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net: add support for DNS SRV requests.

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Fixes #758.

R=rsc, adg
CC=golang-dev
https://golang.org/cl/1078041
This commit is contained in:
Kirklin McDonald 2010-06-30 10:54:24 +10:00 committed by Andrew Gerrand
parent 774333685e
commit 0046d51e06
2 changed files with 82 additions and 23 deletions
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91
src/pkg/net/dnsclient.go
View File

@ -45,14 +45,14 @@ const noSuchHost = "no such host"
// Send a request on the connection and hope for a reply.
// Up to cfg.attempts attempts.
func exchange(cfg *dnsConfig, c Conn, name string) (*dnsMsg, os.Error) {
func exchange(cfg *dnsConfig, c Conn, name string, qtype uint16) (*dnsMsg, os.Error) {
if len(name) >= 256 {
return nil, &DNSError{Error: "name too long", Name: name}
}
out := new(dnsMsg)
out.id = uint16(rand.Int()) ^ uint16(time.Nanoseconds())
out.question = []dnsQuestion{
dnsQuestion{name, dnsTypeA, dnsClassINET},
dnsQuestion{name, qtype, dnsClassINET},
}
out.recursion_desired = true
msg, ok := out.Pack()
@ -93,8 +93,8 @@ func exchange(cfg *dnsConfig, c Conn, name string) (*dnsMsg, os.Error) {
// Find answer for name in dns message.
// On return, if err == nil, addrs != nil.
func answer(name, server string, dns *dnsMsg) (addrs []string, err os.Error) {
addrs = make([]string, 0, len(dns.answer))
func answer(name, server string, dns *dnsMsg, qtype uint16) (addrs []dnsRR, err os.Error) {
addrs = make([]dnsRR, 0, len(dns.answer))
if dns.rcode == dnsRcodeNameError && dns.recursion_available {
return nil, &DNSError{Error: noSuchHost, Name: name}
@ -120,11 +120,10 @@ Cname:
h := rr.Header()
if h.Class == dnsClassINET && h.Name == name {
switch h.Rrtype {
case dnsTypeA:
case qtype:
n := len(addrs)
a := rr.(*dnsRR_A).A
addrs = addrs[0 : n+1]
addrs[n] = IPv4(byte(a>>24), byte(a>>16), byte(a>>8), byte(a)).String()
addrs[n] = rr
case dnsTypeCNAME:
// redirect to cname
name = rr.(*dnsRR_CNAME).Cname
@ -143,7 +142,7 @@ Cname:
// Do a lookup for a single name, which must be rooted
// (otherwise answer will not find the answers).
func tryOneName(cfg *dnsConfig, name string) (addrs []string, err os.Error) {
func tryOneName(cfg *dnsConfig, name string, qtype uint16) (addrs []dnsRR, err os.Error) {
if len(cfg.servers) == 0 {
return nil, &DNSError{Error: "no DNS servers", Name: name}
}
@ -160,13 +159,13 @@ func tryOneName(cfg *dnsConfig, name string) (addrs []string, err os.Error) {
err = cerr
continue
}
msg, merr := exchange(cfg, c, name)
msg, merr := exchange(cfg, c, name, qtype)
c.Close()
if merr != nil {
err = merr
continue
}
addrs, err = answer(name, server, msg)
addrs, err = answer(name, server, msg, qtype)
if err == nil || err.(*DNSError).Error == noSuchHost {
break
}
@ -174,6 +173,16 @@ func tryOneName(cfg *dnsConfig, name string) (addrs []string, err os.Error) {
return
}
func convertRR_A(records []dnsRR) []string {
addrs := make([]string, len(records))
for i := 0; i < len(records); i++ {
rr := records[i]
a := rr.(*dnsRR_A).A
addrs[i] = IPv4(byte(a>>24), byte(a>>16), byte(a>>8), byte(a)).String()
}
return addrs
}
var cfg *dnsConfig
var dnserr os.Error
@ -223,10 +232,7 @@ func isDomainName(s string) bool {
