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Add loopback support #68

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Add loopback support #68

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b8bb7c9
Add loopback support
urjitbhatia Feb 3, 2020
91abbac
Merge remote-tracking branch 'official/master' into loopbackSupport
urjitbhatia Jul 6, 2021
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47 changes: 32 additions & 15 deletions server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -22,8 +22,17 @@ const (
)

// Register a service by given arguments. This call will take the system's hostname
// and lookup IP by that hostname.
// This call will take the system's hostname and lookup IP by that hostname.
func Register(instance, service, domain string, port int, text []string, ifaces []net.Interface) (*Server, error) {
return register(instance, service, domain, port, text, ifaces, false)
}

// RegisterWithLoopback registers a service by given arguments but also registers on local loopback interface.
// and lookup IP by that hostname.
func RegisterWithLoopback(instance, service, domain string, port int, text []string, ifaces []net.Interface) (*Server, error) {
return register(instance, service, domain, port, text, ifaces, true)
}
func register(instance, service, domain string, port int, text []string, ifaces []net.Interface, loopback bool) (*Server, error) {
entry := NewServiceEntry(instance, service, domain)
entry.Port = port
entry.Text = text
Expand Down Expand Up @@ -58,7 +67,7 @@ func Register(instance, service, domain string, port int, text []string, ifaces
}

for _, iface := range ifaces {
v4, v6 := addrsForInterface(&iface)
v4, v6 := addrsForInterface(&iface, loopback)
entry.AddrIPv4 = append(entry.AddrIPv4, v4...)
entry.AddrIPv6 = append(entry.AddrIPv6, v6...)
}
Expand All @@ -71,7 +80,7 @@ func Register(instance, service, domain string, port int, text []string, ifaces
if err != nil {
return nil, err
}

s.loopback = loopback
s.service = entry
go s.mainloop()
go s.probe()
Expand Down Expand Up @@ -146,6 +155,7 @@ type Server struct {
ipv4conn *ipv4.PacketConn
ipv6conn *ipv6.PacketConn
ifaces []net.Interface
loopback bool

shouldShutdown chan struct{}
shutdownLock sync.Mutex
Expand Down Expand Up @@ -621,7 +631,7 @@ func (s *Server) appendAddrs(list []dns.RR, ttl uint32, ifIndex int, flushCache
if len(v4) == 0 && len(v6) == 0 {
iface, _ := net.InterfaceByIndex(ifIndex)
if iface != nil {
a4, a6 := addrsForInterface(iface)
a4, a6 := addrsForInterface(iface, s.loopback)
v4 = append(v4, a4...)
v6 = append(v6, a6...)
}
Expand Down Expand Up @@ -663,20 +673,27 @@ func (s *Server) appendAddrs(list []dns.RR, ttl uint32, ifIndex int, flushCache
return list
}

func addrsForInterface(iface *net.Interface) ([]net.IP, []net.IP) {
func addrsForInterface(iface *net.Interface, loopback bool) ([]net.IP, []net.IP) {
var v4, v6, v6local []net.IP
addrs, _ := iface.Addrs()
for _, address := range addrs {
if ipnet, ok := address.(*net.IPNet); ok && !ipnet.IP.IsLoopback() {
if ipnet.IP.To4() != nil {
v4 = append(v4, ipnet.IP)
} else {
switch ip := ipnet.IP.To16(); ip != nil {
case ip.IsGlobalUnicast():
v6 = append(v6, ipnet.IP)
case ip.IsLinkLocalUnicast():
v6local = append(v6local, ipnet.IP)
}
ipnet, ok := address.(*net.IPNet)
if !ok {
continue
}
if ipnet.IP.IsLoopback() && !loopback {
// loopback is disabled - skip
continue
}

if ipnet.IP.To4() != nil {
v4 = append(v4, ipnet.IP)
} else {
switch ip := ipnet.IP.To16(); ip != nil {
case ip.IsGlobalUnicast():
v6 = append(v6, ipnet.IP)
case ip.IsLinkLocalUnicast():
v6local = append(v6local, ipnet.IP)
}
}
}
Expand Down
78 changes: 64 additions & 14 deletions service_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,9 +17,16 @@ var (
mdnsPort = 8888
)

