Align with go library layout

1 files changed, 582 insertions, 0 deletions

diff --git a/conn_linux.go b/conn_linux.go
new file mode 100644
index 0000000..cdba74f
--- /dev/null
+++ b/conn_linux.go
@@ -0,0 +1,582 @@
+/* Copyright 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This implements userspace semantics of "sticky sockets", modeled after
+ * WireGuard's kernelspace implementation.
+ */
+
+package main
+
+import (
+	"encoding/binary"
+	"errors"
+	"golang.org/x/sys/unix"
+	"net"
+	"strconv"
+	"unsafe"
+)
+
+/* Supports source address caching
+ *
+ * Currently there is no way to achieve this within the net package:
+ * See e.g. https://github.com/golang/go/issues/17930
+ * So this code is remains platform dependent.
+ */
+type NativeEndpoint struct {
+	src unix.RawSockaddrInet6
+	dst unix.RawSockaddrInet6
+}
+
+type NativeBind struct {
+	sock4 int
+	sock6 int
+}
+
+var _ Endpoint = (*NativeEndpoint)(nil)
+var _ Bind = NativeBind{}
+
+type IPv4Source struct {
+	src     unix.RawSockaddrInet4
+	Ifindex int32
+}
+
+func htons(val uint16) uint16 {
+	var out [unsafe.Sizeof(val)]byte
+	binary.BigEndian.PutUint16(out[:], val)
+	return *((*uint16)(unsafe.Pointer(&out[0])))
+}
+
+func ntohs(val uint16) uint16 {
+	tmp := ((*[unsafe.Sizeof(val)]byte)(unsafe.Pointer(&val)))
+	return binary.BigEndian.Uint16((*tmp)[:])
+}
+
+func CreateEndpoint(s string) (Endpoint, error) {
+	var end NativeEndpoint
+	addr, err := parseEndpoint(s)
+	if err != nil {
+		return nil, err
+	}
+
+	ipv4 := addr.IP.To4()
+	if ipv4 != nil {
+		dst := (*unix.RawSockaddrInet4)(unsafe.Pointer(&end.dst))
+		dst.Family = unix.AF_INET
+		dst.Port = htons(uint16(addr.Port))
+		dst.Zero = [8]byte{}
+		copy(dst.Addr[:], ipv4)
+		end.ClearSrc()
+		return &end, nil
+	}
+
+	ipv6 := addr.IP.To16()
+	if ipv6 != nil {
+		zone, err := zoneToUint32(addr.Zone)
+		if err != nil {
+			return nil, err
+		}
+		dst := &end.dst
+		dst.Family = unix.AF_INET6
+		dst.Port = htons(uint16(addr.Port))
+		dst.Flowinfo = 0
+		dst.Scope_id = zone
+		copy(dst.Addr[:], ipv6[:])
+		end.ClearSrc()
+		return &end, nil
+	}
+
+	return nil, errors.New("Failed to recognize IP address format")
+}
+
+func CreateBind(port uint16) (Bind, uint16, error) {
+	var err error
+	var bind NativeBind
+
+	bind.sock6, port, err = create6(port)
+	if err != nil {
+		return nil, port, err
+	}
+
+	bind.sock4, port, err = create4(port)
+	if err != nil {
+		unix.Close(bind.sock6)
+	}
+	return bind, port, err
+}
+
+func (bind NativeBind) SetMark(value uint32) error {
+	err := unix.SetsockoptInt(
+		bind.sock6,
+		unix.SOL_SOCKET,
+		unix.SO_MARK,
+		int(value),
+	)
+
+	if err != nil {
+		return err
+	}
+
+	return unix.SetsockoptInt(
+		bind.sock4,
+		unix.SOL_SOCKET,
+		unix.SO_MARK,
+		int(value),
+	)
+}
+
+func closeUnblock(fd int) error {
+	// shutdown to unblock readers
+	unix.Shutdown(fd, unix.SHUT_RD)
+	return unix.Close(fd)
+}
+
+func (bind NativeBind) Close() error {
