Pull request: all: fix lint and naming issues vol. 2

Merge in DNS/adguard-home from 2276-fix-lint-2 to master

Updates #2276.

Squashed commit of the following:

commit 24760b9586bb31be134ef9518dbece485560b1a0
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Dec 7 14:39:50 2020 +0300

    all: fix lint and naming issues vol. 2

internal/dhcpd/dhcpd.go

@@ -52,6 +52,7 @@ type ServerConfig struct {
 	HTTPRegister func(string, string, func(http.ResponseWriter, *http.Request)) `yaml:"-"`
 }
 
+// OnLeaseChangedT is a callback for lease changes.
 type OnLeaseChangedT func(flags int)
 
 // flags for onLeaseChanged()
@@ -74,6 +75,7 @@ type Server struct {
 	onLeaseChanged []OnLeaseChangedT
 }
 
+// ServerInterface is an interface for servers.
 type ServerInterface interface {
 	Leases(flags int) []Lease
 	SetOnLeaseChanged(onLeaseChanged OnLeaseChangedT)

internal/dhcpd/nclient4/client.go

@@ -19,9 +19,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"log"
 	"net"
-	"os"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -317,26 +315,6 @@ func WithTimeout(d time.Duration) ClientOpt {
 	}
 }
 
-// WithSummaryLogger logs one-line DHCPv4 message summaries when sent & received.
-func WithSummaryLogger() ClientOpt {
-	return func(c *Client) (err error) {
-		c.logger = ShortSummaryLogger{
-			Printfer: log.New(os.Stderr, "[dhcpv4] ", log.LstdFlags),
-		}
-		return
-	}
-}
-
-// WithDebugLogger logs multi-line full DHCPv4 messages when sent & received.
-func WithDebugLogger() ClientOpt {
-	return func(c *Client) (err error) {
-		c.logger = DebugLogger{
-			Printfer: log.New(os.Stderr, "[dhcpv4] ", log.LstdFlags),
-		}
-		return
-	}
-}
-
 // WithLogger set the logger (see interface Logger).
 func WithLogger(newLogger Logger) ClientOpt {
 	return func(c *Client) (err error) {

internal/dhcpd/routeradv.go

@@ -180,15 +180,18 @@ func (ra *raCtx) Init() error {
 	data := createICMPv6RAPacket(params)
 
 	var err error
+	success := false
 	ipAndScope := ra.ipAddr.String() + "%" + ra.ifaceName
 	ra.conn, err = icmp.ListenPacket("ip6:ipv6-icmp", ipAndScope)
 	if err != nil {
 		return fmt.Errorf("dhcpv6 ra: icmp.ListenPacket: %w", err)
 	}
-	success := false
 	defer func() {
 		if !success {
-			ra.Close()
+			cerr := ra.Close()
+			if cerr != nil {
+				log.Error("closing context: %s", cerr)
+			}
 		}
 	}()
 
@@ -227,13 +230,15 @@ func (ra *raCtx) Init() error {
 	return nil
 }
 
-// Close - close module
-func (ra *raCtx) Close() {
+// Close closes the module.
+func (ra *raCtx) Close() (err error) {
 	log.Debug("dhcpv6 ra: closing")
 
 	ra.stop.Store(1)
 
 	if ra.conn != nil {
-		ra.conn.Close()
+		return ra.conn.Close()
 	}
+
+	return nil
 }

internal/dhcpd/v46_windows.go

@@ -1,11 +1,12 @@
+// +build windows
+
 package dhcpd
 
 // 'u-root/u-root' package, a dependency of 'insomniacslk/dhcp' package, doesn't build on Windows
 
 import "net"
 
-type winServer struct {
-}
+type winServer struct{}
 
 func (s *winServer) ResetLeases(leases []*Lease)            {}
 func (s *winServer) GetLeases(flags int) []Lease            { return nil }

internal/dhcpd/v6.go

@@ -628,7 +628,10 @@ func (s *v6Server) Start() error {
 
 // Stop - stop server
 func (s *v6Server) Stop() {
-	s.ra.Close()
+	err := s.ra.Close()
+	if err != nil {
+		log.Error("dhcpv6: s.ra.Close: %s", err)
+	}
 
 	// DHCPv6 server may not be initialized if ra_slaac_only=true
 	if s.srv == nil {
@@ -636,10 +639,11 @@ func (s *v6Server) Stop() {
 	}
 
 	log.Debug("DHCPv6: stopping")
-	err := s.srv.Close()
+	err = s.srv.Close()
 	if err != nil {
 		log.Error("DHCPv6: srv.Close: %s", err)
 	}
+
 	// now server.Serve() will return
 	s.srv = nil
 }