Pull request 2254: 4923 gopacket DHCP vol.9

Updates #4923.

Squashed commit of the following:

commit 0532241
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Jul 9 18:18:35 2024 +0300

    dhcpsvc: imp docs

commit 083da36
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Jul 9 15:28:52 2024 +0300

    dhcpsvc: imp code, tests

commit 22e37e5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Jul 8 19:31:43 2024 +0300

    dhcpsvc: imp tests

commit 83ec7c5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Jul 8 18:56:21 2024 +0300

    dhcpsvc: add db

internal/dhcpsvc/config.go

@@ -3,6 +3,7 @@ package dhcpsvc
 import (
 	"fmt"
 	"log/slog"
+	"os"
 	"time"
 
 	"github.com/AdguardTeam/golibs/errors"
@@ -23,7 +24,8 @@ type Config struct {
 	// clients' hostnames.
 	LocalDomainName string
 
-	// TODO(e.burkov):  Add DB path.
+	// DBFilePath is the path to the database file containing the DHCP leases.
+	DBFilePath string
 
 	// ICMPTimeout is the timeout for checking another DHCP server's presence.
 	ICMPTimeout time.Duration
@@ -64,6 +66,12 @@ func (conf *Config) Validate() (err error) {
 		errs = append(errs, err)
 	}
 
+	// This is a best-effort check for the file accessibility.  The file will be
+	// checked again when it is opened later.
+	if _, err = os.Stat(conf.DBFilePath); err != nil && !errors.Is(err, os.ErrNotExist) {
+		errs = append(errs, fmt.Errorf("db file path %q: %w", conf.DBFilePath, err))
+	}
+
 	if len(conf.Interfaces) == 0 {
 		errs = append(errs, errNoInterfaces)
 

internal/dhcpsvc/config_test.go

@@ -1,13 +1,16 @@
 package dhcpsvc_test
 
 import (
+	"path/filepath"
 	"testing"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/dhcpsvc"
 	"github.com/AdguardTeam/golibs/testutil"
 )
 
 func TestConfig_Validate(t *testing.T) {
+	leasesPath := filepath.Join(t.TempDir(), "leases.json")
+
 	testCases := []struct {
 		name       string
 		conf       *dhcpsvc.Config
@@ -25,13 +28,15 @@ func TestConfig_Validate(t *testing.T) {
 		conf: &dhcpsvc.Config{
 			Enabled:    true,
 			Interfaces: testInterfaceConf,
+			DBFilePath: leasesPath,
 		},
 		wantErrMsg: `bad domain name "": domain name is empty`,
 	}, {
 		conf: &dhcpsvc.Config{
 			Enabled:         true,
 			LocalDomainName: testLocalTLD,
 			Interfaces:      nil,
+			DBFilePath:      leasesPath,
 		},
 		name:       "no_interfaces",
 		wantErrMsg: "no interfaces specified",
@@ -40,6 +45,7 @@ func TestConfig_Validate(t *testing.T) {
 			Enabled:         true,
 			LocalDomainName: testLocalTLD,
 			Interfaces:      nil,
+			DBFilePath:      leasesPath,
 		},
 		name:       "no_interfaces",
 		wantErrMsg: "no interfaces specified",
@@ -50,6 +56,7 @@ func TestConfig_Validate(t *testing.T) {
 			Interfaces: map[string]*dhcpsvc.InterfaceConfig{
 				"eth0": nil,
 			},
+			DBFilePath: leasesPath,
 		},
 		name:       "nil_interface",
 		wantErrMsg: `interface "eth0": config is nil`,
@@ -63,6 +70,7 @@ func TestConfig_Validate(t *testing.T) {
 					IPv6: &dhcpsvc.IPv6Config{Enabled: false},
 				},
 			},
+			DBFilePath: leasesPath,
 		},
 		name:       "nil_ipv4",
 		wantErrMsg: `interface "eth0": ipv4: config is nil`,
@@ -76,6 +84,7 @@ func TestConfig_Validate(t *testing.T) {
 					IPv6: nil,
 				},
 			},
+			DBFilePath: leasesPath,
 		},
 		name:       "nil_ipv6",
 		wantErrMsg: `interface "eth0": ipv6: config is nil`,

