Pull request: 2582 invalid hostname vol.3

Merge in DNS/adguard-home from 2582-zero-byte to master

Updates #2582.

Squashed commit of the following:

commit 88db23f26cd6ee9978310c7030f6866b9ef58785
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Thu Mar 11 13:01:02 2021 +0300

    dhcpd: rm temporary workaround

internal/dhcpd/v4.go

@@ -7,7 +7,6 @@ import (
 	"encoding/binary"
 	"fmt"
 	"net"
-	"strings"
 	"sync"
 	"time"
 
@@ -464,16 +463,7 @@ func (s *v4Server) processRequest(req, resp *dhcpv4.DHCPv4) (*Lease, bool) {
 	}
 
 	if lease.Expiry.Unix() != leaseExpireStatic {
-		// The trimming is required since some devices include trailing
-		// zero-byte in DHCP option length calculation.
-		//
-		// See https://github.com/AdguardTeam/AdGuardHome/issues/2582.
-		//
-		// TODO(e.burkov): Remove after the trimming for hostname option
-		// will be added into github.com/insomniacslk/dhcp module.
-		hostnameStr := strings.TrimRight(string(hostname), "\x00")
-
-		lease.Hostname = hostnameStr
+		lease.Hostname = string(hostname)
 		s.commitLease(lease)
 	} else if len(lease.Hostname) != 0 {
 		o := &optFQDN{

internal/dhcpd/v6.go

@@ -46,7 +46,8 @@ func ip6InRange(start, ip net.IP) bool {
 	if len(start) != 16 {
 		return false
 	}
-	//lint:ignore SA1021 TODO(e.burkov): Ignore this for now, think about using masks.
+	//lint:ignore SA1021 TODO(e.burkov): Ignore this for now, think about
+	// using masks.
 	if !bytes.Equal(start[:15], ip[:15]) {
 		return false
 	}