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1 // Copyright 2011 The Go Authors. All rights reserved.
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2 // Use of this source code is governed by a BSD-style
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3 // license that can be found in the LICENSE file.
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4
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5 // +build cgo,!netgo
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145
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6 // +build aix darwin dragonfly freebsd hurd linux netbsd openbsd solaris
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111
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7
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8 package net
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9
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10 /*
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11 #include <sys/types.h>
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12 #include <sys/socket.h>
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13 #include <netinet/in.h>
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14 #include <netdb.h>
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15 #include <unistd.h>
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16 #include <string.h>
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145
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17
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18 // If nothing else defined EAI_OVERFLOW, make sure it has a value.
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19 #ifndef EAI_OVERFLOW
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20 #define EAI_OVERFLOW -12
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21 #endif
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111
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22 */
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23
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24 import (
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25 "context"
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26 "syscall"
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27 "unsafe"
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28 )
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29
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30 //extern getaddrinfo
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131
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31 func libc_getaddrinfo(node *byte, service *byte, hints *syscall.Addrinfo, res **syscall.Addrinfo) int32
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111
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32
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33 //extern freeaddrinfo
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34 func libc_freeaddrinfo(res *syscall.Addrinfo)
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35
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36 //extern gai_strerror
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37 func libc_gai_strerror(errcode int) *byte
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38
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39 // bytePtrToString takes a NUL-terminated array of bytes and convert
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40 // it to a Go string.
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41 func bytePtrToString(p *byte) string {
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42 a := (*[10000]byte)(unsafe.Pointer(p))
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43 i := 0
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44 for a[i] != 0 {
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45 i++
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46 }
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47 return string(a[:i])
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48 }
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49
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50 // An addrinfoErrno represents a getaddrinfo, getnameinfo-specific
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51 // error number. It's a signed number and a zero value is a non-error
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52 // by convention.
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53 type addrinfoErrno int
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54
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55 func (eai addrinfoErrno) Error() string { return bytePtrToString(libc_gai_strerror(int(eai))) }
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56 func (eai addrinfoErrno) Temporary() bool { return eai == syscall.EAI_AGAIN }
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57 func (eai addrinfoErrno) Timeout() bool { return false }
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58
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59 type portLookupResult struct {
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60 port int
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61 err error
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62 }
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63
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64 type ipLookupResult struct {
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65 addrs []IPAddr
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66 cname string
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67 err error
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68 }
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69
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70 type reverseLookupResult struct {
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71 names []string
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72 err error
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73 }
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74
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75 func cgoLookupHost(ctx context.Context, name string) (hosts []string, err error, completed bool) {
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145
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76 addrs, err, completed := cgoLookupIP(ctx, "ip", name)
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111
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77 for _, addr := range addrs {
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78 hosts = append(hosts, addr.String())
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79 }
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80 return
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81 }
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82
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83 func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
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84 var hints syscall.Addrinfo
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85 switch network {
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86 case "": // no hints
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87 case "tcp", "tcp4", "tcp6":
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88 hints.Ai_socktype = syscall.SOCK_STREAM
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89 hints.Ai_protocol = syscall.IPPROTO_TCP
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90 case "udp", "udp4", "udp6":
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91 hints.Ai_socktype = syscall.SOCK_DGRAM
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92 hints.Ai_protocol = syscall.IPPROTO_UDP
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93 default:
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94 return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}, true
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95 }
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145
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96 switch ipVersion(network) {
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97 case '4':
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98 hints.Ai_family = syscall.AF_INET
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99 case '6':
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100 hints.Ai_family = syscall.AF_INET6
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111
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101 }
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102 if ctx.Done() == nil {
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103 port, err := cgoLookupServicePort(&hints, network, service)
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104 return port, err, true
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105 }
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106 result := make(chan portLookupResult, 1)
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107 go cgoPortLookup(result, &hints, network, service)
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108 select {
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109 case r := <-result:
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110 return r.port, r.err, true
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111 case <-ctx.Done():
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112 // Since there isn't a portable way to cancel the lookup,
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113 // we just let it finish and write to the buffered channel.
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114 return 0, mapErr(ctx.Err()), false
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115 }
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116 }
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117
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118 func cgoLookupServicePort(hints *syscall.Addrinfo, network, service string) (port int, err error) {
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119 s, err := syscall.BytePtrFromString(service)
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120 if err != nil {
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121 return 0, err
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122 }
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123 // Lowercase the service name in the memory passed to C.