+	err1 := closeUnblock(bind.sock6)
+	err2 := closeUnblock(bind.sock4)
+	if err1 != nil {
+		return err1
+	}
+	return err2
+}
+
+func (bind NativeBind) ReceiveIPv6(buff []byte) (int, Endpoint, error) {
+	var end NativeEndpoint
+	n, err := receive6(
+		bind.sock6,
+		buff,
+		&end,
+	)
+	return n, &end, err
+}
+
+func (bind NativeBind) ReceiveIPv4(buff []byte) (int, Endpoint, error) {
+	var end NativeEndpoint
+	n, err := receive4(
+		bind.sock4,
+		buff,
+		&end,
+	)
+	return n, &end, err
+}
+
+func (bind NativeBind) Send(buff []byte, end Endpoint) error {
+	nend := end.(*NativeEndpoint)
+	switch nend.dst.Family {
+	case unix.AF_INET6:
+		return send6(bind.sock6, nend, buff)
+	case unix.AF_INET:
+		return send4(bind.sock4, nend, buff)
+	default:
+		return errors.New("Unknown address family of destination")
+	}
+}
+
+func sockaddrToString(addr unix.RawSockaddrInet6) string {
+	var udpAddr net.UDPAddr
+
+	switch addr.Family {
+	case unix.AF_INET6:
+		udpAddr.Port = int(ntohs(addr.Port))
+		udpAddr.IP = addr.Addr[:]
+		return udpAddr.String()
+
+	case unix.AF_INET:
+		ptr := (*unix.RawSockaddrInet4)(unsafe.Pointer(&addr))
+		udpAddr.Port = int(ntohs(ptr.Port))
+		udpAddr.IP = net.IPv4(
+			ptr.Addr[0],
+			ptr.Addr[1],
+			ptr.Addr[2],
+			ptr.Addr[3],
+		)
+		return udpAddr.String()
+
+	default:
+		return "<unknown address family>"
+	}
+}
+
+func rawAddrToIP(addr unix.RawSockaddrInet6) net.IP {
+	switch addr.Family {
+	case unix.AF_INET6:
+		return addr.Addr[:]
+	case unix.AF_INET:
+		ptr := (*unix.RawSockaddrInet4)(unsafe.Pointer(&addr))
+		return net.IPv4(
+			ptr.Addr[0],
+			ptr.Addr[1],
+			ptr.Addr[2],
+			ptr.Addr[3],
+		)
+	default:
+		return nil
+	}
+}
+
+func (end *NativeEndpoint) SrcIP() net.IP {
+	return rawAddrToIP(end.src)
+}
+
+func (end *NativeEndpoint) DstIP() net.IP {
+	return rawAddrToIP(end.dst)
+}
+
+func (end *NativeEndpoint) DstToBytes() []byte {
+	ptr := unsafe.Pointer(&end.src)
+	arr := (*[unix.SizeofSockaddrInet6]byte)(ptr)
+	return arr[:]
+}
+
+func (end *NativeEndpoint) SrcToString() string {
+	return sockaddrToString(end.src)
+}
+
+func (end *NativeEndpoint) DstToString() string {
+	return sockaddrToString(end.dst)
+}
+
+func (end *NativeEndpoint) ClearDst() {
+	end.dst = unix.RawSockaddrInet6{}
+}
+
+func (end *NativeEndpoint) ClearSrc() {
+	end.src = unix.RawSockaddrInet6{}
+}
+
+func zoneToUint32(zone string) (uint32, error) {
+	if zone == "" {
+		return 0, nil
+	}
+	if intr, err := net.InterfaceByName(zone); err == nil {
+		return uint32(intr.Index), nil
+	}
+	n, err := strconv.ParseUint(zone, 10, 32)
+	return uint32(n), err
+}
+
+func create4(port uint16) (int, uint16, error) {
+
+	// create socket
+
+	fd, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		0,
+	)
+
+	if err != nil {
+		return -1, 0, err
+	}
+
+	addr := unix.SockaddrInet4{
+		Port: int(port),
+	}
+
+	// set sockopts and bind
+
+	if err := func() error {
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.SOL_SOCKET,
