public:
+	constexpr int GetFamily() const {
+		return ai_family;
+	}
+
+	constexpr int GetType() const {
+		return ai_socktype;
+	}
+
+	constexpr int GetProtocol() const {
+		return ai_protocol;
+	}
+
+	constexpr operator SocketAddress() const {
+		return {ai_addr, (SocketAddress::size_type)ai_addrlen};
+	}
+};
+
+class AddressInfoList {
+	struct addrinfo *value = nullptr;
+
+public:
+	AddressInfoList() = default;
+	explicit AddressInfoList(struct addrinfo *_value):value(_value) {}
+
+	AddressInfoList(AddressInfoList &&src)
+		:value(std::exchange(src.value, nullptr)) {}
+
+	~AddressInfoList() {
+		freeaddrinfo(value);
+	}
+
+	AddressInfoList &operator=(AddressInfoList &&src) {
+		std::swap(value, src.value);
+		return *this;
+	}
+
+	bool empty() const {
+		return value == nullptr;
+	}
+
+	const AddressInfo &front() const {
+		return *(const AddressInfo *)value;
+	}
+
+	/**
+	 * Pick the best address from the list, e.g. prefer IPv6 over
+	 * IPv4 (if both are available).  We do this because binding
+	 * to an IPv6 wildcard address also allows accepting IPv4
+	 * connections.
+	 */
+	gcc_pure
+	const AddressInfo &GetBest() const;
+
+	class const_iterator {
+		struct addrinfo *cursor;
+
+	public:
+		explicit constexpr const_iterator(struct addrinfo *_cursor)
+			:cursor(_cursor) {}
+
+		constexpr bool operator==(const_iterator other) const {
+			return cursor == other.cursor;
+		}
+
+		constexpr bool operator!=(const_iterator other) const {
+			return cursor != other.cursor;
+		}
+
+		const_iterator &operator++() {
+			cursor = cursor->ai_next;
+			return *this;
+		}
+
+		constexpr const AddressInfo &operator*() const {
+			return *(const AddressInfo *)cursor;
+		}
+
+		constexpr const AddressInfo *operator->() const {
+			return (const AddressInfo *)cursor;
+		}
+	};
+
+	const_iterator begin() const {
+		return const_iterator(value);
+	}
+
+	const_iterator end() const {
+		return const_iterator(nullptr);
+	}
+};
+
+#endif

src/net/HostParser.cxx

+/*
+ * Copyright 2007-2017 Content Management AG
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "HostParser.hxx"
+#include "util/CharUtil.hxx"
+
+#include <string.h>
+
+static inline bool
+IsValidHostnameChar(char ch)
+{
+	return IsAlphaNumericASCII(ch) ||
+		ch == '-' || ch == '.' ||
+		ch == '*'; /* for wildcards */
+}
+
+static inline bool
+IsValidScopeChar(char ch)
+{
+	return IsAlphaNumericASCII(ch) ||
+		ch == '-' || ch == '_';
+}
+
+static const char *
+FindScopeEnd(const char *p)
+{
+	if (*p == '%' && IsValidScopeChar(p[1])) {
+		p += 2;
+		while (IsValidScopeChar(*p))
+			++p;
+	}
+
+	return p;
+}
+
+static inline bool
+IsValidIPv6Char(char ch)
+{
+	return IsDigitASCII(ch) ||
+		(ch >= 'a' && ch <= 'f') ||
+		(ch >= 'A' && ch <= 'F') ||
+		ch == ':';
+}
+
+static const char *
+FindIPv6End(const char *p)
+{
+	while (IsValidIPv6Char(*p))
+		++p;
+
+	/* allow "%scope" after numeric IPv6 address */
+	p = FindScopeEnd(p);
+
+	return p;
+}
+
+ExtractHostResult
+ExtractHost(const char *src)
+{
+	ExtractHostResult result{nullptr, src};
+	const char *hostname;
+
+	if (IsValidHostnameChar(*src)) {
+		const char *colon = nullptr;
+
+		hostname = src++;
+
+		while (IsValidHostnameChar(*src) || *src == ':') {
+			if (*src == ':') {
+				if (colon != nullptr) {
+					/* found a second colon: assume it's an IPv6
+					   address */
+					result.end = FindIPv6End(src + 1);
+					result.host = {hostname, result.end};
+					return result;
+				} else
+					/* remember the position of the first colon */
+					colon = src;
+			}
+
+			++src;
+		}
+
+		if (colon != nullptr)
+			/* hostname ends at colon */
+			src = colon;
+
+		result.end = src;
+		result.host = {hostname, result.end};
+	} else if (src[0] == ':' && src[1] == ':') {
+		/* IPv6 address beginning with "::" */
+		result.end = FindIPv6End(src + 2);
+		result.host = {src, result.end};
+	} else if (src[0] == '[') {
+		/* "[hostname]:port" (IPv6?) */
+
+		hostname = ++src;
+		const char *end = strchr(hostname, ']');
+		if (end == nullptr || end == hostname)
+			/* failed, return nullptr */
+			return result;
+
+		result.host = {hostname, end};
+		result.end = end + 1;
+	} else {
+		/* failed, return nullptr */
+	}
+
+	return result;
+}

