Source file src/net/lookup_windows.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package net
     6  
     7  import (
     8  	"context"
     9  	"internal/syscall/windows"
    10  	"os"
    11  	"runtime"
    12  	"syscall"
    13  	"time"
    14  	"unsafe"
    15  )
    16  
    17  // cgoAvailable set to true to indicate that the cgo resolver
    18  // is available on Windows. Note that on Windows the cgo resolver
    19  // does not actually use cgo.
    20  const cgoAvailable = true
    21  
    22  const (
    23  	_DNS_ERROR_RCODE_NAME_ERROR = syscall.Errno(9003)
    24  	_DNS_INFO_NO_RECORDS        = syscall.Errno(9501)
    25  
    26  	_WSAHOST_NOT_FOUND = syscall.Errno(11001)
    27  	_WSATRY_AGAIN      = syscall.Errno(11002)
    28  	_WSATYPE_NOT_FOUND = syscall.Errno(10109)
    29  )
    30  
    31  func winError(call string, err error) error {
    32  	switch err {
    33  	case _WSAHOST_NOT_FOUND, _DNS_ERROR_RCODE_NAME_ERROR, _DNS_INFO_NO_RECORDS:
    34  		return errNoSuchHost
    35  	}
    36  	return os.NewSyscallError(call, err)
    37  }
    38  
    39  func getprotobyname(name string) (proto int, err error) {
    40  	p, err := syscall.GetProtoByName(name)
    41  	if err != nil {
    42  		return 0, winError("getprotobyname", err)
    43  	}
    44  	return int(p.Proto), nil
    45  }
    46  
    47  // lookupProtocol looks up IP protocol name and returns correspondent protocol number.
    48  func lookupProtocol(ctx context.Context, name string) (int, error) {
    49  	// GetProtoByName return value is stored in thread local storage.
    50  	// Start new os thread before the call to prevent races.
    51  	type result struct {
    52  		proto int
    53  		err   error
    54  	}
    55  	ch := make(chan result, 1) // buffer so that next goroutine never blocks
    56  	go func() {
    57  		if err := acquireThread(ctx); err != nil {
    58  			ch <- result{err: mapErr(err)}
    59  			return
    60  		}
    61  		defer releaseThread()
    62  		runtime.LockOSThread()
    63  		defer runtime.UnlockOSThread()
    64  		proto, err := getprotobyname(name)
    65  		ch <- result{proto: proto, err: err}
    66  	}()
    67  	select {
    68  	case r := <-ch:
    69  		if r.err != nil {
    70  			if proto, err := lookupProtocolMap(name); err == nil {
    71  				return proto, nil
    72  			}
    73  			r.err = newDNSError(r.err, name, "")
    74  		}
    75  		return r.proto, r.err
    76  	case <-ctx.Done():
    77  		return 0, newDNSError(mapErr(ctx.Err()), name, "")
    78  	}
    79  }
    80  
    81  func (r *Resolver) lookupHost(ctx context.Context, name string) ([]string, error) {
    82  	ips, err := r.lookupIP(ctx, "ip", name)
    83  	if err != nil {
    84  		return nil, err
    85  	}
    86  	addrs := make([]string, 0, len(ips))
    87  	for _, ip := range ips {
    88  		addrs = append(addrs, ip.String())
    89  	}
    90  	return addrs, nil
    91  }
    92  
    93  func (r *Resolver) lookupIP(ctx context.Context, network, name string) ([]IPAddr, error) {
    94  	if order, conf := systemConf().hostLookupOrder(r, name); order != hostLookupCgo {
    95  		return r.goLookupIP(ctx, network, name, order, conf)
    96  	}
    97  
    98  	// TODO(bradfitz,brainman): use ctx more. See TODO below.
