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- // Copyright (C) 2014 The Syncthing Authors.
- //
- // This Source Code Form is subject to the terms of the Mozilla Public
- // License, v. 2.0. If a copy of the MPL was not distributed with this file,
- // You can obtain one at https://mozilla.org/MPL/2.0/.
- package beacon
- import (
- "context"
- "errors"
- "net"
- "time"
- "golang.org/x/net/ipv6"
- )
- func NewMulticast(addr string) Interface {
- c := newCast("multicastBeacon")
- c.addReader(func(ctx context.Context) error {
- return readMulticasts(ctx, c.outbox, addr)
- })
- c.addWriter(func(ctx context.Context) error {
- return writeMulticasts(ctx, c.inbox, addr)
- })
- return c
- }
- func writeMulticasts(ctx context.Context, inbox <-chan []byte, addr string) error {
- gaddr, err := net.ResolveUDPAddr("udp6", addr)
- if err != nil {
- l.Debugln(err)
- return err
- }
- conn, err := net.ListenPacket("udp6", ":0")
- if err != nil {
- l.Debugln(err)
- return err
- }
- doneCtx, cancel := context.WithCancel(ctx)
- defer cancel()
- go func() {
- <-doneCtx.Done()
- conn.Close()
- }()
- pconn := ipv6.NewPacketConn(conn)
- wcm := &ipv6.ControlMessage{
- HopLimit: 1,
- }
- for {
- var bs []byte
- select {
- case bs = <-inbox:
- case <-doneCtx.Done():
- return doneCtx.Err()
- }
- intfs, err := net.Interfaces()
- if err != nil {
- l.Debugln(err)
- return err
- }
- success := 0
- for _, intf := range intfs {
- if intf.Flags&net.FlagRunning == 0 || intf.Flags&net.FlagMulticast == 0 {
- continue
- }
- wcm.IfIndex = intf.Index
- pconn.SetWriteDeadline(time.Now().Add(time.Second))
- _, err = pconn.WriteTo(bs, wcm, gaddr)
- pconn.SetWriteDeadline(time.Time{})
- if err != nil {
- l.Debugln(err, "on write to", gaddr, intf.Name)
- continue
- }
- l.Debugf("sent %d bytes to %v on %s", len(bs), gaddr, intf.Name)
- success++
- select {
- case <-doneCtx.Done():
- return doneCtx.Err()
- default:
- }
- }
- if success == 0 {
- return err
- }
- }
- }
- func readMulticasts(ctx context.Context, outbox chan<- recv, addr string) error {
- gaddr, err := net.ResolveUDPAddr("udp6", addr)
- if err != nil {
- l.Debugln(err)
- return err
- }
- conn, err := net.ListenPacket("udp6", addr)
- if err != nil {
- l.Debugln(err)
- return err
- }
- doneCtx, cancel := context.WithCancel(ctx)
- defer cancel()
- go func() {
- <-doneCtx.Done()
- conn.Close()
- }()
- intfs, err := net.Interfaces()
- if err != nil {
- l.Debugln(err)
- return err
- }
- pconn := ipv6.NewPacketConn(conn)
- joined := 0
- for _, intf := range intfs {
- err := pconn.JoinGroup(&intf, &net.UDPAddr{IP: gaddr.IP})
- if err != nil {
- l.Debugln("IPv6 join", intf.Name, "failed:", err)
- } else {
- l.Debugln("IPv6 join", intf.Name, "success")
- }
- joined++
- }
- if joined == 0 {
- l.Debugln("no multicast interfaces available")
- return errors.New("no multicast interfaces available")
- }
- bs := make([]byte, 65536)
- for {
- select {
- case <-doneCtx.Done():
- return doneCtx.Err()
- default:
- }
- n, _, addr, err := pconn.ReadFrom(bs)
- if err != nil {
- l.Debugln(err)
- return err
- }
- l.Debugf("recv %d bytes from %s", n, addr)
- c := make([]byte, n)
- copy(c, bs)
- select {
- case outbox <- recv{c, addr}:
- default:
- l.Debugln("dropping message")
- }
- }
- }
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