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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
*
* This implements userspace semantics of "sticky sockets", modeled after
* WireGuard's kernelspace implementation. This is more or less a straight port
* of the sticky-sockets.c example code:
* https://git.zx2c4.com/WireGuard/tree/contrib/examples/sticky-sockets/sticky-sockets.c
*
* 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.
*/
package device
import (
"sync"
"unsafe"
"golang.org/x/sys/unix"
"golang.zx2c4.com/wireguard/conn"
"golang.zx2c4.com/wireguard/rwcancel"
)
func (device *Device) startRouteListener(bind conn.Bind) (*rwcancel.RWCancel, error) {
if !conn.StdNetSupportsStickySockets {
return nil, nil
}
if _, ok := bind.(*conn.StdNetBind); !ok {
return nil, nil
}
netlinkSock, err := createNetlinkRouteSocket()
if err != nil {
return nil, err
}
netlinkCancel, err := rwcancel.NewRWCancel(netlinkSock)
if err != nil {
unix.Close(netlinkSock)
return nil, err
}
go device.routineRouteListener(bind, netlinkSock, netlinkCancel)
return netlinkCancel, nil
}
func (device *Device) routineRouteListener(bind conn.Bind, netlinkSock int, netlinkCancel *rwcancel.RWCancel) {
type peerEndpointPtr struct {
peer *Peer
endpoint *conn.Endpoint
}
var reqPeer map[uint32]peerEndpointPtr
var reqPeerLock sync.Mutex
defer netlinkCancel.Close()
defer unix.Close(netlinkSock)
for msg := make([]byte, 1<<16); ; {
var err error
var msgn int
for {
msgn, _, _, _, err = unix.Recvmsg(netlinkSock, msg[:], nil, 0)
if err == nil || !rwcancel.RetryAfterError(err) {
break
}
if !netlinkCancel.ReadyRead() {
return
}
}
if err != nil {
return
}
for remain := msg[:msgn]; len(remain) >= unix.SizeofNlMsghdr; {
hdr := *(*unix.NlMsghdr)(unsafe.Pointer(&remain[0]))
if uint(hdr.Len) > uint(len(remain)) {
break
}
switch hdr.Type {
case unix.RTM_NEWROUTE, unix.RTM_DELROUTE:
if hdr.Seq <= MaxPeers && hdr.Seq > 0 {
if uint(len(remain)) < uint(hdr.Len) {
break
}
if hdr.Len > unix.SizeofNlMsghdr+unix.SizeofRtMsg {
attr := remain[unix.SizeofNlMsghdr+unix.SizeofRtMsg:]
for {
if uint(len(attr)) < uint(unix.SizeofRtAttr) {
break
}
attrhdr := *(*unix.RtAttr)(unsafe.Pointer(&attr[0]))
if attrhdr.Len < unix.SizeofRtAttr || uint(len(attr)) < uint(attrhdr.Len) {
break
}
if attrhdr.Type == unix.RTA_OIF && attrhdr.Len == unix.SizeofRtAttr+4 {
ifidx := *(*uint32)(unsafe.Pointer(&attr[unix.SizeofRtAttr]))
reqPeerLock.Lock()
if reqPeer == nil {
reqPeerLock.Unlock()
break
}
pePtr, ok := reqPeer[hdr.Seq]
reqPeerLock.Unlock()
if !ok {
break
}
pePtr.peer.endpoint.Lock()
if &pePtr.peer.endpoint.val != pePtr.endpoint {
pePtr.peer.endpoint.Unlock()
break
}
if uint32(pePtr.peer.endpoint.val.(*conn.StdNetEndpoint).SrcIfidx()) == ifidx {
pePtr.peer.endpoint.Unlock()
break
}
pePtr.peer.endpoint.clearSrcOnTx = true
pePtr.peer.endpoint.Unlock()
}
attr = attr[attrhdr.Len:]
}
}
break
}
reqPeerLock.Lock()
reqPeer = make(map[uint32]peerEndpointPtr)
reqPeerLock.Unlock()
go func() {
device.peers.RLock()
i := uint32(1)
for _, peer := range device.peers.keyMap {
peer.endpoint.Lock()
if peer.endpoint.val == nil {
peer.endpoint.Unlock()
continue
}
nativeEP, _ := peer.endpoint.val.(*conn.StdNetEndpoint)
if nativeEP == nil {
peer.endpoint.Unlock()
continue
}
if nativeEP.DstIP().Is6() || nativeEP.SrcIfidx() == 0 {
peer.endpoint.Unlock()
break
}
nlmsg := struct {
hdr unix.NlMsghdr
msg unix.RtMsg
dsthdr unix.RtAttr
dst [4]byte
srchdr unix.RtAttr
src [4]byte
markhdr unix.RtAttr
mark uint32
}{
unix.NlMsghdr{
Type: uint16(unix.RTM_GETROUTE),
Flags: unix.NLM_F_REQUEST,
Seq: i,
},
unix.RtMsg{
Family: unix.AF_INET,
Dst_len: 32,
Src_len: 32,
},
unix.RtAttr{
Len: 8,
Type: unix.RTA_DST,
},
nativeEP.DstIP().As4(),
unix.RtAttr{
Len: 8,
Type: unix.RTA_SRC,
},
nativeEP.SrcIP().As4(),
unix.RtAttr{
Len: 8,
Type: unix.RTA_MARK,
},
device.net.fwmark,
}
nlmsg.hdr.Len = uint32(unsafe.Sizeof(nlmsg))
reqPeerLock.Lock()
reqPeer[i] = peerEndpointPtr{
peer: peer,
endpoint: &peer.endpoint.val,
}
reqPeerLock.Unlock()
peer.endpoint.Unlock()
i++
_, err := netlinkCancel.Write((*[unsafe.Sizeof(nlmsg)]byte)(unsafe.Pointer(&nlmsg))[:])
if err != nil {
break
}
}
device.peers.RUnlock()
}()
}
remain = remain[hdr.Len:]
}
}
}
func createNetlinkRouteSocket() (int, error) {
sock, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW|unix.SOCK_CLOEXEC, unix.NETLINK_ROUTE)
if err != nil {
return -1, err
}
saddr := &unix.SockaddrNetlink{
Family: unix.AF_NETLINK,
Groups: unix.RTMGRP_IPV4_ROUTE,
}
err = unix.Bind(sock, saddr)
if err != nil {
unix.Close(sock)
return -1, err
}
return sock, nil
}
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