Cluster service implementation with basic local state and IPAM manager

internal/machine/cluster/ipam.go

@@ -0,0 +1,76 @@
+package cluster
+
+import (
+	"errors"
+	"fmt"
+	"go4.org/netipx"
+	"net/netip"
+)
+
+// IPAM is an in-memory IP address manager for allocating and releasing subnets for machines from a cluster network.
+type IPAM struct {
+	network   netip.Prefix
+	allocated netipx.IPSetBuilder
+}
+
+func NewIPAM(network netip.Prefix) (*IPAM, error) {
+	if !network.IsValid() || network.Bits() == 0 {
+		return nil, errors.New("invalid network")
+	}
+	return &IPAM{
+		network: network.Masked(),
+	}, nil
+}
+
+// NewIPAMWithAllocated creates a new IPAM with the given network and already allocated subnets.
+func NewIPAMWithAllocated(network netip.Prefix, subnets []netip.Prefix) (*IPAM, error) {
+	ipam, err := NewIPAM(network)
+	if err != nil {
+		return nil, err
+	}
+	for _, sn := range subnets {
+		if err = ipam.AllocateSubnet(sn); err != nil {
+			return nil, fmt.Errorf("allocate subnet %s: %w", sn, err)
+		}
+	}
+	return ipam, nil
+}
+
+func (ipam *IPAM) AllocateSubnetLen(bits int) (netip.Prefix, error) {
+	if bits < ipam.network.Bits() || bits > ipam.network.Addr().BitLen() {
+		return netip.Prefix{}, errors.New("invalid subnet size")
+	}
+
+	subnet := netip.PrefixFrom(ipam.network.Addr(), bits)
+	for ipam.network.Contains(subnet.Addr()) {
+		ipset, err := ipam.allocated.IPSet()
+		if err != nil {
+			return netip.Prefix{}, fmt.Errorf("get allocated IP set: %w", err)
+		}
+		if !ipset.OverlapsPrefix(subnet) {
+			ipam.allocated.AddPrefix(subnet)
+			return subnet, nil
+		}
+
+		nextSubnetAddr := netipx.PrefixLastIP(subnet).Next()
+		subnet = netip.PrefixFrom(nextSubnetAddr, bits)
+	}
+
+	return netip.Prefix{}, errors.New("no available subnet")
+}
+
+func (ipam *IPAM) AllocateSubnet(subnet netip.Prefix) error {
+	subnetLastIP := netipx.PrefixLastIP(subnet)
+	if !ipam.network.Contains(subnet.Addr()) || !ipam.network.Contains(subnetLastIP) {
+		return errors.New("subnet not in network")
+	}
+	ipset, err := ipam.allocated.IPSet()
+	if err != nil {
+		return fmt.Errorf("get allocated IP set: %w", err)
+	}
+	if ipset.OverlapsPrefix(subnet) {
+		return errors.New("subnet overlaps with allocated subnets")
+	}
+	ipam.allocated.AddPrefix(subnet)
+	return nil
+}