/
dnsresolver.go
48 lines (41 loc) · 1.22 KB
/
dnsresolver.go
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// Unless explicitly stated otherwise all files in this repository are licensed
// under the Apache License Version 2.0.
// This product includes software developed at Datadog (https://www.datadoghq.com/).
// Copyright 2019 Datadog, Inc.
package utils
import (
"fmt"
"net"
"regexp"
"sort"
"strings"
)
// DNSResolverIface is an interface for the DNSResolver
type DNSResolverIface interface {
Resolve(entry string) ([]string, error)
}
// DNSResolver is the DNS resolver
type DNSResolver struct {
re *regexp.Regexp
}
// NewDNSResolver instantiate a new DNSResolver
func NewDNSResolver() *DNSResolver {
re := regexp.MustCompile(`^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9]\.?)$`)
return &DNSResolver{
re: re,
}
}
// Resolve takes a domain name and returns the
func (r *DNSResolver) Resolve(entry string) ([]string, error) {
if !r.isValidEntry(entry) {
return nil, fmt.Errorf("invalid host: %s", entry)
}
addrs, err := net.LookupHost(entry)
sort.Strings(addrs)
return addrs, err
}
// isValidEntry verifies if an entry is a valid dns hostname
func (r *DNSResolver) isValidEntry(host string) bool {
host = strings.Trim(host, " ")
return r.re.MatchString(host)
}