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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2022 WireGuard LLC. All Rights Reserved.
*/
package conn
import (
"errors"
"net"
"net/netip"
"sync"
"syscall"
)
// StdNetBind is meant to be a temporary solution on platforms for which
// the sticky socket / source caching behavior has not yet been implemented.
// It uses the Go's net package to implement networking.
// See LinuxSocketBind for a proper implementation on the Linux platform.
type StdNetBind struct {
mu sync.Mutex // protects following fields
ipv4 *net.UDPConn
ipv6 *net.UDPConn
blackhole4 bool
blackhole6 bool
}
func NewStdNetBind() Bind { return &StdNetBind{} }
type StdNetEndpoint netip.AddrPort
var (
_ Bind = (*StdNetBind)(nil)
_ Endpoint = StdNetEndpoint{}
)
func (*StdNetBind) ParseEndpoint(s string) (Endpoint, error) {
e, err := netip.ParseAddrPort(s)
return asEndpoint(e), err
}
func (StdNetEndpoint) ClearSrc() {}
func (e StdNetEndpoint) DstIP() netip.Addr {
return (netip.AddrPort)(e).Addr()
}
func (e StdNetEndpoint) SrcIP() netip.Addr {
return netip.Addr{} // not supported
}
func (e StdNetEndpoint) DstToBytes() []byte {
b, _ := (netip.AddrPort)(e).MarshalBinary()
return b
}
func (e StdNetEndpoint) DstToString() string {
return (netip.AddrPort)(e).String()
}
func (e StdNetEndpoint) SrcToString() string {
return ""
}
func listenNet(network string, port int) (*net.UDPConn, int, error) {
conn, err := net.ListenUDP(network, &net.UDPAddr{Port: port})
if err != nil {
return nil, 0, err
}
// Retrieve port.
laddr := conn.LocalAddr()
uaddr, err := net.ResolveUDPAddr(
laddr.Network(),
laddr.String(),
)
if err != nil {
return nil, 0, err
}
return conn, uaddr.Port, nil
}
func (bind *StdNetBind) Open(uport uint16) ([]ReceiveFunc, uint16, error) {
bind.mu.Lock()
defer bind.mu.Unlock()
var err error
var tries int
if bind.ipv4 != nil || bind.ipv6 != nil {
return nil, 0, ErrBindAlreadyOpen
}
// Attempt to open ipv4 and ipv6 listeners on the same port.
// If uport is 0, we can retry on failure.
again:
port := int(uport)
var ipv4, ipv6 *net.UDPConn
ipv4, port, err = listenNet("udp4", port)
if err != nil && !errors.Is(err, syscall.EAFNOSUPPORT) {
return nil, 0, err
}
// Listen on the same port as we're using for ipv4.
ipv6, port, err = listenNet("udp6", port)
if uport == 0 && errors.Is(err, syscall.EADDRINUSE) && tries < 100 {
ipv4.Close()
tries++
goto again
}
if err != nil && !errors.Is(err, syscall.EAFNOSUPPORT) {
ipv4.Close()
return nil, 0, err
}
var fns []ReceiveFunc
if ipv4 != nil {
fns = append(fns, bind.makeReceiveIPv4(ipv4))
bind.ipv4 = ipv4
}
if ipv6 != nil {
fns = append(fns, bind.makeReceiveIPv6(ipv6))
bind.ipv6 = ipv6
}
if len(fns) == 0 {
return nil, 0, syscall.EAFNOSUPPORT
}
return fns, uint16(port), nil
}
func (bind *StdNetBind) Close() error {
bind.mu.Lock()
defer bind.mu.Unlock()
var err1, err2 error
if bind.ipv4 != nil {
err1 = bind.ipv4.Close()
bind.ipv4 = nil
}
if bind.ipv6 != nil {
err2 = bind.ipv6.Close()
bind.ipv6 = nil
}
bind.blackhole4 = false
bind.blackhole6 = false
if err1 != nil {
return err1
}
return err2
}
func (*StdNetBind) makeReceiveIPv4(conn *net.UDPConn) ReceiveFunc {
return func(buff []byte) (int, Endpoint, error) {
n, endpoint, err := conn.ReadFromUDPAddrPort(buff)
return n, asEndpoint(endpoint), err
}
}
func (*StdNetBind) makeReceiveIPv6(conn *net.UDPConn) ReceiveFunc {
return func(buff []byte) (int, Endpoint, error) {
n, endpoint, err := conn.ReadFromUDPAddrPort(buff)
return n, asEndpoint(endpoint), err
}
}
func (bind *StdNetBind) Send(buff []byte, endpoint Endpoint) error {
var err error
nend, ok := endpoint.(StdNetEndpoint)
if !ok {
return ErrWrongEndpointType
}
addrPort := netip.AddrPort(nend)
bind.mu.Lock()
blackhole := bind.blackhole4
conn := bind.ipv4
if addrPort.Addr().Is6() {
blackhole = bind.blackhole6
conn = bind.ipv6
}
bind.mu.Unlock()
if blackhole {
return nil
}
if conn == nil {
return syscall.EAFNOSUPPORT
}
_, err = conn.WriteToUDPAddrPort(buff, addrPort)
return err
}
// endpointPool contains a re-usable set of mapping from netip.AddrPort to Endpoint.
// This exists to reduce allocations: Putting a netip.AddrPort in an Endpoint allocates,
// but Endpoints are immutable, so we can re-use them.
var endpointPool = sync.Pool{
New: func() any {
return make(map[netip.AddrPort]Endpoint)
},
}
// asEndpoint returns an Endpoint containing ap.
func asEndpoint(ap netip.AddrPort) Endpoint {
m := endpointPool.Get().(map[netip.AddrPort]Endpoint)
defer endpointPool.Put(m)
e, ok := m[ap]
if !ok {
e = Endpoint(StdNetEndpoint(ap))
m[ap] = e
}
return e
}
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