fix: Fix connection interface binding, JSON lease DB

pkg/leases/leases.go

@@ -1,8 +1,11 @@
 package leases
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
+	"os"
+	"path/filepath"
 	"time"
 
 	"github.com/adrianokf/go-dhcp/pkg/types"
@@ -16,12 +19,14 @@ const (
 	Requested
 )
 
+const DumpFile = "/var/lib/go-dhcp/leases.json"
+
 type Lease struct {
-	TransactionId types.TxId
-	TTL           time.Time
-	State         LeaseState
-	ClientAddr    types.HwAddr
-	Address       types.Ipv4Addr
+	TransactionId types.TxId     `json:"TransactionID"`
+	TTL           time.Time      `json:"TTL"`
+	State         LeaseState     `json:"State"`
+	ClientAddr    types.HwAddr   `json:"ClientAddr"`
+	Address       types.Ipv4Addr `json:"Address"`
 }
 
 type ILeaseManager interface {
@@ -35,9 +40,51 @@ type LeaseManager struct {
 	count  byte
 }
 
+func (m LeaseManager) DumpLeases() {
+	err := os.MkdirAll(filepath.Dir(DumpFile), 0755)
+	if err != nil {
+		zap.S().Panic(err)
+	}
+
+	f, err := os.Create(DumpFile)
+	if err != nil {
+		zap.S().Panic(err)
+	}
+	defer f.Close()
+
+	leases := make([]Lease, len(m.leases))
+	for _, l := range m.leases {
+		leases = append(leases, l)
+	}
+
+	enc := json.NewEncoder(f)
+	enc.Encode(leases)
+	f.Sync()
+}
+
+func LoadLeases() (map[types.TxId]Lease, error) {
+	var leaseMap = make(map[types.TxId]Lease)
+
+	data, err := os.ReadFile(DumpFile)
+	if err != nil {
+		return leaseMap, err
+	}
+	var leases []Lease
+	json.Unmarshal(data, &leases)
+
+	for _, l := range leases {
+		leaseMap[l.TransactionId] = l
+	}
+	return leaseMap, nil
+}
+
 func NewLeaseManager() *LeaseManager {
+	leases, err := LoadLeases()
+	if err != nil {
+		zap.S().Warnf("Could not restore saved leases from %s: %s", DumpFile, err)
+	}
 	m := &LeaseManager{
-		leases: make(map[types.TxId]Lease),
+		leases: leases,
 	}
 	return m
 }
@@ -62,6 +109,9 @@ func (m *LeaseManager) Request(xid types.TxId, clientAddr types.HwAddr) (*Lease,
 	m.count += 1
 
 	zap.S().Debug("lease=", lease)
+
+	m.DumpLeases()
+
 	return &lease, nil
 }
 
@@ -71,6 +121,9 @@ func (m LeaseManager) Release(l Lease) error {
 		return fmt.Errorf("invalid lease %v", l)
 	}
 	delete(m.leases, l.TransactionId)
+
+	m.DumpLeases()
+
 	return nil
 }