m/t/nanoswitch: long term leases for IP addresses
This makes the nanoswitch DHCP server not allocate a new IP address for
every DISCOVERY packet, and instead re-uses already allocated IP
addresses as much as possible.
Effectively, this allows each node to have the same IP address, even if
its DHCP client restarts or the whole node reboots.
Change-Id: Ic276f8bd3cc3b531056ad05f7947ff544d8cc5d2
Reviewed-on: https://review.monogon.dev/c/monogon/+/679
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/test/nanoswitch/nanoswitch.go b/metropolis/test/nanoswitch/nanoswitch.go
index 5cc2077..c09d8ec 100644
--- a/metropolis/test/nanoswitch/nanoswitch.go
+++ b/metropolis/test/nanoswitch/nanoswitch.go
@@ -71,6 +71,10 @@
func runDHCPServer(link netlink.Link) supervisor.Runnable {
currentIP := net.IP{10, 1, 0, 1}
+ // Map from stringified MAC address to IP address, allowing handing out the
+ // same IP to a given MAC on re-discovery.
+ leases := make(map[string]net.IP)
+
return func(ctx context.Context) error {
laddr := net.UDPAddr{
IP: net.IPv4(0, 0, 0, 0),
@@ -92,9 +96,16 @@
case dhcpv4.MessageTypeDiscover:
reply.UpdateOption(dhcpv4.OptMessageType(dhcpv4.MessageTypeOffer))
defaultLeaseOptions(reply)
- currentIP[3]++ // Works only because it's a /24
- reply.YourIPAddr = currentIP
- supervisor.Logger(ctx).Infof("Replying with DHCP IP %s", reply.YourIPAddr.String())
+ hwaddr := m.ClientHWAddr.String()
+ // Either hand out already allocated address from leases, or allocate new.
+ if ip, ok := leases[hwaddr]; ok {
+ reply.YourIPAddr = ip
+ } else {
+ leases[hwaddr] = currentIP
+ reply.YourIPAddr = currentIP
+ currentIP[3]++ // Works only because it's a /24
+ }
+ supervisor.Logger(ctx).Infof("Replying with DHCP IP %s to %s", reply.YourIPAddr.String(), hwaddr)
case dhcpv4.MessageTypeRequest:
reply.UpdateOption(dhcpv4.OptMessageType(dhcpv4.MessageTypeAck))
defaultLeaseOptions(reply)