wireguard-go/conn/bind_linux.go
Josh Bleecher Snyder 10533c3e73 all: make conn.Bind.Open return a slice of receive functions
Instead of hard-coding exactly two sources from which
to receive packets (an IPv4 source and an IPv6 source),
allow the conn.Bind to specify a set of sources.

Beneficial consequences:

* If there's no IPv6 support on a system,
  conn.Bind.Open can choose not to return a receive function for it,
  which is simpler than tracking that state in the bind.
  This simplification removes existing data races from both
  conn.StdNetBind and bindtest.ChannelBind.
* If there are more than two sources on a system,
  the conn.Bind no longer needs to add a separate muxing layer.

Signed-off-by: Josh Bleecher Snyder <josharian@gmail.com>
2021-04-02 11:07:08 -06:00

580 lines
11 KiB
Go

/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
*/
package conn
import (
"errors"
"net"
"strconv"
"sync"
"syscall"
"unsafe"
"golang.org/x/sys/unix"
)
type ipv4Source struct {
Src [4]byte
Ifindex int32
}
type ipv6Source struct {
src [16]byte
// ifindex belongs in dst.ZoneId
}
type LinuxSocketEndpoint struct {
mu sync.Mutex
dst [unsafe.Sizeof(unix.SockaddrInet6{})]byte
src [unsafe.Sizeof(ipv6Source{})]byte
isV6 bool
}
func (endpoint *LinuxSocketEndpoint) Src4() *ipv4Source { return endpoint.src4() }
func (endpoint *LinuxSocketEndpoint) Dst4() *unix.SockaddrInet4 { return endpoint.dst4() }
func (endpoint *LinuxSocketEndpoint) IsV6() bool { return endpoint.isV6 }
func (endpoint *LinuxSocketEndpoint) src4() *ipv4Source {
return (*ipv4Source)(unsafe.Pointer(&endpoint.src[0]))
}
func (endpoint *LinuxSocketEndpoint) src6() *ipv6Source {
return (*ipv6Source)(unsafe.Pointer(&endpoint.src[0]))
}
func (endpoint *LinuxSocketEndpoint) dst4() *unix.SockaddrInet4 {
return (*unix.SockaddrInet4)(unsafe.Pointer(&endpoint.dst[0]))
}
func (endpoint *LinuxSocketEndpoint) dst6() *unix.SockaddrInet6 {
return (*unix.SockaddrInet6)(unsafe.Pointer(&endpoint.dst[0]))
}
// LinuxSocketBind uses sendmsg and recvmsg to implement a full bind with sticky sockets on Linux.
type LinuxSocketBind struct {
// mu guards sock4 and sock6 and the associated fds.
// As long as someone holds mu (read or write), the associated fds are valid.
mu sync.RWMutex
sock4 int
sock6 int
}
func NewLinuxSocketBind() Bind { return &LinuxSocketBind{sock4: -1, sock6: -1} }
func NewDefaultBind() Bind { return NewLinuxSocketBind() }
var _ Endpoint = (*LinuxSocketEndpoint)(nil)
var _ Bind = (*LinuxSocketBind)(nil)
func (*LinuxSocketBind) ParseEndpoint(s string) (Endpoint, error) {
var end LinuxSocketEndpoint
addr, err := parseEndpoint(s)
if err != nil {
return nil, err
}
ipv4 := addr.IP.To4()
if ipv4 != nil {
dst := end.dst4()
end.isV6 = false
dst.Port = addr.Port
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.dst6()
end.isV6 = true
dst.Port = addr.Port
dst.ZoneId = zone
copy(dst.Addr[:], ipv6[:])
end.ClearSrc()
return &end, nil
}
return nil, errors.New("invalid IP address")
}
func (bind *LinuxSocketBind) Open(port uint16) ([]ReceiveFunc, uint16, error) {
bind.mu.Lock()
defer bind.mu.Unlock()
var err error
var newPort uint16
var tries int
if bind.sock4 != -1 || bind.sock6 != -1 {
return nil, 0, ErrBindAlreadyOpen
}
originalPort := port
again:
port = originalPort
var sock4, sock6 int
// Attempt ipv6 bind, update port if successful.
sock6, newPort, err = create6(port)
if err != nil {