    99  
   100  	var family int32 = syscall.AF_UNSPEC
   101  	switch ipVersion(network) {
   102  	case '4':
   103  		family = syscall.AF_INET
   104  	case '6':
   105  		family = syscall.AF_INET6
   106  	}
   107  
   108  	getaddr := func() ([]IPAddr, error) {
   109  		if err := acquireThread(ctx); err != nil {
   110  			return nil, newDNSError(mapErr(err), name, "")
   111  		}
   112  		defer releaseThread()
   113  		hints := syscall.AddrinfoW{
   114  			Family:   family,
   115  			Socktype: syscall.SOCK_STREAM,
   116  			Protocol: syscall.IPPROTO_IP,
   117  		}
   118  		var result *syscall.AddrinfoW
   119  		name16p, err := syscall.UTF16PtrFromString(name)
   120  		if err != nil {
   121  			return nil, newDNSError(err, name, "")
   122  		}
   123  
   124  		dnsConf := getSystemDNSConfig()
   125  		start := time.Now()
   126  
   127  		var e error
   128  		for i := 0; i < dnsConf.attempts; i++ {
   129  			e = syscall.GetAddrInfoW(name16p, nil, &hints, &result)
   130  			if e == nil || e != _WSATRY_AGAIN || time.Since(start) > dnsConf.timeout {
   131  				break
   132  			}
   133  		}
   134  		if e != nil {
   135  			return nil, newDNSError(winError("getaddrinfow", e), name, "")
   136  		}
   137  		defer syscall.FreeAddrInfoW(result)
   138  		addrs := make([]IPAddr, 0, 5)
   139  		for ; result != nil; result = result.Next {
   140  			addr := unsafe.Pointer(result.Addr)
   141  			switch result.Family {
   142  			case syscall.AF_INET:
   143  				a := (*syscall.RawSockaddrInet4)(addr).Addr
   144  				addrs = append(addrs, IPAddr{IP: copyIP(a[:])})
   145  			case syscall.AF_INET6:
   146  				a := (*syscall.RawSockaddrInet6)(addr).Addr
   147  				zone := zoneCache.name(int((*syscall.RawSockaddrInet6)(addr).Scope_id))
   148  				addrs = append(addrs, IPAddr{IP: copyIP(a[:]), Zone: zone})
   149  			default:
   150  				return nil, newDNSError(syscall.EWINDOWS, name, "")
   151  			}
   152  		}
   153  		return addrs, nil
   154  	}
   155  
   156  	type ret struct {
   157  		addrs []IPAddr
   158  		err   error
   159  	}
   160  
   161  	var ch chan ret
   162  	if ctx.Err() == nil {
   163  		ch = make(chan ret, 1)
   164  		go func() {
   165  			addr, err := getaddr()
   166  			ch <- ret{addrs: addr, err: err}
   167  		}()
   168  	}
   169  
   170  	select {
   171  	case r := <-ch:
   172  		return r.addrs, r.err
   173  	case <-ctx.Done():
   174  		// TODO(bradfitz,brainman): cancel the ongoing
   175  		// GetAddrInfoW? It would require conditionally using
   176  		// GetAddrInfoEx with lpOverlapped, which requires
   177  		// Windows 8 or newer. I guess we'll need oldLookupIP,
   178  		// newLookupIP, and newerLookUP.
   179  		//
   180  		// For now we just let it finish and write to the
   181  		// buffered channel.
   182  		return nil, newDNSError(mapErr(ctx.Err()), name, "")
   183  	}
   184  }
   185  
   186  func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int, error) {
   187  	if systemConf().mustUseGoResolver(r) {
   188  		return lookupPortMap(network, service)
   189  	}
   190  
   191  	// TODO(bradfitz): finish ctx plumbing
   192  	if err := acquireThread(ctx); err != nil {
   193  		return 0, newDNSError(mapErr(err), network+"/"+service, "")
   194  	}
   195  	defer releaseThread()
   196  
   197  	var hints syscall.AddrinfoW
   198  
   199  	switch network {
   200  	case "ip": // no hints
   201  	case "tcp", "tcp4", "tcp6":
   202  		hints.Socktype = syscall.SOCK_STREAM
   203  		hints.Protocol = syscall.IPPROTO_TCP
   204  	case "udp", "udp4", "udp6":
   205  		hints.Socktype = syscall.SOCK_DGRAM
   206  		hints.Protocol = syscall.IPPROTO_UDP
   207  	default:
   208  		return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}
   209  	}
   210  
   211  	switch ipVersion(network) {
   212  	case '4':
   213  		hints.Family = syscall.AF_INET
   214  	case '6':
   215  		hints.Family = syscall.AF_INET6
   216  	}
   217  
   218  	var result *syscall.AddrinfoW
   219  	e := syscall.GetAddrInfoW(nil, syscall.StringToUTF16Ptr(service), &hints, &result)
   220  	if e != nil {
   221  		if port, err := lookupPortMap(network, service); err == nil {
   222  			return port, nil
   223  		}
   224  
   225  		// The _WSATYPE_NOT_FOUND error is returned by GetAddrInfoW
   226  		// when the service name is unknown. We are also checking
   227  		// for _WSAHOST_NOT_FOUND here to match the cgo (unix) version
   228  		// cgo_unix.go (cgoLookupServicePort).
