// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build cgo,!netgo
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// +build darwin dragonfly freebsd linux netbsd openbsd solaris
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package net
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/*
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netdb.h>
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#include <unistd.h>
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#include <string.h>
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*/
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import "C"
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import (
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"context"
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"syscall"
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"unsafe"
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)
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// An addrinfoErrno represents a getaddrinfo, getnameinfo-specific
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// error number. It's a signed number and a zero value is a non-error
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// by convention.
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type addrinfoErrno int
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func (eai addrinfoErrno) Error() string { return C.GoString(C.gai_strerror(C.int(eai))) }
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func (eai addrinfoErrno) Temporary() bool { return eai == C.EAI_AGAIN }
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func (eai addrinfoErrno) Timeout() bool { return false }
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type portLookupResult struct {
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port int
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err error
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}
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type ipLookupResult struct {
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addrs []IPAddr
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cname string
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err error
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}
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type reverseLookupResult struct {
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names []string
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err error
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}
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func cgoLookupHost(ctx context.Context, name string) (hosts []string, err error, completed bool) {
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addrs, err, completed := cgoLookupIP(ctx, "ip", name)
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for _, addr := range addrs {
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hosts = append(hosts, addr.String())
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}
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return
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}
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func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
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var hints C.struct_addrinfo
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switch network {
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case "": // no hints
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case "tcp", "tcp4", "tcp6":
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hints.ai_socktype = C.SOCK_STREAM
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hints.ai_protocol = C.IPPROTO_TCP
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case "udp", "udp4", "udp6":
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hints.ai_socktype = C.SOCK_DGRAM
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hints.ai_protocol = C.IPPROTO_UDP
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default:
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return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}, true
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}
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switch ipVersion(network) {
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case '4':
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hints.ai_family = C.AF_INET
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case '6':
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hints.ai_family = C.AF_INET6
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}
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if ctx.Done() == nil {
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port, err := cgoLookupServicePort(&hints, network, service)
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return port, err, true
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}
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result := make(chan portLookupResult, 1)
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go cgoPortLookup(result, &hints, network, service)
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select {
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case r := <-result:
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return r.port, r.err, true
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case <-ctx.Done():
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// Since there isn't a portable way to cancel the lookup,
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// we just let it finish and write to the buffered channel.
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return 0, mapErr(ctx.Err()), false
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}
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}
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func cgoLookupServicePort(hints *C.struct_addrinfo, network, service string) (port int, err error) {
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cservice := make([]byte, len(service)+1)
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copy(cservice, service)
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// Lowercase the C service name.
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for i, b := range cservice[:len(service)] {
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cservice[i] = lowerASCII(b)
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}
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var res *C.struct_addrinfo
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gerrno, err := C.getaddrinfo(nil, (*C.char)(unsafe.Pointer(&cservice[0])), hints, &res)
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if gerrno != 0 {
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switch gerrno {
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case C.EAI_SYSTEM:
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if err == nil { // see golang.org/issue/6232
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err = syscall.EMFILE
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}
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default:
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err = addrinfoErrno(gerrno)
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}
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return 0, &DNSError{Err: err.Error(), Name: network + "/" + service}
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}
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defer C.freeaddrinfo(res)
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for r := res; r != nil; r = r.ai_next {
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switch r.ai_family {
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case C.AF_INET:
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sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.ai_addr))
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p := (*[2]byte)(unsafe.Pointer(&sa.Port))
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return int(p[0])<<8 | int(p[1]), nil
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case C.AF_INET6:
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sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.ai_addr))
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p := (*[2]byte)(unsafe.Pointer(&sa.Port))
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return int(p[0])<<8 | int(p[1]), nil
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}
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}
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return 0, &DNSError{Err: "unknown port", Name: network + "/" + service}
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}
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func cgoPortLookup(result chan<- portLookupResult, hints *C.struct_addrinfo, network, service string) {
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port, err := cgoLookupServicePort(hints, network, service)
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result <- portLookupResult{port, err}
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}
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func cgoLookupIPCNAME(network, name string) (addrs []IPAddr, cname string, err error) {
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acquireThread()
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defer releaseThread()
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var hints C.struct_addrinfo
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hints.ai_flags = cgoAddrInfoFlags
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hints.ai_socktype = C.SOCK_STREAM
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hints.ai_family = C.AF_UNSPEC
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switch ipVersion(network) {
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case '4':
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hints.ai_family = C.AF_INET
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case '6':
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hints.ai_family = C.AF_INET6
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}
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h := make([]byte, len(name)+1)
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copy(h, name)
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var res *C.struct_addrinfo
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gerrno, err := C.getaddrinfo((*C.char)(unsafe.Pointer(&h[0])), nil, &hints, &res)
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if gerrno != 0 {
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switch gerrno {
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case C.EAI_SYSTEM:
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if err == nil {
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// err should not be nil, but sometimes getaddrinfo returns
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// gerrno == C.EAI_SYSTEM with err == nil on Linux.
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// The report claims that it happens when we have too many
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// open files, so use syscall.EMFILE (too many open files in system).
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// Most system calls would return ENFILE (too many open files),
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// so at the least EMFILE should be easy to recognize if this
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// comes up again. golang.org/issue/6232.
