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net: add support for DNS SRV requests.
Fixes #758. R=rsc, adg CC=golang-dev https://golang.org/cl/1078041
This commit is contained in:
Kirklin McDonald
Andrew Gerrand
parent
774333685e
commit
0046d51e06
@ -45,14 +45,14 @@ const noSuchHost = "no such host"
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// Send a request on the connection and hope for a reply.
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// Up to cfg.attempts attempts.
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func exchange(cfg *dnsConfig, c Conn, name string) (*dnsMsg, os.Error) {
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func exchange(cfg *dnsConfig, c Conn, name string, qtype uint16) (*dnsMsg, os.Error) {
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if len(name) >= 256 {
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return nil, &DNSError{Error: "name too long", Name: name}
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}
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out := new(dnsMsg)
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out.id = uint16(rand.Int()) ^ uint16(time.Nanoseconds())
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out.question = []dnsQuestion{
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dnsQuestion{name, dnsTypeA, dnsClassINET},
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dnsQuestion{name, qtype, dnsClassINET},
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}
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out.recursion_desired = true
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msg, ok := out.Pack()
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@ -93,8 +93,8 @@ func exchange(cfg *dnsConfig, c Conn, name string) (*dnsMsg, os.Error) {
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// Find answer for name in dns message.
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// On return, if err == nil, addrs != nil.
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func answer(name, server string, dns *dnsMsg) (addrs []string, err os.Error) {
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addrs = make([]string, 0, len(dns.answer))
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func answer(name, server string, dns *dnsMsg, qtype uint16) (addrs []dnsRR, err os.Error) {
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addrs = make([]dnsRR, 0, len(dns.answer))
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if dns.rcode == dnsRcodeNameError && dns.recursion_available {
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return nil, &DNSError{Error: noSuchHost, Name: name}
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@ -120,11 +120,10 @@ Cname:
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h := rr.Header()
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if h.Class == dnsClassINET && h.Name == name {
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switch h.Rrtype {
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case dnsTypeA:
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case qtype:
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n := len(addrs)
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a := rr.(*dnsRR_A).A
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addrs = addrs[0 : n+1]
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addrs[n] = IPv4(byte(a>>24), byte(a>>16), byte(a>>8), byte(a)).String()
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addrs[n] = rr
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case dnsTypeCNAME:
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// redirect to cname
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name = rr.(*dnsRR_CNAME).Cname
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@ -143,7 +142,7 @@ Cname:
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// Do a lookup for a single name, which must be rooted
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// (otherwise answer will not find the answers).
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func tryOneName(cfg *dnsConfig, name string) (addrs []string, err os.Error) {
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func tryOneName(cfg *dnsConfig, name string, qtype uint16) (addrs []dnsRR, err os.Error) {
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if len(cfg.servers) == 0 {
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return nil, &DNSError{Error: "no DNS servers", Name: name}
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}
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@ -160,13 +159,13 @@ func tryOneName(cfg *dnsConfig, name string) (addrs []string, err os.Error) {
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err = cerr
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continue
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}
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msg, merr := exchange(cfg, c, name)
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msg, merr := exchange(cfg, c, name, qtype)
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c.Close()
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if merr != nil {
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err = merr
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continue
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}
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addrs, err = answer(name, server, msg)
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addrs, err = answer(name, server, msg, qtype)
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if err == nil || err.(*DNSError).Error == noSuchHost {
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break
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}
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@ -174,6 +173,16 @@ func tryOneName(cfg *dnsConfig, name string) (addrs []string, err os.Error) {
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return
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}
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func convertRR_A(records []dnsRR) []string {
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addrs := make([]string, len(records))
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for i := 0; i < len(records); i++ {
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rr := records[i]
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a := rr.(*dnsRR_A).A
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addrs[i] = IPv4(byte(a>>24), byte(a>>16), byte(a>>8), byte(a)).String()
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}
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return addrs
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}
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var cfg *dnsConfig
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var dnserr os.Error
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@ -223,10 +232,7 @@ func isDomainName(s string) bool {
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return ok
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}
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// LookupHost looks for name using the local hosts file and DNS resolver.