   229  		if e == _WSATYPE_NOT_FOUND || e == _WSAHOST_NOT_FOUND {
   230  			return 0, newDNSError(errUnknownPort, network+"/"+service, "")
   231  		}
   232  		return 0, newDNSError(winError("getaddrinfow", e), network+"/"+service, "")
   233  	}
   234  	defer syscall.FreeAddrInfoW(result)
   235  	if result == nil {
   236  		return 0, newDNSError(syscall.EINVAL, network+"/"+service, "")
   237  	}
   238  	addr := unsafe.Pointer(result.Addr)
   239  	switch result.Family {
   240  	case syscall.AF_INET:
   241  		a := (*syscall.RawSockaddrInet4)(addr)
   242  		return int(syscall.Ntohs(a.Port)), nil
   243  	case syscall.AF_INET6:
   244  		a := (*syscall.RawSockaddrInet6)(addr)
   245  		return int(syscall.Ntohs(a.Port)), nil
   246  	}
   247  	return 0, newDNSError(syscall.EINVAL, network+"/"+service, "")
   248  }
   249  
   250  func (r *Resolver) lookupCNAME(ctx context.Context, name string) (string, error) {
   251  	if order, conf := systemConf().hostLookupOrder(r, name); order != hostLookupCgo {
   252  		return r.goLookupCNAME(ctx, name, order, conf)
   253  	}
   254  
   255  	// TODO(bradfitz): finish ctx plumbing
   256  	if err := acquireThread(ctx); err != nil {
   257  		return "", newDNSError(mapErr(err), name, "")
   258  	}
   259  	defer releaseThread()
   260  	var rec *syscall.DNSRecord
   261  	e := syscall.DnsQuery(name, syscall.DNS_TYPE_CNAME, 0, nil, &rec, nil)
   262  	// windows returns DNS_INFO_NO_RECORDS if there are no CNAME-s
   263  	if errno, ok := e.(syscall.Errno); ok && errno == syscall.DNS_INFO_NO_RECORDS {
   264  		// if there are no aliases, the canonical name is the input name
   265  		return absDomainName(name), nil
   266  	}
   267  	if e != nil {
   268  		return "", newDNSError(winError("dnsquery", e), name, "")
   269  	}
   270  	defer syscall.DnsRecordListFree(rec, 1)
   271  
   272  	resolved := resolveCNAME(syscall.StringToUTF16Ptr(name), rec)
   273  	cname := windows.UTF16PtrToString(resolved)
   274  	return absDomainName(cname), nil
   275  }
   276  
   277  func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
   278  	if systemConf().mustUseGoResolver(r) {
   279  		return r.goLookupSRV(ctx, service, proto, name)
   280  	}
   281  	// TODO(bradfitz): finish ctx plumbing
   282  	if err := acquireThread(ctx); err != nil {
   283  		return "", nil, newDNSError(mapErr(err), name, "")
   284  	}
   285  	defer releaseThread()
   286  	var target string
   287  	if service == "" && proto == "" {
   288  		target = name
   289  	} else {
   290  		target = "_" + service + "._" + proto + "." + name
   291  	}
   292  	var rec *syscall.DNSRecord
   293  	e := syscall.DnsQuery(target, syscall.DNS_TYPE_SRV, 0, nil, &rec, nil)
   294  	if e != nil {
   295  		return "", nil, newDNSError(winError("dnsquery", e), name, "")
   296  	}
   297  	defer syscall.DnsRecordListFree(rec, 1)
   298  
   299  	srvs := make([]*SRV, 0, 10)
   300  	for _, p := range validRecs(rec, syscall.DNS_TYPE_SRV, target) {
   301  		v := (*syscall.DNSSRVData)(unsafe.Pointer(&p.Data[0]))
   302  		srvs = append(srvs, &SRV{absDomainName(syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Target))[:])), v.Port, v.Priority, v.Weight})
   303  	}
   304  	byPriorityWeight(srvs).sort()
   305  	return absDomainName(target), srvs, nil
   306  }
   307  
   308  func (r *Resolver) lookupMX(ctx context.Context, name string) ([]*MX, error) {
   309  	if systemConf().mustUseGoResolver(r) {
   310  		return r.goLookupMX(ctx, name)
   311  	}
   312  	// TODO(bradfitz): finish ctx plumbing.
