From aee09d29e9d622362fdfa85b3cacf45daf05658a Mon Sep 17 00:00:00 2001
From: Ainar Garipov <a.garipov@adguard.com>
Date: Wed, 21 Apr 2021 14:42:19 +0300
Subject: [PATCH] Pull request: dhcpd: fix dbload panic

Closes #2991.

Squashed commit of the following:

commit cd820a9a903d628aa5964f8f973edc7bb7993ae5
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Apr 21 14:34:45 2021 +0300

    dhcpd: fix err handling

commit 775b834683f0edb5954b20fedb896e6af1fa843e
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Apr 21 14:21:41 2021 +0300

    dhcpd: fix build for go1.15

commit 8441d6fffa72cc6890fad2df76559e21819786d6
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Apr 21 14:05:08 2021 +0300

    dhcpd: fix dbload panic
---
 Makefile                | 12 ++++++++----
 internal/dhcpd/dhcpd.go |  6 ++----
 internal/dhcpd/v4.go    | 28 +++++++++++++++++++++++-----
 internal/home/home.go   |  5 ++++-
 4 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/Makefile b/Makefile
index d4441c47..52cb1d57 100644
--- a/Makefile
+++ b/Makefile
@@ -9,6 +9,10 @@ CLIENT_BETA_DIR = client2
 CLIENT_DIR = client
 COMMIT = $$(git rev-parse --short HEAD)
 DIST_DIR = dist
+# TODO(a.garipov): Find out a way to make this work in GNU Make.
+#
+#  GO = $${GO:-go}
+#
 GO = go
 GOPROXY = https://goproxy.cn|https://proxy.golang.org|direct
 GPG_KEY = devteam@adguard.com
@@ -93,10 +97,10 @@ go-check: go-tools go-lint go-test
 # A quick check to make sure that all supported operating systems can be
 # typechecked and built successfully.
 go-os-check:
-	env GOOS='darwin'  go vet ./internal/...
-	env GOOS='freebsd' go vet ./internal/...
-	env GOOS='linux'   go vet ./internal/...
-	env GOOS='windows' go vet ./internal/...
+	env GOOS='darwin'  $(GO) vet ./internal/...
+	env GOOS='freebsd' $(GO) vet ./internal/...
+	env GOOS='linux'   $(GO) vet ./internal/...
+	env GOOS='windows' $(GO) vet ./internal/...
 
 openapi-lint: ; cd ./openapi/ && $(YARN) test
 openapi-show: ; cd ./openapi/ && $(YARN) start
diff --git a/internal/dhcpd/dhcpd.go b/internal/dhcpd/dhcpd.go
index 26388cb0..3d2b8a8b 100644
--- a/internal/dhcpd/dhcpd.go
+++ b/internal/dhcpd/dhcpd.go
@@ -242,16 +242,14 @@ func (s *Server) WriteDiskConfig(c *ServerConfig) {
 }
 
 // Start will listen on port 67 and serve DHCP requests.
-func (s *Server) Start() error {
-	err := s.srv4.Start()
+func (s *Server) Start() (err error) {
+	err = s.srv4.Start()
 	if err != nil {
-		log.Error("DHCPv4: start: %s", err)
 		return err
 	}
 
 	err = s.srv6.Start()
 	if err != nil {
-		log.Error("DHCPv6: start: %s", err)
 		return err
 	}
 
diff --git a/internal/dhcpd/v4.go b/internal/dhcpd/v4.go
index 2a4bbc27..5cbfc370 100644
--- a/internal/dhcpd/v4.go
+++ b/internal/dhcpd/v4.go
@@ -51,6 +51,12 @@ func (s *v4Server) WriteDiskConfig6(c *V6ServerConf) {
 
 // ResetLeases - reset leases
 func (s *v4Server) ResetLeases(leases []*Lease) {
+	if !s.conf.Enabled {
+		return
+	}
+
+	s.leasedOffsets = newBitSet()
+	s.leaseHosts = aghstrings.NewSet()
 	s.leases = nil
 
 	for _, l := range leases {
@@ -826,7 +832,9 @@ func (s *v4Server) packetHandler(conn net.PacketConn, peer net.Addr, req *dhcpv4
 }
 
 // Start starts the IPv4 DHCP server.
-func (s *v4Server) Start() error {
+func (s *v4Server) Start() (err error) {
+	defer agherr.Annotate("dhcpv4: %w", &err)
+
 	if !s.conf.Enabled {
 		return nil
 	}
@@ -834,14 +842,14 @@ func (s *v4Server) Start() error {
 	ifaceName := s.conf.InterfaceName
 	iface, err := net.InterfaceByName(ifaceName)
 	if err != nil {
-		return fmt.Errorf("dhcpv4: finding interface %s by name: %w", ifaceName, err)
+		return fmt.Errorf("finding interface %s by name: %w", ifaceName, err)
 	}
 
 	log.Debug("dhcpv4: starting...")
 
 	dnsIPAddrs, err := ifaceDNSIPAddrs(iface, ipVersion4, defaultMaxAttempts, defaultBackoff)
 	if err != nil {
-		return fmt.Errorf("dhcpv4: interface %s: %w", ifaceName, err)
+		return fmt.Errorf("interface %s: %w", ifaceName, err)
 	}
 
 	if len(dnsIPAddrs) == 0 {
@@ -863,8 +871,18 @@ func (s *v4Server) Start() error {
 	log.Info("dhcpv4: listening")
 
 	go func() {
-		err = s.srv.Serve()
-		log.Debug("dhcpv4: srv.Serve: %s", err)
+		serr := s.srv.Serve()
+		// TODO(a.garipov): Uncomment in Go 1.16.
+		//
+		//   if errors.Is(serr, net.ErrClosed) {
+		//           log.Info("dhcpv4: server is closed")
+		//
+		//           return
+		//   }
+
+		if serr != nil {
+			log.Error("dhcpv4: srv.Serve: %s", serr)
+		}
 	}()
 
 	// Signal to the clients containers in packages home and dnsforward that
diff --git a/internal/home/home.go b/internal/home/home.go
index 4a590639..b202d187 100644
--- a/internal/home/home.go
+++ b/internal/home/home.go
@@ -332,7 +332,10 @@ func run(args options) {
 		}()
 
 		if Context.dhcpServer != nil {
-			_ = Context.dhcpServer.Start()
+			err = Context.dhcpServer.Start()
+			if err != nil {
+				log.Error("starting dhcp server: %s", err)
+			}
 		}
 	}