/* * Copyright (c) 2000-2012 Apple Inc. All rights reserved. * * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. The rights granted to you under the License * may not be used to create, or enable the creation or redistribution of, * unlawful or unlicensed copies of an Apple operating system, or to * circumvent, violate, or enable the circumvention or violation of, any * terms of an Apple operating system software license agreement. * * Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95 * $FreeBSD: src/sys/netinet/tcp_timer.c,v 1.34.2.11 2001/08/22 00:59:12 silby Exp $ */ #include #include #include #include #include #include #include #include #include #include #include #include #include /* before tcp_seq.h, for tcp_random18() */ #include #include #include #include #include #if INET6 #include #endif #include #include #include #include #include #include #include #if INET6 #include #endif #include #if TCPDEBUG #include #endif #include #include extern void postevent(struct socket *, struct sockbuf *, int); #define DBG_FNC_TCP_FAST NETDBG_CODE(DBG_NETTCP, (5 << 8)) #define DBG_FNC_TCP_SLOW NETDBG_CODE(DBG_NETTCP, (5 << 8) | 1) #define TIMERENTRY_TO_TP(te) ((struct tcpcb *)((uintptr_t)te - offsetof(struct tcpcb, tentry.le.le_next))) #define VERIFY_NEXT_LINK(elm,field) do { \ if (LIST_NEXT((elm),field) != NULL && \ LIST_NEXT((elm),field)->field.le_prev != \ &((elm)->field.le_next)) \ panic("Bad link elm %p next->prev != elm", (elm)); \ } while(0) #define VERIFY_PREV_LINK(elm,field) do { \ if (*(elm)->field.le_prev != (elm)) \ panic("Bad link elm %p prev->next != elm", (elm)); \ } while(0) static int background_io_trigger = 5; SYSCTL_INT(_net_inet_tcp, OID_AUTO, background_io_trigger, CTLFLAG_RW | CTLFLAG_LOCKED, &background_io_trigger, 0, "Background IO Trigger Setting"); static int sysctl_msec_to_ticks SYSCTL_HANDLER_ARGS { #pragma unused(arg1, arg2) int error, s, tt; tt = *(int *)oidp->oid_arg1; s = tt * 1000 / TCP_RETRANSHZ;; error = sysctl_handle_int(oidp, &s, 0, req); if (error || !req->newptr) return (error); tt = s * TCP_RETRANSHZ / 1000; if (tt < 1) return (EINVAL); *(int *)oidp->oid_arg1 = tt; return (0); } int tcp_keepinit; SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", ""); int tcp_keepidle; SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", ""); int tcp_keepintvl; SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", ""); int tcp_msl; SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime"); /* * Avoid DoS via TCP Robustness in Persist Condition (see http://www.ietf.org/id/draft-ananth-tcpm-persist-02.txt) * by allowing a system wide maximum persistence timeout value when in Zero Window Probe mode. * Expressed in milliseconds to be consistent without timeout related values, the TCP socket option is in seconds. */ u_int32_t tcp_max_persist_timeout = 0; SYSCTL_PROC(_net_inet_tcp, OID_AUTO, max_persist_timeout, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_max_persist_timeout, 0, sysctl_msec_to_ticks, "I", "Maximum persistence timout for ZWP"); static int always_keepalive = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW | CTLFLAG_LOCKED, &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); /* This parameter determines how long the timer list will stay in fast mode even * though all connections are idle. In fast mode, the timer will fire more frequently * anticipating new data. */ int timer_fastmode_idlemax = TCP_FASTMODE_IDLEGEN_MAX; SYSCTL_INT(_net_inet_tcp, OID_AUTO, timer_fastmode_idlemax, CTLFLAG_RW | CTLFLAG_LOCKED, &timer_fastmode_idlemax, 0, "Maximum idle generations in fast mode"); /* * See tcp_syn_backoff[] for interval values between SYN retransmits; * the value set below defines the number of retransmits, before we * disable the timestamp and window scaling options during subsequent * SYN retransmits. Setting it to 0 disables the dropping off of those * two options. */ static int tcp_broken_peer_syn_rxmit_thres = 7; SYSCTL_INT(_net_inet_tcp, OID_AUTO, broken_peer_syn_rxmit_thres, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_broken_peer_syn_rxmit_thres, 0, "Number of retransmitted SYNs before " "TCP disables