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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package net
import (
"os"
)
func query(filename, query string, bufSize int) (res []string, err os.Error) {
file, err := os.OpenFile(filename, os.O_RDWR, 0)
if err != nil {
return
}
defer file.Close()
_, err = file.WriteString(query)
if err != nil {
return
}
_, err = file.Seek(0, 0)
if err != nil {
return
}
buf := make([]byte, bufSize)
for {
n, _ := file.Read(buf)
if n <= 0 {
break
}
res = append(res, string(buf[:n]))
}
return
}
func queryCS(net, host, service string) (res []string, err os.Error) {
switch net {
case "tcp4", "tcp6":
net = "tcp"
case "udp4", "udp6":
net = "udp"
}
if host == "" {
host = "*"
}
return query("/net/cs", net+"!"+host+"!"+service, 128)
}
func queryCS1(net string, ip IP, port int) (clone, dest string, err os.Error) {
ips := "*"
if !ip.IsUnspecified() {
ips = ip.String()
}
lines, err := queryCS(net, ips, itoa(port))
if err != nil {
return
}
f := getFields(lines[0])
if len(f) < 2 {
return "", "", os.NewError("net: bad response from ndb/cs")
}
clone, dest = f[0], f[1]
return
}
func queryDNS(addr string, typ string) (res []string, err os.Error) {
return query("/net/dns", addr+" "+typ, 1024)
}
// LookupHost looks up the given host using the local resolver.
// It returns an array of that host's addresses.
func LookupHost(host string) (addrs []string, err os.Error) {
// Use /net/cs insead of /net/dns because cs knows about
// host names in local network (e.g. from /lib/ndb/local)
lines, err := queryCS("tcp", host, "1")
if err != nil {
return
}
for _, line := range lines {
f := getFields(line)
if len(f) < 2 {
continue
}
addr := f[1]
if i := byteIndex(addr, '!'); i >= 0 {
addr = addr[:i] // remove port
}
if ParseIP(addr) == nil {
continue
}
addrs = append(addrs, addr)
}
return
}
// LookupIP looks up host using the local resolver.
// It returns an array of that host's IPv4 and IPv6 addresses.
func LookupIP(host string) (ips []IP, err os.Error) {
addrs, err := LookupHost(host)
if err != nil {
return
}
for _, addr := range addrs {
if ip := ParseIP(addr); ip != nil {
ips = append(ips, ip)
}
}
return
}
// LookupPort looks up the port for the given network and service.
func LookupPort(network, service string) (port int, err os.Error) {
switch network {
case "tcp4", "tcp6":
network = "tcp"
case "udp4", "udp6":
network = "udp"
}
lines, err := queryCS(network, "127.0.0.1", service)
if err != nil {
return
}
unknownPortError := &AddrError{"unknown port", network + "/" + service}
if len(lines) == 0 {
return 0, unknownPortError
}
f := getFields(lines[0])
if len(f) < 2 {
return 0, unknownPortError
}
s := f[1]
if i := byteIndex(s, '!'); i >= 0 {
s = s[i+1:] // remove address
}
if n, _, ok := dtoi(s, 0); ok {
return n, nil
}
return 0, unknownPortError
}
// LookupCNAME returns the canonical DNS host for the given name.
// Callers that do not care about the canonical name can call
// LookupHost or LookupIP directly; both take care of resolving
// the canonical name as part of the lookup.
func LookupCNAME(name string) (cname string, err os.Error) {
lines, err := queryDNS(name, "cname")
if err != nil {
return
}
if len(lines) > 0 {
if f := getFields(lines[0]); len(f) >= 3 {
return f[2] + ".", nil
}
}
return "", os.NewError("net: bad response from ndb/dns")
}
// 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
lines, err := queryDNS(target, "srv")
if err != nil {
return
}
for _, line := range lines {
f := getFields(line)
if len(f) < 6 {
continue
}
port, _, portOk := dtoi(f[2], 0)
priority, _, priorityOk := dtoi(f[3], 0)
weight, _, weightOk := dtoi(f[4], 0)
if !(portOk && priorityOk && weightOk) {
continue
}
addrs = append(addrs, &SRV{f[5], uint16(port), uint16(priority), uint16(weight)})
cname = f[0]
}
byPriorityWeight(addrs).sort()
return
}
// LookupMX returns the DNS MX records for the given domain name sorted by preference.
func LookupMX(name string) (mx []*MX, err os.Error) {
lines, err := queryDNS(name, "mx")
if err != nil {
return
}
for _, line := range lines {
f := getFields(line)
if len(f) < 4 {
continue
}
if pref, _, ok := dtoi(f[2], 0); ok {
mx = append(mx, &MX{f[3], uint16(pref)})
}
}
byPref(mx).sort()
return
}
// 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) {
arpa, err := reverseaddr(addr)
if err != nil {
return
}
lines, err := queryDNS(arpa, "ptr")
if err != nil {
return
}
for _, line := range lines {
f := getFields(line)
if len(f) < 3 {
continue
}
name = append(name, f[2])
}
return
}