dhcpsvc: multiplex dhcpv4

internal/dhcpsvc/serve.go

@@ -0,0 +1,102 @@
+package dhcpsvc
+
+import (
+	"context"
+	"fmt"
+	"net/netip"
+
+	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/logutil/slogutil"
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/layers"
+)
+
+func (srv *DHCPServer) serve(ctx context.Context) {
+	defer slogutil.RecoverAndLog(ctx, srv.logger)
+
+	for pkt := range srv.packetSource.Packets() {
+		etherLayer, ok := pkt.Layer(layers.LayerTypeEthernet).(*layers.Ethernet)
+		if !ok {
+			srv.logger.DebugContext(ctx, "skipping non-ethernet packet")
+
+			continue
+		}
+
+		var err error
+		switch typ := etherLayer.EthernetType; typ {
+		case layers.EthernetTypeIPv4:
+			err = srv.serveV4(ctx, pkt)
+		case layers.EthernetTypeIPv6:
+			// TODO(e.burkov):  Handle DHCPv6 as well.
+		default:
+			srv.logger.DebugContext(ctx, "skipping ethernet packet", "type", typ)
+
+			continue
+		}
+
+		if err != nil {
+			srv.logger.ErrorContext(ctx, "serving", slogutil.KeyError, err)
+		}
+	}
+}
+
+// serveV4 handles the ethernet packet of IPv4 type.
+func (srv *DHCPServer) serveV4(ctx context.Context, pkt gopacket.Packet) (err error) {
+	defer func() { err = errors.Annotate(err, "serving dhcpv4: %w") }()
+
+	msg, ok := pkt.Layer(layers.LayerTypeDHCPv4).(*layers.DHCPv4)
+	if !ok {
+		srv.logger.DebugContext(ctx, "skipping non-dhcpv4 packet")
+
+		return nil
+	}
+
+	// TODO(e.burkov):  Handle duplicate Xid.
+
+	typ, ok := msgType(msg)
+	if !ok {
+		return errors.Error("no message type in the dhcpv4 message")
+	}
+
+	return srv.handleDHCPv4(ctx, typ, msg)
+}
+
+// handleDHCPv4 handles the DHCPv4 message of the given type.
+func (srv *DHCPServer) handleDHCPv4(
+	ctx context.Context,
+	typ layers.DHCPMsgType,
+	msg *layers.DHCPv4,
+) (err error) {
+	// Each interface should handle the DISCOVER and REQUEST messages offer and
+	// allocate the available leases.  The RELEASE and DECLINE messages should
+	// be handled by the server itself as it should remove the lease.
+	switch typ {
+	case layers.DHCPMsgTypeDiscover:
+		for _, iface := range srv.interfaces4 {
+			go iface.handleDiscover(ctx, msg)
+		}
+	case layers.DHCPMsgTypeRequest:
+		for _, iface := range srv.interfaces4 {
+			go iface.handleRequest(ctx, msg)
+		}
+	case layers.DHCPMsgTypeRelease:
+		addr, ok := netip.AddrFromSlice(msg.ClientIP)
+		if !ok {
+			return fmt.Errorf("invalid client ip in the release message")
+		}
+
+		return srv.removeLeaseByAddr(ctx, addr)
+	case layers.DHCPMsgTypeDecline:
+		addr, ok := requestedIP(msg)
+		if !ok {
+			return fmt.Errorf("no requested ip in the decline message")
+		}
+
+		return srv.removeLeaseByAddr(ctx, addr)
+	default:
+		// TODO(e.burkov):  Handle DHCPINFORM.
+		return fmt.Errorf("dhcpv4 message type: %w: %v", errors.ErrBadEnumValue, typ)
+	}
+
+	return nil
+}