func startMDNS(ctx context.Context, port int, name, service, domain string) {
func startMDNS(ctx context.Context, port int, name, service, domain string, loopback bool) {
// 5353 is default mdns port
server, err := Register(name, service, domain, port, []string{"txtv=0", "lo=1", "la=2"}, nil)
var server *Server
var err error

if loopback {
server, err = RegisterWithLoopback(name, service, domain, port, []string{"txtv=0", "lo=1", "la=2"}, nil)
} else {
server, err = Register(name, service, domain, port, []string{"txtv=0", "lo=1", "la=2"}, nil)
}
if err != nil {
panic(errors.Wrap(err, "while registering mdns service"))
}
Expand All @@ -29,14 +36,42 @@ func startMDNS(ctx context.Context, port int, name, service, domain string) {
<-ctx.Done()

log.Printf("Shutting down.")
}

func verifyResult(expectedResult *ServiceEntry, expectLoopback bool, t *testing.T) {
if expectedResult.Domain != mdnsDomain {
t.Fatalf("Expected domain is %s, but got %s", mdnsDomain, expectedResult.Domain)
}
if expectedResult.Service != mdnsService {
t.Fatalf("Expected service is %s, but got %s", mdnsService, expectedResult.Service)
}
if expectedResult.Instance != mdnsName {
t.Fatalf("Expected instance is %s, but got %s", mdnsName, expectedResult.Instance)
}
if expectedResult.Port != mdnsPort {
t.Fatalf("Expected port is %d, but got %d", mdnsPort, expectedResult.Port)
}
foundLoopback := false
for _, addr := range expectedResult.AddrIPv4 {
if addr.IsLoopback() {
foundLoopback = true
break
}
}
if expectLoopback && !foundLoopback {
t.Fatal("Expected AddrIPv4 to include loopback")
}
if !expectLoopback && foundLoopback {
t.Fatal("Unexpected AddrIPv4 loopback result")
}
}

func TestBasic(t *testing.T) {
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

go startMDNS(ctx, mdnsPort, mdnsName, mdnsService, mdnsDomain)
loopback := false
go startMDNS(ctx, mdnsPort, mdnsName, mdnsService, mdnsDomain, loopback)

time.Sleep(time.Second)

Expand All @@ -54,18 +89,33 @@ func TestBasic(t *testing.T) {
t.Fatalf("Expected number of service entries is 1, but got %d", len(entries))
}
result := <-entries
if result.Domain != mdnsDomain {
t.Fatalf("Expected domain is %s, but got %s", mdnsDomain, result.Domain)
}
if result.Service != mdnsService {
t.Fatalf("Expected service is %s, but got %s", mdnsService, result.Service)
verifyResult(result, loopback, t)
}

func TestWithLoopback(t *testing.T) {
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

loopback := true
go startMDNS(ctx, mdnsPort, mdnsName, mdnsService, mdnsDomain, loopback)

time.Sleep(time.Second)

resolver, err := NewResolver(nil)
if err != nil {
t.Fatalf("Expected create resolver success, but got %v", err)
}
if result.Instance != mdnsName {
t.Fatalf("Expected instance is %s, but got %s", mdnsName, result.Instance)
entries := make(chan *ServiceEntry, 100)
if err := resolver.Browse(ctx, mdnsService, mdnsDomain, entries); err != nil {
t.Fatalf("Expected browse success, but got %v", err)
}
if result.Port != mdnsPort {
t.Fatalf("Expected port is %d, but got %d", mdnsPort, result.Port)
<-ctx.Done()

if len(entries) != 1 {
t.Fatalf("Expected number of service entries is 1, but got %d", len(entries))
}
result := <-entries
verifyResult(result, loopback, t)
}

func TestNoRegister(t *testing.T) {
Expand Down Expand Up @@ -96,7 +146,7 @@ func TestSubtype(t *testing.T) {
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

go startMDNS(ctx, mdnsPort, mdnsName, mdnsSubtype, mdnsDomain)
go startMDNS(ctx, mdnsPort, mdnsName, mdnsSubtype, mdnsDomain, false)

time.Sleep(time.Second)

Expand Down Expand Up @@ -132,7 +182,7 @@ func TestSubtype(t *testing.T) {
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

go startMDNS(ctx, mdnsPort, mdnsName, mdnsSubtype, mdnsDomain)
go startMDNS(ctx, mdnsPort, mdnsName, mdnsSubtype, mdnsDomain, false)

time.Sleep(time.Second)

Expand Down