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Source file src/net/lookup_windows.go

Documentation: net

     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  	"unsafe"
    14  )
    15  
    16  const _WSAHOST_NOT_FOUND = syscall.Errno(11001)
    17  
    18  func winError(call string, err error) error {
    19  	switch err {
    20  	case _WSAHOST_NOT_FOUND:
    21  		return errNoSuchHost
    22  	}
    23  	return os.NewSyscallError(call, err)
    24  }
    25  
    26  func getprotobyname(name string) (proto int, err error) {
    27  	p, err := syscall.GetProtoByName(name)
    28  	if err != nil {
    29  		return 0, winError("getprotobyname", err)
    30  	}
    31  	return int(p.Proto), nil
    32  }
    33  
    34  // lookupProtocol looks up IP protocol name and returns correspondent protocol number.
    35  func lookupProtocol(ctx context.Context, name string) (int, error) {
    36  	// GetProtoByName return value is stored in thread local storage.
    37  	// Start new os thread before the call to prevent races.
    38  	type result struct {
    39  		proto int
    40  		err   error
    41  	}
    42  	ch := make(chan result) // unbuffered
    43  	go func() {
    44  		acquireThread()
    45  		defer releaseThread()
    46  		runtime.LockOSThread()
    47  		defer runtime.UnlockOSThread()
    48  		proto, err := getprotobyname(name)
    49  		select {
    50  		case ch <- result{proto: proto, err: err}:
    51  		case <-ctx.Done():
    52  		}
    53  	}()
    54  	select {
    55  	case r := <-ch:
    56  		if r.err != nil {
    57  			if proto, err := lookupProtocolMap(name); err == nil {
    58  				return proto, nil
    59  			}
    60  
    61  			dnsError := &DNSError{Err: r.err.Error(), Name: name}
    62  			if r.err == errNoSuchHost {
    63  				dnsError.IsNotFound = true
    64  			}
    65  			r.err = dnsError
    66  		}
    67  		return r.proto, r.err
    68  	case <-ctx.Done():
    69  		return 0, mapErr(ctx.Err())
    70  	}
    71  }
    72  
    73  func (r *Resolver) lookupHost(ctx context.Context, name string) ([]string, error) {
    74  	ips, err := r.lookupIP(ctx, "ip", name)
    75  	if err != nil {
    76  		return nil, err
    77  	}
    78  	addrs := make([]string, 0, len(ips))
    79  	for _, ip := range ips {
    80  		addrs = append(addrs, ip.String())
    81  	}
    82  	return addrs, nil
    83  }
    84  
    85  func (r *Resolver) lookupIP(ctx context.Context, network, name string) ([]IPAddr, error) {
    86  	// TODO(bradfitz,brainman): use ctx more. See TODO below.
    87  
    88  	var family int32 = syscall.AF_UNSPEC
    89  	switch ipVersion(network) {
    90  	case '4':
    91  		family = syscall.AF_INET
    92  	case '6':
    93  		family = syscall.AF_INET6
    94  	}
    95  
    96  	getaddr := func() ([]IPAddr, error) {
    97  		acquireThread()
    98  		defer releaseThread()
    99  		hints := syscall.AddrinfoW{
   100  			Family:   family,
   101  			Socktype: syscall.SOCK_STREAM,
   102  			Protocol: syscall.IPPROTO_IP,
   103  		}
   104  		var result *syscall.AddrinfoW
   105  		name16p, err := syscall.UTF16PtrFromString(name)
   106  		if err != nil {
   107  			return nil, &DNSError{Name: name, Err: err.Error()}
   108  		}
   109  		e := syscall.GetAddrInfoW(name16p, nil, &hints, &result)
   110  		if e != nil {
   111  			err := winError("getaddrinfow", e)
   112  			dnsError := &DNSError{Err: err.Error(), Name: name}
   113  			if err == errNoSuchHost {
   114  				dnsError.IsNotFound = true
   115  			}
   116  			return nil, dnsError
   117  		}
   118  		defer syscall.FreeAddrInfoW(result)
   119  		addrs := make([]IPAddr, 0, 5)
   120  		for ; result != nil; result = result.Next {