internal/dhcpsvc/db.go

@@ -0,0 +1,192 @@
+package dhcpsvc
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/fs"
+	"net"
+	"net/netip"
+	"os"
+	"slices"
+	"strings"
+	"time"
+
+	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/logutil/slogutil"
+	"github.com/google/renameio/v2/maybe"
+)
+
+// dataVersion is the current version of the stored DHCP leases structure.
+const dataVersion = 1
+
+// databasePerm is the permissions for the database file.
+const databasePerm fs.FileMode = 0o640
+
+// dataLeases is the structure of the stored DHCP leases.
+type dataLeases struct {
+	// Leases is the list containing stored DHCP leases.
+	Leases []*dbLease `json:"leases"`
+
+	// Version is the current version of the structure.
+	Version int `json:"version"`
+}
+
+// dbLease is the structure of stored lease.
+type dbLease struct {
+	Expiry   string     `json:"expires"`
+	IP       netip.Addr `json:"ip"`
+	Hostname string     `json:"hostname"`
+	HWAddr   string     `json:"mac"`
+	IsStatic bool       `json:"static"`
+}
+
+// compareNames returns the result of comparing the hostnames of dl and other
+// lexicographically.
+func (dl *dbLease) compareNames(other *dbLease) (res int) {
+	return strings.Compare(dl.Hostname, other.Hostname)
+}
+
+// toDBLease converts *Lease to *dbLease.
+func toDBLease(l *Lease) (dl *dbLease) {
+	var expiryStr string
+	if !l.IsStatic {
+		// The front-end is waiting for RFC 3999 format of the time value.  It
+		// also shouldn't got an Expiry field for static leases.
+		//
+		// See https://github.com/AdguardTeam/AdGuardHome/issues/2692.
+		expiryStr = l.Expiry.Format(time.RFC3339)
+	}
+
+	return &dbLease{
+		Expiry:   expiryStr,
+		Hostname: l.Hostname,
+		HWAddr:   l.HWAddr.String(),
+		IP:       l.IP,
+		IsStatic: l.IsStatic,
+	}
+}
+
+// toInternal converts dl to *Lease.
+func (dl *dbLease) toInternal() (l *Lease, err error) {
+	mac, err := net.ParseMAC(dl.HWAddr)
+	if err != nil {
+		return nil, fmt.Errorf("parsing hardware address: %w", err)
+	}
+
+	expiry := time.Time{}
+	if !dl.IsStatic {
+		expiry, err = time.Parse(time.RFC3339, dl.Expiry)
+		if err != nil {
+			return nil, fmt.Errorf("parsing expiry time: %w", err)
+		}
+	}
+
+	return &Lease{
+		Expiry:   expiry,
+		IP:       dl.IP,
+		Hostname: dl.Hostname,
+		HWAddr:   mac,
+		IsStatic: dl.IsStatic,
+	}, nil
+}
+
+// dbLoad loads stored leases.  It must only be called before the service has
+// been started.
+func (srv *DHCPServer) dbLoad(ctx context.Context) (err error) {
+	defer func() { err = errors.Annotate(err, "loading db: %w") }()
+
+	file, err := os.Open(srv.dbFilePath)
+	if err != nil {
+		if !errors.Is(err, os.ErrNotExist) {
+			return fmt.Errorf("reading db: %w", err)
+		}
+
+		srv.logger.DebugContext(ctx, "no db file found")
+
+		return nil
+	}
+
+	dl := &dataLeases{}
+	err = json.NewDecoder(file).Decode(dl)
+	if err != nil {
+		return fmt.Errorf("decoding db: %w", err)
+	}
+
+	srv.resetLeases()
+	srv.addDBLeases(ctx, dl.Leases)
+
+	return nil
+}
+
+// addDBLeases adds leases to the server.
+func (srv *DHCPServer) addDBLeases(ctx context.Context, leases []*dbLease) {
+	var v4, v6 uint
+	for i, l := range leases {
+		lease, err := l.toInternal()
+		if err != nil {
+			srv.logger.WarnContext(ctx, "converting lease", "idx", i, slogutil.KeyError, err)
+
+			continue
+		}
+
+		iface, err := srv.ifaceForAddr(l.IP)
+		if err != nil {
+			srv.logger.WarnContext(ctx, "searching lease iface", "idx", i, slogutil.KeyError, err)
+
+			continue
+		}
+
+		err = srv.leases.add(lease, iface)
+		if err != nil {
+			srv.logger.WarnContext(ctx, "adding lease", "idx", i, slogutil.KeyError, err)
+
+			continue
+		}
+
+		if l.IP.Is4() {
+			v4++
+		} else {
+			v6++
+		}
+	}
+
+	// TODO(e.burkov):  Group by interface.
+	srv.logger.InfoContext(ctx, "loaded leases", "v4", v4, "v6", v6, "total", len(leases))
+}
+
+// writeDB writes leases to the database file.  It expects the
+// [DHCPServer.leasesMu] to be locked.
+func (srv *DHCPServer) dbStore(ctx context.Context) (err error) {
+	defer func() { err = errors.Annotate(err, "writing db: %w") }()
+
+	dl := &dataLeases{
+		// Avoid writing null into the database file if there are no leases.
+		Leases:  make([]*dbLease, 0, srv.leases.len()),
+		Version: dataVersion,
+	}
+
+	srv.leases.rangeLeases(func(l *Lease) (cont bool) {
+		lease := toDBLease(l)
+		i, _ := slices.BinarySearchFunc(dl.Leases, lease, (*dbLease).compareNames)
+		dl.Leases = slices.Insert(dl.Leases, i, lease)
+
+		return true
+	})
+
+	buf, err := json.Marshal(dl)
+	if err != nil {
+		// Don't wrap the error since it's informative enough as is.
+		return err
+	}
+
+	err = maybe.WriteFile(srv.dbFilePath, buf, databasePerm)
+	if err != nil {
+		// Don't wrap the error since it's informative enough as is.
+		return err
+	}
+
+	srv.logger.InfoContext(ctx, "stored leases", "num", len(dl.Leases), "file", srv.dbFilePath)
+
+	return nil
+}

