Decouple proxy impl. for UDP from redudp like redsocks

Makefile

@@ -1,4 +1,6 @@
-OBJS := parser.o main.o redsocks.o log.o direct.o ipcache.o autoproxy.o encrypt.o shadowsocks.o http-connect.o socks4.o socks5.o http-relay.o base.o base64.o md5.o http-auth.o utils.o redudp.o tcpdns.o gen/version.o
+OBJS := parser.o main.o redsocks.o log.o direct.o ipcache.o autoproxy.o encrypt.o shadowsocks.o http-connect.o \
+        socks4.o socks5.o http-relay.o base.o base64.o md5.o http-auth.o utils.o redudp.o socks5-udp.o \
+        tcpdns.o gen/version.o
 SRCS := $(OBJS:.o=.c)
 CONF := config.h
 DEPS := .depend

redsocks.conf.example

@@ -101,6 +101,9 @@ redudp {
 	login = username;
 	password = pazzw0rd;
 
+	// know types: socks5
+	type = socks5;
+
 	// kernel does not give us this information, so we have to duplicate it
 	// in both iptables rules and configuration file.  By the way, you can
 	// set `local_ip' to 127.45.67.89 if you need more than 65535 ports to
@@ -109,8 +112,11 @@ redudp {
 	dest_ip = 8.8.8.8;
 	dest_port = 53;
 
+        // Do not set it large if this section is for DNS requests. Otherwise,
+        // you may encounter out of file descriptor problem. For DNS requests,
+        // 10s is adequate.
 	udp_timeout = 30;
-	udp_timeout_stream = 180;
+	// udp_timeout_stream = 180;
 }
 
 tcpdns {