mirror of
https://github.com/lukaszraczylo/kportal.git
synced 2026-10-18 05:15:43 +00:00
fix(mdns): answer hostname A queries after TTL (#96)
* fix(mdns): answer hostname A queries after TTL Zeroconf answers only service queries. The A record for <alias>.local expired from the OS cache after 120 seconds and lookups then failed. Vendor zeroconf v1.0.0 with one change: it now answers A and AAAA queries for the registered hostname. Fixes #95. * fix(deps): update golang.org/x/net to v0.60.0 govulncheck reports several x/net advisories fixed in v0.60.0. The Security Scan job fails on them.
This commit is contained in:
Vendored
+456
@@ -0,0 +1,456 @@
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package zeroconf
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import (
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"context"
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"fmt"
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"net"
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"strings"
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"golang.org/x/net/ipv4"
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"golang.org/x/net/ipv6"
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"time"
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"github.com/cenkalti/backoff"
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"github.com/miekg/dns"
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)
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// IPType specifies the IP traffic the client listens for.
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// This does not guarantee that only mDNS entries of this sepcific
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// type passes. E.g. typical mDNS packets distributed via IPv4, often contain
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// both DNS A and AAAA entries.
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type IPType uint8
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// Options for IPType.
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const (
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IPv4 = 0x01
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IPv6 = 0x02
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IPv4AndIPv6 = (IPv4 | IPv6) //< Default option.
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)
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type clientOpts struct {
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listenOn IPType
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ifaces []net.Interface
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}
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// ClientOption fills the option struct to configure intefaces, etc.
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type ClientOption func(*clientOpts)
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// SelectIPTraffic selects the type of IP packets (IPv4, IPv6, or both) this
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// instance listens for.
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// This does not guarantee that only mDNS entries of this sepcific
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// type passes. E.g. typical mDNS packets distributed via IPv4, may contain
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// both DNS A and AAAA entries.
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func SelectIPTraffic(t IPType) ClientOption {
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return func(o *clientOpts) {
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o.listenOn = t
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}
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}
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// SelectIfaces selects the interfaces to query for mDNS records
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func SelectIfaces(ifaces []net.Interface) ClientOption {
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return func(o *clientOpts) {
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o.ifaces = ifaces
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}
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}
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// Resolver acts as entry point for service lookups and to browse the DNS-SD.
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type Resolver struct {
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c *client
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}
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// NewResolver creates a new resolver and joins the UDP multicast groups to
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// listen for mDNS messages.
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func NewResolver(options ...ClientOption) (*Resolver, error) {
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// Apply default configuration and load supplied options.
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var conf = clientOpts{
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listenOn: IPv4AndIPv6,
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}
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for _, o := range options {
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if o != nil {
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o(&conf)
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}
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}
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c, err := newClient(conf)
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if err != nil {
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return nil, err
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}
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return &Resolver{
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c: c,
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}, nil
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}
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// Browse for all services of a given type in a given domain.
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func (r *Resolver) Browse(ctx context.Context, service, domain string, entries chan<- *ServiceEntry) error {
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params := defaultParams(service)
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if domain != "" {
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params.Domain = domain
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}
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params.Entries = entries
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ctx, cancel := context.WithCancel(ctx)
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go r.c.mainloop(ctx, params)
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err := r.c.query(params)
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if err != nil {
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cancel()
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return err
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}
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// If previous probe was ok, it should be fine now. In case of an error later on,
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// the entries' queue is closed.
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go func() {
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if err := r.c.periodicQuery(ctx, params); err != nil {
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cancel()
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}
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}()
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return nil
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}
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// Lookup a specific service by its name and type in a given domain.
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func (r *Resolver) Lookup(ctx context.Context, instance, service, domain string, entries chan<- *ServiceEntry) error {
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params := defaultParams(service)
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params.Instance = instance
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if domain != "" {
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params.Domain = domain
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}
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params.Entries = entries
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ctx, cancel := context.WithCancel(ctx)
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go r.c.mainloop(ctx, params)
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err := r.c.query(params)
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if err != nil {
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// cancel mainloop
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cancel()
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return err
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}
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// If previous probe was ok, it should be fine now. In case of an error later on,
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// the entries' queue is closed.
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go func() {
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if err := r.c.periodicQuery(ctx, params); err != nil {
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cancel()
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}
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}()
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return nil
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}
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// defaultParams returns a default set of QueryParams.
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func defaultParams(service string) *LookupParams {
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return NewLookupParams("", service, "local", make(chan *ServiceEntry))
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}
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// Client structure encapsulates both IPv4/IPv6 UDP connections.
