1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
|
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build darwin dragonfly freebsd linux netbsd openbsd solaris
package net
import (
"context"
"sync"
)
var onceReadProtocols sync.Once
// readProtocols loads contents of /etc/protocols into protocols map
// for quick access.
func readProtocols() {
if file, err := open("/etc/protocols"); err == nil {
for line, ok := file.readLine(); ok; line, ok = file.readLine() {
// tcp 6 TCP # transmission control protocol
if i := byteIndex(line, '#'); i >= 0 {
line = line[0:i]
}
f := getFields(line)
if len(f) < 2 {
continue
}
if proto, _, ok := dtoi(f[1], 0); ok {
if _, ok := protocols[f[0]]; !ok {
protocols[f[0]] = proto
}
for _, alias := range f[2:] {
if _, ok := protocols[alias]; !ok {
protocols[alias] = proto
}
}
}
}
file.close()
}
}
// lookupProtocol looks up IP protocol name in /etc/protocols and
// returns correspondent protocol number.
func lookupProtocol(_ context.Context, name string) (int, error) {
onceReadProtocols.Do(readProtocols)
proto, found := protocols[name]
if !found {
return 0, &AddrError{Err: "unknown IP protocol specified", Addr: name}
}
return proto, nil
}
func lookupHost(ctx context.Context, host string) (addrs []string, err error) {
order := systemConf().hostLookupOrder(host)
if order == hostLookupCgo {
if addrs, err, ok := cgoLookupHost(ctx, host); ok {
return addrs, err
}
// cgo not available (or netgo); fall back to Go's DNS resolver
order = hostLookupFilesDNS
}
return goLookupHostOrder(ctx, host, order)
}
func lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
order := systemConf().hostLookupOrder(host)
if order == hostLookupCgo {
if addrs, err, ok := cgoLookupIP(ctx, host); ok {
return addrs, err
}
// cgo not available (or netgo); fall back to Go's DNS resolver
order = hostLookupFilesDNS
}
return goLookupIPOrder(ctx, host, order)
}
func lookupPort(ctx context.Context, network, service string) (int, error) {
// TODO: use the context if there ever becomes a need. Related
// is issue 15321. But port lookup generally just involves
// local files, and the os package has no context support. The
// files might be on a remote filesystem, though. This should
// probably race goroutines if ctx != context.Background().
if systemConf().canUseCgo() {
if port, err, ok := cgoLookupPort(ctx, network, service); ok {
return port, err
}
}
return goLookupPort(network, service)
}
func lookupCNAME(ctx context.Context, name string) (string, error) {
if systemConf().canUseCgo() {
if cname, err, ok := cgoLookupCNAME(ctx, name); ok {
return cname, err
}
}
return goLookupCNAME(ctx, name)
}
func lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
var target string
if service == "" && proto == "" {
target = name
} else {
target = "_" + service + "._" + proto + "." + name
}
cname, rrs, err := lookup(ctx, target, dnsTypeSRV)
if err != nil {
return "", nil, err
}
srvs := make([]*SRV, len(rrs))
for i, rr := range rrs {
rr := rr.(*dnsRR_SRV)
srvs[i] = &SRV{Target: rr.Target, Port: rr.Port, Priority: rr.Priority, Weight: rr.Weight}
}
byPriorityWeight(srvs).sort()
return cname, srvs, nil
}
func lookupMX(ctx context.Context, name string) ([]*MX, error) {
_, rrs, err := lookup(ctx, name, dnsTypeMX)
if err != nil {
return nil, err
}
mxs := make([]*MX, len(rrs))
for i, rr := range rrs {
rr := rr.(*dnsRR_MX)
mxs[i] = &MX{Host: rr.Mx, Pref: rr.Pref}
}
byPref(mxs).sort()
return mxs, nil
}
func lookupNS(ctx context.Context, name string) ([]*NS, error) {
_, rrs, err := lookup(ctx, name, dnsTypeNS)
if err != nil {
return nil, err
}
nss := make([]*NS, len(rrs))
for i, rr := range rrs {
nss[i] = &NS{Host: rr.(*dnsRR_NS).Ns}
}
return nss, nil
}
func lookupTXT(ctx context.Context, name string) ([]string, error) {
_, rrs, err := lookup(ctx, name, dnsTypeTXT)
if err != nil {
return nil, err
}
txts := make([]string, len(rrs))
for i, rr := range rrs {
txts[i] = rr.(*dnsRR_TXT).Txt
}
return txts, nil
}
func lookupAddr(ctx context.Context, addr string) ([]string, error) {
if systemConf().canUseCgo() {
if ptrs, err, ok := cgoLookupPTR(ctx, addr); ok {
return ptrs, err
}
}
return goLookupPTR(ctx, addr)
}
|