+			unix.SO_REUSEADDR,
+			1,
+		); err != nil {
+			return err
+		}
+
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.IPPROTO_IP,
+			unix.IP_PKTINFO,
+			1,
+		); err != nil {
+			return err
+		}
+
+		return unix.Bind(fd, &addr)
+	}(); err != nil {
+		unix.Close(fd)
+	}
+
+	return fd, uint16(addr.Port), err
+}
+
+func create6(port uint16) (int, uint16, error) {
+
+	// create socket
+
+	fd, err := unix.Socket(
+		unix.AF_INET6,
+		unix.SOCK_DGRAM,
+		0,
+	)
+
+	if err != nil {
+		return -1, 0, err
+	}
+
+	// set sockopts and bind
+
+	addr := unix.SockaddrInet6{
+		Port: int(port),
+	}
+
+	if err := func() error {
+
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.SOL_SOCKET,
+			unix.SO_REUSEADDR,
+			1,
+		); err != nil {
+			return err
+		}
+
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.IPPROTO_IPV6,
+			unix.IPV6_RECVPKTINFO,
+			1,
+		); err != nil {
+			return err
+		}
+
+		if err := unix.SetsockoptInt(
+			fd,
+			unix.IPPROTO_IPV6,
+			unix.IPV6_V6ONLY,
+			1,
+		); err != nil {
+			return err
+		}
+
+		return unix.Bind(fd, &addr)
+
+	}(); err != nil {
+		unix.Close(fd)
+	}
+
+	return fd, uint16(addr.Port), err
+}
+
+func send6(sock int, end *NativeEndpoint, buff []byte) error {
+
+	// construct message header
+
+	var iovec unix.Iovec
+	iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
+	iovec.SetLen(len(buff))
+
+	cmsg := struct {
+		cmsghdr unix.Cmsghdr
+		pktinfo unix.Inet6Pktinfo
+	}{
+		unix.Cmsghdr{
+			Level: unix.IPPROTO_IPV6,
+			Type:  unix.IPV6_PKTINFO,
+			Len:   unix.SizeofInet6Pktinfo + unix.SizeofCmsghdr,
+		},
+		unix.Inet6Pktinfo{
+			Addr:    end.src.Addr,
+			Ifindex: end.src.Scope_id,
+		},
+	}
+
+	msghdr := unix.Msghdr{
+		Iov:     &iovec,
+		Iovlen:  1,
+		Name:    (*byte)(unsafe.Pointer(&end.dst)),
+		Namelen: unix.SizeofSockaddrInet6,
+		Control: (*byte)(unsafe.Pointer(&cmsg)),
+	}
+
+	msghdr.SetControllen(int(unsafe.Sizeof(cmsg)))
+
+	// sendmsg(sock, &msghdr, 0)
+
+	_, _, errno := unix.Syscall(
+		unix.SYS_SENDMSG,
+		uintptr(sock),
+		uintptr(unsafe.Pointer(&msghdr)),
+		0,
+	)
+
+	if errno == 0 {
+		return nil
+	}
+
+	// clear src and retry
+
+	if errno == unix.EINVAL {
+		end.ClearSrc()
+		cmsg.pktinfo = unix.Inet6Pktinfo{}
+		_, _, errno = unix.Syscall(
+			unix.SYS_SENDMSG,
+			uintptr(sock),
+			uintptr(unsafe.Pointer(&msghdr)),
+			0,
+		)
+	}
+
+	return errno
+}
+
+func send4(sock int, end *NativeEndpoint, buff []byte) error {
+
+	// construct message header
+
+	var iovec unix.Iovec
+	iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
+	iovec.SetLen(len(buff))
+
+	src4 := (*IPv4Source)(unsafe.Pointer(&end.src))
+
+	cmsg := struct {
+		cmsghdr unix.Cmsghdr
+		pktinfo unix.Inet4Pktinfo
+	}{
+		unix.Cmsghdr{
+			Level: unix.IPPROTO_IP,
+			Type:  unix.IP_PKTINFO,
+			Len:   unix.SizeofInet4Pktinfo + unix.SizeofCmsghdr,
+		},
+		unix.Inet4Pktinfo{
+			Spec_dst: src4.src.Addr,
+			Ifindex:  src4.Ifindex,
