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rework the client-side API, remove the Resolver, make Browse and Lookup package-level functions #100

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rework the client-side API, remove the Resolver, make Browse and Lookup package-level functions #100

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2d856fa
remove the Resolver
marten-seemann Jul 4, 2021
513aee2
make Lookup and Resolve blocking calls
marten-seemann Jul 4, 2021
5d79d01
wait for the mainloop to complete before return Lookup and Browse
marten-seemann Jul 4, 2021
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7 changes: 1 addition & 6 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -29,12 +29,6 @@ This package requires **Go 1.7** (context in std lib) or later.
## Browse for services in your local network

```go
// Discover all services on the network (e.g. _workstation._tcp)
resolver, err := zeroconf.NewResolver(nil)
if err != nil {
log.Fatalln("Failed to initialize resolver:", err.Error())
}

entries := make(chan *zeroconf.ServiceEntry)
go func(results <-chan *zeroconf.ServiceEntry) {
for entry := range results {
Expand All @@ -45,6 +39,7 @@ go func(results <-chan *zeroconf.ServiceEntry) {

ctx, cancel := context.WithTimeout(context.Background(), time.Second*15)
defer cancel()
// Discover all services on the network (e.g. _workstation._tcp)
err = resolver.Browse(ctx, "_workstation._tcp", "local.", entries)
if err != nil {
log.Fatalln("Failed to browse:", err.Error())
Expand Down
124 changes: 51 additions & 73 deletions client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,13 @@ const (
IPv4AndIPv6 = (IPv4 | IPv6) //< Default option.
)

// Client structure encapsulates both IPv4/IPv6 UDP connections.
type client struct {
ipv4conn *ipv4.PacketConn
ipv6conn *ipv6.PacketConn
ifaces []net.Interface
}

type clientOpts struct {
listenOn IPType
ifaces []net.Interface
Expand All @@ -52,99 +59,70 @@ func SelectIfaces(ifaces []net.Interface) ClientOption {
}
}

// Resolver acts as entry point for service lookups and to browse the DNS-SD.
type Resolver struct {
c *client
}

// NewResolver creates a new resolver and joins the UDP multicast groups to
// listen for mDNS messages.
func NewResolver(options ...ClientOption) (*Resolver, error) {
// Apply default configuration and load supplied options.
var conf = clientOpts{
listenOn: IPv4AndIPv6,
}
for _, o := range options {
if o != nil {
o(&conf)
}
}

c, err := newClient(conf)
// Browse for all services of a given type in a given domain.
func Browse(ctx context.Context, service, domain string, entries chan<- *ServiceEntry, opts ...ClientOption) error {
cl, err := newClient(applyOpts(opts...))
if err != nil {
return nil, err
return err
}
return &Resolver{
c: c,
}, nil
}

// Browse for all services of a given type in a given domain.
func (r *Resolver) Browse(ctx context.Context, service, domain string, entries chan<- *ServiceEntry) error {
params := defaultParams(service)
if domain != "" {
params.Domain = domain
}
params.Entries = entries
params.isBrowsing = true
ctx, cancel := context.WithCancel(ctx)
go r.c.mainloop(ctx, params)
return cl.run(ctx, params)
}

err := r.c.query(params)
// Lookup a specific service by its name and type in a given domain.
func Lookup(ctx context.Context, instance, service, domain string, entries chan<- *ServiceEntry, opts ...ClientOption) error {
cl, err := newClient(applyOpts(opts...))
if err != nil {
cancel()
return err
}
// If previous probe was ok, it should be fine now. In case of an error later on,
// the entries' queue is closed.
go func() {
if err := r.c.periodicQuery(ctx, params); err != nil {
cancel()
}
}()

return nil
}

// Lookup a specific service by its name and type in a given domain.
func (r *Resolver) Lookup(ctx context.Context, instance, service, domain string, entries chan<- *ServiceEntry) error {
params := defaultParams(service)
params.Instance = instance
if domain != "" {
params.Domain = domain
}
params.Entries = entries
ctx, cancel := context.WithCancel(ctx)
go r.c.mainloop(ctx, params)
err := r.c.query(params)
if err != nil {
// cancel mainloop
cancel()
return err
return cl.run(ctx, params)
}

func applyOpts(options ...ClientOption) clientOpts {
// Apply default configuration and load supplied options.
var conf = clientOpts{
listenOn: IPv4AndIPv6,
}
// If previous probe was ok, it should be fine now. In case of an error later on,
// the entries' queue is closed.
go func() {
if err := r.c.periodicQuery(ctx, params); err != nil {
cancel()
for _, o := range options {
if o != nil {
o(&conf)
}
}
return conf
}

func (c *client) run(ctx context.Context, params *lookupParams) error {
ctx, cancel := context.WithCancel(ctx)
done := make(chan struct{})
go func() {
defer close(done)
c.mainloop(ctx, params)
}()

return nil
// If previous probe was ok, it should be fine now. In case of an error later on,
// the entries' queue is closed.
err := c.periodicQuery(ctx, params)
cancel()
<-done
return err
}

// defaultParams returns a default set of QueryParams.
