Hi,
Avoid a useless increment and decrement of of the tcp syn cache
refcount by unexpanding the SYN_CACHE_TIMER_ARM() macro in the timer
callback.
ok?
bluhm
Index: netinet/tcp_input.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_input.c,v
retrieving revision 1.390
diff -u -p -r1.390 tcp_input.c
--- netinet/tcp_input.c 28 Aug 2023 14:50:01 -0000 1.390
+++ netinet/tcp_input.c 3 Sep 2023 18:04:13 -0000
@@ -3159,19 +3159,6 @@ syn_cache_put(struct syn_cache *sc)
pool_put(&syn_cache_pool, sc);
}
-/*
- * We don't estimate RTT with SYNs, so each packet starts with the default
- * RTT and each timer step has a fixed timeout value.
- */
-#define SYN_CACHE_TIMER_ARM(sc)
\
-do { \
- TCPT_RANGESET((sc)->sc_rxtcur, \
- TCPTV_SRTTDFLT * tcp_backoff[(sc)->sc_rxtshift], TCPTV_MIN, \
- TCPTV_REXMTMAX); \
- if (timeout_add_msec(&(sc)->sc_timer, (sc)->sc_rxtcur)) \
- refcnt_take(&(sc)->sc_refcnt); \
-} while (/*CONSTCOND*/0)
-
void
syn_cache_init(void)
{
@@ -3300,11 +3287,17 @@ syn_cache_insert(struct syn_cache *sc, s
}
/*
- * Initialize the entry's timer.
+ * Initialize the entry's timer. We don't estimate RTT
+ * with SYNs, so each packet starts with the default RTT
+ * and each timer step has a fixed timeout value.
*/
sc->sc_rxttot = 0;
sc->sc_rxtshift = 0;
- SYN_CACHE_TIMER_ARM(sc);
+ TCPT_RANGESET(sc->sc_rxtcur,
+ TCPTV_SRTTDFLT * tcp_backoff[sc->sc_rxtshift], TCPTV_MIN,
+ TCPTV_REXMTMAX);
+ if (timeout_add_msec(&sc->sc_timer, sc->sc_rxtcur))
+ refcnt_take(&sc->sc_refcnt);
/* Link it from tcpcb entry */
refcnt_take(&sc->sc_refcnt);
@@ -3365,15 +3358,12 @@ syn_cache_timer(void *arg)
/* Advance the timer back-off. */
sc->sc_rxtshift++;
- SYN_CACHE_TIMER_ARM(sc);
+ TCPT_RANGESET(sc->sc_rxtcur,
+ TCPTV_SRTTDFLT * tcp_backoff[sc->sc_rxtshift], TCPTV_MIN,
+ TCPTV_REXMTMAX);
+ if (!timeout_add_msec(&sc->sc_timer, sc->sc_rxtcur))
+ syn_cache_put(sc);
- /*
- * Decrement reference of this timer. We know there is another timer
- * as we just added it. So just deref, free is not necessary.
- */
- lastref = refcnt_rele(&sc->sc_refcnt);
- KASSERT(lastref == 0);
- (void)lastref;
NET_UNLOCK();
return;
