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For scalability and configurability, we need dynamic clients in v4.

Right now, we have static / global clients. This is fine for 90% of the deployments.

Dynamic clients will let us have clients per listener, per source IP, per connection (e.g. NAT).

In Phase 1, we will add dynamic clients to the network side, as dynamic / global clients. No "per connection" clients will be created.

In Phase 2, we will add per-connection dynamic clients.

Phase 1

1.1 The network side proto_radius_udp has a local set of clients.

1.2. These clients have an "outsranding" counters, so we know how many outstanding requests are using them. Even when expired, the clients can only be deleted when this counter hits zero.

1.3. The dynamic client code is configurable, so that it can be enabled or disabled.

dynamic_clients {

1.4. The dynamic client code has source network ranges where it accepts packets from.

dynamic_clients {
    network =
    network =

1.5. The dynamic clients run a new client subsection of the current virtual server, for received packets. This subsection looks at the decoded RADIUS packet, and returns FreeRADIUS VSAs as attributes in the reply. These reply attributes are used to create a dynamic client. The dynamic client is then inserted into the local tree, with a lifetime.

1.6. When proto_radius_udp receives a packet from a previously unknown source, it checks for dynamic clients enabled. If not enabled, it's rejected. If enabled, it compares the source IP to the list of allowed source networks. If there's no match, it's rejected. Otherwise, the dynamic client code is started.

For now, we don't check for NAT. i.e. each client is distinguished only by source IP, not by port. If we later add NAT capability, clients will be distinguished by connection, not by source port.

1.7. The packet is added immediately as a dynamic client, but is marked with a "pending" flag. Packets received from this client are not processed, but instead added to a pending queue. This means having a local copy of the packets, probably via talloc() and memory copies.

1.8. The number of these packets is limited. That limit is configurable.

dynamic_clients {
    max_pending_packets = 65536

1.9. There should be a timer on these packets. If the client is not defined within 1/10s, all of the additional packets should be discarded. This timer should be configurable.

1.10. The first received packet is processed through the worker (exactly how will be described later).*

1.11. If a NAK is received from the worker, the pending client definition is removed, and all pending packets are discarded.

1.12. If an ACK is received, the format is raw data (not VPs). The worker will need to create a client definition, and send it to the network side as a reply packet. The network side will then use those fields to update the "pending" client definition, and remove the "pending" flag.

1.13. At that point, the pending packets are removed from the queue, and processed through the normal network side, by calling fr_network_listen_read()

Corner cases

This code uses the standard packet tracking mechanisms. i.e. if a duplicate is received, ignore it. If a conflicting packet is received, drop either the new one or the old one.

How things will work

proto_radius_udp, mod_read:

  • if inst->list (i.e. there are pending packets)

    • remove entry from list
    • copy address, client, packet
    • do bottom half of processing from mod_read()
  • otherwise read from socket

  • look in global list. If not found, look in dynamic client list

    • if !found && in allowed networks, return dynamic_client_alloc(inst, packet, length, address)
      • otherwise disallow, and return 0
      • this is a negative cache entry. Update the expiry time, by adding 30s.
    • if found, && !client->active, return dynamic_client_check(inst, packet, length, address, client)
      • otherwise it's an active dynamic client, it's OK
  • otherwise do bottom half of processing from mod_read()

Function dynamic_client_alloc()

  • if inst->num_pending_clients is too many, return 0

  • increment inst->num_pending_clients

  • alloc the client, parented from the instance

  • fill in various fields (e.g. src IP)
  • set client->active = false
  • set client->dynamic = true
  • insert client into dynamic client list
  • call dynamic_client_packet_save() to save the packet
  • return the packet to the network code

Function dynamic_client_packet_save()

  • if client->num_pending_packets is too many, drop
  • look up packet in inst->dynamic_client_tracking

    • do similar logic as in bottom half of mod_read()
    • but skip the packet verify, stats, etc.
    • SAME -> drop packet
    • UPDATED - shouldn't happen (this is new packet after old reply)
    • CONFLICTING - drop packet
    • other - drop packet
    • NEW, continue
  • allocate new structure, parented from instance and fill it in

    • tracking table entry,
    • dlist
    • ptr to client
    • talloc_memdup() the packet

    • add to tail of client->list

  • increment client->num_pending_packets

  • return 0

    • we rely on other things to clean up the client && it's packets

function mod_set_process() in proto_radius

  • if !client->active
    • set request->process to proto_radius_dynamic_client()

function mod_encode()

  • If !client->active
    • look for attributes to define packet, and create client definition if so
    • encode it as raw data, or encode 1-byte "nak" if not found

function mod_write()

  • if !client->active
    • decode raw packet as either client or NAK
    • if NAK, free all of the pending packets
      • set client->unknown, and set cleanup timer,
      • return
    • if OK, update client definition
      • set client to active
      • decrement inst->num_pending_clients
      • move list of pending packets to inst->list
      • call fr_network_listen_read()


Has methods:

  • new client - 'recv' section
  • add client - 'send' section
  • deny client - 'send reject' section

It also looks at the attributes necessary to define a client. If they are missing or incomplete, it complains, and runs the 'deny client' section.