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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.h 8.1 (Berkeley) 6/10/93 * $FreeBSD: src/sys/netinet/tcp_timer.h,v 1.18 1999/12/29 04:41:03 peter Exp $ */ #ifndef _NETINET_TCP_TIMER_H_ #define _NETINET_TCP_TIMER_H_ #include <sys/appleapiopts.h> #ifdef KERNEL #include <kern/thread_call.h> #endif /* KERNEL */ /* * Definitions of the TCP timers. */ #define TCPT_NTIMERS 5 /* Keep the external definition the same for binary compatibility */ #define TCPT_NTIMERS_EXT 4 #define TCPT_REXMT 0 /* retransmit */ #define TCPT_PERSIST 1 /* retransmit persistence */ #define TCPT_KEEP 2 /* keep alive */ #define TCPT_2MSL 3 /* 2*msl quiet time timer */ #define TCPT_DELACK 4 /* delayed ack timer */ #define TCPT_MAX 4 #define TCPT_NONE (TCPT_MAX + 1) /* * The TCPT_REXMT timer is used to force retransmissions. * The TCP has the TCPT_REXMT timer set whenever segments * have been sent for which ACKs are expected but not yet * received. If an ACK is received which advances tp->snd_una, * then the retransmit timer is cleared (if there are no more * outstanding segments) or reset to the base value (if there * are more ACKs expected). Whenever the retransmit timer goes off, * we retransmit one unacknowledged segment, and do a backoff * on the retransmit timer. * * The TCPT_PERSIST timer is used to keep window size information * flowing even if the window goes shut. If all previous transmissions * have been acknowledged (so that there are no retransmissions in progress), * and the window is too small to bother sending anything, then we start * the TCPT_PERSIST timer. When it expires, if the window is nonzero, * we go to transmit state. Otherwise, at intervals send a single byte * into the peer's window to force him to update our window information. * We do this at most as often as TCPT_PERSMIN time intervals, * but no more frequently than the current estimate of round-trip * packet time. The TCPT_PERSIST timer is cleared whenever we receive * a window update from the peer. * * The TCPT_KEEP timer is used to keep connections alive. If an * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, * but not yet established, then we drop the connection. Once the connection * is established, if the connection is idle for TCPTV_KEEP_IDLE time * (and keepalives have been enabled on the socket), we begin to probe * the connection. We force the peer to send us a segment by sending: * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> * This segment is (deliberately) outside the window, and should elicit * an ack segment in response from the peer. If, despite the TCPT_KEEP * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE * amount of time probing, then we drop the connection. */ #ifdef PRIVATE /* * Time constants. */ #define TCPTV_MSL ( 15*TCP_RETRANSHZ) /* max seg lifetime (hah!) */ #define TCPTV_SRTTBASE 0 /* base roundtrip time; if 0, no idea yet */ #define TCPTV_RTOBASE ( 1*TCP_RETRANSHZ) /* assumed RTO if no info */ #define TCPTV_SRTTDFLT ( 1*TCP_RETRANSHZ) /* assumed RTT if no info */ #define TCPTV_PERSMIN ( 5*TCP_RETRANSHZ) /* retransmit persistence */ #define TCPTV_PERSMAX ( 60*TCP_RETRANSHZ) /* maximum persist interval */ #define TCPTV_KEEP_INIT ( 75*TCP_RETRANSHZ) /* initial connect keep alive */ #define TCPTV_KEEP_IDLE (120*60*TCP_RETRANSHZ) /* dflt time before probing */ #define TCPTV_KEEPINTVL ( 75*TCP_RETRANSHZ) /* default probe interval */ #define TCPTV_KEEPCNT 8 /* max probes before drop */ #define TCPTV_REXMTMAX ( 64*TCP_RETRANSHZ ) /* max allowable REXMT value */ #define TCPTV_REXMTMIN ( TCP_RETRANSHZ/33 ) /* min REXMT for non-local connections */ #define TCPTV_UNACKWIN ( TCP_RETRANSHZ/10 ) /* Window for counting rcv bytes to see if ack-stretching can start (default 100 ms) */ #define TCPTV_MAXRCVIDLE (TCP_RETRANSHZ/5 ) /* Receiver idle time, avoid ack-stretching after that*/ #define TCPTV_RCVBUFIDLE (TCP_RETRANSHZ/2) /* Receiver idle time, for rcv socket buffer resizing */ /* No ack stretching during slow-start, until we see some packets. * By the time the receiver gets 512 packets, the senders cwnd * should open by a few hundred packets consdering the * slow-start progression. */ #define TCP_RCV_SS_PKTCOUNT 512 #define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ #ifdef TCPTIMERS static char *tcptimers[] = { "REXMT", "PERSIST", "KEEP", "2MSL" , "DELACK"}; #endif #ifdef KERNEL /* We consider persist, keep and 2msl as slow timers which can be coalesced * at a higher granularity (500 ms). Rexmt and delayed ack are considered fast * timers which fire in the order of 100ms. * * The following conditional is to check if a timer is one of the slow timers. This * is fast and works well for now. If we add more slow timers for any reason, * we may need to change this. */ #define IS_TIMER_SLOW(ind) ((ind & 0x3) != 0) struct tcptimerlist; struct tcptimerentry { LIST_ENTRY(tcptimerentry) le; /* links for timer list */ uint32_t timer_start; /* tcp clock when the timer was started */ uint16_t index; /* index of lowest timer that needs to run first */ uint32_t runtime; /* deadline at which the first timer has to fire */ }; LIST_HEAD(timerlisthead, tcptimerentry); struct tcptimerlist { struct timerlisthead lhead; /* head of the list of timer entries */ lck_mtx_t *mtx; /* lock to protect the list */ lck_attr_t *mtx_attr; /* mutex attributes */ lck_grp_t *mtx_grp; /* mutex group definition */ lck_grp_attr_t *mtx_grp_attr; /* mutex group attributes */ uint32_t fast_quantum; /* minimum time quantum to coalesce fast timers */ uint32_t slow_quantum; /* minimum time quantum to coalesce slow timers */ thread_call_t call; /* call entry */ uint32_t runtime; /* time at which this list is going to run */ uint32_t entries; /* Number of entries on the list */ uint32_t maxentries; /* Max number of entries at any time */ /* Set desired mode when timer list running */ boolean_t running; /* Set when timer list is being processed */ #define TCP_TIMERLIST_FASTMODE 0x1 #define TCP_TIMERLIST_SLOWMODE 0x2 uint32_t mode; /* Current mode, fast or slow */ uint32_t pref_mode; /* Preferred mode set by a connection, fast or slow */ uint32_t pref_offset; /* Preferred offset set by a connection */ uint32_t idlegen; /* Number of times the list has been idle in fast mode */ struct tcptimerentry *next_te; /* Store the next timer entry pointer to process */ }; #define TCP_FASTMODE_IDLEGEN_MAX 20 /* Approximately 2 seconds */ /* * Minimum retransmit timeout is set to 30ms. We add a slop of * 200 ms to the retransmit value to account for processing * variance and delayed ack. This extra 200ms will help to avoid * spurious retransmits by taking into consideration the receivers * that wait for delayed ack timer instead of generating an ack * for every two packets. * * On a local link, the minimum retransmit timeout is 100ms and * variance is set to 0. This will make the sender a little bit more * aggressive on local link. When the connection is not established yet, * there is no need to add an extra 200ms to retransmit timeout because * the initial value is high (1s) and delayed ack is not a problem in * that case. */ #define TCPTV_REXMTSLOP ( TCP_RETRANSHZ/5 ) /* rexmt slop allowed (200 ms) */ /* macro to decide when retransmit slop (described above) should be added */ #define TCP_ADD_REXMTSLOP(tp) (tp->t_state >= TCPS_ESTABLISHED) #define TCPT_RANGESET(tv, value, tvmin, tvmax, addslop) do { \ (tv) = ((addslop) ? tcp_rexmt_slop : 0) + (value); \ if ((uint32_t)(tv) < (uint32_t)(tvmin)) \ (tv) = (tvmin); \ else if ((uint32_t)(tv) > (uint32_t)(tvmax)) \ (tv) = (tvmax); \ } while(0) #define TCP_KEEPIDLE(tp) \ (tp->t_keepidle && (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) ? \ tp->t_keepidle : tcp_keepidle) /* Since we did not add rexmt slop for local connections, we should add * it to idle timeout. Otherwise local connections will reach idle state * quickly */ #define TCP_IDLETIMEOUT(tp) \ (((TCP_ADD_REXMTSLOP(tp)) ? 0 : tcp_rexmt_slop) + tp->t_rxtcur) extern int tcp_keepinit; /* time to establish connection */ extern int tcp_keepidle; /* time before keepalive probes begin */ extern int tcp_keepintvl; /* time between keepalive probes */ extern int tcp_maxidle; /* time to drop after starting probes */ extern int tcp_delack; /* delayed ack timer */ extern int tcp_maxpersistidle; extern int tcp_msl; extern int tcp_ttl; /* time to live for TCP segs */ extern int tcp_backoff[]; extern int tcp_rexmt_slop; extern u_int32_t tcp_max_persist_timeout; /* Maximum persistence for Zero Window Probes */ #define OFFSET_FROM_START(tp, off) ((tcp_now + (off)) - (tp)->tentry.timer_start) #endif /* KERNEL */ #endif /* PRIVATE */ #endif /* !_NETINET_TCP_TIMER_H_ */