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// 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]); 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)
return lookupProtocolMap(name)
}
func (r *Resolver) lookupHost(ctx context.Context, host string) (addrs []string, err error) {
order := systemConf().hostLookupOrder(host)
if !r.PreferGo && 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 (r *Resolver) lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
if r.PreferGo {
return goLookupIP(ctx, host)
}
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
}
addrs, _, err = goLookupIPCNAMEOrder(ctx, host, order)
return
}
func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int, error) {
if !r.PreferGo && systemConf().canUseCgo() {
if port, err, ok := cgoLookupPort(ctx, network, service); ok {
if err != nil {
// Issue 18213: if cgo fails, first check to see whether we
// have the answer baked-in to the net package.
if port, err := goLookupPort(network, service); err == nil {
return port, nil
}
}
return port, err
}
}
return goLookupPort(network, service)
}
func (r *Resolver) lookupCNAME(ctx context.Context, name string) (string, error) {
if !r.PreferGo && systemConf().canUseCgo() {
if cname, err, ok := cgoLookupCNAME(ctx, name); ok {
return cname, err
}
}
return goLookupCNAME(ctx, name)
}
func (*Resolver) 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 (*Resolver) 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 (*Resolver) 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 (r *Resolver) 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 (r *Resolver) lookupAddr(ctx context.Context, addr string) ([]string, error) {
if !r.PreferGo && systemConf().canUseCgo() {
if ptrs, err, ok := cgoLookupPTR(ctx, addr); ok {
return ptrs, err
}
}
return goLookupPTR(ctx, addr)
}
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