rfc1323 and rfc1644 during the rest of attempts"); static int tcp_timer_advanced = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcp_timer_advanced, CTLFLAG_RD | CTLFLAG_LOCKED, &tcp_timer_advanced, 0, "Number of times one of the timers was advanced"); static int tcp_resched_timerlist = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcp_resched_timerlist, CTLFLAG_RD | CTLFLAG_LOCKED, &tcp_resched_timerlist, 0, "Number of times timer list was rescheduled as part of processing a packet"); int tcp_pmtud_black_hole_detect = 1 ; SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_pmtud_black_hole_detect, 0, "Path MTU Discovery Black Hole Detection"); int tcp_pmtud_black_hole_mss = 1200 ; SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_pmtud_black_hole_mss, 0, "Path MTU Discovery Black Hole Detection lowered MSS"); static int tcp_keepcnt = TCPTV_KEEPCNT; static int tcp_gc_done = FALSE; /* perfromed garbage collection of "used" sockets */ /* max idle probes */ int tcp_maxpersistidle; /* max idle time in persist */ int tcp_maxidle; /* TCP delack timer is set to 100 ms. Since the processing of timer list in fast * mode will happen no faster than 100 ms, the delayed ack timer will fire some where * between 100 and 200 ms. */ int tcp_delack = TCP_RETRANSHZ / 10; struct inpcbhead time_wait_slots[N_TIME_WAIT_SLOTS]; int cur_tw_slot = 0; /* tcp timer list */ struct tcptimerlist tcp_timer_list; /* The frequency of running through the TCP timer list in * fast and slow mode can be configured. */ SYSCTL_UINT(_net_inet_tcp, OID_AUTO, timer_fastquantum, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_timer_list.fast_quantum, TCP_FASTTIMER_QUANTUM, "Frequency of running timer list in fast mode"); SYSCTL_UINT(_net_inet_tcp, OID_AUTO, timer_slowquantum, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_timer_list.slow_quantum, TCP_SLOWTIMER_QUANTUM, "Frequency of running timer list in slow mode"); static void tcp_remove_timer(struct tcpcb *tp); static void tcp_sched_timerlist(uint32_t offset); static uint32_t tcp_run_conn_timer(struct tcpcb *tp, uint16_t *next_index); static void tcp_sched_timers(struct tcpcb *tp); static inline void tcp_set_lotimer_index(struct tcpcb *); /* Macro to compare two timers. If there is a reset of the sign bit, it is * safe to assume that the timer has wrapped around. By doing signed comparision, * we take care of wrap around such that the value with the sign bit reset is * actually ahead of the other. */ static inline int32_t timer_diff(uint32_t t1, uint32_t toff1, uint32_t t2, uint32_t toff2) { return (int32_t)((t1 + toff1) - (t2 + toff2)); }; /* Returns true if the timer is on the timer list */ #define TIMER_IS_ON_LIST(tp) ((tp)->t_flags & TF_TIMER_ONLIST) void add_to_time_wait_locked(struct tcpcb *tp, uint32_t delay); void add_to_time_wait(struct tcpcb *tp, uint32_t delay) ; static void tcp_garbage_collect(struct inpcb *, int); void add_to_time_wait_locked(struct tcpcb *tp, uint32_t delay) { int tw_slot; struct inpcbinfo *pcbinfo = &tcbinfo; uint32_t timer; /* pcb list should be locked when we get here */ lck_rw_assert(pcbinfo->mtx, LCK_RW_ASSERT_EXCLUSIVE); LIST_REMOVE(tp->t_inpcb, inp_list); /* if (tp->t_timer[TCPT_2MSL] <= 0) tp->t_timer[TCPT_2MSL] = 1; */ /* * Because we're pulling this pcb out of the main TCP pcb list, * we need to recalculate the TCPT_2MSL timer value for tcp_slowtimo * higher timer granularity. */ timer = (delay / TCP_RETRANSHZ) * PR_SLOWHZ; tp->t_rcvtime = (tp->t_rcvtime / TCP_RETRANSHZ) * PR_SLOWHZ; tp->t_rcvtime += timer & (N_TIME_WAIT_SLOTS - 1); tw_slot = (timer & (N_TIME_WAIT_SLOTS - 1)) + cur_tw_slot; if (tw_slot >= N_TIME_WAIT_SLOTS) tw_slot -= N_TIME_WAIT_SLOTS; LIST_INSERT_HEAD(&time_wait_slots[tw_slot], tp->t_inpcb, inp_list); } void add_to_time_wait(struct tcpcb *tp, uint32_t delay) { struct inpcbinfo *pcbinfo = &tcbinfo; if (!lck_rw_try_lock_exclusive(pcbinfo->mtx)) { tcp_unlock(tp->t_inpcb->inp_socket, 0, 0); lck_rw_lock_exclusive(pcbinfo->mtx); tcp_lock(tp->t_inpcb->inp_socket, 0, 0); } add_to_time_wait_locked(tp, delay); lck_rw_done(pcbinfo->mtx); } static void tcp_garbage_collect(struct inpcb *inp, int