func defaultParams(service string) *lookupParams {
return newLookupParams("", service, "local", false, make(chan *ServiceEntry))
}

// Client structure encapsulates both IPv4/IPv6 UDP connections.
type client struct {
ipv4conn *ipv4.PacketConn
ipv6conn *ipv6.PacketConn
ifaces []net.Interface
}

// Client structure constructor
func newClient(opts clientOpts) (*client, error) {
ifaces := opts.ifaces
Expand Down Expand Up @@ -381,6 +359,10 @@ func (c *client) periodicQuery(ctx context.Context, params *lookupParams) error
}
}()
for {
// Do periodic query.
if err := c.query(params); err != nil {
return err
}
// Backoff and cancel logic.
wait := bo.NextBackOff()
if wait == backoff.Stop {
Expand All @@ -391,6 +373,7 @@ func (c *client) periodicQuery(ctx context.Context, params *lookupParams) error
} else {
timer.Reset(wait)
}

select {
case <-timer.C:
// Wait for next iteration.
Expand All @@ -399,12 +382,11 @@ func (c *client) periodicQuery(ctx context.Context, params *lookupParams) error
// Done here. Received a matching mDNS entry.
return nil
case <-ctx.Done():
if params.isBrowsing {
return nil
}
return ctx.Err()
}
// Do periodic query.
if err := c.query(params); err != nil {
return err
}
}
}

Expand All @@ -428,11 +410,7 @@ func (c *client) query(params *lookupParams) error {
m.SetQuestion(serviceName, dns.TypePTR)
}
m.RecursionDesired = false
if err := c.sendQuery(m); err != nil {
return err
}

return nil
return c.sendQuery(m)
}

// Pack the dns.Msg and write to available connections (multicast)
Expand Down
9 changes: 2 additions & 7 deletions examples/resolv/client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,12 +18,6 @@ var (
func main() {
flag.Parse()

// Discover all services on the network (e.g. _workstation._tcp)
resolver, err := zeroconf.NewResolver(nil)
if err != nil {
log.Fatalln("Failed to initialize resolver:", err.Error())
}

entries := make(chan *zeroconf.ServiceEntry)
go func(results <-chan *zeroconf.ServiceEntry) {
for entry := range results {
Expand All @@ -34,7 +28,8 @@ func main() {

ctx, cancel := context.WithTimeout(context.Background(), time.Second*time.Duration(*waitTime))
defer cancel()
err = resolver.Browse(ctx, *service, *domain, entries)
// Discover all services on the network (e.g. _workstation._tcp)
err := zeroconf.Browse(ctx, *service, *domain, entries)
if err != nil {
log.Fatalln("Failed to browse:", err.Error())
}
Expand Down
25 changes: 4 additions & 21 deletions service_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -40,12 +40,8 @@ func TestBasic(t *testing.T) {

time.Sleep(time.Second)

resolver, err := NewResolver(nil)
if err != nil {
t.Fatalf("Expected create resolver success, but got %v", err)
}
entries := make(chan *ServiceEntry, 100)
if err := resolver.Browse(ctx, mdnsService, mdnsDomain, entries); err != nil {
if err := Browse(ctx, mdnsService, mdnsDomain, entries); err != nil {
t.Fatalf("Expected browse success, but got %v", err)
}
<-ctx.Done()
Expand All @@ -69,11 +65,6 @@ func TestBasic(t *testing.T) {
}

func TestNoRegister(t *testing.T) {
resolver, err := NewResolver(nil)
if err != nil {
t.Fatalf("Expected create resolver success, but got %v", err)
}

// before register, mdns resolve shuold not have any entry
entries := make(chan *ServiceEntry)
go func(results <-chan *ServiceEntry) {
Expand All @@ -84,7 +75,7 @@ func TestNoRegister(t *testing.T) {
}(entries)

ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
if err := resolver.Browse(ctx, mdnsService, mdnsDomain, entries); err != nil {
if err := Browse(ctx, mdnsService, mdnsDomain, entries); err != nil {
t.Fatalf("Expected browse success, but got %v", err)
}
<-ctx.Done()
Expand All @@ -100,12 +91,8 @@ func TestSubtype(t *testing.T) {

time.Sleep(time.Second)

resolver, err := NewResolver(nil)
if err != nil {
t.Fatalf("Expected create resolver success, but got %v", err)
}
entries := make(chan *ServiceEntry, 100)
if err := resolver.Browse(ctx, mdnsSubtype, mdnsDomain, entries); err != nil {
if err := Browse(ctx, mdnsSubtype, mdnsDomain, entries); err != nil {
t.Fatalf("Expected browse success, but got %v", err)
}
<-ctx.Done()
Expand Down Expand Up @@ -136,12 +123,8 @@ func TestSubtype(t *testing.T) {

time.Sleep(time.Second)

resolver, err := NewResolver(nil)
if err != nil {
t.Fatalf("Expected create resolver success, but got %v", err)
}
entries := make(chan *ServiceEntry, 100)
if err := resolver.Browse(ctx, mdnsService, mdnsDomain, entries); err != nil {
if err := Browse(ctx, mdnsService, mdnsDomain, entries); err != nil {
t.Fatalf("Expected browse success, but got %v", err)
}
<-ctx.Done()
Expand Down