Source file src/pkg/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 netbsd 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	}