istimewait) { struct socket *so; struct tcpcb *tp; so = inp->inp_socket; tp = intotcpcb(inp); /* * Skip if still in use or busy; it would have been more efficient * if we were to test so_usecount against 0, but this isn't possible * due to the current implementation of tcp_dropdropablreq() where * overflow sockets that are eligible for garbage collection have * their usecounts set to 1. */ if (so->so_usecount > 1 || !lck_mtx_try_lock_spin(&inp->inpcb_mtx)) return; /* Check again under the lock */ if (so->so_usecount > 1) { lck_mtx_unlock(&inp->inpcb_mtx); return; } /* * Overflowed socket dropped from the listening queue? Do this * only if we are called to clean up the time wait slots, since * tcp_dropdropablreq() considers a socket to have been fully * dropped after add_to_time_wait() is finished. * Also handle the case of connections getting closed by the peer while in the queue as * seen with rdar://6422317 * */ if (so->so_usecount == 1 && ((istimewait && (so->so_flags & SOF_OVERFLOW)) || ((tp != NULL) && (tp->t_state == TCPS_CLOSED) && (so->so_head != NULL) && ((so->so_state & (SS_INCOMP|SS_CANTSENDMORE|SS_CANTRCVMORE)) == (SS_INCOMP|SS_CANTSENDMORE|SS_CANTRCVMORE))))) { if (inp->inp_state != INPCB_STATE_DEAD) { /* Become a regular mutex */ lck_mtx_convert_spin(&inp->inpcb_mtx); #if INET6 if (INP_CHECK_SOCKAF(so, AF_INET6)) in6_pcbdetach(inp); else #endif /* INET6 */ in_pcbdetach(inp); } so->so_usecount--; lck_mtx_unlock(&inp->inpcb_mtx); return; } else if (inp->inp_wantcnt != WNT_STOPUSING) { lck_mtx_unlock(&inp->inpcb_mtx); return; } /* * We get here because the PCB is no longer searchable (WNT_STOPUSING); * detach (if needed) and dispose if it is dead (usecount is 0). This * covers all cases, including overflow sockets and those that are * considered as "embryonic", i.e. created by sonewconn() in TCP input * path, and have not yet been committed. For the former, we reduce * the usecount to 0 as done by the code above. For the latter, the * usecount would have reduced to 0 as part calling soabort() when the * socket is dropped at the end of tcp_input(). */ if (so->so_usecount == 0) { DTRACE_TCP4(state__change, void, NULL, struct inpcb *, inp, struct tcpcb *, tp, int32_t, TCPS_CLOSED); /* Become a regular mutex */ lck_mtx_convert_spin(&inp->inpcb_mtx); /* If this tp still happens to be on the timer list, * take it out */ if (TIMER_IS_ON_LIST(tp)) { tcp_remove_timer(tp); } if (inp->inp_state != INPCB_STATE_DEAD) { #if INET6 if (INP_CHECK_SOCKAF(so, AF_INET6)) in6_pcbdetach(inp); else #endif /* INET6 */ in_pcbdetach(inp); } in_pcbdispose(inp); } else { lck_mtx_unlock(&inp->inpcb_mtx); } } void tcp_slowtimo(void) { struct inpcb *inp, *nxt; struct tcpcb *tp; #if TCPDEBUG int ostate; #endif #if KDEBUG static int tws_checked = 0; #endif struct inpcbinfo *pcbinfo = &tcbinfo; KERNEL_DEBUG(DBG_FNC_TCP_SLOW | DBG_FUNC_START, 0,0,0,0,0); tcp_maxidle = tcp_keepcnt * tcp_keepintvl; /* Update tcp_now here as it may get used while processing the slow timer */ calculate_tcp_clock(); /* Garbage collect socket/tcpcb: We need to acquire the list lock * exclusively to do this */ if (lck_rw_try_lock_exclusive(pcbinfo->mtx) == FALSE) { if (tcp_gc_done == TRUE) { /* don't sweat it this time. cleanup was done last time */ tcp_gc_done = FALSE; KERNEL_DEBUG(DBG_FNC_TCP_SLOW | DBG_FUNC_END, tws_checked, cur_tw_slot,0,0,0); return; /* Upgrade failed and lost lock - give up this time. */ } lck_rw_lock_exclusive(pcbinfo->mtx); /* Upgrade failed, lost lock now take it again exclusive */ } tcp_gc_done = TRUE; /* * Process the items in the current time-wait slot */ #if KDEBUG tws_checked = 0; #endif KERNEL_DEBUG(DBG_FNC_TCP_SLOW | DBG_FUNC_NONE, tws_checked,0,0,0,0); LIST_FOREACH(inp, &time_wait_slots[cur_tw_slot], inp_list) { #if KDEBUG tws_checked++; #endif if (in_pcb_checkstate(inp, WNT_ACQUIRE, 0) == WNT_STOPUSING) continue; tcp_lock(inp->inp_socket, 1, 0); if (in_pcb_checkstate(inp, WNT_RELEASE, 1) == WNT_STOPUSING) goto twunlock; tp = intotcpcb(inp); if (tp == NULL) /* tp already closed, remove from list */ goto twunlock; if (tp->t_timer[TCPT_2MSL] >= N_TIME_WAIT_SLOTS) { tp->t_timer[TCPT_2MSL] -= N_TIME_WAIT_SLOTS; tp->t_rcvtime += N_TIME_WAIT_SLOTS; } else tp->t_timer[TCPT_2MSL] = 0; if (tp->t_timer[TCPT_2MSL] == 0) { /* That pcb is ready for a close */ tcp_free_sackholes(tp); tp = tcp_close(tp); } twunlock: tcp_unlock(inp->inp_socket, 1, 0); } LIST_FOREACH_SAFE(inp, &tcb, inp_list, nxt) { tcp_garbage_collect(inp, 0); } /* Now cleanup the time wait ones */ LIST_FOREACH_SAFE(inp, &time_wait_slots[cur_tw_slot], inp_list, nxt) { tcp_garbage_collect(inp, 1); } if (++cur_tw_slot >= N_TIME_WAIT_SLOTS) cur_tw_slot = 0; lck_rw_done(pcbinfo->mtx); KERNEL_DEBUG(DBG_FNC_TCP_SLOW | DBG_FUNC_END, tws_checked, cur_tw_slot,0,0,0); } /* * Cancel all timers for TCP tp. */ void tcp_canceltimers(tp) struct tcpcb *tp; { register int i; tcp_remove_timer(tp); for (i = 0; i < TCPT_NTIMERS; i++) tp->t_timer[i] = 0; tp->tentry.timer_start = tcp_now; tp->tentry.index = TCPT_NONE; } int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; int tcp_backoff[TCP_MAXRXTSHIFT + 1] = { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ /* * TCP timer processing. */ struct tcpcb * tcp_timers(tp, timer) register struct tcpcb *tp; int timer; { register int rexmt; struct socket *so; struct tcptemp *t_template; int optlen = 0; int idle_time = 0; #if TCPDEBUG int ostate; #endif #if INET6 int isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV4) == 0; #endif /* INET6 */ so = tp->t_inpcb->inp_socket; idle_time = tcp_now - tp->t_rcvtime; switch (timer) { /* * 2 MSL timeout in shutdown went off. If we're closed but * still waiting for peer to close and connection has been idle * too long, or if 2MSL time is up from TIME_WAIT or FIN_WAIT_2, * delete connection control block. * Otherwise, (this case shouldn't happen) check again in a bit * we keep the socket in the main list in that case. */ case TCPT_2MSL: tcp_free_sackholes(tp); if (tp->t_state != TCPS_TIME_WAIT && tp->t_state != TCPS_FIN_WAIT_2 && ((idle_time > 0) && (idle_time < tcp_maxidle))) { tp->t_timer[TCPT_2MSL] = OFFSET_FROM_START(tp, (u_int32_t)tcp_keepintvl); } else { tp = tcp_close(tp); return(tp); } break; /* * Retransmission timer went off. Message has not * been acked within retransmit interval. Back off * to a longer retransmit interval and retransmit one segment. */ case TCPT_REXMT: /* Drop a connection in the retransmit timer * 1. If we have retransmitted more than TCP_MAXRXTSHIFT times * 2. If the time spent in this retransmission episode is more than * the time limit set with TCP_RXT_CONNDROPTIME socket option * 3. If TCP_RXT_FINDROP socket option was set and we have already * retransmitted the FIN 3 times without receiving an ack */ if (++tp->t_rxtshift > TCP_MAXRXTSHIFT || (tp->rxt_conndroptime > 0 && tp->rxt_start > 0 && (tcp_now - tp->rxt_start) >= tp->rxt_conndroptime) || ((tp->t_flagsext & TF_RXTFINDROP) != 0 && (tp->t_flags & TF_SENTFIN) != 0 && tp->t_rxtshift >= 4)) { if ((tp->t_flagsext & TF_RXTFINDROP) != 0) { tcpstat.tcps_rxtfindrop++; } else { tcpstat.tcps_timeoutdrop++; } tp->t_rxtshift = TCP_MAXRXTSHIFT; postevent(so, 0, EV_TIMEOUT); soevent(so, (SO_FILT_HINT_LOCKED|SO_FILT_HINT_TIMEOUT)); tp = tcp_drop(tp, tp->t_softerror ? tp->t_softerror : ETIMEDOUT); break; } if (tp->t_rxtshift == 1) { /* * first retransmit; record ssthresh and cwnd so they can * be recovered if this turns out to be a "bad" retransmit. * A retransmit is considered "bad" if an ACK for this * segment is received within RTT/2 interval; the assumption * here is that the ACK was already in flight. See * "On Estimating End-to-End Network Path Properties" by * Allman and Paxson for more details. */ tp->snd_cwnd_prev = tp->snd_cwnd; tp->snd_ssthresh_prev = tp->snd_ssthresh; tp->snd_recover_prev = tp->snd_recover; if (IN_FASTRECOVERY(tp)) tp->t_flags |= TF_WASFRECOVERY; else tp->t_flags &= ~TF_WASFRECOVERY; tp->t_badrxtwin = tcp_now + (tp->t_srtt >> (TCP_RTT_SHIFT)); /* Set the time at which retransmission on this * connection started */ tp->rxt_start = tcp_now; } tcpstat.tcps_rexmttimeo++; if (tp->t_state == TCPS_SYN_SENT) rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; else rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; TCPT_RANGESET(tp->t_rxtcur, rexmt, tp->t_rttmin, TCPTV_REXMTMAX, TCP_ADD_REXMTSLOP(tp)); tp->t_timer[TCPT_REXMT] = OFFSET_FROM_START(tp, tp->t_rxtcur); if (INP_WAIT_FOR_IF_FEEDBACK(tp->t_inpcb)) goto fc_output; tcp_free_sackholes(tp); /* * Check for potential Path MTU Discovery Black Hole */ if (tcp_pmtud_black_hole_detect && (tp->t_state == TCPS_ESTABLISHED)) { if (((tp->t_flags & (TF_PMTUD|TF_MAXSEGSNT)) == (TF_PMTUD|TF_MAXSEGSNT)) && (tp->t_rxtshift == 2)) { /* * Enter Path MTU Black-hole Detection mechanism: * - Disable Path MTU Discovery (IP "DF" bit). * - Reduce MTU to lower value than what we negociated with peer. */ tp->t_flags &= ~TF_PMTUD; /* Disable Path MTU Discovery for now */ tp->t_flags |= TF_BLACKHOLE; /* Record that we may have found a black hole */ optlen = tp->t_maxopd - tp->t_maxseg; tp->t_pmtud_saved_maxopd = tp->t_maxopd; /* Keep track of previous MSS */ if (tp->t_maxopd > tcp_pmtud_black_hole_mss) tp->t_maxopd = tcp_pmtud_black_hole_mss; /* Reduce the MSS to intermediary value */ else { tp->t_maxopd = /* use the default MSS */ #if INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt; } tp->t_maxseg = tp->t_maxopd - optlen; /* * Reset the slow-start flight size as it may depends on the new MSS */ if (CC_ALGO(tp)->cwnd_init != NULL) CC_ALGO(tp)->cwnd_init(tp); } /* * If further retransmissions are still unsuccessful with a lowered MTU, * maybe this isn't a Black Hole and we restore the previous MSS and * blackhole detection flags. */ else { if ((tp->t_flags & TF_BLACKHOLE) && (tp->t_rxtshift > 4)) { tp->t_flags |= TF_PMTUD; tp->t_flags &= ~TF_BLACKHOLE; optlen = tp->t_maxopd - tp->t_maxseg; tp->t_maxopd = tp->t_pmtud_saved_maxopd; tp->t_maxseg = tp->t_maxopd - optlen; /* * Reset the slow-start flight size as it may depends on the new MSS */ if (CC_ALGO(tp)->cwnd_init != NULL) CC_ALGO(tp)->cwnd_init(tp); } } } /* * Disable rfc1323 and rfc1644 if we haven't got any response to * our SYN (after we reach the threshold) to work-around some * broken terminal servers (most of which have hopefully been * retired) that have bad VJ header compression code which * trashes TCP segments containing unknown-to-them TCP options. */ if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == tcp_broken_peer_syn_rxmit_thres)) tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC); /* * If losing, let the lower level know and try for * a better route. Also, if we backed off this far, * our srtt estimate is probably bogus. Clobber it * so we'll take the next rtt measurement as our srtt; * move the current srtt into rttvar to keep the current * retransmit times until then. */ if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { #if INET6 if (isipv6) in6_losing(tp->t_inpcb); else #endif /* INET6 */ in_losing(tp->t_inpcb); tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); tp->t_srtt = 0; } tp->snd_nxt = tp->snd_una; /* * Note: We overload snd_recover to function also as the * snd_last variable described in RFC 2582 */ tp->snd_recover = tp->snd_max; /* * Force a segment to be sent. */ tp->t_flags |= TF_ACKNOW; /* * If timing a segment in this window, stop the timer. */ tp->t_rtttime = 0; if (CC_ALGO(tp)->after_timeout != NULL) CC_ALGO(tp)->after_timeout(tp); tp->t_dupacks = 0; EXIT_FASTRECOVERY(tp); /* CWR notifications are to be sent on new data right after * RTOs, Fast Retransmits and ECE notification receipts. */ if ((tp->ecn_flags & TE_ECN_ON) == TE_ECN_ON) { tp->ecn_flags |= TE_SENDCWR; } fc_output: DTRACE_TCP5(cc, void, NULL, struct inpcb *, tp->t_inpcb, struct tcpcb *, tp, struct tcphdr *, NULL, int32_t, TCP_CC_REXMT_TIMEOUT); (void) tcp_output(tp); break; /* * Persistance timer into zero window. * Force a byte to be output, if possible. */ case TCPT_PERSIST: tcpstat.tcps_persisttimeo++; /* * Hack: if the peer is dead/unreachable, we do not * time out if the window is closed. After a full * backoff, drop the connection if the idle time * (no responses to probes) reaches the maximum * backoff that we would use if retransmitting. * * Drop the connection if we reached the maximum allowed time for * Zero Window Probes without a non-zero update from the peer. * See rdar://5805356 */ if ((tp->t_rxtshift == TCP_MAXRXTSHIFT && (idle_time >= tcp_maxpersistidle || idle_time >= TCP_REXMTVAL(tp) * tcp_totbackoff)) || ((tp->t_persist_stop != 0) && TSTMP_LEQ(tp->t_persist_stop, tcp_now))) { tcpstat.tcps_persistdrop++; postevent(so, 0, EV_TIMEOUT); soevent(so, (SO_FILT_HINT_LOCKED|SO_FILT_HINT_TIMEOUT)); tp = tcp_drop(tp, ETIMEDOUT); break; } tcp_setpersist(tp); tp->t_force = 1; (void) tcp_output(tp); tp->t_force = 0; break; /* * Keep-alive timer went off; send something * or drop connection if idle for too long. */ case TCPT_KEEP: tcpstat.tcps_keeptimeo++; if (tp->t_state < TCPS_ESTABLISHED) goto dropit; if ((always_keepalive || tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && (tp->t_state <= TCPS_CLOSING || tp->t_state == TCPS_FIN_WAIT_2)) { if (idle_time >= TCP_KEEPIDLE(tp) + (u_int32_t)tcp_maxidle) goto dropit; /* * Send a packet designed to force a response * if the peer is up and reachable: * either an ACK if the connection is still alive, * or an RST if the peer has closed the connection * due to timeout or reboot. * Using sequence number tp->snd_una-1 * causes the transmitted zero-length segment * to lie outside the receive window; * by the protocol spec, this requires the * correspondent TCP to respond. */ tcpstat.tcps_keepprobe++; t_template = tcp_maketemplate(tp); if (t_template) { unsigned int ifscope, nocell = 0; if (tp->t_inpcb->inp_flags & INP_BOUND_IF) ifscope = tp->t_inpcb->inp_boundifp->if_index; else ifscope = IFSCOPE_NONE; /* * If the socket isn't allowed to use the * cellular interface, indicate it as such. */ if (tp->t_inpcb->inp_flags & INP_NO_IFT_CELLULAR) nocell = 1; tcp_respond(tp, t_template->tt_ipgen, &t_template->tt_t, (struct mbuf *)NULL, tp->rcv_nxt, tp->snd_una - 1, 0, ifscope, nocell); (void) m_free(dtom(t_template)); } tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, tcp_keepintvl); } else tp->t_timer[TCPT_KEEP] = OFFSET_FROM_START(tp, TCP_KEEPIDLE(tp)); break; case TCPT_DELACK: if (tcp_delack_enabled && (tp->t_flags & TF_DELACK)) { tp->t_flags &= ~TF_DELACK; tp->t_timer[TCPT_DELACK] = 0; tp->t_flags |= TF_ACKNOW; /* If delayed ack timer fired while we are stretching acks, * go back to acking every other packet */ if ((tp->t_flags & TF_STRETCHACK) != 0) tcp_reset_stretch_ack(tp); /* If we are measuring inter packet arrival jitter for * throttling a connection, this delayed ack might be * the reason for accumulating some jitter. So let's * restart the measurement. */ CLEAR_IAJ_STATE(tp); tcpstat.tcps_delack++; (void) tcp_output(tp); } break; #if TCPDEBUG if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, PRU_SLOWTIMO); #endif dropit: tcpstat.tcps_keepdrops++; postevent(so, 0, EV_TIMEOUT); soevent(so, (SO_FILT_HINT_LOCKED|SO_FILT_HINT_TIMEOUT)); tp = tcp_drop(tp, ETIMEDOUT); break; } return (tp); } /* Remove a timer entry from timer list */ void tcp_remove_timer(struct tcpcb *tp) { struct tcptimerlist *listp = &tcp_timer_list; lck_mtx_assert(&tp->t_inpcb->inpcb_mtx, LCK_MTX_ASSERT_OWNED); if (!(TIMER_IS_ON_LIST(tp))) { return; } lck_mtx_lock(listp->mtx); /* Check if pcb is on timer list again after acquiring the lock */ if (!(TIMER_IS_ON_LIST(tp))) { lck_mtx_unlock(listp->mtx); return; } if (listp->next_te != NULL && listp->next_te == &tp->tentry) listp->next_te = LIST_NEXT(&tp->tentry, le); LIST_REMOVE(&tp->tentry, le); tp->t_flags &= ~(TF_TIMER_ONLIST); listp->entries--; tp->tentry.le.le_next = NULL; tp->tentry.le.le_prev = NULL; lck_mtx_unlock(listp->mtx); } /* Function to check if the timerlist needs to be rescheduled to run * the timer entry correctly. Basically, this is to check if we can avoid * taking the list lock. */ static boolean_t need_to_resched_timerlist(uint32_t runtime, uint16_t index) { struct tcptimerlist *listp = &tcp_timer_list; int32_t diff; boolean_t is_fast; if (runtime == 0 || index == TCPT_NONE) return FALSE; is_fast = !