engine: handle inbound KILL — forget users, reintroduce bots

KILL was never parsed, so a killed user lingered in services' state (stale
session, session-limit slot, channel membership) and a killed services bot
vanished for good. The parser now surfaces UserKilled; a killed real user is
forgotten like a QUIT (shared forget_user helper), while a killed bot is
dropped and reconciled so it is reintroduced and rejoins its channels.

api/src/lib.rs

@@ -43,6 +43,9 @@ pub enum NetEvent {
     // the source uid; our own changes are filtered out by the protocol layer.
     TopicChange { channel: String, setter: String, topic: String },
     Quit { uid: String },
+    // A user was forcibly removed (KILL). Handled like a quit, except a killed
+    // services bot is reintroduced rather than forgotten.
+    UserKilled { uid: String },
     // An ircd relaying an IRCv3 account-registration request to us as the authority.
     AccountRequest { reqid: String, origin: String, kind: String, account: String, p2: String, p3: String },
     // An ircd relaying a SASL exchange step to us (the SASL agent). mode = H/S/C/D.

modules/protocol/inspircd/src/lib.rs

@@ -202,6 +202,12 @@ impl Protocol for InspIrcd {
                 }
             }
             "QUIT" => vec![NetEvent::Quit { uid: source.unwrap_or_default() }],
+            // :<src> KILL <uid> :<reason> — a user forcibly removed. We forget
+            // them (or reintroduce, if it was one of our bots).
+            "KILL" => match tokens.next() {
+                Some(uid) if !uid.is_empty() => vec![NetEvent::UserKilled { uid: uid.to_string() }],
+                _ => vec![],
+            },
             // ENCAP <target> <subcmd> …  — we care about relayed SASL and the
             // account-registration relay (the ircd's account module forwards a
             // leaf's REGISTER/VERIFY/RESEND/STATUS to us, the authority server).
@@ -465,6 +471,13 @@ mod tests {
         assert!(p.parse(":0IR METADATA 0IRAAAAAB ssl_cert :deadbeef").is_empty(), "non-account keys ignored");
     }
 
+    // A KILL surfaces as a UserKilled for the target uid.
+    #[test]
+    fn parses_kill() {
+        let ev = proto().parse(":0IR KILL 0IRAAAAAB :bye now");
+        assert!(matches!(ev.as_slice(), [NetEvent::UserKilled { uid }] if uid == "0IRAAAAAB"), "{ev:?}");
+    }
+
     // A UID burst introduces the user under their current nick.
     #[test]
     fn parses_uid_burst() {

src/engine/mod.rs

@@ -533,6 +533,15 @@ impl Engine {
         }
     }
 
+    // Forget a user who left the network (QUIT or KILL): drop their membership,
+    // any half-finished SASL exchange, and their pending nick-protection timer.
+    fn forget_user(&mut self, uid: &str) {
+        self.network.user_quit(uid);
+        self.sasl_sessions.remove(uid);
+        self.pending_enforce.retain(|p| p.uid != uid);
+        self.forget_chatter_everywhere(uid);
+    }
+
     // Log a single session out of `account`, telling them why (services-sourced).
     fn logout_uid(&mut self, uid: &str, account: &str, reason: &str) {
         self.network.clear_account(uid);
@@ -1031,10 +1040,21 @@ impl Engine {
                 }
             }
             NetEvent::Quit { uid } => {
-                self.network.user_quit(&uid);
-                self.sasl_sessions.remove(&uid); // drop any half-finished exchange
-                self.pending_enforce.retain(|p| p.uid != uid);
-                self.forget_chatter_everywhere(&uid);
+                self.forget_user(&uid);
+                Vec::new()
+            }
+            NetEvent::UserKilled { uid } => {
+                // If the ircd killed one of our bots, forget it so reconcile
+                // reintroduces it (and rejoins its channels); a killed real user is
+                // simply gone.
+                if let Some(bot_lc) = self.bot_uids.iter().find_map(|(lc, u)| (u == &uid).then(|| lc.clone())) {
+                    self.bot_uids.remove(&bot_lc);
+                    self.bot_idents.remove(&bot_lc);
+                    self.network.bot_forget(&bot_lc);
+                    self.bot_channels.retain(|(b, _)| *b != bot_lc);
+                    return self.reconcile_bots();
+                }
+                self.forget_user(&uid);
                 Vec::new()
             }
             NetEvent::Privmsg { from, to, text } => self.dispatch(&from, &to, &text),

