xref: /aosp_15_r20/external/openscreen/osp/go/mdns.go (revision 3f982cf4871df8771c9d4abe6e9a6f8d829b2736)

// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package osp

// TODO(jophba):
// - Make our own abstraction that has
//   .InstanceName, .HostName, .MetadataVersion, .FingerPrint
//   rather than using mdns.ServiceEntry
// - Advertise TXT (text below) with "fp" and "mv"

import (
	"context"

	mdns "github.com/grandcat/zeroconf"
)

const (
	MdnsServiceType = "_openscreen._udp"
	MdnsDomain      = "local"
)

// Returns a channel of mDNS entries.  The critical parts are
// entry.Target (service name) entry.HostName, entry.AddrIPv4, and
// entry.AddrIPv6.
func BrowseMdns(ctx context.Context) (<-chan *mdns.ServiceEntry, error) {
	entries := make(chan *mdns.ServiceEntry)

	resolver, err := mdns.NewResolver(nil)
	if err != nil {
		return entries, err
	}

	err = resolver.Browse(ctx, MdnsServiceType, MdnsDomain, entries)
	return entries, err
}

// Returns a channel of mDNS entries. The critical parts are,
// entry.HostName, entry.AddrIPv4, and entry.AddrIPv6.
func LookupMdns(ctx context.Context, target string) (<-chan *mdns.ServiceEntry, error) {
	entries := make(chan *mdns.ServiceEntry)

	resolver, err := mdns.NewResolver(nil)
	if err != nil {
		return entries, err
	}

	err = resolver.Lookup(ctx, target, MdnsServiceType, MdnsDomain, entries)
	return entries, err
}

func RunMdnsServer(ctx context.Context, instance string, port int) error {
	var text []string
	server, err := mdns.Register(instance, MdnsServiceType, MdnsDomain, port, text, nil /* ifaces */)
	if err != nil {
		return err
	}
	waitUntilDone(ctx)
	server.Shutdown()
	return nil
}