   313  	if err := acquireThread(ctx); err != nil {
   314  		return nil, newDNSError(mapErr(err), name, "")
   315  	}
   316  	defer releaseThread()
   317  	var rec *syscall.DNSRecord
   318  	e := syscall.DnsQuery(name, syscall.DNS_TYPE_MX, 0, nil, &rec, nil)
   319  	if e != nil {
   320  		return nil, newDNSError(winError("dnsquery", e), name, "")
   321  	}
   322  	defer syscall.DnsRecordListFree(rec, 1)
   323  
   324  	mxs := make([]*MX, 0, 10)
   325  	for _, p := range validRecs(rec, syscall.DNS_TYPE_MX, name) {
   326  		v := (*syscall.DNSMXData)(unsafe.Pointer(&p.Data[0]))
   327  		mxs = append(mxs, &MX{absDomainName(windows.UTF16PtrToString(v.NameExchange)), v.Preference})
   328  	}
   329  	byPref(mxs).sort()
   330  	return mxs, nil
   331  }
   332  
   333  func (r *Resolver) lookupNS(ctx context.Context, name string) ([]*NS, error) {
   334  	if systemConf().mustUseGoResolver(r) {
   335  		return r.goLookupNS(ctx, name)
   336  	}
   337  	// TODO(bradfitz): finish ctx plumbing.
   338  	if err := acquireThread(ctx); err != nil {
   339  		return nil, newDNSError(mapErr(err), name, "")
   340  	}
   341  	defer releaseThread()
   342  	var rec *syscall.DNSRecord
   343  	e := syscall.DnsQuery(name, syscall.DNS_TYPE_NS, 0, nil, &rec, nil)
   344  	if e != nil {
   345  		return nil, newDNSError(winError("dnsquery", e), name, "")
   346  	}
   347  	defer syscall.DnsRecordListFree(rec, 1)
   348  
   349  	nss := make([]*NS, 0, 10)
   350  	for _, p := range validRecs(rec, syscall.DNS_TYPE_NS, name) {
   351  		v := (*syscall.DNSPTRData)(unsafe.Pointer(&p.Data[0]))
   352  		nss = append(nss, &NS{absDomainName(syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Host))[:]))})
   353  	}
   354  	return nss, nil
   355  }
   356  
   357  func (r *Resolver) lookupTXT(ctx context.Context, name string) ([]string, error) {
   358  	if systemConf().mustUseGoResolver(r) {
   359  		return r.goLookupTXT(ctx, name)
   360  	}
   361  	// TODO(bradfitz): finish ctx plumbing.
