diff options
Diffstat (limited to 'net/ipv4/tcp_input.c')
| -rw-r--r-- | net/ipv4/tcp_input.c | 4959 |
1 files changed, 4959 insertions, 0 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c new file mode 100644 index 00000000000..25049273590 --- /dev/null +++ b/net/ipv4/tcp_input.c @@ -0,0 +1,4959 @@ +/* + * INET An implementation of the TCP/IP protocol suite for the LINUX + * operating system. INET is implemented using the BSD Socket + * interface as the means of communication with the user level. + * + * Implementation of the Transmission Control Protocol(TCP). + * + * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $ + * + * Authors: Ross Biro, <bir7@leland.Stanford.Edu> + * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> + * Mark Evans, <evansmp@uhura.aston.ac.uk> + * Corey Minyard <wf-rch!minyard@relay.EU.net> + * Florian La Roche, <flla@stud.uni-sb.de> + * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> + * Linus Torvalds, <torvalds@cs.helsinki.fi> + * Alan Cox, <gw4pts@gw4pts.ampr.org> + * Matthew Dillon, <dillon@apollo.west.oic.com> + * Arnt Gulbrandsen, <agulbra@nvg.unit.no> + * Jorge Cwik, <jorge@laser.satlink.net> + */ + +/* + * Changes: + * Pedro Roque : Fast Retransmit/Recovery. + * Two receive queues. + * Retransmit queue handled by TCP. + * Better retransmit timer handling. + * New congestion avoidance. + * Header prediction. + * Variable renaming. + * + * Eric : Fast Retransmit. + * Randy Scott : MSS option defines. + * Eric Schenk : Fixes to slow start algorithm. + * Eric Schenk : Yet another double ACK bug. + * Eric Schenk : Delayed ACK bug fixes. + * Eric Schenk : Floyd style fast retrans war avoidance. + * David S. Miller : Don't allow zero congestion window. + * Eric Schenk : Fix retransmitter so that it sends + * next packet on ack of previous packet. + * Andi Kleen : Moved open_request checking here + * and process RSTs for open_requests. + * Andi Kleen : Better prune_queue, and other fixes. + * Andrey Savochkin: Fix RTT measurements in the presnce of + * timestamps. + * Andrey Savochkin: Check sequence numbers correctly when + * removing SACKs due to in sequence incoming + * data segments. + * Andi Kleen: Make sure we never ack data there is not + * enough room for. Also make this condition + * a fatal error if it might still happen. + * Andi Kleen: Add tcp_measure_rcv_mss to make + * connections with MSS<min(MTU,ann. MSS) + * work without delayed acks. + * Andi Kleen: Process packets with PSH set in the + * fast path. + * J Hadi Salim: ECN support + * Andrei Gurtov, + * Pasi Sarolahti, + * Panu Kuhlberg: Experimental audit of TCP (re)transmission + * engine. Lots of bugs are found. + * Pasi Sarolahti: F-RTO for dealing with spurious RTOs + * Angelo Dell'Aera: TCP Westwood+ support + */ + +#include <linux/config.h> +#include <linux/mm.h> +#include <linux/module.h> +#include <linux/sysctl.h> +#include <net/tcp.h> +#include <net/inet_common.h> +#include <linux/ipsec.h> +#include <asm/unaligned.h> + +int sysctl_tcp_timestamps = 1; +int sysctl_tcp_window_scaling = 1; +int sysctl_tcp_sack = 1; +int sysctl_tcp_fack = 1; +int sysctl_tcp_reordering = TCP_FASTRETRANS_THRESH; +int sysctl_tcp_ecn; +int sysctl_tcp_dsack = 1; +int sysctl_tcp_app_win = 31; +int sysctl_tcp_adv_win_scale = 2; + +int sysctl_tcp_stdurg; +int sysctl_tcp_rfc1337; +int sysctl_tcp_max_orphans = NR_FILE; +int sysctl_tcp_frto; +int sysctl_tcp_nometrics_save; +int sysctl_tcp_westwood; +int sysctl_tcp_vegas_cong_avoid; + +int sysctl_tcp_moderate_rcvbuf = 1; + +/* Default values of the Vegas variables, in fixed-point representation + * with V_PARAM_SHIFT bits to the right of the binary point. + */ +#define V_PARAM_SHIFT 1 +int sysctl_tcp_vegas_alpha = 1<<V_PARAM_SHIFT; +int sysctl_tcp_vegas_beta = 3<<V_PARAM_SHIFT; +int sysctl_tcp_vegas_gamma = 1<<V_PARAM_SHIFT; +int sysctl_tcp_bic = 1; +int sysctl_tcp_bic_fast_convergence = 1; +int sysctl_tcp_bic_low_window = 14; +int sysctl_tcp_bic_beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */ + +#define FLAG_DATA 0x01 /* Incoming frame contained data. */ +#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ +#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ +#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ +#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ +#define FLAG_DATA_SACKED 0x20 /* New SACK. */ +#define FLAG_ECE 0x40 /* ECE in this ACK */ +#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ +#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ + +#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) +#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) +#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) +#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) + +#define IsReno(tp) ((tp)->rx_opt.sack_ok == 0) +#define IsFack(tp) ((tp)->rx_opt.sack_ok & 2) +#define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4) + +#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) + +/* Adapt the MSS value used to make delayed ack decision to the + * real world. + */ +static inline void tcp_measure_rcv_mss(struct tcp_sock *tp, + struct sk_buff *skb) +{ + unsigned int len, lss; + + lss = tp->ack.last_seg_size; + tp->ack.last_seg_size = 0; + + /* skb->len may jitter because of SACKs, even if peer + * sends good full-sized frames. + */ + len = skb->len; + if (len >= tp->ack.rcv_mss) { + tp->ack.rcv_mss = len; + } else { + /* Otherwise, we make more careful check taking into account, + * that SACKs block is variable. + * + * "len" is invariant segment length, including TCP header. + */ + len += skb->data - skb->h.raw; + if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) || + /* If PSH is not set, packet should be + * full sized, provided peer TCP is not badly broken. + * This observation (if it is correct 8)) allows + * to handle super-low mtu links fairly. + */ + (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && + !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) { + /* Subtract also invariant (if peer is RFC compliant), + * tcp header plus fixed timestamp option length. + * Resulting "len" is MSS free of SACK jitter. + */ + len -= tp->tcp_header_len; + tp->ack.last_seg_size = len; + if (len == lss) { + tp->ack.rcv_mss = len; + return; + } + } + tp->ack.pending |= TCP_ACK_PUSHED; + } +} + +static void tcp_incr_quickack(struct tcp_sock *tp) +{ + unsigned quickacks = tp->rcv_wnd/(2*tp->ack.rcv_mss); + + if (quickacks==0) + quickacks=2; + if (quickacks > tp->ack.quick) + tp->ack.quick = min(quickacks, TCP_MAX_QUICKACKS); +} + +void tcp_enter_quickack_mode(struct tcp_sock *tp) +{ + tcp_incr_quickack(tp); + tp->ack.pingpong = 0; + tp->ack.ato = TCP_ATO_MIN; +} + +/* Send ACKs quickly, if "quick" count is not exhausted + * and the session is not interactive. + */ + +static __inline__ int tcp_in_quickack_mode(struct tcp_sock *tp) +{ + return (tp->ack.quick && !tp->ack.pingpong); +} + +/* Buffer size and advertised window tuning. + * + * 1. Tuning sk->sk_sndbuf, when connection enters established state. + */ + +static void tcp_fixup_sndbuf(struct sock *sk) +{ + int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + + sizeof(struct sk_buff); + + if (sk->sk_sndbuf < 3 * sndmem) + sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]); +} + +/* 2. Tuning advertised window (window_clamp, rcv_ssthresh) + * + * All tcp_full_space() is split to two parts: "network" buffer, allocated + * forward and advertised in receiver window (tp->rcv_wnd) and + * "application buffer", required to isolate scheduling/application + * latencies from network. + * window_clamp is maximal advertised window. It can be less than + * tcp_full_space(), in this case tcp_full_space() - window_clamp + * is reserved for "application" buffer. The less window_clamp is + * the smoother our behaviour from viewpoint of network, but the lower + * throughput and the higher sensitivity of the connection to losses. 