Right now the session socket is always ready to read more data. At the
same time only MSG_PROCESS_LIMIT messages are pulled of the msgbuf read
queue. As a result the SE may buffer a lot of messages.

This throttles the POLLIN event by checking that no more than
MSG_PROCESS_LIMIT are ready. If more are queued the POLLIN is skipped.
The code will still run session_process_msg on every poll round and so the
queue len will shrink by MSG_PROCESS_LIMIT.

This is now possible that the ibuf API includes msgbuf_readlen.
-- 
:wq Claudio

Index: session.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/session.c,v
diff -u -p -r1.540 session.c
--- session.c	24 Jul 2026 05:01:01 -0000	1.540
+++ session.c	10 Sep 2026 18:45:59 -0000
@@ -414,7 +414,9 @@ session_main(int debug, int verbose)
 			}
 
 			/* are we waiting for a write? */
-			events = POLLIN;
+			events = 0;
+			if (msgbuf_readlen(p->wbuf) < MSG_PROCESS_LIMIT)
+				events |= POLLIN;
 			if (msgbuf_queuelen(p->wbuf) > 0 ||
 			    p->state == STATE_CONNECT)
 				events |= POLLOUT;