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124 for i := 0; i < len(service); i++ {
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125 bp := (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(s)) + uintptr(i)))
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126 *bp = lowerASCII(*bp)
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127 }
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128 var res *syscall.Addrinfo
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129 syscall.Entersyscall()
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130 gerrno := libc_getaddrinfo(nil, s, hints, &res)
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131 syscall.Exitsyscall()
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132 if gerrno != 0 {
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133 isTemporary := false
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111
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134 switch gerrno {
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135 case syscall.EAI_SYSTEM:
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136 errno := syscall.GetErrno()
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137 if errno == 0 { // see golang.org/issue/6232
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138 errno = syscall.EMFILE
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139 }
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140 err = errno
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141 default:
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142 err = addrinfoErrno(gerrno)
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145
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143 isTemporary = addrinfoErrno(gerrno).Temporary()
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111
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144 }
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145
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145 return 0, &DNSError{Err: err.Error(), Name: network + "/" + service, IsTemporary: isTemporary}
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111
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146 }
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147 defer libc_freeaddrinfo(res)
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148
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149 for r := res; r != nil; r = r.Ai_next {
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150 switch r.Ai_family {
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151 case syscall.AF_INET:
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152 sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.Ai_addr))
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153 p := (*[2]byte)(unsafe.Pointer(&sa.Port))
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154 return int(p[0])<<8 | int(p[1]), nil
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155 case syscall.AF_INET6:
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156 sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.Ai_addr))
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157 p := (*[2]byte)(unsafe.Pointer(&sa.Port))
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158 return int(p[0])<<8 | int(p[1]), nil
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159 }
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160 }
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161 return 0, &DNSError{Err: "unknown port", Name: network + "/" + service}
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162 }
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163
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164 func cgoPortLookup(result chan<- portLookupResult, hints *syscall.Addrinfo, network, service string) {
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165 port, err := cgoLookupServicePort(hints, network, service)
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166 result <- portLookupResult{port, err}
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167 }
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168
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145
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169 func cgoLookupIPCNAME(network, name string) (addrs []IPAddr, cname string, err error) {
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111
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170 acquireThread()
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171 defer releaseThread()
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172
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173 var hints syscall.Addrinfo
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174 hints.Ai_flags = int32(cgoAddrInfoFlags)
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175 hints.Ai_socktype = syscall.SOCK_STREAM
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176 hints.Ai_family = syscall.AF_UNSPEC
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177 switch ipVersion(network) {
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178 case '4':
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179 hints.Ai_family = syscall.AF_INET
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180 case '6':
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181 hints.Ai_family = syscall.AF_INET6
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182 }
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111
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183
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184 h := syscall.StringBytePtr(name)
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185 var res *syscall.Addrinfo
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186 syscall.Entersyscall()
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187 gerrno := libc_getaddrinfo(h, nil, &hints, &res)
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188 syscall.Exitsyscall()
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189 if gerrno != 0 {
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190 isErrorNoSuchHost := false
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191 isTemporary := false
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111
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192 switch gerrno {
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193 case syscall.EAI_SYSTEM:
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194 errno := syscall.GetErrno()
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195 if errno == 0 {
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196 // err should not be nil, but sometimes getaddrinfo returns
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197 // gerrno == C.EAI_SYSTEM with err == nil on Linux.
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198 // The report claims that it happens when we have too many
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199 // open files, so use syscall.EMFILE (too many open files in system).
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200 // Most system calls would return ENFILE (too many open files),
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201 // so at the least EMFILE should be easy to recognize if this
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202 // comes up again. golang.org/issue/6232.
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203 errno = syscall.EMFILE
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204 }
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205 err = errno
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206 case syscall.EAI_NONAME:
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207 err = errNoSuchHost
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208 isErrorNoSuchHost = true
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111
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209 default:
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210 err = addrinfoErrno(gerrno)
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211 isTemporary = addrinfoErrno(gerrno).Temporary()
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111
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212 }
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145
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213
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214 return nil, "", &DNSError{Err: err.Error(), Name: name, IsNotFound: isErrorNoSuchHost, IsTemporary: isTemporary}
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111
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215 }
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216 defer libc_freeaddrinfo(res)
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217
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218 if res != nil {
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219 cname = bytePtrToString((*byte)(unsafe.Pointer(res.Ai_canonname)))
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220 if cname == "" {
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221 cname = name
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222 }
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223 if len(cname) > 0 && cname[len(cname)-1] != '.' {
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224 cname += "."
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225 }
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226 }
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227 for r := res; r != nil; r = r.Ai_next {
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228 // We only asked for SOCK_STREAM, but check anyhow.