8) + * + * rcv_ssthresh is more strict window_clamp used at "slow start" + * phase to predict further behaviour of this connection. + * It is used for two goals: + * - to enforce header prediction at sender, even when application + * requires some significant "application buffer". It is check #1. + * - to prevent pruning of receive queue because of misprediction + * of receiver window. Check #2. + * + * The scheme does not work when sender sends good segments opening + * window and then starts to feed us spagetti. But it should work + * in common situations. Otherwise, we have to rely on queue collapsing. + */ + +/* Slow part of check#2. */ +static int __tcp_grow_window(struct sock *sk, struct tcp_sock *tp, + struct sk_buff *skb) +{ + /* Optimize this! */ + int truesize = tcp_win_from_space(skb->truesize)/2; + int window = tcp_full_space(sk)/2; + + while (tp->rcv_ssthresh <= window) { + if (truesize <= skb->len) + return 2*tp->ack.rcv_mss; + + truesize >>= 1; + window >>= 1; + } + return 0; +} + +static inline void tcp_grow_window(struct sock *sk, struct tcp_sock *tp, + struct sk_buff *skb) +{ + /* Check #1 */ + if (tp->rcv_ssthresh < tp->window_clamp && + (int)tp->rcv_ssthresh < tcp_space(sk) && + !tcp_memory_pressure) { + int incr; + + /* Check #2. Increase window, if skb with such overhead + * will fit to rcvbuf in future. + */ + if (tcp_win_from_space(skb->truesize) <= skb->len) + incr = 2*tp->advmss; + else + incr = __tcp_grow_window(sk, tp, skb); + + if (incr) { + tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp); + tp->ack.quick |= 1; + } + } +} + +/* 3. Tuning rcvbuf, when connection enters established state. */ + +static void tcp_fixup_rcvbuf(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); + + /* Try to select rcvbuf so that 4 mss-sized segments + * will fit to window and correspoding skbs will fit to our rcvbuf. + * (was 3; 4 is minimum to allow fast retransmit to work.) + */ + while (tcp_win_from_space(rcvmem) < tp->advmss) + rcvmem += 128; + if (sk->sk_rcvbuf < 4 * rcvmem) + sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); +} + +/* 4. Try to fixup all. It is made iimediately after connection enters + * established state. + */ +static void tcp_init_buffer_space(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + int maxwin; + + if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) + tcp_fixup_rcvbuf(sk); + if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) + tcp_fixup_sndbuf(sk); + + tp->rcvq_space.space = tp->rcv_wnd; + + maxwin = tcp_full_space(sk); + + if (tp->window_clamp >= maxwin) { + tp->window_clamp = maxwin; + + if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) + tp->window_clamp = max(maxwin - + (maxwin >> sysctl_tcp_app_win), + 4 * tp->advmss); + } + + /* Force reservation of one segment. */ + if (sysctl_tcp_app_win && + tp->window_clamp > 2 * tp->advmss && + tp->window_clamp + tp->advmss > maxwin) + tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); + + tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +static void init_bictcp(struct tcp_sock *tp) +{ + tp->bictcp.cnt = 0; + + tp->bictcp.last_max_cwnd = 0; + tp->bictcp.last_cwnd = 0; + tp->bictcp.last_stamp = 0; +} + +/* 5. Recalculate window clamp after socket hit its memory bounds. */ +static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp) +{ + struct sk_buff *skb; + unsigned int app_win = tp->rcv_nxt - tp->copied_seq; + int ofo_win = 0; + + tp->ack.quick = 0; + + skb_queue_walk(&tp->out_of_order_queue, skb) { + ofo_win += skb->len; + } + + /* If overcommit is due to out of order segments, + * do not clamp window. Try to expand rcvbuf instead. + */ + if (ofo_win) { + if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && + !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && + !tcp_memory_pressure && + atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) + sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), + sysctl_tcp_rmem[2]); + } + if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) { + app_win += ofo_win; + if (atomic_read(&sk->sk_rmem_alloc) >= 2 * sk->sk_rcvbuf) + app_win >>= 1; + if (app_win > tp->ack.rcv_mss) + app_win -= tp->ack.rcv_mss; + app_win = max(app_win, 2U*tp->advmss); + + if (!ofo_win) + tp->window_clamp = min(tp->window_clamp, app_win); + tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss); + } +} + +/* Receiver "autotuning" code. + * + * The algorithm for RTT estimation w/o timestamps is based on + * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. + * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> + * + * More detail on this code can be found at + * <http://www.psc.edu/~jheffner/senior_thesis.ps>, + * though this reference is out of date. A new paper + * is pending. + */ +static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) +{ + u32 new_sample = tp->rcv_rtt_est.rtt; + long m = sample; + + if (m == 0) + m = 1; + + if (new_sample != 0) { + /* If we sample in larger samples in the non-timestamp + * case, we could grossly overestimate the RTT especially + * with chatty applications or bulk transfer apps which + * are stalled on filesystem I/O. + * + * Also, since we are only going for a minimum in the + * non-timestamp case, we do not smoothe things out + * else with timestamps disabled convergance takes too + * long. + */ + if (!win_dep) { + m -= (new_sample >> 3); + new_sample += m; + } else if (m < new_sample) + new_sample = m << 3; + } else { + /* No previous mesaure. */ + new_sample = m << 3; + } + + if (tp->rcv_rtt_est.rtt != new_sample) + tp->rcv_rtt_est.rtt = new_sample; +} + +static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) +{ + if (tp->rcv_rtt_est.time == 0) + goto new_measure; + if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) + return; + tcp_rcv_rtt_update(tp, + jiffies - tp->rcv_rtt_est.time, + 1); + +new_measure: + tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; + tp->rcv_rtt_est.time = tcp_time_stamp; +} + +static inline void tcp_rcv_rtt_measure_ts(struct tcp_sock *tp, struct sk_buff *skb) +{ + if (tp->rx_opt.rcv_tsecr && + (TCP_SKB_CB(skb)->end_seq - + TCP_SKB_CB(skb)->seq >= tp->ack.rcv_mss)) + tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); +} + +/* + * This function should be called every time data is copied to user space. + * It calculates the appropriate TCP receive buffer space. + */ +void tcp_rcv_space_adjust(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + int time; + int space; + + if (tp->rcvq_space.time == 0) + goto new_measure; + + time = tcp_time_stamp - tp->rcvq_space.time; + if (time < (tp->rcv_rtt_est.rtt >> 3) || + tp->rcv_rtt_est.rtt == 0) + return; + + space = 2 * (tp->copied_seq - tp->rcvq_space.seq); + + space = max(tp->rcvq_space.space, space); + + if (tp->rcvq_space.space != space) { + int rcvmem; + + tp->rcvq_space.space = space; + + if (sysctl_tcp_moderate_rcvbuf) { + int new_clamp = space; + + /* Receive space grows, normalize in order to + * take into account packet headers and sk_buff + * structure overhead. + */ + space /= tp->advmss; + if (!space) + space = 1; + rcvmem = (tp->advmss + MAX_TCP_HEADER + + 16 + sizeof(struct sk_buff)); + while (tcp_win_from_space(rcvmem) < tp->advmss) + rcvmem += 128; + space *= rcvmem; + space = min(space, sysctl_tcp_rmem[2]); + if (space > sk->sk_rcvbuf) { + sk->sk_rcvbuf = space; + + /* Make the window clamp follow along. */ + tp->window_clamp = new_clamp; + } + } + } + +new_measure: + tp->rcvq_space.seq = tp->copied_seq; + tp->rcvq_space.time = tcp_time_stamp; +} + +/* There is something which you must keep in mind when you analyze the + * behavior of the tp->ato delayed ack timeout interval. When a + * connection starts up, we want to ack as quickly as possible. The + * problem is that "good" TCP's do slow start at the beginning of data + * transmission. The means that until we send the first few ACK's the + * sender will sit on his end and only queue most of his data, because + * he can only send snd_cwnd unacked packets at any given time. For + * each ACK we send, he increments snd_cwnd and transmits more of his + * queue. -DaveM + */ +static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb) +{ + u32 now; + + tcp_schedule_ack(tp); + + tcp_measure_rcv_mss(tp, skb); + + tcp_rcv_rtt_measure(tp); + + now = tcp_time_stamp; + + if (!tp->ack.ato) { + /* The _first_ data packet received, initialize + * delayed ACK engine. + */ + tcp_incr_quickack(tp); + tp->ack.ato = TCP_ATO_MIN; + } else { + int m = now - tp->ack.lrcvtime; + + if (m <= TCP_ATO_MIN/2) { + /* The fastest case is the first. */ + tp->ack.ato = (tp->ack.ato>>1) + TCP_ATO_MIN/2; + } else if (m < tp->ack.ato) { + tp->ack.ato = (tp->ack.ato>>1) + m; + if (tp->ack.ato > tp->rto) + tp->ack.ato = tp->rto; + } else if (m > tp->rto) { + /* Too long gap. Apparently sender falled