libgo/go/net/cgo_unix.go

   1 // Copyright 2011 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 // +build cgo,!netgo
   6 // +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
   7
   8 package net
   9
  10 /*
  11 #include <sys/types.h>
  12 #include <sys/socket.h>
  13 #include <netinet/in.h>
  14 #include <netdb.h>
  15 #include <stdlib.h>
  16 #include <unistd.h>
  17 #include <string.h>
  18 */
  19
  20 import (
  21         "context"
  22         "syscall"
  23         "unsafe"
  24 )
  25
  26 //extern getaddrinfo
  27 func libc_getaddrinfo(node *byte, service *byte, hints *syscall.Addrinfo, res **syscall.Addrinfo) int
  28
  29 //extern freeaddrinfo
  30 func libc_freeaddrinfo(res *syscall.Addrinfo)
  31
  32 //extern gai_strerror
  33 func libc_gai_strerror(errcode int) *byte
  34
  35 // bytePtrToString takes a NUL-terminated array of bytes and convert
  36 // it to a Go string.
  37 func bytePtrToString(p *byte) string {
  38         a := (*[10000]byte)(unsafe.Pointer(p))
  39         i := 0
  40         for a[i] != 0 {
  41                 i++
  42         }
  43         return string(a[:i])
  44 }
  45
  46 // An addrinfoErrno represents a getaddrinfo, getnameinfo-specific
  47 // error number. It's a signed number and a zero value is a non-error
  48 // by convention.
  49 type addrinfoErrno int
  50
  51 func (eai addrinfoErrno) Error() string   { return bytePtrToString(libc_gai_strerror(int(eai))) }
  52 func (eai addrinfoErrno) Temporary() bool { return eai == syscall.EAI_AGAIN }
  53 func (eai addrinfoErrno) Timeout() bool   { return false }
  54
  55 type portLookupResult struct {
  56         port int
  57         err  error
  58 }
  59
  60 type ipLookupResult struct {
  61         addrs []IPAddr
  62         cname string
  63         err   error
  64 }
  65
  66 type reverseLookupResult struct {
  67         names []string
  68         err   error
  69 }
  70
  71 func cgoLookupHost(ctx context.Context, name string) (hosts []string, err error, completed bool) {
  72         addrs, err, completed := cgoLookupIP(ctx, name)
  73         for _, addr := range addrs {
  74                 hosts = append(hosts, addr.String())
  75         }
  76         return
  77 }
  78
  79 func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
  80         var hints syscall.Addrinfo
  81         switch network {
  82         case "": // no hints
  83         case "tcp", "tcp4", "tcp6":
  84                 hints.Ai_socktype = syscall.SOCK_STREAM
  85                 hints.Ai_protocol = syscall.IPPROTO_TCP
  86         case "udp", "udp4", "udp6":
  87                 hints.Ai_socktype = syscall.SOCK_DGRAM
  88                 hints.Ai_protocol = syscall.IPPROTO_UDP
  89         default:
  90                 return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}, true
  91         }
  92         if len(network) >= 4 {
  93                 switch network[3] {
  94                 case '4':
  95                         hints.Ai_family = syscall.AF_INET
  96                 case '6':
  97                         hints.Ai_family = syscall.AF_INET6
  98                 }
  99         }
 100         if ctx.Done() == nil {
 101                 port, err := cgoLookupServicePort(&hints, network, service)
 102                 return port, err, true
 103         }
 104         result := make(chan portLookupResult, 1)
 105         go cgoPortLookup(result, &hints, network, service)
 106         select {
 107         case r := <-result:
 108                 return r.port, r.err, true
 109         case <-ctx.Done():
 110                 // Since there isn't a portable way to cancel the lookup,
 111                 // we just let it finish and write to the buffered channel.
 112                 return 0, mapErr(ctx.Err()), false
 113         }
 114 }
 115
 116 func cgoLookupServicePort(hints *syscall.Addrinfo, network, service string) (port int, err error) {
 117         s, err := syscall.BytePtrFromString(service)
 118         if err != nil {
 119                 return 0, err
 120         }
 121         // Lowercase the service name in the memory passed to C.