+		},
+	}
+
+	msghdr := unix.Msghdr{
+		Iov:     &iovec,
+		Iovlen:  1,
+		Name:    (*byte)(unsafe.Pointer(&end.dst)),
+		Namelen: unix.SizeofSockaddrInet4,
+		Control: (*byte)(unsafe.Pointer(&cmsg)),
+		Flags:   0,
+	}
+	msghdr.SetControllen(int(unsafe.Sizeof(cmsg)))
+
+	// sendmsg(sock, &msghdr, 0)
+
+	_, _, errno := unix.Syscall(
+		unix.SYS_SENDMSG,
+		uintptr(sock),
+		uintptr(unsafe.Pointer(&msghdr)),
+		0,
+	)
+
+	// clear source and try again
+
+	if errno == unix.EINVAL {
+		end.ClearSrc()
+		cmsg.pktinfo = unix.Inet4Pktinfo{}
+		_, _, errno = unix.Syscall(
+			unix.SYS_SENDMSG,
+			uintptr(sock),
+			uintptr(unsafe.Pointer(&msghdr)),
+			0,
+		)
+	}
+
+	// errno = 0 is still an error instance
+
+	if errno == 0 {
+		return nil
+	}
+
+	return errno
+}
+
+func receive4(sock int, buff []byte, end *NativeEndpoint) (int, error) {
+
+	// contruct message header
+
+	var iovec unix.Iovec
+	iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
+	iovec.SetLen(len(buff))
+
+	var cmsg struct {
+		cmsghdr unix.Cmsghdr
+		pktinfo unix.Inet4Pktinfo
+	}
+
+	var msghdr unix.Msghdr
+	msghdr.Iov = &iovec
+	msghdr.Iovlen = 1
+	msghdr.Name = (*byte)(unsafe.Pointer(&end.dst))
+	msghdr.Namelen = unix.SizeofSockaddrInet4
+	msghdr.Control = (*byte)(unsafe.Pointer(&cmsg))
+	msghdr.SetControllen(int(unsafe.Sizeof(cmsg)))
+
+	// recvmsg(sock, &mskhdr, 0)
+
+	size, _, errno := unix.Syscall(
+		unix.SYS_RECVMSG,
+		uintptr(sock),
+		uintptr(unsafe.Pointer(&msghdr)),
+		0,
+	)
+
+	if errno != 0 {
+		return 0, errno
+	}
+
+	// update source cache
+
+	if cmsg.cmsghdr.Level == unix.IPPROTO_IP &&
+		cmsg.cmsghdr.Type == unix.IP_PKTINFO &&
+		cmsg.cmsghdr.Len >= unix.SizeofInet4Pktinfo {
+		src4 := (*IPv4Source)(unsafe.Pointer(&end.src))
+		src4.src.Family = unix.AF_INET
+		src4.src.Addr = cmsg.pktinfo.Spec_dst
+		src4.Ifindex = cmsg.pktinfo.Ifindex
+	}
+
+	return int(size), nil
+}
+
+func receive6(sock int, buff []byte, end *NativeEndpoint) (int, error) {
+
+	// contruct message header
+
+	var iovec unix.Iovec
+	iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
+	iovec.SetLen(len(buff))
+
+	var cmsg struct {
+		cmsghdr unix.Cmsghdr
+		pktinfo unix.Inet6Pktinfo
+	}
+
+	var msg unix.Msghdr
+	msg.Iov = &iovec
+	msg.Iovlen = 1
+	msg.Name = (*byte)(unsafe.Pointer(&end.dst))
+	msg.Namelen = uint32(unix.SizeofSockaddrInet6)
+	msg.Control = (*byte)(unsafe.Pointer(&cmsg))
+	msg.SetControllen(int(unsafe.Sizeof(cmsg)))
+
+	// recvmsg(sock, &mskhdr, 0)
+
+	size, _, errno := unix.Syscall(
+		unix.SYS_RECVMSG,
+		uintptr(sock),
+		uintptr(unsafe.Pointer(&msg)),
+		0,
+	)
+
+	if errno != 0 {
+		return 0, errno
+	}
+
+	// update source cache
+
+	if cmsg.cmsghdr.Level == unix.IPPROTO_IPV6 &&
+		cmsg.cmsghdr.Type == unix.IPV6_PKTINFO &&
+		cmsg.cmsghdr.Len >= unix.SizeofInet6Pktinfo {
+		end.src.Family = unix.AF_INET6
+		end.src.Addr = cmsg.pktinfo.Addr
+		end.src.Scope_id = cmsg.pktinfo.Ifindex
+	}
+
+	return int(size), nil
+}