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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.
//go:build cgo && !netgo && (aix || darwin || dragonfly || freebsd || hurd || linux || netbsd || openbsd || solaris)
package net
/*
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <unistd.h>
#include <string.h>
// If nothing else defined EAI_OVERFLOW, make sure it has a value.
#ifndef EAI_OVERFLOW
#define EAI_OVERFLOW -12
#endif
*/
import (
"context"
"syscall"
"unsafe"
)
//extern getaddrinfo
func libc_getaddrinfo(node *byte, service *byte, hints *syscall.Addrinfo, res **syscall.Addrinfo) int32
//extern freeaddrinfo
func libc_freeaddrinfo(res *syscall.Addrinfo)
//extern gai_strerror
func libc_gai_strerror(errcode int) *byte
// bytePtrToString takes a NUL-terminated array of bytes and convert
// it to a Go string.
func bytePtrToString(p *byte) string {
a := (*[10000]byte)(unsafe.Pointer(p))
i := 0
for a[i] != 0 {
i++
}
return string(a[:i])
}
// An addrinfoErrno represents a getaddrinfo, getnameinfo-specific
// error number. It's a signed number and a zero value is a non-error
// by convention.
type addrinfoErrno int
func (eai addrinfoErrno) Error() string { return bytePtrToString(libc_gai_strerror(int(eai))) }
func (eai addrinfoErrno) Temporary() bool { return eai == syscall.EAI_AGAIN }
func (eai addrinfoErrno) Timeout() bool { return false }
type portLookupResult struct {
port int
err error
}
type ipLookupResult struct {
addrs []IPAddr
cname string
err error
}
type reverseLookupResult struct {
names []string
err error
}
func cgoLookupHost(ctx context.Context, name string) (hosts []string, err error, completed bool) {
addrs, err, completed := cgoLookupIP(ctx, "ip", name)
for _, addr := range addrs {
hosts = append(hosts, addr.String())
}
return
}
func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
var hints syscall.Addrinfo
switch network {
case "": // no hints
case "tcp", "tcp4", "tcp6":
hints.Ai_socktype = syscall.SOCK_STREAM
hints.Ai_protocol = syscall.IPPROTO_TCP
case "udp", "udp4", "udp6":
hints.Ai_socktype = syscall.SOCK_DGRAM
hints.Ai_protocol = syscall.IPPROTO_UDP
default:
return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}, true
}
switch ipVersion(network) {
case '4':
hints.Ai_family = syscall.AF_INET
case '6':
hints.Ai_family = syscall.AF_INET6
}
if ctx.Done() == nil {
port, err := cgoLookupServicePort(&hints, network, service)
return port, err, true
}
result := make(chan portLookupResult, 1)
go cgoPortLookup(result, &hints, network, service)
select {
case r := <-result:
return r.port, r.err, true
case <-ctx.Done():
// Since there isn't a portable way to cancel the lookup,
// we just let it finish and write to the buffered channel.
return 0, mapErr(ctx.Err()), false
}
}
func cgoLookupServicePort(hints *syscall.Addrinfo, network, service string) (port int, err error) {
s, err := syscall.BytePtrFromString(service)
if err != nil {
return 0, err
}
// Lowercase the service name in the memory passed to C.
