resolver: add an asynchronous resolver to make this a serious project

Signed-off-by: hexian000 <hexian000@outlook.com>

README.md

@@ -7,15 +7,16 @@
 
 A lightweight programmable SOCKS4 / SOCKS4A / SOCKS5 / HTTP proxy server that only supports TCP CONNECT requests.
 
-- [Features](#features)
-- [Usage](#usage)
-	- [Basic Usage](#basic-usage)
-	- [Scripting Usage](#scripting-usage)
-- [Runtime Dependencies](#runtime-dependencies)
-- [Building from Source](#building-from-source)
-	- [Dependencies](#dependencies)
-	- [Building with CMake](#building-with-cmake)
-- [Credits](#credits)
+- [neosocksd](#neosocksd)
+	- [Features](#features)
+	- [Usage](#usage)
+		- [Basic Usage](#basic-usage)
+		- [Scripting Usage](#scripting-usage)
+	- [Runtime Dependencies](#runtime-dependencies)
+	- [Building from Source](#building-from-source)
+		- [Dependencies](#dependencies)
+		- [Building with CMake](#building-with-cmake)
+	- [Credits](#credits)
 
 ## Features
 
@@ -120,3 +121,4 @@ See [m.sh](m.sh) for more information about cross compiling support.
 Thanks to:
 - [libev](http://software.schmorp.de/pkg/libev.html)
 - [Lua](https://www.lua.org/)
+- [c-ares](https://c-ares.org/)

src/CMakeLists.txt

@@ -3,6 +3,7 @@ add_executable(neosocksd
     conf.c conf.h
     sockutil.c sockutil.h
     dialer.c dialer.h
+    resolver.c resolver.h
     ruleset.c ruleset.h
     transfer.c transfer.h
     forward.c forward.h
@@ -68,6 +69,22 @@ endif()
 target_include_directories(neosocksd SYSTEM PRIVATE ${LIBEV_INCLUDE_DIR})
 target_link_libraries(neosocksd PRIVATE ${LIBEV_LIBRARY})
 
+# find c-ares
+find_path(LIBCARES_INCLUDE_DIR NAMES ares.h)
+if(BUILD_STATIC OR LINK_STATIC_LIBS)
+    find_library(LIBCARES_LIBRARY NAMES libcares.a)
+else()
+    find_library(LIBCARES_LIBRARY NAMES cares)
+endif()
+if((EXISTS ${LIBCARES_INCLUDE_DIR}) AND (EXISTS ${LIBCARES_LIBRARY}))
+    message(STATUS "c-ares: ${LIBCARES_LIBRARY}")
+    set(WITH_CARES ON)
+else()
+    message(FATAL_ERROR "c-ares not found")
+endif()
+target_include_directories(neosocksd SYSTEM PRIVATE ${LIBCARES_INCLUDE_DIR})
+target_link_libraries(neosocksd PRIVATE ${LIBCARES_LIBRARY})
+
 # find lua
 find_path(LUA_INCLUDE_DIR
     NAMES luaconf.h lua.h lualib.h lauxlib.h

src/conf.c

@@ -1,6 +1,7 @@
 #include "conf.h"
 #include "utils/slog.h"
 #include "utils/minmax.h"
+
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -28,26 +29,31 @@ struct config conf_default(void)
 	return conf;
 }
 
-static bool conf_check_range(
-	const char *key, const size_t value, const size_t min, const size_t max)
-{
-	if (value < min || value > max) {
-		LOGE_F("config: %s is out of range (%zu - %zu)", key, min, max);
-		return false;
-	}
-	return true;
-}
-
 #define RANGE_CHECK(conf, key, min, max)                                       \
-	conf_check_range(#key, (conf)->key, min, max)
+	do {                                                                   \
+		if ((intmax_t)((conf)->key) < (intmax_t)(min) ||               \
+		    (intmax_t)((conf)->key) > (intmax_t)(max)) {               \
+			LOGE_F("config: %s is out of range (%s - %s)", #key,   \
+			       #min, #max);                                    \
+			return false;                                          \
+		}                                                              \
+	} while (0)
+
+#define RANGE_CHECK_FLOAT(conf, key, min, max)                                 \
+	do {                                                                   \
+		if (!(((conf)->key) >= (min) && ((conf)->key) <= (max))) {     \
+			LOGE_F("config: %s is out of range (%s - %s)", #key,   \
+			       #min, #max);                                    \
+			return false;                                          \
+		}                                                              \
+	} while (0)
 
 bool conf_check(const struct config *restrict conf)
 {
-	const bool range_ok =
-		RANGE_CHECK(conf, startup_limit_start, 1, SIZE_MAX) &&
-		RANGE_CHECK(conf, startup_limit_rate, 0, 100) &&
-		RANGE_CHECK(conf, startup_limit_full, 1, SIZE_MAX) &&
-		RANGE_CHECK(
-			conf, log_level, LOG_LEVEL_SILENCE, LOG_LEVEL_VERBOSE);
-	return range_ok;
+	RANGE_CHECK_FLOAT(conf, timeout, 5.0, 86400.0);
+	RANGE_CHECK(conf, startup_limit_start, 1, INT_MAX);
+	RANGE_CHECK(conf, startup_limit_rate, 0, 100);
+	RANGE_CHECK(conf, startup_limit_full, 1, INT_MAX);
+	RANGE_CHECK(conf, log_level, LOG_LEVEL_SILENCE, LOG_LEVEL_VERBOSE);
+	return true;
 }

src/config.h.in

@@ -12,6 +12,8 @@
 #cmakedefine01 HAVE_SO_REUSEPORT
 #cmakedefine01 HAVE_TCP_FASTOPEN
 
