feat: relay several servers, registered through the control API

diagrams/ban.puml

@@ -9,13 +9,14 @@ participant "ET server" as et
 actor "Player\n203.0.113.7" as player
 
 note over admin, et : the ET server shows the player as <front-wg>:51234
+note over admin, control : every call carries the key the server registered with
 admin -> control : GET /sessions
 control --> admin : [{client: 203.0.113.7:27960, port: 51234}]
 note right of admin : port 51234 = 203.0.113.7
 
 == Ban ==
 admin -> control : PUT /bans/203.0.113.7\n{reason, minutes}
-control -> control : bans.json (atomic write)\ncut 203.0.113.7's sessions
+control -> control : bans-<port>.json (atomic write)\ncut 203.0.113.7's sessions
 player -> relay : game packets
 relay -> relay : banned: dropped
 note over et : no packet: times the player out

diagrams/pairing.puml

@@ -0,0 +1,29 @@
+@startuml
+skinparam shadowing false
+title Registering a server (pairing)
+
+participant "Admin tool\n(etadm)" as admin
+participant "ET server\n<et-server>:27960" as et
+participant "etrelay control API\n<front-wg>:8090" as control
+participant "Masters" as master
+
+note over admin : picks a key once\n(kept on its side)
+admin -> et : rcon: sets etrelay_proof <fingerprint of the key>
+admin -> control : PUT /server {port: 27960, upstream_port: 27960, key}\nBearer: the relay's token
+control -> control : port offered and free?\n(409: held by another server)
+control -> et : getstatus
+et --> control : statusResponse\n...\\etrelay_proof\\<fingerprint>...
+control -> control : fingerprint == sha256(key)?\n(403: not shown)
+control -> control : bind :27960, keep sha256(key)\nin servers.json
+control --> admin : 200 {port, upstream, since, alive}
+admin -> et : rcon: set etrelay_proof ""
+control -> master : heartbeat EnemyTerritory-1\nfrom :27960
+
+== Later ==
+admin -> control : GET /sessions, /bans...\nBearer: the key (names the server)
+control --> admin : this server's only
+note over admin, control : 401 (the relay lost its state):\nthe admin tool registers again
+admin -> control : DELETE /server
+control -> master : heartbeat ETFlatline-1
+note over control : port freed, bans dropped
+@enduml

diagrams/tasks.puml

@@ -2,14 +2,18 @@
 skinparam shadowing false
 title Tasks and data flow
 
-rectangle "relay loop (main task)" as loop {
+rectangle "relay loop (one per server)" as loop {
   card "public socket\nrecv_from" as recv
   card "filter\n(commands, query rate)" as filter
 }
 
-rectangle "shared state (Mutex)" as shared {
+rectangle "server state (Mutex, one per server)" as shared {
   card "sessions:\nHashMap<client, Session>" as map
-  card "bans\n(bans.json)" as bans
+  card "bans\n(bans-<port>.json)" as bans
+}
+
+rectangle "registry (Mutex)" as registry {
+  card "servers by public port,\ntheir key's hash\n(servers.json)" as servers
 }
 
 rectangle "session task (one per client)" as st {
@@ -17,12 +21,13 @@ rectangle "session task (one per client)" as st {
   card "upstream socket\n(connected to ET)" as up
 }
 
-rectangle "heartbeat task" as hb {
+rectangle "heartbeat task (one per server)" as hb {
   card "interval 5 min" as tick
   card "probe socket" as probe
 }
 
 rectangle "control API task (axum)" as ctl {
+  card "PUT/GET/DELETE /server" as pairing
   card "GET /sessions\nGET/PUT/DELETE /bans" as routes
 }
 
@@ -36,4 +41,7 @@ tick --> probe : getinfo
 tick --> recv : heartbeat via public socket
 routes --> map : list ports,\ndrop a banned IP's sessions
 routes --> bans : set / lift
+routes --> servers : key -> server
+pairing --> servers : register / leave
+servers --> loop : start / stop\n(with its heartbeat)
 @enduml