to + * restart window, so that we send ACKs quickly. + */ + tcp_incr_quickack(tp); + sk_stream_mem_reclaim(sk); + } + } + tp->ack.lrcvtime = now; + + TCP_ECN_check_ce(tp, skb); + + if (skb->len >= 128) + tcp_grow_window(sk, tp, skb); +} + +/* When starting a new connection, pin down the current choice of + * congestion algorithm. + */ +void tcp_ca_init(struct tcp_sock *tp) +{ + if (sysctl_tcp_westwood) + tp->adv_cong = TCP_WESTWOOD; + else if (sysctl_tcp_bic) + tp->adv_cong = TCP_BIC; + else if (sysctl_tcp_vegas_cong_avoid) { + tp->adv_cong = TCP_VEGAS; + tp->vegas.baseRTT = 0x7fffffff; + tcp_vegas_enable(tp); + } +} + +/* Do RTT sampling needed for Vegas. + * Basically we: + * o min-filter RTT samples from within an RTT to get the current + * propagation delay + queuing delay (we are min-filtering to try to + * avoid the effects of delayed ACKs) + * o min-filter RTT samples from a much longer window (forever for now) + * to find the propagation delay (baseRTT) + */ +static inline void vegas_rtt_calc(struct tcp_sock *tp, __u32 rtt) +{ + __u32 vrtt = rtt + 1; /* Never allow zero rtt or baseRTT */ + + /* Filter to find propagation delay: */ + if (vrtt < tp->vegas.baseRTT) + tp->vegas.baseRTT = vrtt; + + /* Find the min RTT during the last RTT to find + * the current prop. delay + queuing delay: + */ + tp->vegas.minRTT = min(tp->vegas.minRTT, vrtt); + tp->vegas.cntRTT++; +} + +/* Called to compute a smoothed rtt estimate. The data fed to this + * routine either comes from timestamps, or from segments that were + * known _not_ to have been retransmitted [see Karn/Partridge + * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 + * piece by Van Jacobson. + * NOTE: the next three routines used to be one big routine. + * To save cycles in the RFC 1323 implementation it was better to break + * it up into three procedures. -- erics + */ +static void tcp_rtt_estimator(struct tcp_sock *tp, __u32 mrtt) +{ + long m = mrtt; /* RTT */ + + if (tcp_vegas_enabled(tp)) + vegas_rtt_calc(tp, mrtt); + + /* The following amusing code comes from Jacobson's + * article in SIGCOMM '88. Note that rtt and mdev + * are scaled versions of rtt and mean deviation. + * This is designed to be as fast as possible + * m stands for "measurement". + * + * On a 1990 paper the rto value is changed to: + * RTO = rtt + 4 * mdev + * + * Funny. This algorithm seems to be very broken. + * These formulae increase RTO, when it should be decreased, increase + * too slowly, when it should be incresed fastly, decrease too fastly + * etc. I guess in BSD RTO takes ONE value, so that it is absolutely + * does not matter how to _calculate_ it. Seems, it was trap + * that VJ failed to avoid. 8) + */ + if(m == 0) + m = 1; + if (tp->srtt != 0) { + m -= (tp->srtt >> 3); /* m is now error in rtt est */ + tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ + if (m < 0) { + m = -m; /* m is now abs(error) */ + m -= (tp->mdev >> 2); /* similar update on mdev */ + /* This is similar to one of Eifel findings. + * Eifel blocks mdev updates when rtt decreases. + * This solution is a bit different: we use finer gain + * for mdev in this case (alpha*beta). + * Like Eifel it also prevents growth of rto, + * but also it limits too fast rto decreases, + * happening in pure Eifel. + */ + if (m > 0) + m >>= 3; + } else { + m -= (tp->mdev >> 2); /* similar update on mdev */ + } + tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ + if (tp->mdev > tp->mdev_max) { + tp->mdev_max = tp->mdev; + if (tp->mdev_max > tp->rttvar) + tp->rttvar = tp->mdev_max; + } + if (after(tp->snd_una, tp->rtt_seq)) { + if (tp->mdev_max < tp->rttvar) + tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2; + tp->rtt_seq = tp->snd_nxt; + tp->mdev_max = TCP_RTO_MIN; + } + } else { + /* no previous measure. */ + tp->srtt = m<<3; /* take the measured time to be rtt */ + tp->mdev = m<<1; /* make sure rto = 3*rtt */ + tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); + tp->rtt_seq = tp->snd_nxt; + } + + tcp_westwood_update_rtt(tp, tp->srtt >> 3); +} + +/* Calculate rto without backoff. This is the second half of Van Jacobson's + * routine referred to above. + */ +static inline void