 122         for i := 0; i < len(service); i++ {
 123                 bp := (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(s)) + uintptr(i)))
 124                 *bp = lowerASCII(*bp)
 125         }
 126         var res *syscall.Addrinfo
 127         syscall.Entersyscall()
 128         gerrno := libc_getaddrinfo(nil, s, hints, &res)
 129         syscall.Exitsyscall()
 130         if gerrno != 0 {
 131                 switch gerrno {
 132                 case syscall.EAI_SYSTEM:
 133                         errno := syscall.GetErrno()
 134                         if errno == 0 { // see golang.org/issue/6232
 135                                 errno = syscall.EMFILE
 136                         }
 137                         err = errno
 138                 default:
 139                         err = addrinfoErrno(gerrno)
 140                 }
 141                 return 0, &DNSError{Err: err.Error(), Name: network + "/" + service}
 142         }
 143         defer libc_freeaddrinfo(res)
 144
 145         for r := res; r != nil; r = r.Ai_next {
 146                 switch r.Ai_family {
 147                 case syscall.AF_INET:
 148                         sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.Ai_addr))
 149                         p := (*[2]byte)(unsafe.Pointer(&sa.Port))
 150                         return int(p[0])<<8 | int(p[1]), nil
 151                 case syscall.AF_INET6:
 152                         sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.Ai_addr))
 153                         p := (*[2]byte)(unsafe.Pointer(&sa.Port))
 154                         return int(p[0])<<8 | int(p[1]), nil
 155                 }
 156         }
 157         return 0, &DNSError{Err: "unknown port", Name: network + "/" + service}
 158 }
 159
 160 func cgoPortLookup(result chan<- portLookupResult, hints *syscall.Addrinfo, network, service string) {
 161         port, err := cgoLookupServicePort(hints, network, service)
 162         result <- portLookupResult{port, err}
 163 }
 164
 165 func cgoLookupIPCNAME(name string) (addrs []IPAddr, cname string, err error) {
 166         acquireThread()
 167         defer releaseThread()
 168
 169         var hints syscall.Addrinfo
 170         hints.Ai_flags = int32(cgoAddrInfoFlags)
 171         hints.Ai_socktype = syscall.SOCK_STREAM
 172
 173         h := syscall.StringBytePtr(name)
 174         var res *syscall.Addrinfo
 175         syscall.Entersyscall()
 176         gerrno := libc_getaddrinfo(h, nil, &hints, &res)
 177         syscall.Exitsyscall()
 178         if gerrno != 0 {
 179                 switch gerrno {
 180                 case syscall.EAI_SYSTEM:
 181                         errno := syscall.GetErrno()
 182                         if errno == 0 {
 183                                 // err should not be nil, but sometimes getaddrinfo returns
 184                                 // gerrno == C.EAI_SYSTEM with err == nil on Linux.
 185                                 // The report claims that it happens when we have too many
 186                                 // open files, so use syscall.EMFILE (too many open files in system).
 187                                 // Most system calls would return ENFILE (too many open files),
 188                                 // so at the least EMFILE should be easy to recognize if this
 189                                 // comes up again. golang.org/issue/6232.
 190                                 errno = syscall.EMFILE
 191                         }
 192                         err = errno
 193                 case syscall.EAI_NONAME:
 194                         err = errNoSuchHost
 195                 default:
 196                         err = addrinfoErrno(gerrno)
 197                 }
 198                 return nil, "", &DNSError{Err: err.Error(), Name: name}
 199         }
 200         defer libc_freeaddrinfo(res)
 201
 202         if res != nil {
 203                 cname = bytePtrToString((*byte)(unsafe.Pointer(res.Ai_canonname)))
 204                 if cname == "" {
 205                         cname = name
 206                 }
 207                 if len(cname) > 0 && cname[len(cname)-1] != '.' {
 208                         cname += "."
 209                 }
 210         }
 211         for r := res; r != nil; r = r.Ai_next {
 212                 // We only asked for SOCK_STREAM, but check anyhow.
