libgo/go/net/port_unix.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 aix darwin dragonfly freebsd js,wasm linux netbsd openbsd solaris nacl
   6
   7 // Read system port mappings from /etc/services
   8
   9 package net
  10
  11 import "sync"
  12
  13 var onceReadServices sync.Once
  14
  15 func readServices() {
  16         file, err := open("/etc/services")
  17         if err != nil {
  18                 return
  19         }
  20         defer file.close()
  21
  22         for line, ok := file.readLine(); ok; line, ok = file.readLine() {
  23                 // "http 80/tcp www www-http # World Wide Web HTTP"
  24                 if i := byteIndex(line, '#'); i >= 0 {
  25                         line = line[:i]
  26                 }
  27                 f := getFields(line)
  28                 if len(f) < 2 {
  29                         continue
  30                 }
  31                 portnet := f[1] // "80/tcp"
  32                 port, j, ok := dtoi(portnet)
  33                 if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
  34                         continue
  35                 }
  36                 netw := portnet[j+1:] // "tcp"
  37                 m, ok1 := services[netw]
  38                 if !ok1 {
  39                         m = make(map[string]int)
  40                         services[netw] = m
  41                 }
  42                 for i := 0; i < len(f); i++ {
  43                         if i != 1 { // f[1] was port/net
  44                                 m[f[i]] = port
  45                         }
  46                 }
  47         }
  48 }
  49
  50 // goLookupPort is the native Go implementation of LookupPort.
  51 func goLookupPort(network, service string) (port int, err error) {
  52         onceReadServices.Do(readServices)
  53         return lookupPortMap(network, service)
  54 }