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-rw-r--r--src/pkg/net/dnsclient.go367
1 files changed, 20 insertions, 347 deletions
diff --git a/src/pkg/net/dnsclient.go b/src/pkg/net/dnsclient.go
index ae9ca8430..280b19453 100644
--- a/src/pkg/net/dnsclient.go
+++ b/src/pkg/net/dnsclient.go
@@ -2,16 +2,6 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
-// DNS client: see RFC 1035.
-// Has to be linked into package net for Dial.
-
-// TODO(rsc):
-// Check periodically whether /etc/resolv.conf has changed.
-// Could potentially handle many outstanding lookups faster.
-// Could have a small cache.
-// Random UDP source port (net.Dial should do that for us).
-// Random request IDs.
-
package net
import (
@@ -19,9 +9,6 @@ import (
"fmt"
"os"
"rand"
- "sync"
- "time"
- "sort"
)
// DNSError represents a DNS lookup error.
@@ -49,54 +36,31 @@ func (e *DNSError) Temporary() bool { return e.IsTimeout }
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, 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{
- {name, qtype, dnsClassINET},
- }
- out.recursion_desired = true
- msg, ok := out.Pack()
- if !ok {
- return nil, &DNSError{Error: "internal error - cannot pack message", Name: name}
+// reverseaddr returns the in-addr.arpa. or ip6.arpa. hostname of the IP
+// address addr suitable for rDNS (PTR) record lookup or an error if it fails
+// to parse the IP address.
+func reverseaddr(addr string) (arpa string, err os.Error) {
+ ip := ParseIP(addr)
+ if ip == nil {
+ return "", &DNSError{Error: "unrecognized address", Name: addr}
}
-
- for attempt := 0; attempt < cfg.attempts; attempt++ {
- n, err := c.Write(msg)
- if err != nil {
- return nil, err
- }
-
- c.SetReadTimeout(int64(cfg.timeout) * 1e9) // nanoseconds
-
- buf := make([]byte, 2000) // More than enough.
- n, err = c.Read(buf)
- if err != nil {
- if e, ok := err.(Error); ok && e.Timeout() {
- continue
- }
- return nil, err
- }
- buf = buf[0:n]
- in := new(dnsMsg)
- if !in.Unpack(buf) || in.id != out.id {
- continue
- }
- return in, nil
+ if ip.To4() != nil {
+ return fmt.Sprintf("%d.%d.%d.%d.in-addr.arpa.", ip[15], ip[14], ip[13], ip[12]), nil
}
- var server string
- if a := c.RemoteAddr(); a != nil {
- server = a.String()
+ // Must be IPv6
+ var buf bytes.Buffer
+ // Add it, in reverse, to the buffer
+ for i := len(ip) - 1; i >= 0; i-- {
+ s := fmt.Sprintf("%02x", ip[i])
+ buf.WriteByte(s[1])
+ buf.WriteByte('.')
+ buf.WriteByte(s[0])
+ buf.WriteByte('.')
}
- return nil, &DNSError{Error: "no answer from server", Name: name, Server: server, IsTimeout: true}
+ // Append "ip6.arpa." and return (buf already has the final .)
+ return buf.String() + "ip6.arpa.", nil
}
-
// Find answer for name in dns message.
// On return, if err == nil, addrs != nil.
func answer(name, server string, dns *dnsMsg, qtype uint16) (cname string, addrs []dnsRR, err os.Error) {
@@ -150,63 +114,6 @@ Cname:
return "", nil, &DNSError{Error: "too many redirects", Name: name, Server: server}
}
-// Do a lookup for a single name, which must be rooted
-// (otherwise answer will not find the answers).
-func tryOneName(cfg *dnsConfig, name string, qtype uint16) (cname string, addrs []dnsRR, err os.Error) {
- if len(cfg.servers) == 0 {
- return "", nil, &DNSError{Error: "no DNS servers", Name: name}
- }
- for i := 0; i < len(cfg.servers); i++ {
- // Calling Dial here is scary -- we have to be sure
- // not to dial a name that will require a DNS lookup,
- // or Dial will call back here to translate it.
- // The DNS config parser has already checked that
- // all the cfg.servers[i] are IP addresses, which
- // Dial will use without a DNS lookup.