internal/dhcpsvc/db_internal_test.go

@@ -0,0 +1,4 @@
+package dhcpsvc
+
+// DatabasePerm is the permissions for the test database file.
+const DatabasePerm = databasePerm

internal/dhcpsvc/dhcpsvc_test.go

@@ -0,0 +1,66 @@
+package dhcpsvc_test
+
+import (
+	"net"
+	"net/netip"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/dhcpsvc"
+	"github.com/AdguardTeam/golibs/logutil/slogutil"
+	"github.com/stretchr/testify/require"
+)
+
+// testLocalTLD is a common local TLD for tests.
+const testLocalTLD = "local"
+
+// testTimeout is a common timeout for tests and contexts.
+const testTimeout time.Duration = 10 * time.Second
+
+// discardLog is a logger to discard test output.
+var discardLog = slogutil.NewDiscardLogger()
+
+// testInterfaceConf is a common set of interface configurations for tests.
+var testInterfaceConf = map[string]*dhcpsvc.InterfaceConfig{
+	"eth0": {
+		IPv4: &dhcpsvc.IPv4Config{
+			Enabled:       true,
+			GatewayIP:     netip.MustParseAddr("192.168.0.1"),
+			SubnetMask:    netip.MustParseAddr("255.255.255.0"),
+			RangeStart:    netip.MustParseAddr("192.168.0.2"),
+			RangeEnd:      netip.MustParseAddr("192.168.0.254"),
+			LeaseDuration: 1 * time.Hour,
+		},
+		IPv6: &dhcpsvc.IPv6Config{
+			Enabled:       true,
+			RangeStart:    netip.MustParseAddr("2001:db8::1"),
+			LeaseDuration: 1 * time.Hour,
+			RAAllowSLAAC:  true,
+			RASLAACOnly:   true,
+		},
+	},
+	"eth1": {
+		IPv4: &dhcpsvc.IPv4Config{
+			Enabled:       true,
+			GatewayIP:     netip.MustParseAddr("172.16.0.1"),
+			SubnetMask:    netip.MustParseAddr("255.255.255.0"),
+			RangeStart:    netip.MustParseAddr("172.16.0.2"),
+			RangeEnd:      netip.MustParseAddr("172.16.0.255"),
+			LeaseDuration: 1 * time.Hour,
+		},
+		IPv6: &dhcpsvc.IPv6Config{
+			Enabled:       true,
+			RangeStart:    netip.MustParseAddr("2001:db9::1"),
+			LeaseDuration: 1 * time.Hour,
+			RAAllowSLAAC:  true,
+			RASLAACOnly:   true,
+		},
+	},
+}
+
+// mustParseMAC parses a hardware address from s and requires no errors.
+func mustParseMAC(t require.TestingT, s string) (mac net.HardwareAddr) {
+	mac, err := net.ParseMAC(s)
+	require.NoError(t, err)
+
+	return mac
+}

internal/dhcpsvc/leaseindex.go

@@ -124,3 +124,18 @@ func (idx *leaseIndex) update(l *Lease, iface *netInterface) (err error) {
 
 	return nil
 }
+
+// rangeLeases calls f for each lease in idx in an unspecified order until f
+// returns false.
+func (idx *leaseIndex) rangeLeases(f func(l *Lease) (cont bool)) {
+	for _, l := range idx.byName {
+		if !f(l) {
+			break
+		}
+	}
+}
+
+// len returns the number of leases in idx.
+func (idx *leaseIndex) len() (l uint) {
+	return uint(len(idx.byAddr))
+}