// 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.
// +build cgo,!netgo
// +build darwin dragonfly freebsd 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>
*/
import "C"
import (
"context"
"syscall"
"unsafe"
)
// 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 C.GoString(C.gai_strerror(C.int(eai))) }
func (eai addrinfoErrno) Temporary() bool { return eai == C.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 C.struct_addrinfo
switch network {
case "": // no hints
case "tcp", "tcp4", "tcp6":
hints.ai_socktype = C.SOCK_STREAM
hints.ai_protocol = C.IPPROTO_TCP
case "udp", "udp4", "udp6":
hints.ai_socktype = C.SOCK_DGRAM
hints.ai_protocol = C.IPPROTO_UDP
default:
return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}, true
}
switch ipVersion(network) {
case '4':
hints.ai_family = C.AF_INET
case '6':
hints.ai_family = C.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 *C.struct_addrinfo, network, service string) (port int, err error) {
cservice := make([]byte, len(service)+1)
copy(cservice, service)
// Lowercase the C service name.
for i, b := range cservice[:len(service)] {
cservice[i] = lowerASCII(b)
}
var res *C.struct_addrinfo
gerrno, err := C.getaddrinfo(nil, (*C.char)(unsafe.Pointer(&cservice[0])), hints, &res)
if gerrno != 0 {
switch gerrno {
case C.EAI_SYSTEM:
if err == nil { // see golang.org/issue/6232
err = syscall.EMFILE
}
default:
err = addrinfoErrno(gerrno)
}
return 0, &DNSError{Err: err.Error(), Name: network + "/" + service}
}
defer C.freeaddrinfo(res)
for r := res; r != nil; r = r.ai_next {
switch r.ai_family {
case C.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 C.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 *C.struct_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 C.struct_addrinfo
hints.ai_flags = cgoAddrInfoFlags
hints.ai_socktype = C.SOCK_STREAM
hints.ai_family = C.AF_UNSPEC
switch ipVersion(network) {
case '4':
hints.ai_family = C.AF_INET
case '6':
hints.ai_family = C.AF_INET6
}
h := make([]byte, len(name)+1)
copy(h, name)
var res *C.struct_addrinfo
gerrno, err := C.getaddrinfo((*C.char)(unsafe.Pointer(&h[0])), nil, &hints, &res)
if gerrno != 0 {
switch gerrno {
case C.EAI_SYSTEM:
if err == nil {
// 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.
err = syscall.EMFILE
}
case C.EAI_NONAME:
err = errNoSuchHost
default:
err = addrinfoErrno(gerrno)
}
return nil, "", &DNSError{Err: err.Error(), Name: name}
}
defer C.freeaddrinfo(res)
if res != nil {
cname = C.GoString(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 != C.SOCK_STREAM {
continue
}
switch r.ai_family {
case C.AF_INET:
sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.ai_addr))
addr := IPAddr{IP: copyIP(sa.Addr[:])}
addrs = append(addrs, addr)
case C.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 *C.struct_sockaddr, salen C.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 != C.EAI_OVERFLOW {
break
}
}
if gerrno != 0 {
switch gerrno {
case C.EAI_SYSTEM:
if err == nil { // see golang.org/issue/6232
err = syscall.EMFILE
}
default:
err = addrinfoErrno(gerrno)
}
return nil, &DNSError{Err: err.Error(), Name: addr}
}
for i := 0; i < len(b); i++ {
if b[i] == 0 {
b = b[:i]
break
}
}
return []string{absDomainName(b)}, nil
}
func cgoReverseLookup(result chan<- reverseLookupResult, addr string, sa *C.struct_sockaddr, salen C.socklen_t) {
names, err := cgoLookupAddrPTR(addr, sa, salen)
result <- reverseLookupResult{names, err}
}
func cgoSockaddr(ip IP, zone string) (*C.struct_sockaddr, C.socklen_t) {
if ip4 := ip.To4(); ip4 != nil {
return cgoSockaddrInet4(ip4), C.socklen_t(syscall.SizeofSockaddrInet4)
}
if ip6 := ip.To16(); ip6 != nil {
return cgoSockaddrInet6(ip6, zoneCache.index(zone)), C.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
}