- server := cfg.servers[i] + ":53"
- c, cerr := Dial("udp", server)
- if cerr != nil {
- err = cerr
- continue
- }
- msg, merr := exchange(cfg, c, name, qtype)
- c.Close()
- if merr != nil {
- err = merr
- continue
- }
- cname, addrs, err = answer(name, server, msg, qtype)
- if err == nil || err.(*DNSError).Error == noSuchHost {
- break
- }
- }
- return
-}
-
-func convertRR_A(records []dnsRR) []IP {
- addrs := make([]IP, len(records))
- for i, rr := range records {
- a := rr.(*dnsRR_A).A
- addrs[i] = IPv4(byte(a>>24), byte(a>>16), byte(a>>8), byte(a))
- }
- return addrs
-}
-
-func convertRR_AAAA(records []dnsRR) []IP {
- addrs := make([]IP, len(records))
- for i, rr := range records {
- a := make(IP, 16)
- copy(a, rr.(*dnsRR_AAAA).AAAA[:])
- addrs[i] = a
- }
- return addrs
-}
-
-var cfg *dnsConfig
-var dnserr os.Error
-
-func loadConfig() { cfg, dnserr = dnsReadConfig() }
-
func isDomainName(s string) bool {
// See RFC 1035, RFC 3696.
if len(s) == 0 {
@@ -255,141 +162,6 @@ func isDomainName(s string) bool {
return ok
}
-var onceLoadConfig sync.Once
-
-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}
- }
- onceLoadConfig.Do(loadConfig)
- if dnserr != nil || cfg == nil {
- err = dnserr
- return
- }
- // If name is rooted (trailing dot) or has enough dots,
- // try it by itself first.
- rooted := len(name) > 0 && name[len(name)-1] == '.'
- if rooted || count(name, '.') >= cfg.ndots {
- rname := name
- if !rooted {
- rname += "."
- }
- // Can try as ordinary name.
- cname, addrs, err = tryOneName(cfg, rname, qtype)
- if err == nil {
- return
- }
- }
- if rooted {
- return
- }
-
- // Otherwise, try suffixes.
- for i := 0; i < len(cfg.search); i++ {
- rname := name + "." + cfg.search[i]
- if rname[len(rname)-1] != '.' {
- rname += "."
- }
- cname, addrs, err = tryOneName(cfg, rname, qtype)
- if err == nil {
- return
- }
- }
-
- // Last ditch effort: try unsuffixed.
- rname := name
- if !rooted {
- rname += "."
- }
- cname, addrs, err = tryOneName(cfg, rname, qtype)
- if err == nil {
- return
- }
- return
-}
-
-// goLookupHost is the native Go implementation of LookupHost.
-// Used only if cgoLookupHost refuses to handle the request
-// (that is, only if cgoLookupHost is the stub in cgo_stub.go).
-// Normally we let cgo use the C library resolver instead of
-// depending on our lookup code, so that Go and C get the same
-// answers.
-func goLookupHost(name string) (addrs []string, err os.Error) {
- // Use entries from /etc/hosts if they match.
- addrs = lookupStaticHost(name)
- if len(addrs) > 0 {
- return
- }
- onceLoadConfig.Do(loadConfig)
- if dnserr != nil || cfg == nil {
- err = dnserr
- return
- }
- ips, err := goLookupIP(name)
- if err != nil {
- return
- }
- addrs = make([]string, 0, len(ips))
- for _, ip := range ips {
- addrs = append(addrs, ip.String())
- }
- return
-}
-
-// goLookupIP is the native Go implementation of LookupIP.
-// Used only if cgoLookupIP refuses to handle the request
-// (that is, only if cgoLookupIP is the stub in cgo_stub.go).
-// Normally we let cgo use the C library resolver instead of
-// depending on our lookup code, so that Go and C get the same
-// answers.
-func goLookupIP(name string) (addrs []IP, err os.Error) {
- onceLoadConfig.Do(loadConfig)
- if dnserr != nil || cfg == nil {
- err = dnserr
- return
- }
- var records []dnsRR
- var cname string
- cname, records, err = lookup(name, dnsTypeA)
- if err != nil {
- return
- }
- addrs = convertRR_A(records)
- if cname != "" {
- name = cname
- }
- _, records, err = lookup(name, dnsTypeAAAA)
- if err != nil && len(addrs) > 0 {
- // Ignore error because A lookup succeeded.
- err = nil
- }
- if err != nil {
- return
- }
- addrs = append(addrs, convertRR_AAAA(records)...)
- return
-}
-
-// goLookupCNAME is the native Go implementation of LookupCNAME.
-// Used only if cgoLookupCNAME refuses to handle the request
-// (that is, only if cgoLookupCNAME is the stub in cgo_stub.go).
