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;