return ok
}
// LookupHost looks for name using the local hosts file and DNS resolver.
// It returns the canonical name for the host and an array of that
// host's addresses.
func LookupHost(name string) (cname string, addrs []string, err os.Error) {
func lookup(name string, qtype uint16) (cname string, addrs []dnsRR, err os.Error) {
if !isDomainName(name) {
return name, nil, &DNSError{Error: "invalid domain name", Name: name}
}
@ -235,12 +241,6 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
err = dnserr
return
}
// Use entries from /etc/hosts if they match.
addrs = lookupStaticHost(name)
if len(addrs) > 0 {
cname = name
return
}
// If name is rooted (trailing dot) or has enough dots,
// try it by itself first.
rooted := len(name) > 0 && name[len(name)-1] == '.'
@ -250,7 +250,7 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
rname += "."
}
// Can try as ordinary name.
addrs, err = tryOneName(cfg, rname)
addrs, err = tryOneName(cfg, rname, qtype)
if err == nil {
cname = rname
return
@ -266,7 +266,7 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
if rname[len(rname)-1] != '.' {
rname += "."
}
addrs, err = tryOneName(cfg, rname)
addrs, err = tryOneName(cfg, rname, qtype)
if err == nil {
cname = rname
return
@ -278,10 +278,55 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) {
if !rooted {
rname += "."
}
addrs, err = tryOneName(cfg, rname)
addrs, err = tryOneName(cfg, rname, qtype)
if err == nil {
cname = rname
return
}
return
}
// LookupHost looks for name using the local hosts file and DNS resolver.
// It returns the canonical name for the host and an array of that
// host's addresses.
func LookupHost(name string) (cname string, addrs []string, err os.Error) {
once.Do(loadConfig)
if dnserr != nil || cfg == nil {
err = dnserr
return
}
// Use entries from /etc/hosts if they match.
addrs = lookupStaticHost(name)
if len(addrs) > 0 {
cname = name
return
}
var records []dnsRR
cname, records, err = lookup(name, dnsTypeA)
if err != nil {
return
}
addrs = convertRR_A(records)
return
}
type SRV struct {
Target string
Port uint16
Priority uint16
Weight uint16
}
func LookupSRV(name string) (cname string, addrs []*SRV, err os.Error) {
var records []dnsRR
cname, records, err = lookup(name, dnsTypeSRV)
if err != nil {
return
}
addrs = make([]*SRV, len(records))
for i := 0; i < len(records); i++ {
r := records[i].(*dnsRR_SRV)
addrs[i] = &SRV{r.Target, r.Port, r.Priority, r.Weight}
}
return
}

14
src/pkg/net/dnsmsg.go
View File

@ -50,6 +50,7 @@ const (
dnsTypeMINFO = 14
dnsTypeMX = 15
dnsTypeTXT = 16
dnsTypeSRV = 33
// valid dnsQuestion.qtype only
dnsTypeAXFR = 252
@ -226,6 +227,18 @@ func (rr *dnsRR_TXT) Header() *dnsRR_Header {
return &rr.Hdr
}
type dnsRR_SRV struct {
Hdr dnsRR_Header
Priority uint16
Weight uint16
Port uint16
Target string "domain-name"
}
func (rr *dnsRR_SRV) Header() *dnsRR_Header {
return &rr.Hdr
}
type dnsRR_A struct {
Hdr dnsRR_Header
A uint32 "ipv4"
@ -255,6 +268,7 @@ var rr_mk = map[int]func() dnsRR{
dnsTypePTR: func() dnsRR { return new(dnsRR_PTR) },
dnsTypeSOA: func() dnsRR { return new(dnsRR_SOA) },
dnsTypeTXT: func() dnsRR { return new(dnsRR_TXT) },
dnsTypeSRV: func() dnsRR { return new(dnsRR_SRV) },
dnsTypeA: func() dnsRR { return new(dnsRR_A) },
}