(IS_TIMER_SLOW(index)); /* If the list is being processed then the state of the list is in flux. * In this case always acquire the lock and set the state correctly. */ if (listp->running) { return TRUE; } diff = timer_diff(listp->runtime, 0, runtime, 0); if (diff <= 0) { /* The list is going to run before this timer */ return FALSE; } else { if (is_fast) { if (diff <= listp->fast_quantum) return FALSE; } else { if (diff <= listp->slow_quantum) return FALSE; } } return TRUE; } void tcp_sched_timerlist(uint32_t offset) { uint64_t deadline = 0; struct tcptimerlist *listp = &tcp_timer_list; lck_mtx_assert(listp->mtx, LCK_MTX_ASSERT_OWNED); listp->runtime = tcp_now + offset; clock_interval_to_deadline(offset, NSEC_PER_SEC / TCP_RETRANSHZ, &deadline); thread_call_enter_delayed(listp->call, deadline); } /* Function to run the timers for a connection. * * Returns the offset of next timer to be run for this connection which * can be used to reschedule the timerlist. */ uint32_t tcp_run_conn_timer(struct tcpcb *tp, uint16_t *next_index) { struct socket *so; uint16_t i = 0, index = TCPT_NONE, lo_index = TCPT_NONE; uint32_t timer_val, offset = 0, lo_timer = 0; int32_t diff; boolean_t needtorun[TCPT_NTIMERS]; int count = 0; VERIFY(tp != NULL); bzero(needtorun, sizeof(needtorun)); tcp_lock(tp->t_inpcb->inp_socket, 1, 0); so = tp->t_inpcb->inp_socket; /* Release the want count on inp */ if (in_pcb_checkstate(tp->t_inpcb, WNT_RELEASE, 1) == WNT_STOPUSING) { if (TIMER_IS_ON_LIST(tp)) { tcp_remove_timer(tp); } /* Looks like the TCP connection got closed while we * were waiting for the lock.. Done */ goto done; } /* Since the timer thread needs to wait for tcp lock, it may race * with another thread that can cancel or reschedule the timer that is * about to run. Check if we need to run anything. */ index = tp->tentry.index; timer_val = tp->t_timer[index]; if (index == TCPT_NONE || tp->tentry.runtime == 0) goto done; diff = timer_diff(tp->tentry.runtime, 0, tcp_now, 0); if (diff > 0) { if (tp->tentry.index != TCPT_NONE) { offset = diff; *(next_index) = tp->tentry.index; } goto done; } tp->t_timer[index] = 0; if (timer_val > 0) { tp = tcp_timers(tp, index); if (tp == NULL) goto done; } /* Check if there are any other timers that need to be run. While doing it, * adjust the timer values wrt tcp_now. */ for (i = 0; i < TCPT_NTIMERS; ++i) { if (tp->t_timer[i] != 0) { diff = timer_diff(tp->tentry.timer_start, tp->t_timer[i], tcp_now, 0); if (diff <= 0) { tp->t_timer[i] = 0; needtorun[i] = TRUE; count++; } else { tp->t_timer[i] = diff; needtorun[i] = FALSE; if (lo_timer == 0 || diff < lo_timer) { lo_timer = diff; lo_index = i; } } } } tp->tentry.timer_start = tcp_now; tp->tentry.index = lo_index; if (lo_index != TCPT_NONE) { tp->tentry.runtime = tp->tentry.timer_start + tp->t_timer[lo_index]; } else { tp->tentry.runtime = 0; } if (count > 0) { /* run any other timers that are also outstanding at this time. */ for (i = 0; i < TCPT_NTIMERS; ++i) { if (needtorun[i]) { tp->t_timer[i] = 0; tp = tcp_timers(tp, i); if (tp == NULL) goto done; } } tcp_set_lotimer_index(tp); } if (tp->tentry.index < TCPT_NONE) { offset = tp->t_timer[tp->tentry.index]; *(next_index) = tp->tentry.index; } done: if (tp != NULL && tp->tentry.index == TCPT_NONE) { tcp_remove_timer(tp); } tcp_unlock(so, 1, 0); return offset; } void tcp_run_timerlist(void * arg1, void * arg2) { #pragma unused(arg1, arg2) struct tcptimerentry *te, *next_te; struct tcptimerlist *listp = &tcp_timer_list; struct tcpcb *tp; uint32_t next_timer = 0; uint16_t index = TCPT_NONE; boolean_t need_fast = FALSE; uint32_t active_count = 0; uint32_t mode = TCP_TIMERLIST_FASTMODE; calculate_tcp_clock(); lck_mtx_lock(listp->mtx); listp->running = TRUE; LIST_FOREACH_SAFE(te, &listp->lhead, le, next_te) { uint32_t offset = 0; uint32_t runtime = te->runtime; if (TSTMP_GT(runtime, tcp_now)) { offset = timer_diff(runtime, 0, tcp_now, 0); if (next_timer == 0 || offset < next_timer) { next_timer = offset; } continue; } active_count++; tp = TIMERENTRY_TO_TP(te); /* Acquire an inp wantcnt on the inpcb so that the socket won't get * detached even if tcp_close is called */ if (in_pcb_checkstate(tp->t_inpcb, WNT_ACQUIRE, 0) == WNT_STOPUSING) { /* Some how this pcb went into dead state while on the timer list, * just take it off the list. Since the timer list entry pointers * are protected by the timer list lock, we can do it here */ if (TIMER_IS_ON_LIST(tp)) { tp->t_flags &= ~(TF_TIMER_ONLIST); LIST_REMOVE(&tp->tentry, le); listp->entries--; tp->tentry.le.le_next = NULL; tp->tentry.le.le_prev = NULL; } continue; } /* Store the next timerentry pointer before releasing the list lock. * If that entry has to be removed when we release the lock, this * pointer will be updated to the element after that. */ listp->next_te = next_te; VERIFY_NEXT_LINK(&tp->tentry, le); VERIFY_PREV_LINK(&tp->tentry, le); lck_mtx_unlock(listp->mtx); index = TCPT_NONE; offset = tcp_run_conn_timer(tp, &index); lck_mtx_lock(listp->mtx); next_te = listp->next_te; listp->next_te = NULL; if (offset > 0) { if (index < TCPT_NONE) { /* Check if this is a fast_timer. */ if (!need_fast && !(IS_TIMER_SLOW(index))) { need_fast = TRUE; } if (next_timer == 0 || offset < next_timer) { next_timer = offset; } } } } if (!LIST_EMPTY(&listp->lhead)) { if (listp->mode == TCP_TIMERLIST_FASTMODE) { if (need_fast || active_count > 0 || listp->pref_mode == TCP_TIMERLIST_FASTMODE) { listp->idlegen = 0; } else { listp->idlegen++; if (listp->idlegen > timer_fastmode_idlemax) { mode = TCP_TIMERLIST_SLOWMODE; listp->idlegen = 0; } } } else { if (!need_fast) { mode = TCP_TIMERLIST_SLOWMODE; } } if (mode == TCP_TIMERLIST_FASTMODE || listp->pref_mode == TCP_TIMERLIST_FASTMODE) { next_timer = listp->fast_quantum; } else { if (listp->pref_offset != 0 && listp->pref_offset < next_timer) next_timer = listp->pref_offset; if (next_timer < listp->slow_quantum) next_timer = listp->slow_quantum; } listp->mode = mode; tcp_sched_timerlist(next_timer); } else { /* No need to reschedule this timer */ listp->runtime = 0; } listp->running = FALSE; listp->pref_mode = 0; listp->pref_offset = 0; lck_mtx_unlock(listp->mtx); } /* Function to verify if a change in timer state is required for a connection */ void tcp_sched_timers(struct tcpcb *tp) { struct tcptimerentry *te = &tp->tentry; uint16_t index = te->index; struct tcptimerlist *listp = &tcp_timer_list; uint32_t offset = 0; boolean_t is_fast; int list_locked = 0; if (tp->t_inpcb->inp_state == INPCB_STATE_DEAD) { /* Just return without adding the dead pcb to the list */ if (TIMER_IS_ON_LIST(tp)) { tcp_remove_timer(tp); } return; } if (index == TCPT_NONE) { tcp_remove_timer(tp); return; } is_fast = !(IS_TIMER_SLOW(index)); offset = te->runtime - tcp_now; if (offset == 0) { offset = 1; tcp_timer_advanced++; } if (is_fast) offset = listp->fast_quantum; if (!TIMER_IS_ON_LIST(tp)) { if (!list_locked) { lck_mtx_lock(listp->mtx); list_locked = 1; } LIST_INSERT_HEAD(&listp->lhead, te, le); tp->t_flags |= TF_TIMER_ONLIST; listp->entries++; if (listp->entries > listp->maxentries) listp->maxentries = listp->entries; /* if the list is not scheduled, just schedule it */ if (listp->runtime == 0) goto schedule; } /* timer entry is currently on the list */ if (need_to_resched_timerlist(te->runtime, index)) { tcp_resched_timerlist++; if (!list_locked) { lck_mtx_lock(listp->mtx); list_locked = 1; } VERIFY_NEXT_LINK(te, le); VERIFY_PREV_LINK(te, le); if (listp->running) { if (is_fast) { listp->pref_mode = TCP_TIMERLIST_FASTMODE; } else if (listp->pref_offset == 0 || ((int)offset) < listp->pref_offset) { listp->pref_offset = offset; } } else { int32_t diff; diff = timer_diff(listp->runtime, 0, tcp_now, offset); if (diff <= 0) { /* The list is going to run before this timer */ goto done; } else { goto schedule; } } } goto done; schedule: if (is_fast) { listp->mode = TCP_TIMERLIST_FASTMODE; listp->idlegen = 0; } tcp_sched_timerlist(offset); done: if (list_locked) lck_mtx_unlock(listp->mtx); return; } void tcp_set_lotimer_index(struct tcpcb *tp) { uint16_t i, lo_index = TCPT_NONE; uint32_t lo_timer = 0; for (i = 0; i < TCPT_NTIMERS; ++i) { if (tp->t_timer[i] != 0 && (lo_timer == 0 || tp->t_timer[i] < lo_timer)) { lo_timer = tp->t_timer[i]; lo_index = i; } } tp->tentry.index = lo_index; if (lo_index != TCPT_NONE) { tp->tentry.runtime = tp->tentry.timer_start + tp->t_timer[lo_index]; } else { tp->tentry.runtime = 0; } } void tcp_check_timer_state(struct tcpcb *tp) { lck_mtx_assert(&tp->t_inpcb->inpcb_mtx, LCK_MTX_ASSERT_OWNED); tcp_set_lotimer_index(tp); tcp_sched_timers(tp); return; }