src/net/HostParser.hxx

+/*
+ * Copyright 2007-2017 Content Management AG
+ * All rights reserved.
+ *
+ * author: Max Kellermann <mk@cm4all.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef NET_HOST_PARSER_HXX
+#define NET_HOST_PARSER_HXX
+
+#include "util/StringView.hxx"
+#include "util/Compiler.h"
+
+/**
+ * Result type for ExtractHost().
+ */
+struct ExtractHostResult {
+	/**
+	 * The host part of the address.
+	 *
+	 * If nothing was parsed, then this is nullptr.
+	 */
+	StringView host;
+
+	/**
+	 * Pointer to the first character that was not parsed.  On
+	 * success, this is usually a pointer to the zero terminator or to
+	 * a colon followed by a port number.
+	 *
+	 * If nothing was parsed, then this is a pointer to the given
+	 * source string.
+	 */
+	const char *end;
+
+	constexpr bool HasFailed() const {
+		return host == nullptr;
+	}
+};
+
+/**
+ * Extract the host from a string in the form "IP:PORT" or
+ * "[IPv6]:PORT".  Stops at the first invalid character (e.g. the
+ * colon).
+ *
+ * @param src the input string
+ */
+gcc_pure
+ExtractHostResult
+ExtractHost(const char *src);
+
+#endif

src/net/Resolver.cxx

 /*
- * Copyright 2003-2017 The Music Player Daemon Project
- * http://www.musicpd.org
+ * Copyright 2007-2017 Content Management AG
+ * All rights reserved.
  *
- * 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.
+ * author: Max Kellermann <mk@cm4all.com>
  *
- * 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.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
  *
- * 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.
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "Resolver.hxx"
+#include "AddressInfo.hxx"
+#include "HostParser.hxx"
 #include "util/RuntimeError.hxx"
-
-#include <string>
+#include "util/CharUtil.hxx"
 
 #ifdef _WIN32
 #include <ws2tcpip.h>
 #else
-#include <sys/types.h>
 #include <sys/socket.h>
 #include <netdb.h>
+#include <net/if.h>
 #endif
 
 #include <string.h>
 #include <stdio.h>
+#include <errno.h>
 
-struct addrinfo *
-resolve_host_port(const char *host_port, unsigned default_port,
-		  int flags, int socktype)
+static inline bool
+ai_is_passive(const struct addrinfo *ai)
 {
-	std::string p(host_port);
-	const char *host = p.c_str(), *port = nullptr;
-
-	if (host_port[0] == '[') {
-		/* IPv6 needs enclosing square braces, to
-		   differentiate between IP colons and the port
-		   separator */
-
-		size_t q = p.find(']', 1);
-		if (q != p.npos && p[q + 1] == ':' && p[q + 2] != 0) {
-			p[q] = 0;
-			port = host + q + 2;
-			++host;
-		}
-	}
+	return ai == nullptr || (ai->ai_flags & AI_PASSIVE) != 0;
+}
+
+#ifndef _WIN32
+
+/**
+ * Check if there is an interface name after '%', and if so, replace
+ * it with the interface index, because getaddrinfo() understands only
+ * the index, not the name (tested on Linux/glibc).
+ */
+static void
+FindAndResolveInterfaceName(char *host, size_t size)
+{
+	char *percent = strchr(host, '%');
+	if (percent == nullptr || percent + 64 > host + size)
+		return;
 
-	if (port == nullptr) {
-		/* port is after the colon, but only if it's the only
-		   colon (don't split IPv6 addresses) */
+	char *interface = percent + 1;
+	if (!IsAlphaASCII(*interface))
+		return;
 
-		auto q = p.find(':');
-		if (q != p.npos && p[q + 1] != 0 &&
-		    p.find(':', q + 1) == p.npos) {
-			p[q] = 0;
-			port = host + q + 1;
+	const unsigned i = if_nametoindex(interface);
+	if (i == 0)
+		throw FormatRuntimeError("No such interface: %s", interface);
+
+	sprintf(interface, "%u", i);
+}
+
+#endif
+
+static int
+Resolve(const char *host_and_port, int default_port,
+	const struct addrinfo *hints,
+	struct addrinfo **ai_r)
+{
+	const char *host, *port;
+	char buffer[256], port_string[16];
+
+	if (host_and_port != nullptr) {
+		const auto eh = ExtractHost(host_and_port);
+		if (eh.HasFailed())
+			return EAI_NONAME;
+
+		if (eh.host.size >= sizeof(buffer)) {
+#ifdef _WIN32
+			return EAI_MEMORY;
+#else
+			errno = ENAMETOOLONG;
+			return EAI_SYSTEM;
+#endif
 		}
-	}
 