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// It returns the canonical name for the host and an array of that
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// host's addresses.
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func LookupHost(name string) (cname string, addrs []string, err os.Error) {
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func lookup(name string, qtype uint16) (cname string, addrs []dnsRR, err os.Error) {
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if !isDomainName(name) {
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return name, nil, &DNSError{Error: "invalid domain name", Name: name}
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}
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@ -235,12 +241,6 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
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err = dnserr
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return
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}
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// Use entries from /etc/hosts if they match.
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addrs = lookupStaticHost(name)
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if len(addrs) > 0 {
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cname = name
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return
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}
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// If name is rooted (trailing dot) or has enough dots,
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// try it by itself first.
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rooted := len(name) > 0 && name[len(name)-1] == '.'
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@ -250,7 +250,7 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
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rname += "."
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}
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// Can try as ordinary name.
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addrs, err = tryOneName(cfg, rname)
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addrs, err = tryOneName(cfg, rname, qtype)
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if err == nil {
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cname = rname
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return
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@ -266,7 +266,7 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
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if rname[len(rname)-1] != '.' {
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rname += "."
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}
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addrs, err = tryOneName(cfg, rname)
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addrs, err = tryOneName(cfg, rname, qtype)
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if err == nil {
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cname = rname
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return
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@ -278,10 +278,55 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
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if !rooted {
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rname += "."
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}
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addrs, err = tryOneName(cfg, rname)
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addrs, err = tryOneName(cfg, rname, qtype)
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if err == nil {
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cname = rname
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return
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}
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return
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}
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// LookupHost looks for name using the local hosts file and DNS resolver.
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// It returns the canonical name for the host and an array of that
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// host's addresses.
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func LookupHost(name string) (cname string, addrs []string, err os.Error) {
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once.Do(loadConfig)
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if dnserr != nil || cfg == nil {
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err = dnserr
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return
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}
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// Use entries from /etc/hosts if they match.
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addrs = lookupStaticHost(name)
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if len(addrs) > 0 {
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cname = name
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return
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}
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var records []dnsRR
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cname, records, err = lookup(name, dnsTypeA)
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if err != nil {
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return
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}
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addrs = convertRR_A(records)
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return
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}
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type SRV struct {
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Target string
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Port uint16
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Priority uint16
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Weight uint16
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}
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func LookupSRV(name string) (cname string, addrs []*SRV, err os.Error) {
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var records []dnsRR
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cname, records, err = lookup(name, dnsTypeSRV)
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if err != nil {
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return
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}
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addrs = make([]*SRV, len(records))
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for i := 0; i < len(records); i++ {
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r := records[i].(*dnsRR_SRV)
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addrs[i] = &SRV{r.Target, r.Port, r.Priority, r.Weight}
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}
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return
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}
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@ -50,6 +50,7 @@ const (
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dnsTypeMINFO = 14
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dnsTypeMX = 15
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dnsTypeTXT = 16
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dnsTypeSRV = 33
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// valid dnsQuestion.qtype only
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dnsTypeAXFR = 252
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@ -226,6 +227,18 @@ func (rr *dnsRR_TXT) Header() *dnsRR_Header {
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return &rr.Hdr
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}
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type dnsRR_SRV struct {
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Hdr dnsRR_Header
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Priority uint16
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Weight uint16
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Port uint16
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Target string "domain-name"
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}
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func (rr *dnsRR_SRV) Header() *dnsRR_Header {
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return &rr.Hdr
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}
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type dnsRR_A struct {
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Hdr dnsRR_Header
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A uint32 "ipv4"
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@ -255,6 +268,7 @@ var rr_mk = map[int]func() dnsRR{
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dnsTypePTR: func() dnsRR { return new(dnsRR_PTR) },
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dnsTypeSOA: func() dnsRR { return new(dnsRR_SOA) },
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dnsTypeTXT: func() dnsRR { return new(dnsRR_TXT) },
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dnsTypeSRV: func() dnsRR { return new(dnsRR_SRV) },
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dnsTypeA: func() dnsRR { return new(dnsRR_A) },
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}
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