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 hurd js,wasm linux netbsd openbsd solaris nacl
   6
   7 // Read system port mappings from /etc/services
   8
   9 package net
  10
  11 import (
  12         "internal/bytealg"
  13         "sync"
  14 )
  15
  16 var onceReadServices sync.Once
  17
  18 func readServices() {
  19         file, err := open("/etc/services")
  20         if err != nil {
  21                 return
  22         }
  23         defer file.close()
  24
  25         for line, ok := file.readLine(); ok; line, ok = file.readLine() {
  26                 // "http 80/tcp www www-http # World Wide Web HTTP"
  27                 if i := bytealg.IndexByteString(line, '#'); i >= 0 {
  28                         line = line[:i]
  29                 }
  30                 f := getFields(line)
  31                 if len(f) < 2 {
  32                         continue
  33                 }
  34                 portnet := f[1] // "80/tcp"
  35                 port, j, ok := dtoi(portnet)
  36                 if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
  37                         continue
  38                 }
  39                 netw := portnet[j+1:] // "tcp"
  40                 m, ok1 := services[netw]
  41                 if !ok1 {
  42                         m = make(map[string]int)
  43                         services[netw] = m
  44                 }
  45                 for i := 0; i < len(f); i++ {
  46                         if i != 1 { // f[1] was port/net
  47                                 m[f[i]] = port
  48                         }
  49                 }
  50         }
  51 }
  52
  53 // goLookupPort is the native Go implementation of LookupPort.
  54 func goLookupPort(network, service string) (port int, err error) {
  55         onceReadServices.Do(readServices)
  56         return lookupPortMap(network, service)
  57 }