   121  			addr := unsafe.Pointer(result.Addr)
   122  			switch result.Family {
   123  			case syscall.AF_INET:
   124  				a := (*syscall.RawSockaddrInet4)(addr).Addr
   125  				addrs = append(addrs, IPAddr{IP: IPv4(a[0], a[1], a[2], a[3])})
   126  			case syscall.AF_INET6:
   127  				a := (*syscall.RawSockaddrInet6)(addr).Addr
   128  				zone := zoneCache.name(int((*syscall.RawSockaddrInet6)(addr).Scope_id))
   129  				addrs = append(addrs, IPAddr{IP: IP{a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], a[11], a[12], a[13], a[14], a[15]}, Zone: zone})
   130  			default:
   131  				return nil, &DNSError{Err: syscall.EWINDOWS.Error(), Name: name}
   132  			}
   133  		}
   134  		return addrs, nil
   135  	}
   136  
   137  	type ret struct {
   138  		addrs []IPAddr
   139  		err   error
   140  	}
   141  
   142  	var ch chan ret
   143  	if ctx.Err() == nil {
   144  		ch = make(chan ret, 1)
   145  		go func() {
   146  			addr, err := getaddr()
   147  			ch <- ret{addrs: addr, err: err}
   148  		}()
   149  	}
   150  
   151  	select {
   152  	case r := <-ch:
   153  		return r.addrs, r.err
   154  	case <-ctx.Done():
   155  		// TODO(bradfitz,brainman): cancel the ongoing
   156  		// GetAddrInfoW? It would require conditionally using
   157  		// GetAddrInfoEx with lpOverlapped, which requires
   158  		// Windows 8 or newer. I guess we'll need oldLookupIP,
   159  		// newLookupIP, and newerLookUP.
   160  		//
   161  		// For now we just let it finish and write to the
   162  		// buffered channel.
   163  		return nil, &DNSError{
   164  			Name:      name,
   165  			Err:       ctx.Err().Error(),
   166  			IsTimeout: ctx.Err() == context.DeadlineExceeded,
   167  		}
   168  	}
   169  }
   170  
   171  func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int, error) {
   172  	if r.preferGo() {
   173  		return lookupPortMap(network, service)
   174  	}
   175  
   176  	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
   177  	acquireThread()
   178  	defer releaseThread()
   179  	var stype int32
   180  	switch network {
   181  	case "tcp4", "tcp6":
   182  		stype = syscall.SOCK_STREAM
   183  	case "udp4", "udp6":
   184  		stype = syscall.SOCK_DGRAM
   185  	}
   186  	hints := syscall.AddrinfoW{
   187  		Family:   syscall.AF_UNSPEC,
   188  		Socktype: stype,
   189  		Protocol: syscall.IPPROTO_IP,
   190  	}
   191  	var result *syscall.AddrinfoW
   192  	e := syscall.GetAddrInfoW(nil, syscall.StringToUTF16Ptr(service), &hints, &result)
   193  	if e != nil {
   194  		if port, err := lookupPortMap(network, service); err == nil {
   195  			return port, nil
   196  		}
   197  		err := winError("getaddrinfow", e)
   198  		dnsError := &DNSError{Err: err.Error(), Name: network + "/" + service}
   199  		if err == errNoSuchHost {
   200  			dnsError.IsNotFound = true
   201  		}
   202  		return 0, dnsError
   203  	}
   204  	defer syscall.FreeAddrInfoW(result)
   205  	if result == nil {
   206  		return 0, &DNSError{Err: syscall.EINVAL.Error(), Name: network + "/" + service}
   207  	}
   208  	addr := unsafe.Pointer(result.Addr)
   209  	switch result.Family {
   210  	case syscall.AF_INET:
   211  		a := (*syscall.RawSockaddrInet4)(addr)
   212  		return int(syscall.Ntohs(a.Port)), nil
   213  	case syscall.AF_INET6:
   214  		a := (*syscall.RawSockaddrInet6)(addr)
   215  		return int(syscall.Ntohs(a.Port)), nil
   216  	}
   217  	return 0, &DNSError{Err: syscall.EINVAL.Error(), Name: network + "/" + service}
   218  }
   219  
   220  func (*Resolver) lookupCNAME(ctx context.Context, name string) (string, error) {
   221  	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
   222  	acquireThread()