for i := 0; i < len(service); i++ {
bp := (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(s)) + uintptr(i)))
*bp = lowerASCII(*bp)
}
var res *syscall.Addrinfo
syscall.Entersyscall()
gerrno := libc_getaddrinfo(nil, s, hints, &res)
syscall.Exitsyscall()
if gerrno != 0 {
isTemporary := false
switch gerrno {
case syscall.EAI_SYSTEM:
errno := syscall.GetErrno()
if errno == 0 { // see golang.org/issue/6232
errno = syscall.EMFILE
}
err = errno
default:
err = addrinfoErrno(gerrno)
isTemporary = addrinfoErrno(gerrno).Temporary()
}
return 0, &DNSError{Err: err.Error(), Name: network + "/" + service, IsTemporary: isTemporary}
}
defer libc_freeaddrinfo(res)
for r := res; r != nil; r = r.Ai_next {
switch r.Ai_family {
case syscall.AF_INET:
sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.Ai_addr))
p := (*[2]byte)(unsafe.Pointer(&sa.Port))
return int(p[0])<<8 | int(p[1]), nil
case syscall.AF_INET6:
sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.Ai_addr))
p := (*[2]byte)(unsafe.Pointer(&sa.Port))
return int(p[0])<<8 | int(p[1]), nil
}
}
return 0, &DNSError{Err: "unknown port", Name: network + "/" + service}
}
func cgoPortLookup(result chan<- portLookupResult, hints *syscall.Addrinfo, network, service string) {
port, err := cgoLookupServicePort(hints, network, service)
result <- portLookupResult{port, err}
}
func cgoLookupIPCNAME(network, name string) (addrs []IPAddr, cname string, err error) {
acquireThread()
defer releaseThread()
var hints syscall.Addrinfo
hints.Ai_flags = int32(cgoAddrInfoFlags)
hints.Ai_socktype = syscall.SOCK_STREAM
hints.Ai_family = syscall.AF_UNSPEC
switch ipVersion(network) {
case '4':
hints.Ai_family = syscall.AF_INET
case '6':
hints.Ai_family = syscall.AF_INET6
}
h := syscall.StringBytePtr(name)
var res *syscall.Addrinfo
syscall.Entersyscall()
gerrno := libc_getaddrinfo(h, nil, &hints, &res)
syscall.Exitsyscall()
if gerrno != 0 {
isErrorNoSuchHost := false
isTemporary := false
switch gerrno {
case syscall.EAI_SYSTEM:
errno := syscall.GetErrno()
if errno == 0 {
// err should not be nil, but sometimes getaddrinfo returns
// gerrno == C.EAI_SYSTEM with err == nil on Linux.
// The report claims that it happens when we have too many
// open files, so use syscall.EMFILE (too many open files in system).
// Most system calls would return ENFILE (too many open files),
// so at the least EMFILE should be easy to recognize if this
// comes up again. golang.org/issue/6232.
errno = syscall.EMFILE
}
err = errno
case syscall.EAI_NONAME:
err = errNoSuchHost
isErrorNoSuchHost = true
default:
err = addrinfoErrno(gerrno)
isTemporary = addrinfoErrno(gerrno).Temporary()
}
return nil, "", &DNSError{Err: err.Error(), Name: name, IsNotFound: isErrorNoSuchHost, IsTemporary: isTemporary}
}
defer libc_freeaddrinfo(res)
if res != nil {
cname = bytePtrToString((*byte)(unsafe.Pointer(res.Ai_canonname)))
if cname == "" {
cname = name
}
if len(cname) > 0 && cname[len(cname)-1] != '.' {
cname += "."
}
}
for r := res; r != nil; r = r.Ai_next {
// We only asked for SOCK_STREAM, but check anyhow.