-// Normally we let cgo use the C library resolver instead of
-// depending on our lookup code, so that Go and C get the same
-// answers.
-func goLookupCNAME(name string) (cname string, err os.Error) {
- onceLoadConfig.Do(loadConfig)
- if dnserr != nil || cfg == nil {
- err = dnserr
- return
- }
- _, rr, err := lookup(name, dnsTypeCNAME)
- if err != nil {
- return
- }
- cname = rr[0].(*dnsRR_CNAME).Cname
- return
-}
-
// An SRV represents a single DNS SRV record.
type SRV struct {
Target string
@@ -436,35 +208,6 @@ func shuffleSRVByWeight(addrs []*SRV) {
}
}
-// LookupSRV tries to resolve an SRV query of the given service,
-// protocol, and domain name, as specified in RFC 2782. In most cases
-// the proto argument can be the same as the corresponding
-// Addr.Network(). The returned records are sorted by priority
-// and randomized by weight within a priority.
-func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err os.Error) {
- target := "_" + service + "._" + proto + "." + name
- var records []dnsRR
- cname, records, err = lookup(target, dnsTypeSRV)
- if err != nil {
- return
- }
- addrs = make([]*SRV, len(records))
- for i, rr := range records {
- r := rr.(*dnsRR_SRV)
- addrs[i] = &SRV{r.Target, r.Port, r.Priority, r.Weight}
- }
- sort.Sort(byPriorityWeight(addrs))
- i := 0
- for j := 1; j < len(addrs); j++ {
- if addrs[i].Priority != addrs[j].Priority {
- shuffleSRVByWeight(addrs[i:j])
- i = j
- }
- }
- shuffleSRVByWeight(addrs[i:len(addrs)])
- return
-}
-
// An MX represents a single DNS MX record.
type MX struct {
Host string
@@ -479,73 +222,3 @@ func (s byPref) Len() int { return len(s) }
func (s byPref) Less(i, j int) bool { return s[i].Pref < s[j].Pref }
func (s byPref) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
-
-// LookupMX returns the DNS MX records for the given domain name sorted by preference.
-func LookupMX(name string) (mx []*MX, err os.Error) {
- _, rr, err := lookup(name, dnsTypeMX)
- if err != nil {
- return
- }
- mx = make([]*MX, len(rr))
- for i := range rr {
- r := rr[i].(*dnsRR_MX)
- mx[i] = &MX{r.Mx, r.Pref}
- }
- // Shuffle the records to match RFC 5321 when sorted
- for i := range mx {
- j := rand.Intn(i + 1)
- mx[i], mx[j] = mx[j], mx[i]
- }
- sort.Sort(byPref(mx))
- return
-}
-
-// reverseaddr returns the in-addr.arpa. or ip6.arpa. hostname of the IP
-// address addr suitable for rDNS (PTR) record lookup or an error if it fails
-// to parse the IP address.
-func reverseaddr(addr string) (arpa string, err os.Error) {
- ip := ParseIP(addr)
- if ip == nil {
- return "", &DNSError{Error: "unrecognized address", Name: addr}
- }
- if ip.To4() != nil {
- return fmt.Sprintf("%d.%d.%d.%d.in-addr.arpa.", ip[15], ip[14], ip[13], ip[12]), nil
- }
- // Must be IPv6
- var buf bytes.Buffer
- // Add it, in reverse, to the buffer
- for i := len(ip) - 1; i >= 0; i-- {
- s := fmt.Sprintf("%02x", ip[i])
- buf.WriteByte(s[1])
- buf.WriteByte('.')
- buf.WriteByte(s[0])
- buf.WriteByte('.')
- }
- // Append "ip6.arpa." and return (buf already has the final .)
- return buf.String() + "ip6.arpa.", nil
-}
-
-// LookupAddr performs a reverse lookup for the given address, returning a list
-// of names mapping to that address.
-func LookupAddr(addr string) (name []string, err os.Error) {
- name = lookupStaticAddr(addr)
- if len(name) > 0 {
- return
- }
- var arpa string
- arpa, err = reverseaddr(addr)
- if err != nil {
- return
- }
- var records []dnsRR
- _, records, err = lookup(arpa, dnsTypePTR)
- if err != nil {
- return
- }
- name = make([]string, len(records))
- for i := range records {
- r := records[i].(*dnsRR_PTR)
- name[i] = r.Ptr
- }
- return
-}
generated by cgit v1.2.3 (git 2.39.1) at 2025-06-01 22:39:56 +0000