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err = syscall.EMFILE
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}
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case C.EAI_NONAME:
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err = errNoSuchHost
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default:
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err = addrinfoErrno(gerrno)
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}
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return nil, "", &DNSError{Err: err.Error(), Name: name}
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}
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defer C.freeaddrinfo(res)
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if res != nil {
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cname = C.GoString(res.ai_canonname)
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if cname == "" {
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cname = name
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}
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if len(cname) > 0 && cname[len(cname)-1] != '.' {
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cname += "."
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}
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}
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for r := res; r != nil; r = r.ai_next {
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// We only asked for SOCK_STREAM, but check anyhow.
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if r.ai_socktype != C.SOCK_STREAM {
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continue
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}
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switch r.ai_family {
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case C.AF_INET:
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sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.ai_addr))
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addr := IPAddr{IP: copyIP(sa.Addr[:])}
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addrs = append(addrs, addr)
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case C.AF_INET6:
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sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.ai_addr))
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addr := IPAddr{IP: copyIP(sa.Addr[:]), Zone: zoneCache.name(int(sa.Scope_id))}
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addrs = append(addrs, addr)
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}
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}
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return addrs, cname, nil
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}
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func cgoIPLookup(result chan<- ipLookupResult, network, name string) {
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addrs, cname, err := cgoLookupIPCNAME(network, name)
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result <- ipLookupResult{addrs, cname, err}
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}
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func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error, completed bool) {
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if ctx.Done() == nil {
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addrs, _, err = cgoLookupIPCNAME(network, name)
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return addrs, err, true
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}
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result := make(chan ipLookupResult, 1)
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go cgoIPLookup(result, network, name)
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select {
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case r := <-result:
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return r.addrs, r.err, true
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case <-ctx.Done():
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return nil, mapErr(ctx.Err()), false
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}
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}
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func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
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if ctx.Done() == nil {
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_, cname, err = cgoLookupIPCNAME("ip", name)
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return cname, err, true
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}
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result := make(chan ipLookupResult, 1)
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go cgoIPLookup(result, "ip", name)
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select {
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case r := <-result:
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return r.cname, r.err, true
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case <-ctx.Done():
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return "", mapErr(ctx.Err()), false
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}
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}
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// These are roughly enough for the following:
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//
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// Source Encoding Maximum length of single name entry
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// Unicast DNS ASCII or <=253 + a NUL terminator
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// Unicode in RFC 5892 252 * total number of labels + delimiters + a NUL terminator
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// Multicast DNS UTF-8 in RFC 5198 or <=253 + a NUL terminator
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// the same as unicast DNS ASCII <=253 + a NUL terminator
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// Local database various depends on implementation
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const (
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nameinfoLen = 64
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maxNameinfoLen = 4096
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)
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func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error, completed bool) {
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var zone string
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ip := parseIPv4(addr)
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if ip == nil {
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ip, zone = parseIPv6Zone(addr)
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}
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if ip == nil {
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return nil, &DNSError{Err: "invalid address", Name: addr}, true
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}
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sa, salen := cgoSockaddr(ip, zone)
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if sa == nil {
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return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}, true
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}
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if ctx.Done() == nil {
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names, err := cgoLookupAddrPTR(addr, sa, salen)
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return names, err, true
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}
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result := make(chan reverseLookupResult, 1)
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go cgoReverseLookup(result, addr, sa, salen)
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select {
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case r := <-result:
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return r.names, r.err, true
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case <-ctx.Done():
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return nil, mapErr(ctx.Err()), false
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}
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}
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func cgoLookupAddrPTR(addr string, sa *C.struct_sockaddr, salen C.socklen_t) (names []string, err error) {
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acquireThread()
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defer releaseThread()
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var gerrno int
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var b []byte
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for l := nameinfoLen; l <= maxNameinfoLen; l *= 2 {
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b = make([]byte, l)
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gerrno, err = cgoNameinfoPTR(b, sa, salen)
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if gerrno == 0 || gerrno != C.EAI_OVERFLOW {
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break
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}
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}
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if gerrno != 0 {
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switch gerrno {
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case C.EAI_SYSTEM:
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if err == nil { // see golang.org/issue/6232
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err = syscall.EMFILE
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}
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default:
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err = addrinfoErrno(gerrno)
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}
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return nil, &DNSError{Err: err.Error(), Name: addr}
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}
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for i := 0; i < len(b); i++ {
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if b[i] == 0 {
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b = b[:i]
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break
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}
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}
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return []string{absDomainName(b)}, nil
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}
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func cgoReverseLookup(result chan<- reverseLookupResult, addr string, sa *C.struct_sockaddr, salen C.socklen_t) {
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names, err := cgoLookupAddrPTR(addr, sa, salen)
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result <- reverseLookupResult{names, err}
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}
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func cgoSockaddr(ip IP, zone string) (*C.struct_sockaddr, C.socklen_t) {
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if ip4 := ip.To4(); ip4 != nil {
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return cgoSockaddrInet4(ip4), C.socklen_t(syscall.SizeofSockaddrInet4)
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}
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if ip6 := ip.To16(); ip6 != nil {
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return cgoSockaddrInet6(ip6, zoneCache.index(zone)), C.socklen_t(syscall.SizeofSockaddrInet6)
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}
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return nil, 0
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}
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func copyIP(x IP) IP {
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if len(x) < 16 {
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return x.To16()
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}
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y := make(IP, len(x))
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copy(y, x)
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return y
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}
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