if r.Ai_socktype != syscall.SOCK_STREAM {
continue
}
switch r.Ai_family {
case syscall.AF_INET:
sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.Ai_addr))
addr := IPAddr{IP: copyIP(sa.Addr[:])}
addrs = append(addrs, addr)
case syscall.AF_INET6:
sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.Ai_addr))
addr := IPAddr{IP: copyIP(sa.Addr[:]), Zone: zoneCache.name(int(sa.Scope_id))}
addrs = append(addrs, addr)
}
}
return addrs, cname, nil
}
func cgoIPLookup(result chan<- ipLookupResult, network, name string) {
addrs, cname, err := cgoLookupIPCNAME(network, name)
result <- ipLookupResult{addrs, cname, err}
}
func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error, completed bool) {
if ctx.Done() == nil {
addrs, _, err = cgoLookupIPCNAME(network, name)
return addrs, err, true
}
result := make(chan ipLookupResult, 1)
go cgoIPLookup(result, network, name)
select {
case r := <-result:
return r.addrs, r.err, true
case <-ctx.Done():
return nil, mapErr(ctx.Err()), false
}
}
func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
if ctx.Done() == nil {
_, cname, err = cgoLookupIPCNAME("ip", name)
return cname, err, true
}
result := make(chan ipLookupResult, 1)
go cgoIPLookup(result, "ip", name)
select {
case r := <-result:
return r.cname, r.err, true
case <-ctx.Done():
return "", mapErr(ctx.Err()), false
}
}
// These are roughly enough for the following:
//
// Source Encoding Maximum length of single name entry
// Unicast DNS ASCII or <=253 + a NUL terminator
// Unicode in RFC 5892 252 * total number of labels + delimiters + a NUL terminator
// Multicast DNS UTF-8 in RFC 5198 or <=253 + a NUL terminator
// the same as unicast DNS ASCII <=253 + a NUL terminator
// Local database various depends on implementation
const (
nameinfoLen = 64
maxNameinfoLen = 4096
)
func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error, completed bool) {
var zone string
ip := parseIPv4(addr)
if ip == nil {
ip, zone = parseIPv6Zone(addr)
}
if ip == nil {
return nil, &DNSError{Err: "invalid address", Name: addr}, true
}
sa, salen := cgoSockaddr(ip, zone)
if sa == nil {
return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}, true
}
if ctx.Done() == nil {
names, err := cgoLookupAddrPTR(addr, sa, salen)
return names, err, true
}
result := make(chan reverseLookupResult, 1)
go cgoReverseLookup(result, addr, sa, salen)
select {
case r := <-result:
return r.names, r.err, true
case <-ctx.Done():
return nil, mapErr(ctx.Err()), false
}
}
func cgoLookupAddrPTR(addr string, sa *syscall.RawSockaddr, salen syscall.Socklen_t) (names []string, err error) {
acquireThread()
defer releaseThread()
var gerrno int
var b []byte
for l := nameinfoLen; l <= maxNameinfoLen; l *= 2 {
b = make([]byte, l)
gerrno, err = cgoNameinfoPTR(b, sa, salen)
if gerrno == 0 || gerrno != syscall.EAI_OVERFLOW {
break
}
}
if gerrno != 0 {
isTemporary := false
switch gerrno {
case syscall.EAI_SYSTEM:
if err == nil { // see golang.org/issue/6232
err = syscall.EMFILE
}
default:
err = addrinfoErrno(gerrno)
isTemporary = addrinfoErrno(gerrno).Temporary()
}
return nil, &DNSError{Err: err.Error(), Name: addr, IsTemporary: isTemporary}
}
for i := 0; i < len(b); i++ {
if b[i] == 0 {
b = b[:i]
break
}
}
return []string{absDomainName(string(b))}, nil
}
func cgoReverseLookup(result chan<- reverseLookupResult, addr string, sa *syscall.RawSockaddr, salen syscall.Socklen_t) {
names, err := cgoLookupAddrPTR(addr, sa, salen)
result <- reverseLookupResult{names, err}
}
func cgoSockaddr(ip IP, zone string) (*syscall.RawSockaddr, syscall.Socklen_t) {
if ip4 := ip.To4(); ip4 != nil {
return cgoSockaddrInet4(ip4), syscall.Socklen_t(syscall.SizeofSockaddrInet4)
}
if ip6 := ip.To16(); ip6 != nil {
return cgoSockaddrInet6(ip6, zoneCache.index(zone)), syscall.Socklen_t(syscall.SizeofSockaddrInet6)
}
return nil, 0
}
func copyIP(x IP) IP {
if len(x) < 16 {
return x.To16()
}
y := make(IP, len(x))
copy(y, x)
return y
}
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