   223  	defer releaseThread()
   224  	var r *syscall.DNSRecord
   225  	e := syscall.DnsQuery(name, syscall.DNS_TYPE_CNAME, 0, nil, &r, nil)
   226  	// windows returns DNS_INFO_NO_RECORDS if there are no CNAME-s
   227  	if errno, ok := e.(syscall.Errno); ok && errno == syscall.DNS_INFO_NO_RECORDS {
   228  		// if there are no aliases, the canonical name is the input name
   229  		return absDomainName([]byte(name)), nil
   230  	}
   231  	if e != nil {
   232  		return "", &DNSError{Err: winError("dnsquery", e).Error(), Name: name}
   233  	}
   234  	defer syscall.DnsRecordListFree(r, 1)
   235  
   236  	resolved := resolveCNAME(syscall.StringToUTF16Ptr(name), r)
   237  	cname := windows.UTF16PtrToString(resolved)
   238  	return absDomainName([]byte(cname)), nil
   239  }
   240  
   241  func (*Resolver) lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
   242  	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
   243  	acquireThread()
   244  	defer releaseThread()
   245  	var target string
   246  	if service == "" && proto == "" {
   247  		target = name
   248  	} else {
   249  		target = "_" + service + "._" + proto + "." + name
   250  	}
   251  	var r *syscall.DNSRecord
   252  	e := syscall.DnsQuery(target, syscall.DNS_TYPE_SRV, 0, nil, &r, nil)
   253  	if e != nil {
   254  		return "", nil, &DNSError{Err: winError("dnsquery", e).Error(), Name: target}
   255  	}
   256  	defer syscall.DnsRecordListFree(r, 1)
   257  
   258  	srvs := make([]*SRV, 0, 10)
   259  	for _, p := range validRecs(r, syscall.DNS_TYPE_SRV, target) {
   260  		v := (*syscall.DNSSRVData)(unsafe.Pointer(&p.Data[0]))
   261  		srvs = append(srvs, &SRV{absDomainName([]byte(syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Target))[:]))), v.Port, v.Priority, v.Weight})
   262  	}
   263  	byPriorityWeight(srvs).sort()
   264  	return absDomainName([]byte(target)), srvs, nil
   265  }
   266  
   267  func (*Resolver) lookupMX(ctx context.Context, name string) ([]*MX, error) {
   268  	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
   269  	acquireThread()
   270  	defer releaseThread()
   271  	var r *syscall.DNSRecord
   272  	e := syscall.DnsQuery(name, syscall.DNS_TYPE_MX, 0, nil, &r, nil)
   273  	if e != nil {
   274  		return nil, &DNSError{Err: winError("dnsquery", e).Error(), Name: name}
   275  	}
   276  	defer syscall.DnsRecordListFree(r, 1)
   277  
   278  	mxs := make([]*MX, 0, 10)
   279  	for _, p := range validRecs(r, syscall.DNS_TYPE_MX, name) {
   280  		v := (*syscall.DNSMXData)(unsafe.Pointer(&p.Data[0]))
   281  		mxs = append(mxs, &MX{absDomainName([]byte(windows.UTF16PtrToString(v.NameExchange))), v.Preference})
   282  	}
   283  	byPref(mxs).sort()
   284  	return mxs, nil
   285  }
   286  
   287  func (*Resolver) lookupNS(ctx context.Context, name string) ([]*NS, error) {
   288  	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
   289  	acquireThread()
   290  	defer releaseThread()
   291  	var r *syscall.DNSRecord
   292  	e := syscall.DnsQuery(name, syscall.DNS_TYPE_NS, 0, nil, &r, nil)
   293  	if e != nil {
   294  		return nil, &DNSError{Err: winError("dnsquery", e).Error(), Name: name}
   295  	}
   296  	defer syscall.DnsRecordListFree(r, 1)
   297  
   298  	nss := make([]*NS, 0, 10)
   299  	for _, p := range validRecs(r, syscall.DNS_TYPE_NS, name) {
   300  		v := (*syscall.DNSPTRData)(unsafe.Pointer(&p.Data[0]))
   301  		nss = append(nss, &NS{absDomainName([]byte(syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Host))[:])))})
   302  	}
   303  	return nss, nil
   304  }
   305  
   306  func (*Resolver) lookupTXT(ctx context.Context, name string) ([]string, error) {
