New: redir proxy

proxy/redir/tcp_darwin.go

@@ -0,0 +1,58 @@
+package redir
+
+import (
+	"net"
+	"syscall"
+	"unsafe"
+
+	"github.com/riobard/go-shadowsocks2/socks"
+)
+
+func parserPacket(c net.Conn) (socks.Addr, error) {
+	const (
+		PfInout     = 0
+		PfIn        = 1
+		PfOut       = 2
+		IOCOut      = 0x40000000
+		IOCIn       = 0x80000000
+		IOCInOut    = IOCIn | IOCOut
+		IOCPARMMask = 0x1FFF
+		LEN         = 4*16 + 4*4 + 4*1
+		// #define	_IOC(inout,group,num,len) (inout | ((len & IOCPARMMask) << 16) | ((group) << 8) | (num))
+		// #define	_IOWR(g,n,t)	_IOC(IOCInOut,	(g), (n), sizeof(t))
+		// #define DIOCNATLOOK		_IOWR('D', 23, struct pfioc_natlook)
+		DIOCNATLOOK = IOCInOut | ((LEN & IOCPARMMask) << 16) | ('D' << 8) | 23
+	)
+
+	fd, err := syscall.Open("/dev/pf", 0, syscall.O_RDONLY)
+	if err != nil {
+		return nil, err
+	}
+	defer syscall.Close(fd)
+
+	nl := struct { // struct pfioc_natlook
+		saddr, daddr, rsaddr, rdaddr       [16]byte
+		sxport, dxport, rsxport, rdxport   [4]byte
+		af, proto, protoVariant, direction uint8
+	}{
+		af:        syscall.AF_INET,
+		proto:     syscall.IPPROTO_TCP,
+		direction: PfOut,
+	}
+	saddr := c.RemoteAddr().(*net.TCPAddr)
+	daddr := c.LocalAddr().(*net.TCPAddr)
+	copy(nl.saddr[:], saddr.IP)
+	copy(nl.daddr[:], daddr.IP)
+	nl.sxport[0], nl.sxport[1] = byte(saddr.Port>>8), byte(saddr.Port)
+	nl.dxport[0], nl.dxport[1] = byte(daddr.Port>>8), byte(daddr.Port)
+
+	if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), DIOCNATLOOK, uintptr(unsafe.Pointer(&nl))); errno != 0 {
+		return nil, errno
+	}
+
+	addr := make([]byte, 1+net.IPv4len+2)
+	addr[0] = socks.AtypIPv4
+	copy(addr[1:1+net.IPv4len], nl.rdaddr[:4])
+	copy(addr[1+net.IPv4len:], nl.rdxport[:2])
+	return addr, nil
+}