add go-tun2socks code

proxy/socks/socks.go

@@ -0,0 +1,162 @@
+// Code in this file are grabbed from https://github.com/nadoo/glider, which
+// is also referencing another repo: https://github.com/shadowsocks/go-shadowsocks2
+
+package socks
+
+import (
+	"errors"
+	"io"
+	"net"
+	"strconv"
+)
+
+// SOCKS request commands as defined in RFC 1928 section 4.
+const (
+	socks5Connect      = 1
+	socks5Bind         = 2
+	socks5UDPAssociate = 3
+)
+
+// SOCKS address types as defined in RFC 1928 section 5.
+const (
+	socks5IP4    = 1
+	socks5Domain = 3
+	socks5IP6    = 4
+)
+
+var socks5Errors = []error{
+	errors.New(""),
+	errors.New("general failure"),
+	errors.New("connection forbidden"),
+	errors.New("network unreachable"),
+	errors.New("host unreachable"),
+	errors.New("connection refused"),
+	errors.New("TTL expired"),
+	errors.New("command not supported"),
+	errors.New("address type not supported"),
+	errors.New("socks5UDPAssociate"),
+}
+
+// MaxAddrLen is the maximum size of SOCKS address in bytes.
+const MaxAddrLen = 1 + 1 + 255 + 2
+
+// ATYP return the address type
+func ATYP(b byte) int {
+	return int(b &^ 0x8)
+}
+
+// Addr represents a SOCKS address as defined in RFC 1928 section 5.
+type Addr []byte
+
+// String serializes SOCKS address a to string form.
+func (a Addr) String() string {
+	var host, port string
+
+	switch ATYP(a[0]) { // address type
+	case socks5Domain:
+		host = string(a[2 : 2+int(a[1])])
+		port = strconv.Itoa((int(a[2+int(a[1])]) << 8) | int(a[2+int(a[1])+1]))
+	case socks5IP4:
+		host = net.IP(a[1 : 1+net.IPv4len]).String()
+		port = strconv.Itoa((int(a[1+net.IPv4len]) << 8) | int(a[1+net.IPv4len+1]))
+	case socks5IP6:
+		host = net.IP(a[1 : 1+net.IPv6len]).String()
+		port = strconv.Itoa((int(a[1+net.IPv6len]) << 8) | int(a[1+net.IPv6len+1]))
+	}
+
+	return net.JoinHostPort(host, port)
+}
+
+// ParseAddr parses the address in string s. Returns nil if failed.
+func ParseAddr(s string) Addr {
+	var addr Addr
+	host, port, err := net.SplitHostPort(s)
+	if err != nil {
+		return nil
+	}
+	if ip := net.ParseIP(host); ip != nil {
+		if ip4 := ip.To4(); ip4 != nil {
+			addr = make([]byte, 1+net.IPv4len+2)
+			addr[0] = socks5IP4
+			copy(addr[1:], ip4)
+		} else {
+			addr = make([]byte, 1+net.IPv6len+2)
+			addr[0] = socks5IP6
+			copy(addr[1:], ip)
+		}
+	} else {
+		if len(host) > 255 {
+			return nil
+		}
+		addr = make([]byte, 1+1+len(host)+2)
+		addr[0] = socks5Domain
+		addr[1] = byte(len(host))
+		copy(addr[2:], host)
+	}
+
+	portnum, err := strconv.ParseUint(port, 10, 16)
+	if err != nil {
+		return nil
+	}
+
+	addr[len(addr)-2], addr[len(addr)-1] = byte(portnum>>8), byte(portnum)
+
+	return addr
+}
+
+func readAddr(r io.Reader, b []byte) (Addr, error) {
+	if len(b) < MaxAddrLen {
+		return nil, io.ErrShortBuffer
+	}
+	_, err := io.ReadFull(r, b[:1]) // read 1st byte for address type
+	if err != nil {
+		return nil, err
+	}
+
+	switch ATYP(b[0]) {
+	case socks5Domain:
+		_, err = io.ReadFull(r, b[1:2]) // read 2nd byte for domain length
+		if err != nil {
+			return nil, err
+		}
+		_, err = io.ReadFull(r, b[2:2+int(b[1])+2])
+		return b[:1+1+int(b[1])+2], err
+	case socks5IP4:
+		_, err = io.ReadFull(r, b[1:1+net.IPv4len+2])
+		return b[:1+net.IPv4len+2], err
+	case socks5IP6:
+		_, err = io.ReadFull(r, b[1:1+net.IPv6len+2])
+		return b[:1+net.IPv6len+2], err
+	}
+
+	return nil, socks5Errors[8]
+}
+
+// SplitAddr slices a SOCKS address from beginning of b. Returns nil if failed.
+func SplitAddr(b []byte) Addr {
+	addrLen := 1
+	if len(b) < addrLen {
+		return nil
+	}
+
+	switch ATYP(b[0]) {
+	case socks5Domain:
+		if len(b) < 2 {
+			return nil
+		}
+		addrLen = 1 + 1 + int(b[1]) + 2
+	case socks5IP4:
+		addrLen = 1 + net.IPv4len + 2
+	case socks5IP6:
+		addrLen = 1 + net.IPv6len + 2
+	default:
+		return nil
+
+	}
+
+	if len(b) < addrLen {
+		return nil
+	}
+
+	return b[:addrLen]
+}