   307  	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
   308  	acquireThread()
   309  	defer releaseThread()
   310  	var r *syscall.DNSRecord
   311  	e := syscall.DnsQuery(name, syscall.DNS_TYPE_TEXT, 0, nil, &r, nil)
   312  	if e != nil {
   313  		return nil, &DNSError{Err: winError("dnsquery", e).Error(), Name: name}
   314  	}
   315  	defer syscall.DnsRecordListFree(r, 1)
   316  
   317  	txts := make([]string, 0, 10)
   318  	for _, p := range validRecs(r, syscall.DNS_TYPE_TEXT, name) {
   319  		d := (*syscall.DNSTXTData)(unsafe.Pointer(&p.Data[0]))
   320  		s := ""
   321  		for _, v := range (*[1 << 10]*uint16)(unsafe.Pointer(&(d.StringArray[0])))[:d.StringCount:d.StringCount] {
   322  			s += windows.UTF16PtrToString(v)
   323  		}
   324  		txts = append(txts, s)
   325  	}
   326  	return txts, nil
   327  }
   328  
   329  func (*Resolver) lookupAddr(ctx context.Context, addr string) ([]string, error) {
   330  	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
   331  	acquireThread()
   332  	defer releaseThread()
   333  	arpa, err := reverseaddr(addr)
   334  	if err != nil {
   335  		return nil, err
   336  	}
   337  	var r *syscall.DNSRecord
   338  	e := syscall.DnsQuery(arpa, syscall.DNS_TYPE_PTR, 0, nil, &r, nil)
   339  	if e != nil {
   340  		return nil, &DNSError{Err: winError("dnsquery", e).Error(), Name: addr}
   341  	}
   342  	defer syscall.DnsRecordListFree(r, 1)
   343  
   344  	ptrs := make([]string, 0, 10)
   345  	for _, p := range validRecs(r, syscall.DNS_TYPE_PTR, arpa) {
   346  		v := (*syscall.DNSPTRData)(unsafe.Pointer(&p.Data[0]))
   347  		ptrs = append(ptrs, absDomainName([]byte(windows.UTF16PtrToString(v.Host))))
   348  	}
   349  	return ptrs, nil
   350  }
   351  
   352  const dnsSectionMask = 0x0003
   353  
   354  // returns only results applicable to name and resolves CNAME entries
   355  func validRecs(r *syscall.DNSRecord, dnstype uint16, name string) []*syscall.DNSRecord {
   356  	cname := syscall.StringToUTF16Ptr(name)
   357  	if dnstype != syscall.DNS_TYPE_CNAME {
   358  		cname = resolveCNAME(cname, r)
   359  	}
   360  	rec := make([]*syscall.DNSRecord, 0, 10)
   361  	for p := r; p != nil; p = p.Next {
   362  		// in case of a local machine, DNS records are returned with DNSREC_QUESTION flag instead of DNS_ANSWER
   363  		if p.Dw&dnsSectionMask != syscall.DnsSectionAnswer && p.Dw&dnsSectionMask != syscall.DnsSectionQuestion {
   364  			continue
   365  		}
   366  		if p.Type != dnstype {
   367  			continue
   368  		}
   369  		if !syscall.DnsNameCompare(cname, p.Name) {
   370  			continue
   371  		}
   372  		rec = append(rec, p)
   373  	}
   374  	return rec
   375  }
   376  
   377  // returns the last CNAME in chain
   378  func resolveCNAME(name *uint16, r *syscall.DNSRecord) *uint16 {
   379  	// limit cname resolving to 10 in case of an infinite CNAME loop
   380  Cname:
   381  	for cnameloop := 0; cnameloop < 10; cnameloop++ {
   382  		for p := r; p != nil; p = p.Next {
   383  			if p.Dw&dnsSectionMask != syscall.DnsSectionAnswer {
   384  				continue
   385  			}
   386  			if p.Type != syscall.DNS_TYPE_CNAME {
   387  				continue
   388  			}
   389  			if !syscall.DnsNameCompare(name, p.Name) {
   390  				continue
   391  			}
   392  			name = (*syscall.DNSPTRData)(unsafe.Pointer(&r.Data[0])).Host
   393  			continue Cname
   394  		}
   395  		break
   396  	}
   397  	return name
   398  }
   399  
   400  // concurrentThreadsLimit returns the number of threads we permit to
   401  // run concurrently doing DNS lookups.
   402  func concurrentThreadsLimit() int {
   403  	return 500
   404  }
   405  

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