-	char buffer[32];
-	if (port == nullptr && default_port != 0) {
-		snprintf(buffer, sizeof(buffer), "%u", default_port);
-		port = buffer;
-	}
+		memcpy(buffer, eh.host.data, eh.host.size);
+		buffer[eh.host.size] = 0;
+		host = buffer;
 
-	if ((flags & AI_PASSIVE) != 0 && strcmp(host, "*") == 0)
+#ifndef _WIN32
+		FindAndResolveInterfaceName(buffer, sizeof(buffer));
+#endif
+
+		port = eh.end;
+		if (*port == ':') {
+			/* port specified */
+			++port;
+		} else if (*port == 0) {
+			/* no port specified */
+			snprintf(port_string, sizeof(port_string), "%d", default_port);
+			port = port_string;
+		} else
+			throw std::runtime_error("Garbage after host name");
+
+		if (ai_is_passive(hints) && strcmp(host, "*") == 0)
+			host = nullptr;
+	} else {
 		host = nullptr;
+		snprintf(port_string, sizeof(port_string), "%d", default_port);
+		port = port_string;
+	}
+
+	return getaddrinfo(host, port, hints, ai_r);
+}
 
+AddressInfoList
+Resolve(const char *host_and_port, int default_port,
+	const struct addrinfo *hints)
+{
+	struct addrinfo *ai;
+	int result = Resolve(host_and_port, default_port, hints, &ai);
+	if (result != 0)
+		throw FormatRuntimeError("Failed to resolve '%s': %s",
+					 host_and_port, gai_strerror(result));
+
+	return AddressInfoList(ai);
+}
+
+AddressInfoList
+Resolve(const char *host_port, unsigned default_port, int flags, int socktype)
+{
 	addrinfo hints;
 	memset(&hints, 0, sizeof(hints));
 	hints.ai_flags = flags;
 	hints.ai_family = AF_UNSPEC;
 	hints.ai_socktype = socktype;
 
-	struct addrinfo *ai;
-	int ret = getaddrinfo(host, port, &hints, &ai);
-	if (ret != 0)
-		throw FormatRuntimeError("Failed to look up '%s': %s",
-					 host_port, gai_strerror(ret));
-
-	return ai;
+	return Resolve(host_port, default_port, &hints);
 }

src/net/Resolver.hxx

 /*
- * Copyright 2003-2017 The Music Player Daemon Project
- * http://www.musicpd.org
+ * Copyright 2007-2017 Content Management AG
+ * All rights reserved.
  *
- * 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.
+ * author: Max Kellermann <mk@cm4all.com>
  *
- * 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.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
  *
- * 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.
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef MPD_RESOLVER_HXX
-#define MPD_RESOLVER_HXX
-
-#include "check.h"
-#include "util/Compiler.h"
+#ifndef NET_RESOLVER_HXX
+#define NET_RESOLVER_HXX
 
 struct addrinfo;
+class AddressInfoList;
 
 /**
- * Resolve a specification in the form "host", "host:port",
- * "[host]:port".  This is a convenience wrapper for getaddrinfo().
+ * Resolve the given host name (which may include a port), and fall
+ * back to the given default port.
  *
- * Throws #std::runtime_error on error.
+ * This is a wrapper for getaddrinfo() and it does not support local
+ * sockets.
  *
- * @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()
+ * Throws on error.
  */
-addrinfo *
-resolve_host_port(const char *host_port, unsigned default_port,
-		  int flags, int socktype);
+AddressInfoList
+Resolve(const char *host_and_port, int default_port,
+	const struct addrinfo *hints);
+
+AddressInfoList
+Resolve(const char *host_port, unsigned default_port, int flags, int socktype);
 
 #endif

test/run_resolver.cxx

@@ -19,20 +19,13 @@
 
 #include "config.h"
 #include "net/Resolver.hxx"
+#include "net/AddressInfo.hxx"
 #include "net/ToString.hxx"
 #include "net/SocketAddress.hxx"
 #include "Log.hxx"
 
 #include <exception>
 
-#ifdef _WIN32
-#include <ws2tcpip.h>
-#include <winsock.h>
-#else
-#include <sys/socket.h>
-#include <netdb.h>
-#endif
-
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -43,15 +36,10 @@ try {
 		return EXIT_FAILURE;
 	}
 
-	struct addrinfo *ai =
-		resolve_host_port(argv[1], 80, AI_PASSIVE, SOCK_STREAM);
-
-	for (const struct addrinfo *i = ai; i != NULL; i = i->ai_next) {
-		const auto s = ToString({i->ai_addr, i->ai_addrlen});
-		printf("%s\n", s.c_str());
+	for (const auto &i : Resolve(argv[1], 80, AI_PASSIVE, SOCK_STREAM)) {
+		printf("%s\n", ToString(i).c_str());
 	}
 
-	freeaddrinfo(ai);
 	return EXIT_SUCCESS;
 } catch (...) {
 	LogError(std::current_exception());