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service.go
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service.go
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package zeroconf
import (
"fmt"
"net"
"sync"
"time"
)
// ServiceRecord contains the basic description of a service, which contains instance name, service type & domain
type ServiceRecord struct {
Instance string `json:"name"` // Instance name (e.g. "My web page")
Service string `json:"type"` // Service name (e.g. _http._tcp.)
Subtypes []string `json:"subtypes"` // Service subtypes
Domain string `json:"domain"` // If blank, assumes "local"
// private variable populated on ServiceRecord creation
serviceName string
serviceInstanceName string
serviceTypeName string
}
// ServiceName returns a complete service name (e.g. _foobar._tcp.local.), which is composed
// of a service name (also referred as service type) and a domain.
func (s *ServiceRecord) ServiceName() string {
return s.serviceName
}
// ServiceInstanceName returns a complete service instance name (e.g. MyDemo\ Service._foobar._tcp.local.),
// which is composed from service instance name, service name and a domain.
func (s *ServiceRecord) ServiceInstanceName() string {
return s.serviceInstanceName
}
// ServiceTypeName returns the complete identifier for a DNS-SD query.
func (s *ServiceRecord) ServiceTypeName() string {
return s.serviceTypeName
}
// NewServiceRecord constructs a ServiceRecord.
func NewServiceRecord(instance, service string, domain string) *ServiceRecord {
service, subtypes := parseSubtypes(service)
s := &ServiceRecord{
Instance: instance,
Service: service,
Domain: domain,
serviceName: fmt.Sprintf("%s.%s.", trimDot(service), trimDot(domain)),
}
for _, subtype := range subtypes {
s.Subtypes = append(s.Subtypes, fmt.Sprintf("%s._sub.%s", trimDot(subtype), s.serviceName))
}
// Cache service instance name
if instance != "" {
s.serviceInstanceName = fmt.Sprintf("%s.%s", trimDot(s.Instance), s.ServiceName())
}
// Cache service type name domain
typeNameDomain := "local"
if len(s.Domain) > 0 {
typeNameDomain = trimDot(s.Domain)
}
s.serviceTypeName = fmt.Sprintf("_services._dns-sd._udp.%s.", typeNameDomain)
return s
}
// LookupParams contains configurable properties to create a service discovery request
type LookupParams struct {
ServiceRecord
Entries chan<- *ServiceEntry // Entries Channel
stopProbing chan struct{}
once sync.Once
}
// NewLookupParams constructs a LookupParams.
func NewLookupParams(instance, service, domain string, entries chan<- *ServiceEntry) *LookupParams {
return &LookupParams{
ServiceRecord: *NewServiceRecord(instance, service, domain),
Entries: entries,
stopProbing: make(chan struct{}),
}
}
// Notify subscriber that no more entries will arrive. Mostly caused
// by an expired context.
func (l *LookupParams) done() {
close(l.Entries)
}
func (l *LookupParams) disableProbing() {
l.once.Do(func() { close(l.stopProbing) })
}
// ServiceEntry represents a browse/lookup result for client API.
// It is also used to configure service registration (server API), which is
// used to answer multicast queries.
type ServiceEntry struct {
ServiceRecord
HostName string `json:"hostname"` // Host machine DNS name
Port int `json:"port"` // Service Port
Text []string `json:"text"` // Service info served as a TXT record
TTL uint32 `json:"ttl"` // TTL of the service record
AddrIPv4 []net.IP `json:"-"` // Host machine IPv4 address
AddrIPv6 []net.IP `json:"-"` // Host machine IPv6 address
}
// NewServiceEntry constructs a ServiceEntry.
func NewServiceEntry(instance, service string, domain string) *ServiceEntry {
return &ServiceEntry{
ServiceRecord: *NewServiceRecord(instance, service, domain),
}
}
func (se *ServiceEntry) nearToExpire(exp int64) bool {
now := time.Now().Unix()
if now-exp > (int64)(se.TTL/2) {
return true
}
return false
}
func (se *ServiceEntry) isEqual(other *ServiceEntry) bool {
if se.HostName != other.HostName {
return false
}
if se.Port != other.Port {
return false
}
if !textSliceAreEqual(se.Text, other.Text) {
return false
}
if !ipSlicesAreEqual(se.AddrIPv4, other.AddrIPv4) {
return false
}
if !ipSlicesAreEqual(se.AddrIPv6, other.AddrIPv6) {
return false
}
return true
}
func ipSlicesAreEqual(ipl1 []net.IP, ipl2 []net.IP) bool {
if len(ipl1) != len(ipl2) {
return false
}
for _, s := range ipl1 {
contains := false
for _, s2 := range ipl2 {
if s.Equal(s2) {
contains = true
break
}
}
if !contains {
return false
}
}
return true
}
func textSliceAreEqual(tl1 []string, tl2 []string) bool {
if len(tl1) != len(tl2) {
return false
}
for _, s := range tl1 {
contains := false
for _, s2 := range tl2 {
if s == s2 {
contains = true
break
}
}
if !contains {
return false
}
}
return true
}