dhcpsvc: imp code, dry

internal/dhcpsvc/dhcpsvc.go

@@ -31,6 +31,8 @@ type Interface interface {
 	// MACByIP returns the MAC address for the given IP address leased.  It
 	// returns nil if there is no such client, due to an assumption that a DHCP
 	// client must always have a MAC address.
+	//
+	// TODO(e.burkov):  Think of a contract for the returned value.
 	MACByIP(ip netip.Addr) (mac net.HardwareAddr)
 
 	// IPByHost returns the IP address of the DHCP client with the given
@@ -46,17 +48,17 @@ type Interface interface {
 	// signatures instead of cloning the whole list.
 	Leases() (ls []*Lease)
 
-	// AddLease adds a new DHCP lease.  It returns an error if the lease is
-	// invalid or already exists.
+	// AddLease adds a new DHCP lease.  l must be valid.  It returns an error if
+	// l already exists.
 	AddLease(l *Lease) (err error)
 
-	// UpdateStaticLease changes an existing DHCP lease.  It returns an error if
-	// there is no lease with such hardware address or if new values are invalid
-	// or already exist.
+	// UpdateStaticLease replaces an existing static DHCP lease.  l must be
+	// valid.  It returns an error if the lease with the given hardware address
+	// doesn't exist or if other values match another existing lease.
 	UpdateStaticLease(l *Lease) (err error)
 
-	// RemoveLease removes an existing DHCP lease.  It returns an error if there
-	// is no lease equal to l.
+	// RemoveLease removes an existing DHCP lease.  l must be valid.  It returns
+	// an error if there is no lease equal to l.
 	RemoveLease(l *Lease) (err error)
 
 	// Reset removes all the DHCP leases.

internal/dhcpsvc/interface.go

@@ -39,8 +39,8 @@ func (iface *netInterface) insertLease(l *Lease) (err error) {
 	return nil
 }
 
-// updateLease changes an existing lease within iface.  It returns an error if
-// there is no lease with such hardware address.
+// updateLease replaces an existing lease within iface with the given one.  It
+// returns an error if there is no lease with such hardware address.
 func (iface *netInterface) updateLease(l *Lease) (prev *Lease, err error) {
 	i, found := slices.BinarySearchFunc(iface.leases, l, compareLeaseMAC)
 	if !found {

internal/dhcpsvc/lease.go

@@ -2,9 +2,11 @@ package dhcpsvc
 
 import (
 	"bytes"
+	"fmt"
 	"net"
 	"net/netip"
 	"slices"
+	"strings"
 	"time"
 )
 
@@ -50,3 +52,107 @@ func (l *Lease) Clone() (clone *Lease) {
 func compareLeaseMAC(a, b *Lease) (res int) {
 	return bytes.Compare(a.HWAddr, b.HWAddr)
 }
+
+// leaseIndex is the set of leases indexed by their identifiers for quick
+// lookup.
+type leaseIndex struct {
+	// byAddr is a lookup shortcut for leases by their IP addresses.
+	byAddr map[netip.Addr]*Lease
+
+	// byName is a lookup shortcut for leases by their hostnames.
+	//
+	// TODO(e.burkov):  Use a slice of leases with the same hostname?
+	byName map[string]*Lease
+}
+
+// leaseByAddr returns a lease by its IP address.
+func (idx *leaseIndex) leaseByAddr(addr netip.Addr) (l *Lease, ok bool) {
+	l, ok = idx.byAddr[addr]
+
+	return l, ok
+}
+
+// leaseByName returns a lease by its hostname.
+func (idx *leaseIndex) leaseByName(name string) (l *Lease, ok bool) {
+	// TODO(e.burkov):  Probably, use a case-insensitive comparison and store in
+	// slice.  This would require a benchmark.
+	l, ok = idx.byName[strings.ToLower(name)]
+
+	return l, ok
+}
+
+// clear removes all leases from idx.
+func (idx *leaseIndex) clear() {
+	clear(idx.byAddr)
+	clear(idx.byName)
+}
+
+// add adds l into idx and into iface.
+func (idx *leaseIndex) add(l *Lease, iface *netInterface) (err error) {
+	loweredName := strings.ToLower(l.Hostname)
+
+	if _, ok := idx.byAddr[l.IP]; ok {
+		return fmt.Errorf("lease for ip %s already exists", l.IP)
+	} else if _, ok = idx.byName[loweredName]; ok {
+		return fmt.Errorf("lease for hostname %s already exists", l.Hostname)
+	}
+
+	err = iface.insertLease(l)
+	if err != nil {
+		return err
+	}
+
+	idx.byAddr[l.IP] = l
+	idx.byName[loweredName] = l
+
+	return nil
+}
+
+// remove removes l from idx and from iface.
+func (idx *leaseIndex) remove(l *Lease, iface *netInterface) (err error) {
+	loweredName := strings.ToLower(l.Hostname)
+
+	if _, ok := idx.byAddr[l.IP]; !ok {
+		return fmt.Errorf("no lease for ip %s", l.IP)
+	} else if _, ok = idx.byName[loweredName]; !ok {
+		return fmt.Errorf("no lease for hostname %s", l.Hostname)
+	}
+
+	err = iface.removeLease(l)
+	if err != nil {
+		return err
+	}
+
+	delete(idx.byAddr, l.IP)
+	delete(idx.byName, loweredName)
+
+	return nil
+}
+
+// update updates l in idx and in iface.
+func (idx *leaseIndex) update(l *Lease, iface *netInterface) (err error) {
+	loweredName := strings.ToLower(l.Hostname)
+
+	existing, ok := idx.byAddr[l.IP]
+	if ok && !slices.Equal(l.HWAddr, existing.HWAddr) {
+		return fmt.Errorf("lease for ip %s already exists", l.IP)
+	}
+
+	existing, ok = idx.byName[loweredName]
+	if ok && !slices.Equal(l.HWAddr, existing.HWAddr) {
+		return fmt.Errorf("lease for hostname %s already exists", l.Hostname)
+	}
+
+	prev, err := iface.updateLease(l)
+	if err != nil {
+		return err
+	}
+
+	delete(idx.byAddr, prev.IP)
+	delete(idx.byName, strings.ToLower(prev.Hostname))
+
+	idx.byAddr[l.IP] = l
+	idx.byName[loweredName] = l
+
+	return nil
+}