+#cmakedefine01 WITH_CARES
+
 #define WITH_TPROXY (!TARGET_POSIX && HAVE_IP_TRANSPARENT)
 #define WITH_NETDEVICE (!TARGET_POSIX && HAVE_SO_BINDTODEVICE)
 #define WITH_REUSEPORT (!TARGET_POSIX && HAVE_SO_REUSEPORT)

src/dialer.c

@@ -1,6 +1,7 @@
 #include "dialer.h"
 #include "net/http.h"
 #include "proto/domain.h"
+#include "resolver.h"
 #include "utils/buffer.h"
 #include "utils/serialize.h"
 #include "utils/slog.h"
@@ -162,6 +163,7 @@ void dialreq_free(struct dialreq *restrict req)
 
 enum dialer_state {
 	STATE_INIT,
+	STATE_RESOLVE,
 	STATE_CONNECT,
 	STATE_HANDSHAKE1,
 	STATE_HANDSHAKE2,
@@ -758,25 +760,17 @@ static bool connect_sa(
 	return true;
 }
 
-static bool connect_domain(
-	struct dialer *restrict d, struct ev_loop *loop,
-	const struct domain_name *domain)
+static void
+resolve_cb(struct ev_loop *loop, const struct sockaddr *sa, void *data)
 {
-	sockaddr_max_t addr;
-
-	char host[FQDN_MAX_LENGTH + 1];
-	memcpy(host, domain->name, domain->len);
-	host[domain->len] = '\0';
-	if (!resolve_hostname(&addr, host, d->conf->resolve_pf)) {
-		return false;
-	}
-
-	const struct sockaddr *sa = &addr.sa;
-	if (LOGLEVEL(LOG_LEVEL_DEBUG)) {
-		char addr_str[64];
-		format_sa(sa, addr_str, sizeof(addr_str));
-		LOG_F(LOG_LEVEL_DEBUG, "resolve: \"%.*s\" is \"%s\"",
-		      (int)domain->len, domain->name, addr_str);
+	struct dialer *restrict d = data;
+	const struct domain_name *restrict domain =
+		d->req->num_proxy > 0 ? &d->req->proxy[0].addr.domain :
+					&d->req->addr.domain;
+	if (sa == NULL) {
+		LOGE_F("name resolution failed: \"%.*s\"", (int)domain->len,
+		       domain->name);
+		return;
 	}
 
 	const uint16_t port = d->req->addr.port;
@@ -793,7 +787,16 @@ static bool connect_domain(
 		FAIL();
 	}
 
-	return connect_sa(d, loop, sa);
+	if (LOGLEVEL(LOG_LEVEL_DEBUG)) {
+		char addr_str[64];
+		format_sa(sa, addr_str, sizeof(addr_str));
+		LOG_F(LOG_LEVEL_DEBUG, "resolve: \"%.*s\" is \"%s\"",
+		      (int)domain->len, domain->name, addr_str);
+	}
+
+	if (!connect_sa(d, loop, sa)) {
+		dialer_fail(d, loop);
+	}
 }
 
 static void
@@ -857,9 +860,11 @@ bool dialer_start(
 		}
 	} break;
 	case ATYP_DOMAIN: {
-		if (!connect_domain(d, loop, &addr->domain)) {
-			return false;
-		}
+		char host[FQDN_MAX_LENGTH + 1];
+		memcpy(host, addr->domain.name, addr->domain.len);
+		host[addr->domain.len] = '\0';
+		d->state = STATE_RESOLVE;
+		resolver_do(loop, host, d->conf->resolve_pf, resolve_cb, d);
 	} break;
 	default:
 		FAIL();

src/main.c

@@ -50,6 +50,9 @@ static void print_usage(const char *argv0)
 		"  -l, --listen <address>     proxy listen address\n"
 		"  --http                     run a HTTP CONNECT server instead of SOCKS\n"
 		"  -f, --forward <address>    run TCP port forwarding instead of SOCKS\n"
+		// "  -x, --proxy [proxy1,[...,[proxyN,]]]<address>\n"
+		// "                             run proxy forwarding instead of SOCKS\n"
+		// "  --nameserver <address>     ignore resolv.conf\n"
 #if WITH_NETDEVICE
 		"  -i, --netdev <name>        bind outgoing connections to network device\n"
 #endif