 213                 if r.Ai_socktype != syscall.SOCK_STREAM {
 214                         continue
 215                 }
 216                 switch r.Ai_family {
 217                 case syscall.AF_INET:
 218                         sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.Ai_addr))
 219                         addr := IPAddr{IP: copyIP(sa.Addr[:])}
 220                         addrs = append(addrs, addr)
 221                 case syscall.AF_INET6:
 222                         sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.Ai_addr))
 223                         addr := IPAddr{IP: copyIP(sa.Addr[:]), Zone: zoneCache.name(int(sa.Scope_id))}
 224                         addrs = append(addrs, addr)
 225                 }
 226         }
 227         return addrs, cname, nil
 228 }
 229
 230 func cgoIPLookup(result chan<- ipLookupResult, name string) {
 231         addrs, cname, err := cgoLookupIPCNAME(name)
 232         result <- ipLookupResult{addrs, cname, err}
 233 }
 234
 235 func cgoLookupIP(ctx context.Context, name string) (addrs []IPAddr, err error, completed bool) {
 236         if ctx.Done() == nil {
 237                 addrs, _, err = cgoLookupIPCNAME(name)
 238                 return addrs, err, true
 239         }
 240         result := make(chan ipLookupResult, 1)
 241         go cgoIPLookup(result, name)
 242         select {
 243         case r := <-result:
 244                 return r.addrs, r.err, true
 245         case <-ctx.Done():
 246                 return nil, mapErr(ctx.Err()), false
 247         }
 248 }
 249
 250 func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
 251         if ctx.Done() == nil {
 252                 _, cname, err = cgoLookupIPCNAME(name)
 253                 return cname, err, true
 254         }
 255         result := make(chan ipLookupResult, 1)
 256         go cgoIPLookup(result, name)
 257         select {
 258         case r := <-result:
 259                 return r.cname, r.err, true
 260         case <-ctx.Done():
 261                 return "", mapErr(ctx.Err()), false
 262         }
 263 }
 264
 265 // These are roughly enough for the following:
 266 //
 267 // Source               Encoding                        Maximum length of single name entry
 268 // Unicast DNS          ASCII or                        <=253 + a NUL terminator
 269 //                      Unicode in RFC 5892             252 * total number of labels + delimiters + a NUL terminator
 270 // Multicast DNS        UTF-8 in RFC 5198 or            <=253 + a NUL terminator
 271 //                      the same as unicast DNS ASCII   <=253 + a NUL terminator
 272 // Local database       various                         depends on implementation
 273 const (
 274         nameinfoLen    = 64
 275         maxNameinfoLen = 4096
 276 )
 277
 278 func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error, completed bool) {
 279         var zone string
 280         ip := parseIPv4(addr)
 281         if ip == nil {
 282                 ip, zone = parseIPv6(addr, true)
 283         }
 284         if ip == nil {
 285                 return nil, &DNSError{Err: "invalid address", Name: addr}, true
 286         }
 287         sa, salen := cgoSockaddr(ip, zone)
 288         if sa == nil {
 289                 return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}, true
 290         }
 291         if ctx.Done() == nil {
 292                 names, err := cgoLookupAddrPTR(addr, sa, salen)
 293                 return names, err, true
 294         }
 295         result := make(chan reverseLookupResult, 1)
 296         go cgoReverseLookup(result, addr, sa, salen)
 297         select {
 298         case r := <-result:
 299                 return r.names, r.err, true
 300         case <-ctx.Done():
 301                 return nil, mapErr(ctx.Err()), false
 302         }
 303 }
 304
 305 func cgoLookupAddrPTR(addr string, sa *syscall.RawSockaddr, salen syscall.Socklen_t) (names []string, err error) {
 306         acquireThread()
 307         defer releaseThread()
 308
 309         var gerrno int
 310         var b []byte
 311         for l := nameinfoLen; l <= maxNameinfoLen; l *= 2 {
 312                 b = make([]byte, l)
 313                 gerrno, err = cgoNameinfoPTR(b, sa, salen)
 314                 if gerrno == 0 || gerrno != syscall.EAI_OVERFLOW {
 315                         break
 316                 }
 317         }
 318         if gerrno != 0 {
 319                 switch gerrno {
 320                 case syscall.EAI_SYSTEM:
 321                         if err == nil { // see golang.org/issue/6232
 322                                 err = syscall.EMFILE
 323                         }
 324                 default:
 325                         err = addrinfoErrno(gerrno)
 326                 }
 327                 return nil, &DNSError{Err: err.Error(), Name: addr}
 328         }
 329         for i := 0; i < len(b); i++ {
 330                 if b[i] == 0 {
 331                         b = b[:i]
 332                         break
 333                 }
 334         }
 335         return []string{absDomainName(b)}, nil
 336 }
 337
 338 func cgoReverseLookup(result chan<- reverseLookupResult, addr string, sa *syscall.RawSockaddr, salen syscall.Socklen_t) {
 339         names, err := cgoLookupAddrPTR(addr, sa, salen)
 340         result <- reverseLookupResult{names, err}
 341 }
 342
 343 func cgoSockaddr(ip IP, zone string) (*syscall.RawSockaddr, syscall.Socklen_t) {
 344         if ip4 := ip.To4(); ip4 != nil {
 345                 return cgoSockaddrInet4(ip4), syscall.Socklen_t(syscall.SizeofSockaddrInet4)
 346         }
 347         if ip6 := ip.To16(); ip6 != nil {
 348                 return cgoSockaddrInet6(ip6, zoneCache.index(zone)), syscall.Socklen_t(syscall.SizeofSockaddrInet6)
 349         }
 350         return nil, 0
 351 }
 352
 353 func copyIP(x IP) IP {
 354         if len(x) < 16 {
 355                 return x.To16()
 356         }
 357         y := make(IP, len(x))
 358         copy(y, x)
 359         return y
 360 }