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// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// LookupHost looks up the given host using the local resolver.
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// It returns an array of that host's addresses.
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func LookupHost(host string) (addrs []string, err error) {
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return lookupHost(host)
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func lookupHostDeadline(host string, deadline time.Time) (addrs []string, err error) {
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if deadline.IsZero() {
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return lookupHost(host)
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// TODO(bradfitz): consider pushing the deadline down into the
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// name resolution functions. But that involves fixing it for
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// the native Go resolver, cgo, Windows, etc.
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// In the meantime, just use a goroutine. Most users affected
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// by http://golang.org/issue/2631 are due to TCP connections
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// to unresponsive hosts, not DNS.
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timeout := deadline.Sub(time.Now())
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t := time.NewTimer(timeout)
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resc := make(chan res, 1)
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a, err := lookupHost(host)
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addrs, err = r.addrs, r.err
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// LookupIP looks up host using the local resolver.
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// It returns an array of that host's IPv4 and IPv6 addresses.
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func LookupIP(host string) (addrs []IP, err error) {
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// LookupPort looks up the port for the given network and service.
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func LookupPort(network, service string) (port int, err error) {
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return lookupPort(network, service)
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// LookupCNAME returns the canonical DNS host for the given name.
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// Callers that do not care about the canonical name can call
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// LookupHost or LookupIP directly; both take care of resolving
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// the canonical name as part of the lookup.
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func LookupCNAME(name string) (cname string, err error) {
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return lookupCNAME(name)
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// LookupSRV tries to resolve an SRV query of the given service,
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// protocol, and domain name. The proto is "tcp" or "udp".
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// The returned records are sorted by priority and randomized
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// by weight within a priority.
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// LookupSRV constructs the DNS name to look up following RFC 2782.
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// That is, it looks up _service._proto.name. To accommodate services
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// publishing SRV records under non-standard names, if both service
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// and proto are empty strings, LookupSRV looks up name directly.
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func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) {
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return lookupSRV(service, proto, name)
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// LookupMX returns the DNS MX records for the given domain name sorted by preference.
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func LookupMX(name string) (mx []*MX, err error) {
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// LookupNS returns the DNS NS records for the given domain name.
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func LookupNS(name string) (ns []*NS, err error) {
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// LookupTXT returns the DNS TXT records for the given domain name.
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func LookupTXT(name string) (txt []string, err error) {
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return lookupTXT(name)
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// LookupAddr performs a reverse lookup for the given address, returning a list
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// of names mapping to that address.
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func LookupAddr(addr string) (name []string, err error) {
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return lookupAddr(addr)