128 lines
3.7 KiB
Go
128 lines
3.7 KiB
Go
package dhcpsvc
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import (
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"context"
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"fmt"
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"net/netip"
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"github.com/AdguardTeam/golibs/errors"
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"github.com/google/gopacket"
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"github.com/google/gopacket/layers"
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)
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// serveV4 handles the ethernet packet of IPv4 type.
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func (srv *DHCPServer) serveV4(
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ctx context.Context,
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rw responseWriter4,
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pkt gopacket.Packet,
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) (err error) {
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defer func() { err = errors.Annotate(err, "serving dhcpv4: %w") }()
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req, ok := pkt.Layer(layers.LayerTypeDHCPv4).(*layers.DHCPv4)
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if !ok {
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srv.logger.DebugContext(ctx, "skipping non-dhcpv4 packet")
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return nil
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}
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// TODO(e.burkov): Handle duplicate Xid.
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if req.Operation != layers.DHCPOpRequest {
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srv.logger.DebugContext(ctx, "skipping non-request dhcpv4 packet")
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return nil
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}
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typ, ok := msg4Type(req)
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if !ok {
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// The "DHCP message type" option - must be included in every DHCP
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// message.
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//
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// See https://datatracker.ietf.org/doc/html/rfc2131#section-3.
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return fmt.Errorf("dhcpv4: message type: %w", errors.ErrNoValue)
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}
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return srv.handleDHCPv4(ctx, rw, typ, req)
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}
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// handleDHCPv4 handles the DHCPv4 message of the given type.
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func (srv *DHCPServer) handleDHCPv4(
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ctx context.Context,
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rw responseWriter4,
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typ layers.DHCPMsgType,
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req *layers.DHCPv4,
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) (err error) {
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// Each interface should handle the DISCOVER and REQUEST messages offer and
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// allocate the available leases. The RELEASE and DECLINE messages should
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// be handled by the server itself as it should remove the lease.
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switch typ {
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case layers.DHCPMsgTypeDiscover:
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srv.handleDiscover(ctx, rw, req)
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case layers.DHCPMsgTypeRequest:
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srv.handleRequest(ctx, rw, req)
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case layers.DHCPMsgTypeRelease:
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// TODO(e.burkov): !! Remove the lease, either allocated or offered.
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case layers.DHCPMsgTypeDecline:
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// TODO(e.burkov): !! Remove the allocated lease. RFC tells it only
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// possible if the client found the address already in use.
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default:
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// TODO(e.burkov): Handle DHCPINFORM.
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return fmt.Errorf("dhcpv4: request type: %w: %v", errors.ErrBadEnumValue, typ)
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}
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return nil
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}
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// handleDiscover handles the DHCPv4 message of discover type.
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func (srv *DHCPServer) handleDiscover(ctx context.Context, rw responseWriter4, req *layers.DHCPv4) {
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// TODO(e.burkov): Check existing leases, either allocated or offered.
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for _, iface := range srv.interfaces4 {
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go iface.handleDiscover(ctx, rw, req)
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}
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}
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// handleRequest handles the DHCPv4 message of request type.
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func (srv *DHCPServer) handleRequest(ctx context.Context, rw responseWriter4, req *layers.DHCPv4) {
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srvID, hasSrvID := serverID4(req)
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reqIP, hasReqIP := requestedIPv4(req)
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switch {
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case hasSrvID && !srvID.IsUnspecified():
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// If the DHCPREQUEST message contains a server identifier option, the
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// message is in response to a DHCPOFFER message. Otherwise, the
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// message is a request to verify or extend an existing lease.
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iface, hasIface := srv.interfaces4.findInterface(srvID)
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if !hasIface {
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srv.logger.DebugContext(ctx, "skipping selecting request", "serverid", srvID)
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return
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}
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iface.handleSelecting(ctx, rw, req, reqIP)
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case hasReqIP && !reqIP.IsUnspecified():
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// Requested IP address option MUST be filled in with client's notion of
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// its previously assigned address.
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iface, hasIface := srv.interfaces4.findInterface(reqIP)
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if !hasIface {
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srv.logger.DebugContext(ctx, "skipping init-reboot request", "requestedip", reqIP)
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return
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}
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iface.handleInitReboot(ctx, rw, req, reqIP)
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default:
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// Server identifier MUST NOT be filled in, requested IP address option
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// MUST NOT be filled in.
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ip, _ := netip.AddrFromSlice(req.ClientIP.To4())
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iface, hasIface := srv.interfaces4.findInterface(ip)
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if !hasIface {
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srv.logger.DebugContext(ctx, "skipping init-reboot request", "clientip", ip)
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return
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}
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iface.handleRenew(ctx, rw, req)
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}
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}
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