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type client struct {
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ipv4conn *ipv4.PacketConn
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ipv6conn *ipv6.PacketConn
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ifaces []net.Interface
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}
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// Client structure constructor
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func newClient(opts clientOpts) (*client, error) {
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ifaces := opts.ifaces
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if len(ifaces) == 0 {
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ifaces = listMulticastInterfaces()
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}
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// IPv4 interfaces
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var ipv4conn *ipv4.PacketConn
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if (opts.listenOn & IPv4) > 0 {
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var err error
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ipv4conn, err = joinUdp4Multicast(ifaces)
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if err != nil {
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return nil, err
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}
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}
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// IPv6 interfaces
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var ipv6conn *ipv6.PacketConn
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if (opts.listenOn & IPv6) > 0 {
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var err error
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ipv6conn, err = joinUdp6Multicast(ifaces)
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if err != nil {
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return nil, err
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}
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}
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return &client{
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ipv4conn: ipv4conn,
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ipv6conn: ipv6conn,
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ifaces: ifaces,
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}, nil
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}
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// Start listeners and waits for the shutdown signal from exit channel
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func (c *client) mainloop(ctx context.Context, params *LookupParams) {
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// start listening for responses
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msgCh := make(chan *dns.Msg, 32)
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if c.ipv4conn != nil {
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go c.recv(ctx, c.ipv4conn, msgCh)
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}
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if c.ipv6conn != nil {
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go c.recv(ctx, c.ipv6conn, msgCh)
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}
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// Iterate through channels from listeners goroutines
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var entries, sentEntries map[string]*ServiceEntry
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sentEntries = make(map[string]*ServiceEntry)
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for {
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select {
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case <-ctx.Done():
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// Context expired. Notify subscriber that we are done here.
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params.done()
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c.shutdown()
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return
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case msg := <-msgCh:
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entries = make(map[string]*ServiceEntry)
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sections := append(msg.Answer, msg.Ns...)
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sections = append(sections, msg.Extra...)
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for _, answer := range sections {
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switch rr := answer.(type) {
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case *dns.PTR:
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if params.ServiceName() != rr.Hdr.Name {
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continue
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}
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if params.ServiceInstanceName() != "" && params.ServiceInstanceName() != rr.Ptr {
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continue
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}
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if _, ok := entries[rr.Ptr]; !ok {
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entries[rr.Ptr] = NewServiceEntry(
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trimDot(strings.Replace(rr.Ptr, rr.Hdr.Name, "", -1)),
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params.Service,
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params.Domain)
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}
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entries[rr.Ptr].TTL = rr.Hdr.Ttl
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case *dns.SRV:
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if params.ServiceInstanceName() != "" && params.ServiceInstanceName() != rr.Hdr.Name {
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continue
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} else if !strings.HasSuffix(rr.Hdr.Name, params.ServiceName()) {
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continue
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}
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if _, ok := entries[rr.Hdr.Name]; !ok {
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entries[rr.Hdr.Name] = NewServiceEntry(
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trimDot(strings.Replace(rr.Hdr.Name, params.ServiceName(), "", 1)),
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params.Service,
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params.Domain)
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}
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entries[rr.Hdr.Name].HostName = rr.Target
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entries[rr.Hdr.Name].Port = int(rr.Port)
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entries[rr.Hdr.Name].TTL = rr.Hdr.Ttl
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case *dns.TXT:
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if params.ServiceInstanceName() != "" && params.ServiceInstanceName() != rr.Hdr.Name {
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continue
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} else if !strings.HasSuffix(rr.Hdr.Name, params.ServiceName()) {
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continue
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}
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if _, ok := entries[rr.Hdr.Name]; !ok {
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entries[rr.Hdr.Name] = NewServiceEntry(
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trimDot(strings.Replace(rr.Hdr.Name, params.ServiceName(), "", 1)),
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params.Service,
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params.Domain)
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}
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entries[rr.Hdr.Name].Text = rr.Txt
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entries[rr.Hdr.Name].TTL = rr.Hdr.Ttl
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}
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}
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// Associate IPs in a second round as other fields should be filled by now.
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for _, answer := range sections {
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switch rr := answer.(type) {
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case *dns.A:
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for k, e := range entries {
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if e.HostName == rr.Hdr.Name {
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entries[k].AddrIPv4 = append(entries[k].AddrIPv4, rr.A)
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}
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}
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case *dns.AAAA:
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for k, e := range entries {
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if e.HostName == rr.Hdr.Name {
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entries[k].AddrIPv6 = append(entries[k].AddrIPv6, rr.AAAA)
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}
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}
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}
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}
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}
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if len(entries) > 0 {
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for k, e := range entries {
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if e.TTL == 0 {
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delete(entries, k)
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delete(sentEntries, k)
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continue
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}
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if _, ok := sentEntries[k]; ok {
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continue
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}
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// If this is an DNS-SD query do not throw PTR away.
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// It is expected to have only PTR for enumeration
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if params.ServiceRecord.ServiceTypeName() != params.ServiceRecord.ServiceName() {
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// Require at least one resolved IP address for ServiceEntry
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// TODO: wait some more time as chances are high both will arrive.
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if len(e.AddrIPv4) == 0 && len(e.AddrIPv6) == 0 {
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continue
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}
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}
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// Submit entry to subscriber and cache it.