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229 if r.Ai_socktype != syscall.SOCK_STREAM {
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230 continue
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231 }
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232 switch r.Ai_family {
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233 case syscall.AF_INET:
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234 sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.Ai_addr))
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235 addr := IPAddr{IP: copyIP(sa.Addr[:])}
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236 addrs = append(addrs, addr)
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237 case syscall.AF_INET6:
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238 sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.Ai_addr))
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239 addr := IPAddr{IP: copyIP(sa.Addr[:]), Zone: zoneCache.name(int(sa.Scope_id))}
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240 addrs = append(addrs, addr)
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241 }
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242 }
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243 return addrs, cname, nil
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244 }
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245
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145
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246 func cgoIPLookup(result chan<- ipLookupResult, network, name string) {
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247 addrs, cname, err := cgoLookupIPCNAME(network, name)
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111
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248 result <- ipLookupResult{addrs, cname, err}
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249 }
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250
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145
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251 func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error, completed bool) {
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111
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252 if ctx.Done() == nil {
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253 addrs, _, err = cgoLookupIPCNAME(network, name)
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111
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254 return addrs, err, true
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255 }
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256 result := make(chan ipLookupResult, 1)
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257 go cgoIPLookup(result, network, name)
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111
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258 select {
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259 case r := <-result:
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260 return r.addrs, r.err, true
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261 case <-ctx.Done():
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262 return nil, mapErr(ctx.Err()), false
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263 }
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264 }
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265
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266 func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
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267 if ctx.Done() == nil {
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268 _, cname, err = cgoLookupIPCNAME("ip", name)
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111
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269 return cname, err, true
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270 }
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271 result := make(chan ipLookupResult, 1)
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145
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272 go cgoIPLookup(result, "ip", name)
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111
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273 select {
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274 case r := <-result:
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275 return r.cname, r.err, true
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276 case <-ctx.Done():
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277 return "", mapErr(ctx.Err()), false
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278 }
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279 }
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280
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281 // These are roughly enough for the following:
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282 //
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283 // Source Encoding Maximum length of single name entry
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284 // Unicast DNS ASCII or <=253 + a NUL terminator
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285 // Unicode in RFC 5892 252 * total number of labels + delimiters + a NUL terminator
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286 // Multicast DNS UTF-8 in RFC 5198 or <=253 + a NUL terminator
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287 // the same as unicast DNS ASCII <=253 + a NUL terminator
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288 // Local database various depends on implementation
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289 const (
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290 nameinfoLen = 64
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291 maxNameinfoLen = 4096
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292 )
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293
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294 func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error, completed bool) {
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295 var zone string
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296 ip := parseIPv4(addr)
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297 if ip == nil {
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131
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298 ip, zone = parseIPv6Zone(addr)
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111
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299 }
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300 if ip == nil {
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301 return nil, &DNSError{Err: "invalid address", Name: addr}, true
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302 }
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303 sa, salen := cgoSockaddr(ip, zone)
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304 if sa == nil {
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305 return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}, true
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306 }
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307 if ctx.Done() == nil {
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308 names, err := cgoLookupAddrPTR(addr, sa, salen)
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309 return names, err, true
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310 }
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311 result := make(chan reverseLookupResult, 1)
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312 go cgoReverseLookup(result, addr, sa, salen)
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313 select {
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314 case r := <-result:
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315 return r.names, r.err, true
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316 case <-ctx.Done():
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317 return nil, mapErr(ctx.Err()), false
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318 }
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319 }
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320
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321 func cgoLookupAddrPTR(addr string, sa *syscall.RawSockaddr, salen syscall.Socklen_t) (names []string, err error) {
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322 acquireThread()
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323 defer releaseThread()
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324
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325 var gerrno int
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326 var b []byte
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327 for l := nameinfoLen; l <= maxNameinfoLen; l *= 2 {
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328 b = make([]byte, l)
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329 gerrno, err = cgoNameinfoPTR(b, sa, salen)
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330 if gerrno == 0 || gerrno != syscall.EAI_OVERFLOW {
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331 break
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332 }
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333 }
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334 if gerrno != 0 {
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335 isTemporary := false
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111
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336 switch gerrno {
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337 case syscall.EAI_SYSTEM:
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338 if err == nil { // see golang.org/issue/6232
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339 err = syscall.EMFILE
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340 }
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341 default:
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342 err = addrinfoErrno(gerrno)
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145
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343 isTemporary = addrinfoErrno(gerrno).Temporary()
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111
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344 }
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145
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345 return nil, &DNSError{Err: err.Error(), Name: addr, IsTemporary: isTemporary}
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111
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346 }
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347 for i := 0; i < len(b); i++ {
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348 if b[i] == 0 {
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349 b = b[:i]
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350 break
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351 }
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352 }
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353 return []string{absDomainName(b)}, nil
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354 }
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355
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356 func cgoReverseLookup(result chan<- reverseLookupResult, addr string, sa *syscall.RawSockaddr, salen syscall.Socklen_t) {
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357 names, err := cgoLookupAddrPTR(addr, sa, salen)
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358 result <- reverseLookupResult{names, err}
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359 }
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360
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361 func cgoSockaddr(ip IP, zone string) (*syscall.RawSockaddr, syscall.Socklen_t) {
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362 if ip4 := ip.To4(); ip4 != nil {
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363 return cgoSockaddrInet4(ip4), syscall.Socklen_t(syscall.SizeofSockaddrInet4)
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364 }
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365 if ip6 := ip.To16(); ip6 != nil {
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366 return cgoSockaddrInet6(ip6, zoneCache.index(zone)), syscall.Socklen_t(syscall.SizeofSockaddrInet6)
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367 }
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368 return nil, 0
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369 }
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370
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371 func copyIP(x IP) IP {
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372 if len(x) < 16 {
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373 return x.To16()
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374 }
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375 y := make(IP, len(x))
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376 copy(y, x)
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377 return y
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378 }
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