netbird/dns/dns.go
Maycon Santos a78fd69f80
Feature/dns client configuration (#563)
Added host configurators for Linux, Windows, and macOS.

The host configurator will update the peer system configuration
 directing DNS queries according to its capabilities.

Some Linux distributions don't support split (match) DNS or custom ports,
 and that will be reported to our management system in another PR
2022-11-23 13:39:42 +01:00

110 lines
2.9 KiB
Go

// Package dns implement dns types and standard methods and functions
// to parse and normalize dns records and configuration
package dns
import (
"fmt"
"github.com/miekg/dns"
"golang.org/x/net/idna"
"net"
"regexp"
"strings"
)
const (
// DefaultDNSPort well-known port number
DefaultDNSPort = 53
// RootZone is a string representation of the root zone
RootZone = "."
// DefaultClass is the class supported by the system
DefaultClass = "IN"
)
const invalidHostLabel = "[^a-zA-Z0-9-]+"
// Config represents a dns configuration that is exchanged between management and peers
type Config struct {
// ServiceEnable indicates if the service should be enabled
ServiceEnable bool
// NameServerGroups contains a list of nameserver group
NameServerGroups []*NameServerGroup
// CustomZones contains a list of custom zone
CustomZones []CustomZone
}
// CustomZone represents a custom zone to be resolved by the dns server
type CustomZone struct {
// Domain is the zone's domain
Domain string
// Records custom zone records
Records []SimpleRecord
}
// SimpleRecord provides a simple DNS record specification for CNAME, A and AAAA records
type SimpleRecord struct {
// Name domain name
Name string
// Type of record, 1 for A, 5 for CNAME, 28 for AAAA. see https://pkg.go.dev/github.com/miekg/dns@v1.1.41#pkg-constants
Type int
// Class dns class, currently use the DefaultClass for all records
Class string
// TTL time-to-live for the record
TTL int
// RData is the actual value resolved in a dns query
RData string
}
// String returns a string of the simple record formatted as:
// <Name> <TTL> <Class> <Type> <RDATA>
func (s SimpleRecord) String() string {
fqdn := dns.Fqdn(s.Name)
return fmt.Sprintf("%s %d %s %s %s", fqdn, s.TTL, s.Class, dns.Type(s.Type).String(), s.RData)
}
// Len returns the length of the RData field, based on its type
func (s SimpleRecord) Len() uint16 {
emptyString := s.RData == ""
switch s.Type {
case 1:
if emptyString {
return 0
}
return net.IPv4len
case 5:
if emptyString || s.RData == "." {
return 1
}
return uint16(len(s.RData) + 1)
case 28:
if emptyString {
return 0
}
return net.IPv6len
default:
return 0
}
}
// GetParsedDomainLabel returns a domain label with max 59 characters,
// parsed for old Hosts.txt requirements, and converted to ASCII and lowercase
func GetParsedDomainLabel(name string) (string, error) {
labels := dns.SplitDomainName(name)
if len(labels) == 0 {
return "", fmt.Errorf("got empty label list for name \"%s\"", name)
}
rawLabel := labels[0]
ascii, err := idna.Punycode.ToASCII(rawLabel)
if err != nil {
return "", fmt.Errorf("unable to convert host lavel to ASCII, error: %v", err)
}
invalidHostMatcher := regexp.MustCompile(invalidHostLabel)
validHost := strings.ToLower(invalidHostMatcher.ReplaceAllString(ascii, "-"))
if len(validHost) > 58 {
validHost = validHost[:59]
}
return validHost, nil
}