if !errors.Is(err, syscall.EAFNOSUPPORT) {
return nil, 0, err
}
} else {
port = newPort
}
// Attempt ipv4 bind, update port if successful.
sock4, newPort, err = create4(port)
if err != nil {
if originalPort == 0 && errors.Is(err, syscall.EADDRINUSE) && tries < 100 {
unix.Close(sock6)
tries++
goto again
}
if !errors.Is(err, syscall.EAFNOSUPPORT) {
unix.Close(sock6)
return nil, 0, err
}
} else {
port = newPort
}
var fns []ReceiveFunc
if sock4 != -1 {
fns = append(fns, makeReceiveIPv4(sock4))
bind.sock4 = sock4
}
if sock6 != -1 {
fns = append(fns, makeReceiveIPv6(sock6))
bind.sock6 = sock6
}
if len(fns) == 0 {
return nil, 0, syscall.EAFNOSUPPORT
}
return fns, port, nil
}
func (bind *LinuxSocketBind) SetMark(value uint32) error {
bind.mu.RLock()
defer bind.mu.RUnlock()
if bind.sock6 != -1 {
err := unix.SetsockoptInt(
bind.sock6,
unix.SOL_SOCKET,
unix.SO_MARK,
int(value),
)
if err != nil {
return err
}
}
if bind.sock4 != -1 {
err := unix.SetsockoptInt(
bind.sock4,
unix.SOL_SOCKET,
unix.SO_MARK,
int(value),
)
if err != nil {
return err
}
}
return nil
}
func (bind *LinuxSocketBind) Close() error {
// Take a readlock to shut down the sockets...
bind.mu.RLock()
if bind.sock6 != -1 {
unix.Shutdown(bind.sock6, unix.SHUT_RDWR)
}
if bind.sock4 != -1 {
unix.Shutdown(bind.sock4, unix.SHUT_RDWR)
}
bind.mu.RUnlock()
// ...and a write lock to close the fd.
// This ensures that no one else is using the fd.
bind.mu.Lock()
defer bind.mu.Unlock()
var err1, err2 error
if bind.sock6 != -1 {
err1 = unix.Close(bind.sock6)
bind.sock6 = -1
}
if bind.sock4 != -1 {
err2 = unix.Close(bind.sock4)
bind.sock4 = -1
}
if err1 != nil {
return err1
}
return err2
}
func makeReceiveIPv6(sock int) ReceiveFunc {
return func(buff []byte) (int, Endpoint, error) {
var end LinuxSocketEndpoint
n, err := receive6(sock, buff, &end)
return n, &end, err
}
}
func makeReceiveIPv4(sock int) ReceiveFunc {
return func(buff []byte) (int, Endpoint, error) {
var end LinuxSocketEndpoint
n, err := receive4(sock, buff, &end)
return n, &end, err
}
}
func (bind *LinuxSocketBind) Send(buff []byte, end Endpoint) error {
nend, ok := end.(*LinuxSocketEndpoint)
if !ok {
return ErrWrongEndpointType
}
bind.mu.RLock()
defer bind.mu.RUnlock()
if !nend.isV6 {
if bind.sock4 == -1 {
return net.ErrClosed
}
return send4(bind.sock4, nend, buff)
} else {
if bind.sock6 == -1 {
return net.ErrClosed
}
return send6(bind.sock6, nend, buff)
}
}
func (end *LinuxSocketEndpoint) SrcIP() net.IP {
if !end.isV6 {
return net.IPv4(
end.src4().Src[0],
end.src4().Src[1],
end.src4().Src[2],
end.src4().Src[3],
)
} else {
return end.src6().src[:]
}
}
func (end *LinuxSocketEndpoint) DstIP() net.IP {
if !end.isV6 {
return net.IPv4(
end.dst4().Addr[0],
end.dst4().Addr[1],
end.dst4().Addr[2],
end.dst4().Addr[3],
)
} else {
return end.dst6().Addr[:]
}
}
func (end *LinuxSocketEndpoint) DstToBytes() []byte {
if !end.isV6 {
return (*[unsafe.Offsetof(end.dst4().Addr) + unsafe.Sizeof(end.dst4().Addr)]byte)(unsafe.Pointer(end.dst4()))[:]
} else {
return (*[unsafe.Offsetof(end.dst6().Addr) + unsafe.Sizeof(end.dst6().Addr)]byte)(unsafe.Pointer(end.dst6()))[:]
}
}
func (end *LinuxSocketEndpoint) SrcToString() string {
return end.SrcIP().String()
}
func (end *LinuxSocketEndpoint) DstToString() string {
var udpAddr net.UDPAddr
udpAddr.IP = end.DstIP()
if !end.isV6 {
udpAddr.Port = end.dst4().Port
} else {