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// This is also a point to possibly stop probing actively for a
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// service entry.
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params.Entries <- e
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sentEntries[k] = e
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params.disableProbing()
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}
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// reset entries
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entries = make(map[string]*ServiceEntry)
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}
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}
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}
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// Shutdown client will close currently open connections and channel implicitly.
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func (c *client) shutdown() {
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if c.ipv4conn != nil {
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c.ipv4conn.Close()
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}
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if c.ipv6conn != nil {
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c.ipv6conn.Close()
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}
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}
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// Data receiving routine reads from connection, unpacks packets into dns.Msg
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// structures and sends them to a given msgCh channel
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func (c *client) recv(ctx context.Context, l interface{}, msgCh chan *dns.Msg) {
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var readFrom func([]byte) (n int, src net.Addr, err error)
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switch pConn := l.(type) {
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case *ipv6.PacketConn:
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readFrom = func(b []byte) (n int, src net.Addr, err error) {
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n, _, src, err = pConn.ReadFrom(b)
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return
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}
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case *ipv4.PacketConn:
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readFrom = func(b []byte) (n int, src net.Addr, err error) {
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n, _, src, err = pConn.ReadFrom(b)
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return
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}
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default:
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return
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}
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buf := make([]byte, 65536)
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var fatalErr error
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for {
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// Handles the following cases:
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// - ReadFrom aborts with error due to closed UDP connection -> causes ctx cancel
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// - ReadFrom aborts otherwise.
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// TODO: the context check can be removed. Verify!
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if ctx.Err() != nil || fatalErr != nil {
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return
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}
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n, _, err := readFrom(buf)
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if err != nil {
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fatalErr = err
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continue
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}
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msg := new(dns.Msg)
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if err := msg.Unpack(buf[:n]); err != nil {
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// log.Printf("[WARN] mdns: Failed to unpack packet: %v", err)
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continue
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}
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select {
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case msgCh <- msg:
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// Submit decoded DNS message and continue.
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case <-ctx.Done():
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// Abort.
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return
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}
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}
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}
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// periodicQuery sens multiple probes until a valid response is received by
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// the main processing loop or some timeout/cancel fires.
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// TODO: move error reporting to shutdown function as periodicQuery is called from
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// go routine context.
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func (c *client) periodicQuery(ctx context.Context, params *LookupParams) error {
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if params.stopProbing == nil {
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return nil
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}
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bo := backoff.NewExponentialBackOff()
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bo.InitialInterval = 4 * time.Second
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bo.MaxInterval = 60 * time.Second
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bo.Reset()
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for {
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// Do periodic query.
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if err := c.query(params); err != nil {
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return err
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}
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// Backoff and cancel logic.
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wait := bo.NextBackOff()
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if wait == backoff.Stop {
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return fmt.Errorf("periodicQuery: abort due to timeout")
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}
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select {
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case <-time.After(wait):
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// Wait for next iteration.
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case <-params.stopProbing:
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// Chan is closed (or happened in the past).
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// Done here. Received a matching mDNS entry.
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return nil
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case <-ctx.Done():
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return ctx.Err()
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}
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}
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}
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// Performs the actual query by service name (browse) or service instance name (lookup),
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// start response listeners goroutines and loops over the entries channel.
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func (c *client) query(params *LookupParams) error {
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var serviceName, serviceInstanceName string
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serviceName = fmt.Sprintf("%s.%s.", trimDot(params.Service), trimDot(params.Domain))
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if params.Instance != "" {
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serviceInstanceName = fmt.Sprintf("%s.%s", params.Instance, serviceName)
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}
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// send the query
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m := new(dns.Msg)
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if serviceInstanceName != "" {
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m.Question = []dns.Question{
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dns.Question{serviceInstanceName, dns.TypeSRV, dns.ClassINET},
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dns.Question{serviceInstanceName, dns.TypeTXT, dns.ClassINET},
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}
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m.RecursionDesired = false
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} else {
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m.SetQuestion(serviceName, dns.TypePTR)
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m.RecursionDesired = false
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}
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if err := c.sendQuery(m); err != nil {
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return err
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}
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return nil
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}
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// Pack the dns.Msg and write to available connections (multicast)
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func (c *client) sendQuery(msg *dns.Msg) error {
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buf, err := msg.Pack()
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if err != nil {
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return err
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}
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if c.ipv4conn != nil {
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var wcm ipv4.ControlMessage
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for ifi := range c.ifaces {
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wcm.IfIndex = c.ifaces[ifi].Index
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c.ipv4conn.WriteTo(buf, &wcm, ipv4Addr)
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}
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}
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if c.ipv6conn != nil {
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var wcm ipv6.ControlMessage
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for ifi := range c.ifaces {
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wcm.IfIndex = c.ifaces[ifi].Index
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c.ipv6conn.WriteTo(buf, &wcm, ipv6Addr)
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}
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}
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return nil
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}
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