libgo/go/net/port.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 // +build darwin freebsd linux openbsd
   6
   7 // Read system port mappings from /etc/services
   8
   9 package net
  10
  11 import "sync"
  12
  13 var services map[string]map[string]int
  14 var servicesError error
  15 var onceReadServices sync.Once
  16
  17 func readServices() {
  18         services = make(map[string]map[string]int)
  19         var file *file
  20         if file, servicesError = open("/etc/services"); servicesError != nil {
  21                 return
  22         }
  23         for line, ok := file.readLine(); ok; line, ok = file.readLine() {
  24                 // "http 80/tcp www www-http # World Wide Web HTTP"
  25                 if i := byteIndex(line, '#'); i >= 0 {
  26                         line = line[0:i]
  27                 }
  28                 f := getFields(line)
  29                 if len(f) < 2 {
  30                         continue
  31                 }
  32                 portnet := f[1] // "tcp/80"
  33                 port, j, ok := dtoi(portnet, 0)
  34                 if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
  35                         continue
  36                 }
  37                 netw := portnet[j+1:] // "tcp"
  38                 m, ok1 := services[netw]
  39                 if !ok1 {
  40                         m = make(map[string]int)
  41                         services[netw] = m
  42                 }
  43                 for i := 0; i < len(f); i++ {
  44                         if i != 1 { // f[1] was port/net
  45                                 m[f[i]] = port
  46                         }
  47                 }
  48         }
  49         file.close()
  50 }
  51
  52 // goLookupPort is the native Go implementation of LookupPort.
  53 func goLookupPort(network, service string) (port int, err error) {
  54         onceReadServices.Do(readServices)
  55
  56         switch network {
  57         case "tcp4", "tcp6":
  58                 network = "tcp"
  59         case "udp4", "udp6":
  60                 network = "udp"
  61         }
  62
  63         if m, ok := services[network]; ok {
  64                 if port, ok = m[service]; ok {
  65                         return
  66                 }
  67         }
  68         return 0, &AddrError{"unknown port", network + "/" + service}
  69 }