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/* 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 (
"errors"
"golang.org/x/sys/unix"
"net"
"strconv"
"unsafe"
)
/* Supports source address caching
*
* It is important that the endpoint is only updated after the packet content has been authenticated.
*
* Currently there is no way to achieve this within the net package:
* See e.g. https://github.com/golang/go/issues/17930
*/
type Endpoint struct {
// source (selected based on dst type)
// (could use RawSockaddrAny and unsafe)
srcIPv6 unix.RawSockaddrInet6
srcIPv4 unix.RawSockaddrInet4
srcIf4 int32
dst unix.RawSockaddrAny
}
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 (end *Endpoint) ClearSrc() {
end.srcIf4 = 0
end.srcIPv4 = unix.RawSockaddrInet4{}
end.srcIPv6 = unix.RawSockaddrInet6{}
}
func (end *Endpoint) Set(s string) error {
addr, err := parseEndpoint(s)
if err != nil {
return err
}
ipv6 := addr.IP.To16()
if ipv6 != nil {
zone, err := zoneToUint32(addr.Zone)
if err != nil {
return err
}
ptr := (*unix.RawSockaddrInet6)(unsafe.Pointer(&end.dst))
ptr.Family = unix.AF_INET6
ptr.Port = uint16(addr.Port)
ptr.Flowinfo = 0
ptr.Scope_id = zone
copy(ptr.Addr[:], ipv6[:])
end.ClearSrc()
return nil
}
ipv4 := addr.IP.To4()
if ipv4 != nil {
ptr := (*unix.RawSockaddrInet4)(unsafe.Pointer(&end.dst))
ptr.Family = unix.AF_INET
ptr.Port = uint16(addr.Port)
ptr.Zero = [8]byte{}
copy(ptr.Addr[:], ipv4)
end.ClearSrc()
return nil
}
return errors.New("Failed to recognize IP address format")
}
func send6(sock uintptr, end *Endpoint, buff []byte) error {
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.Inet6Pktinfo{
Addr: end.srcIPv6.Addr,
Ifindex: end.srcIPv6.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,
sock,
uintptr(unsafe.Pointer(&msghdr)),
0,
)
if errno == unix.EINVAL {
end.ClearSrc()
}
return errno
}
func send4(sock uintptr, end *Endpoint, buff []byte) error {
var iovec unix.Iovec
iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
iovec.SetLen(len(buff))
cmsg := struct {
cmsghdr unix.Cmsghdr
pktinfo unix.Inet4Pktinfo
}{
unix.Cmsghdr{
Level: unix.IPPROTO_IP,
Type: unix.IP_PKTINFO,
Len: unix.SizeofInet6Pktinfo,
},
unix.Inet4Pktinfo{
Spec_dst: end.srcIPv4.Addr,
Ifindex: end.srcIf4,
},
}
msghdr := unix.Msghdr{
Iov: &iovec,
Iovlen: 1,
Name: (*byte)(unsafe.Pointer(&end.dst)),
Namelen: unix.SizeofSockaddrInet4,
Control: (*byte)(unsafe.Pointer(&cmsg)),
}
msghdr.SetControllen(int(unsafe.Sizeof(cmsg)))
// sendmsg(sock, &msghdr, 0)
_, _, errno := unix.Syscall(
unix.SYS_SENDMSG,
sock,
uintptr(unsafe.Pointer(&msghdr)),
0,
)
if errno == unix.EINVAL {
end.ClearSrc()
}
return errno
}
func send(c *net.UDPConn, end *Endpoint, buff []byte) error {
// extract underlying file descriptor
file, err := c.File()
if err != nil {
return err
}
sock := file.Fd()
// send depending on address family of dst
family := *((*uint16)(unsafe.Pointer(&end.dst)))
if family == unix.AF_INET {
return send4(sock, end, buff)
} else if family == unix.AF_INET6 {
return send6(sock, end, buff)
}
return errors.New("Unknown address family of source")
}
func receiveIPv4(end *Endpoint, c *net.UDPConn, buff []byte) (error, *net.UDPAddr, *net.UDPAddr) {
file, err := c.File()
if err != nil {
return err, nil, nil
}
var iovec unix.Iovec
iovec.Base = (*byte)(unsafe.Pointer(&buff[0]))
iovec.SetLen(len(buff))
var cmsg struct {
cmsghdr unix.Cmsghdr
pktinfo unix.Inet6Pktinfo // big enough
}
var msg unix.Msghdr
msg.Iov = &iovec
msg.Iovlen = 1
msg.Name = (*byte)(unsafe.Pointer(&end.dst))
msg.Namelen = uint32(unix.SizeofSockaddrAny)
msg.Control = (*byte)(unsafe.Pointer(&cmsg))
msg.SetControllen(int(unsafe.Sizeof(cmsg)))
_, _, errno := unix.Syscall(
unix.SYS_RECVMSG,
file.Fd(),
uintptr(unsafe.Pointer(&msg)),
0,
)
if errno != 0 {
return errno, nil, nil
}
if cmsg.cmsghdr.Level == unix.IPPROTO_IPV6 &&
cmsg.cmsghdr.Type == unix.IPV6_PKTINFO &&
cmsg.cmsghdr.Len >= unix.SizeofInet6Pktinfo {
}
if cmsg.cmsghdr.Level == unix.IPPROTO_IP &&
cmsg.cmsghdr.Type == unix.IP_PKTINFO &&
cmsg.cmsghdr.Len >= unix.SizeofInet4Pktinfo {
info := (*unix.Inet4Pktinfo)(unsafe.Pointer(&cmsg.pktinfo))
println(info)
}
return nil, nil, nil
}
func setMark(conn *net.UDPConn, value uint32) error {
if conn == nil {
return nil
}
file, err := conn.File()
if err != nil {
return err
}
return unix.SetsockoptInt(
int(file.Fd()),
unix.SOL_SOCKET,
unix.SO_MARK,
int(value),
)
}
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