udpAddr.Port = end.dst6().Port
}
return udpAddr.String()
}
func (end *LinuxSocketEndpoint) ClearDst() {
for i := range end.dst {
end.dst[i] = 0
}
}
func (end *LinuxSocketEndpoint) ClearSrc() {
for i := range end.src {
end.src[i] = 0
}
}
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.IPPROTO_IP,
unix.IP_PKTINFO,
1,
); err != nil {
return err
}
return unix.Bind(fd, &addr)
}(); err != nil {
unix.Close(fd)
return -1, 0, err
}
sa, err := unix.Getsockname(fd)
if err == nil {
addr.Port = sa.(*unix.SockaddrInet4).Port
}
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.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 -1, 0, err
}
sa, err := unix.Getsockname(fd)
if err == nil {
addr.Port = sa.(*unix.SockaddrInet6).Port
}
return fd, uint16(addr.Port), err
}
func send4(sock int, end *LinuxSocketEndpoint, buff []byte) error {
// construct message header
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: end.src4().Src,
Ifindex: end.src4().Ifindex,
},
}
end.mu.Lock()
_, err := unix.SendmsgN(sock, buff, (*[unsafe.Sizeof(cmsg)]byte)(unsafe.Pointer(&cmsg))[:], end.dst4(), 0)
end.mu.Unlock()
if err == nil {
return nil
}
// clear src and retry
if err == unix.EINVAL {
end.ClearSrc()
cmsg.pktinfo = unix.Inet4Pktinfo{}
end.mu.Lock()
_, err = unix.SendmsgN(sock, buff, (*[unsafe.Sizeof(cmsg)]byte)(unsafe.Pointer(&cmsg))[:], end.dst4(), 0)
end.mu.Unlock()
}
return err
}
func send6(sock int, end *LinuxSocketEndpoint, buff []byte) error {
// construct message header
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.src6().src,
Ifindex: end.dst6().ZoneId,
},
}
if cmsg.pktinfo.Addr == [16]byte{} {
cmsg.pktinfo.Ifindex = 0
}
end.mu.Lock()
_, err := unix.SendmsgN(sock, buff, (*[unsafe.Sizeof(cmsg)]byte)(unsafe.Pointer(&cmsg))[:], end.dst6(), 0)
end.mu.Unlock()
if err == nil {
return nil
}
// clear src and retry
if err == unix.EINVAL {
end.ClearSrc()
cmsg.pktinfo = unix.Inet6Pktinfo{}
end.mu.Lock()
_, err = unix.SendmsgN(sock, buff, (*[unsafe.Sizeof(cmsg)]byte)(unsafe.Pointer(&cmsg))[:], end.dst6(), 0)
end.mu.Unlock()
}
return err
}
func receive4(sock int, buff []byte, end *LinuxSocketEndpoint) (int, error) {
// construct message header
var cmsg struct {
cmsghdr unix.Cmsghdr
pktinfo unix.Inet4Pktinfo
}
size, _, _, newDst, err := unix.Recvmsg(sock, buff, (*[unsafe.Sizeof(cmsg)]byte)(unsafe.Pointer(&cmsg))[:], 0)
if err != nil {
return 0, err
}
end.isV6 = false
if newDst4, ok := newDst.(*unix.SockaddrInet4); ok {
*end.dst4() = *newDst4
}
// update source cache
if cmsg.cmsghdr.Level == unix.IPPROTO_IP &&
cmsg.cmsghdr.Type == unix.IP_PKTINFO &&
cmsg.cmsghdr.Len >= unix.SizeofInet4Pktinfo {
end.src4().Src = cmsg.pktinfo.Spec_dst
end.src4().Ifindex = cmsg.pktinfo.Ifindex
}
return size, nil
}
func receive6(sock int, buff []byte, end *LinuxSocketEndpoint) (int, error) {
// construct message header
var cmsg struct {
cmsghdr unix.Cmsghdr
pktinfo unix.Inet6Pktinfo
}
size, _, _, newDst, err := unix.Recvmsg(sock, buff, (*[unsafe.Sizeof(cmsg)]byte)(unsafe.Pointer(&cmsg))[:], 0)
if err != nil {
return 0, err
}
end.isV6 = true
if newDst6, ok := newDst.(*unix.SockaddrInet6); ok {
*end.dst6() = *newDst6
}
// update source cache
if cmsg.cmsghdr.Level == unix.IPPROTO_IPV6 &&
cmsg.cmsghdr.Type == unix.IPV6_PKTINFO &&
cmsg.cmsghdr.Len >= unix.SizeofInet6Pktinfo {
end.src6().src = cmsg.pktinfo.Addr
end.dst6().ZoneId = cmsg.pktinfo.Ifindex
}
return size, nil
}