   362  	if err := acquireThread(ctx); err != nil {
   363  		return nil, newDNSError(mapErr(err), name, "")
   364  	}
   365  	defer releaseThread()
   366  	var rec *syscall.DNSRecord
   367  	e := syscall.DnsQuery(name, syscall.DNS_TYPE_TEXT, 0, nil, &rec, nil)
   368  	if e != nil {
   369  		return nil, newDNSError(winError("dnsquery", e), name, "")
   370  	}
   371  	defer syscall.DnsRecordListFree(rec, 1)
   372  
   373  	txts := make([]string, 0, 10)
   374  	for _, p := range validRecs(rec, syscall.DNS_TYPE_TEXT, name) {
   375  		d := (*syscall.DNSTXTData)(unsafe.Pointer(&p.Data[0]))
   376  		s := ""
   377  		for _, v := range (*[1 << 10]*uint16)(unsafe.Pointer(&(d.StringArray[0])))[:d.StringCount:d.StringCount] {
   378  			s += windows.UTF16PtrToString(v)
   379  		}
   380  		txts = append(txts, s)
   381  	}
   382  	return txts, nil
   383  }
   384  
   385  func (r *Resolver) lookupAddr(ctx context.Context, addr string) ([]string, error) {
   386  	if order, conf := systemConf().addrLookupOrder(r, addr); order != hostLookupCgo {
   387  		return r.goLookupPTR(ctx, addr, order, conf)
   388  	}
   389  
   390  	// TODO(bradfitz): finish ctx plumbing.
   391  	if err := acquireThread(ctx); err != nil {
   392  		return nil, newDNSError(mapErr(err), addr, "")
   393  	}
   394  	defer releaseThread()
   395  	arpa, err := reverseaddr(addr)
   396  	if err != nil {
   397  		return nil, err
   398  	}
   399  	var rec *syscall.DNSRecord
   400  	e := syscall.DnsQuery(arpa, syscall.DNS_TYPE_PTR, 0, nil, &rec, nil)
   401  	if e != nil {
   402  		return nil, newDNSError(winError("dnsquery", e), addr, "")
   403  	}
   404  	defer syscall.DnsRecordListFree(rec, 1)
   405  
   406  	ptrs := make([]string, 0, 10)
   407  	for _, p := range validRecs(rec, syscall.DNS_TYPE_PTR, arpa) {
   408  		v := (*syscall.DNSPTRData)(unsafe.Pointer(&p.Data[0]))
   409  		ptrs = append(ptrs, absDomainName(windows.UTF16PtrToString(v.Host)))
   410  	}
   411  	return ptrs, nil
   412  }
   413  
   414  const dnsSectionMask = 0x0003
   415  
   416  // returns only results applicable to name and resolves CNAME entries.
   417  func validRecs(r *syscall.DNSRecord, dnstype uint16, name string) []*syscall.DNSRecord {
   418  	cname := syscall.StringToUTF16Ptr(name)
   419  	if dnstype != syscall.DNS_TYPE_CNAME {
   420  		cname = resolveCNAME(cname, r)
   421  	}
   422  	rec := make([]*syscall.DNSRecord, 0, 10)
   423  	for p := r; p != nil; p = p.Next {
   424  		// in case of a local machine, DNS records are returned with DNSREC_QUESTION flag instead of DNS_ANSWER
   425  		if p.Dw&dnsSectionMask != syscall.DnsSectionAnswer && p.Dw&dnsSectionMask != syscall.DnsSectionQuestion {
   426  			continue
   427  		}
   428  		if p.Type != dnstype {
   429  			continue
   430  		}
   431  		if !syscall.DnsNameCompare(cname, p.Name) {
   432  			continue
   433  		}
   434  		rec = append(rec, p)
   435  	}
   436  	return rec
   437  }
   438  
   439  // returns the last CNAME in chain.
   440  func resolveCNAME(name *uint16, r *syscall.DNSRecord) *uint16 {
   441  	// limit cname resolving to 10 in case of an infinite CNAME loop
   442  Cname:
   443  	for cnameloop := 0; cnameloop < 10; cnameloop++ {
   444  		for p := r; p != nil; p = p.Next {
   445  			if p.Dw&dnsSectionMask != syscall.DnsSectionAnswer {
   446  				continue
   447  			}
   448  			if p.Type != syscall.DNS_TYPE_CNAME {
   449  				continue
   450  			}
   451  			if !syscall.DnsNameCompare(name, p.Name) {
   452  				continue
   453  			}
   454  			name = (*syscall.DNSPTRData)(unsafe.Pointer(&r.Data[0])).Host
   455  			continue Cname
   456  		}
   457  		break
   458  	}
   459  	return name
   460  }
   461  
   462  // concurrentThreadsLimit returns the number of threads we permit to
   463  // run concurrently doing DNS lookups.
   464  func concurrentThreadsLimit() int {
   465  	return 500
   466  }
   467  

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