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opendns_resolver.go
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/
opendns_resolver.go
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// Copyright (C) 2019-2022, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package dynamicip
import (
"context"
"errors"
"net"
"time"
)
const (
ipResolutionTimeout = 10 * time.Second
openDNSUrl = "resolver1.opendns.com:53"
)
var (
errOpenDNSNoIP = errors.New("openDNS returned no ip")
_ Resolver = &openDNSResolver{}
)
// IFConfigResolves resolves our public IP using openDNS
type openDNSResolver struct {
resolver *net.Resolver
}
func newOpenDNSResolver() Resolver {
return &openDNSResolver{
resolver: &net.Resolver{
PreferGo: true,
Dial: func(ctx context.Context, _, _ string) (net.Conn, error) {
d := net.Dialer{
Timeout: ipResolutionTimeout,
}
return d.DialContext(ctx, "udp", openDNSUrl)
},
},
}
}
func (r *openDNSResolver) Resolve() (net.IP, error) {
ips, err := r.resolver.LookupIP(context.TODO(), "ip", "myip.opendns.com")
if err != nil {
return nil, err
}
if len(ips) == 0 {
return nil, errOpenDNSNoIP
}
return ips[0], nil
}