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// Copyright 2009 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 (
"errors"
"syscall"
"unsafe"
"os"
"sync"
)
var (
protoentLock sync.Mutex
hostentLock sync.Mutex
serventLock sync.Mutex
)
// lookupProtocol looks up IP protocol name and returns correspondent protocol number.
func lookupProtocol(name string) (proto int, err error) {
protoentLock.Lock()
defer protoentLock.Unlock()
p, e := syscall.GetProtoByName(name)
if e != 0 {
return 0, os.NewSyscallError("GetProtoByName", e)
}
return int(p.Proto), nil
}
func LookupHost(name string) (addrs []string, err error) {
ips, err := LookupIP(name)
if err != nil {
return
}
addrs = make([]string, 0, len(ips))
for _, ip := range ips {
addrs = append(addrs, ip.String())
}
return
}
func LookupIP(name string) (addrs []IP, err error) {
hostentLock.Lock()
defer hostentLock.Unlock()
h, e := syscall.GetHostByName(name)
if e != 0 {
return nil, os.NewSyscallError("GetHostByName", e)
}
switch h.AddrType {
case syscall.AF_INET:
i := 0
addrs = make([]IP, 100) // plenty of room to grow
for p := (*[100](*[4]byte))(unsafe.Pointer(h.AddrList)); i < cap(addrs) && p[i] != nil; i++ {
addrs[i] = IPv4(p[i][0], p[i][1], p[i][2], p[i][3])
}
addrs = addrs[0:i]
default: // TODO(vcc): Implement non IPv4 address lookups.
return nil, os.NewSyscallError("LookupHost", syscall.EWINDOWS)
}
return addrs, nil
}
func LookupPort(network, service string) (port int, err error) {
switch network {
case "tcp4", "tcp6":
network = "tcp"
case "udp4", "udp6":
network = "udp"
}
serventLock.Lock()
defer serventLock.Unlock()
s, e := syscall.GetServByName(service, network)
if e != 0 {
return 0, os.NewSyscallError("GetServByName", e)
}
return int(syscall.Ntohs(s.Port)), nil
}
func LookupCNAME(name string) (cname string, err error) {
var r *syscall.DNSRecord
e := syscall.DnsQuery(name, syscall.DNS_TYPE_CNAME, 0, nil, &r, nil)
if int(e) != 0 {
return "", os.NewSyscallError("LookupCNAME", int(e))
}
defer syscall.DnsRecordListFree(r, 1)
if r != nil && r.Type == syscall.DNS_TYPE_CNAME {
v := (*syscall.DNSPTRData)(unsafe.Pointer(&r.Data[0]))
cname = syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Host))[:]) + "."
}
return
}
// LookupSRV tries to resolve an SRV query of the given service,
// protocol, and domain name. The proto is "tcp" or "udp".
// The returned records are sorted by priority and randomized
// by weight within a priority.
//
// LookupSRV constructs the DNS name to look up following RFC 2782.
// That is, it looks up _service._proto.name. To accommodate services
// publishing SRV records under non-standard names, if both service
// and proto are empty strings, LookupSRV looks up name directly.
func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) {
var target string
if service == "" && proto == "" {
target = name
} else {
target = "_" + service + "._" + proto + "." + name
}
var r *syscall.DNSRecord
e := syscall.DnsQuery(target, syscall.DNS_TYPE_SRV, 0, nil, &r, nil)
if int(e) != 0 {
return "", nil, os.NewSyscallError("LookupSRV", int(e))
}
defer syscall.DnsRecordListFree(r, 1)
addrs = make([]*SRV, 0, 10)
for p := r; p != nil && p.Type == syscall.DNS_TYPE_SRV; p = p.Next {
v := (*syscall.DNSSRVData)(unsafe.Pointer(&p.Data[0]))
addrs = append(addrs, &SRV{syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Target))[:]), v.Port, v.Priority, v.Weight})
}
byPriorityWeight(addrs).sort()
return name, addrs, nil
}
func LookupMX(name string) (mx []*MX, err error) {
var r *syscall.DNSRecord
e := syscall.DnsQuery(name, syscall.DNS_TYPE_MX, 0, nil, &r, nil)
if int(e) != 0 {
return nil, os.NewSyscallError("LookupMX", int(e))
}
defer syscall.DnsRecordListFree(r, 1)
mx = make([]*MX, 0, 10)
for p := r; p != nil && p.Type == syscall.DNS_TYPE_MX; p = p.Next {
v := (*syscall.DNSMXData)(unsafe.Pointer(&p.Data[0]))
mx = append(mx, &MX{syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.NameExchange))[:]) + ".", v.Preference})
}
byPref(mx).sort()
return mx, nil
}
func LookupTXT(name string) (txt []string, err error) {
return nil, errors.New("net.LookupTXT is not implemented on Windows")
}
func LookupAddr(addr string) (name []string, err error) {
arpa, err := reverseaddr(addr)
if err != nil {
return nil, err
}
var r *syscall.DNSRecord
e := syscall.DnsQuery(arpa, syscall.DNS_TYPE_PTR, 0, nil, &r, nil)
if int(e) != 0 {
return nil, os.NewSyscallError("LookupAddr", int(e))
}
defer syscall.DnsRecordListFree(r, 1)
name = make([]string, 0, 10)
for p := r; p != nil && p.Type == syscall.DNS_TYPE_PTR; p = p.Next {
v := (*syscall.DNSPTRData)(unsafe.Pointer(&p.Data[0]))
name = append(name, syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Host))[:]))
}
return name, nil
}
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