src/engine/tests.rs

@@ -1860,6 +1860,50 @@
         assert!(out.iter().any(|a| matches!(a, NetAction::ServiceJoin { uid, channel } if uid == &bot_uid && channel == "#c")), "kicked bot rejoins: {out:?}");
     }
 
+    // A KILL forgets a real user, but a killed services bot is reintroduced and
+    // rejoins its channels — an oper can't take a bot down for good.
+    #[test]
+    fn kill_forgets_a_user_and_reintroduces_a_bot() {
+        use echo_botserv::BotServ;
+        use echo_nickserv::NickServ;
+        let path = std::env::temp_dir().join("echo-killbot.jsonl");
+        let _ = std::fs::remove_file(&path);
+        let mut db = Db::open(&path, "42S");
+        db.scram_iterations = 4096;
+        db.register("boss", "password1", None).unwrap();
+        db.register_channel("#c", "boss").unwrap();
+        let mut e = Engine::new(
+            vec![
+                Box::new(NickServ { uid: "42SAAAAAA".into(), guest_nick: "Guest".into(), guest_seq: 0 }),
+                Box::new(BotServ { uid: "42SAAAAAD".into() }),
+            ],
+            db,
+        );
+        e.set_sid("42S".into());
+        let mut opers = std::collections::HashMap::new();
+        opers.insert("boss".to_string(), Privs::default().with(echo_api::Priv::Admin));
+        e.set_opers(opers);
+        let ns = |e: &mut Engine, t: &str| e.handle(NetEvent::Privmsg { from: "000AAAAAB".into(), to: "42SAAAAAA".into(), text: t.into() });
+        let bs = |e: &mut Engine, t: &str| e.handle(NetEvent::Privmsg { from: "000AAAAAB".into(), to: "42SAAAAAD".into(), text: t.into() });
+        e.handle(NetEvent::UserConnect { uid: "000AAAAAB".into(), nick: "boss".into(), host: "h".into() , ip: "0.0.0.0".into() });
+        ns(&mut e, "IDENTIFY password1");
+        bs(&mut e, "BOT ADD Bendy bot serv.host Helper");
+        let bot_uid = bs(&mut e, "ASSIGN #c Bendy").iter().find_map(|a| match a {
+            NetAction::ServiceJoin { uid, channel } if channel == "#c" => Some(uid.clone()),
+            _ => None,
+        }).expect("bot joined on assign");
+
+        // Killing a real user forgets their session.
+        assert_eq!(e.network.account_of("000AAAAAB"), Some("boss"), "identified before the kill");
+        e.handle(NetEvent::UserKilled { uid: "000AAAAAB".into() });
+        assert!(e.network.account_of("000AAAAAB").is_none(), "killed user forgotten");
+
+        // Killing the bot brings it right back and rejoins its channel.
+        let out = e.handle(NetEvent::UserKilled { uid: bot_uid });
+        assert!(out.iter().any(|a| matches!(a, NetAction::IntroduceUser { nick, .. } if nick == "Bendy")), "killed bot reintroduced: {out:?}");
+        assert!(out.iter().any(|a| matches!(a, NetAction::ServiceJoin { channel, .. } if channel == "#c")), "reintroduced bot rejoins #c: {out:?}");
+    }
+
     // A channel that expires with an assigned bot parts the bot in the same
     // sweep — it must not linger in a channel it no longer serves.
     #[test]