tcp_set_rto(struct tcp_sock *tp) +{ + /* Old crap is replaced with new one. 8) + * + * More seriously: + * 1. If rtt variance happened to be less 50msec, it is hallucination. + * It cannot be less due to utterly erratic ACK generation made + * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ + * to do with delayed acks, because at cwnd>2 true delack timeout + * is invisible. Actually, Linux-2.4 also generates erratic + * ACKs in some curcumstances. + */ + tp->rto = (tp->srtt >> 3) + tp->rttvar; + + /* 2. Fixups made earlier cannot be right. + * If we do not estimate RTO correctly without them, + * all the algo is pure shit and should be replaced + * with correct one. It is exaclty, which we pretend to do. + */ +} + +/* NOTE: clamping at TCP_RTO_MIN is not required, current algo + * guarantees that rto is higher. + */ +static inline void tcp_bound_rto(struct tcp_sock *tp) +{ + if (tp->rto > TCP_RTO_MAX) + tp->rto = TCP_RTO_MAX; +} + +/* Save metrics learned by this TCP session. + This function is called only, when TCP finishes successfully + i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. + */ +void tcp_update_metrics(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct dst_entry *dst = __sk_dst_get(sk); + + if (sysctl_tcp_nometrics_save) + return; + + dst_confirm(dst); + + if (dst && (dst->flags&DST_HOST)) { + int m; + + if (tp->backoff || !tp->srtt) { + /* This session failed to estimate rtt. Why? + * Probably, no packets returned in time. + * Reset our results. + */ + if (!(dst_metric_locked(dst, RTAX_RTT))) + dst->metrics[RTAX_RTT-1] = 0; + return; + } + + m = dst_metric(dst, RTAX_RTT) - tp->srtt; + + /* If newly calculated rtt larger than stored one, + * store new one. Otherwise, use EWMA. Remember, + * rtt overestimation is always better than underestimation. + */ + if (!(dst_metric_locked(dst, RTAX_RTT))) { + if (m <= 0) + dst->metrics[RTAX_RTT-1] = tp->srtt; + else + dst->metrics[RTAX_RTT-1] -= (m>>3); + } + + if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { + if (m < 0) + m = -m; + + /* Scale deviation to rttvar fixed point */ + m >>= 1; + if (m < tp->mdev) + m = tp->mdev; + + if (m >= dst_metric(dst, RTAX_RTTVAR)) + dst->metrics[RTAX_RTTVAR-1] = m; + else + dst->metrics[RTAX_RTTVAR-1] -= + (dst->metrics[RTAX_RTTVAR-1] - m)>>2; + } + + if (tp->snd_ssthresh >= 0xFFFF) { + /* Slow start still did not finish. */ + if (dst_metric(dst, RTAX_SSTHRESH) && + !dst_metric_locked(dst, RTAX_SSTHRESH) && + (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) + dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; + if (!dst_metric_locked(dst, RTAX_CWND) && + tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) + dst->metrics[RTAX_CWND-1] = tp->snd_cwnd; + } else if (tp->snd_cwnd > tp->snd_ssthresh && + tp->ca_state == TCP_CA_Open) { + /* Cong. avoidance phase, cwnd is reliable. */ + if (!dst_metric_locked(dst, RTAX_SSTHRESH)) + dst->metrics[RTAX_SSTHRESH-1] = + max(tp->snd_cwnd >> 1, tp->snd_ssthresh); + if (!dst_metric_locked(dst, RTAX_CWND)) + dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1; + } else { + /* Else slow start did not finish, cwnd is non-sense, + ssthresh may be also invalid. + */ + if (!dst_metric_locked(dst, RTAX_CWND)) + dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1; + if (dst->metrics[RTAX_SSTHRESH-1] && + !dst_metric_locked(dst, RTAX_SSTHRESH) && + tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1]) + dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; + } + + if (!dst_metric_locked(dst, RTAX_REORDERING)) { + if (dst->metrics[RTAX_REORDERING-1] < tp->reordering && + tp->reordering != sysctl_tcp_reordering) + dst->metrics[RTAX_REORDERING-1] = tp->reordering; + } + } +} + +/* Numbers are taken from RFC2414. */ +__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) +{ + __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); + + if (!cwnd) { + if (tp->mss_cache_std > 1460) + cwnd = 2; + else + cwnd = (tp->mss_cache_std > 1095) ? 3 : 4; + } + return min_t(__u32, cwnd, tp->snd_cwnd_clamp); +} + +/* Initialize metrics on socket. */ + +static void tcp_init_metrics(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct dst_entry *dst = __sk_dst_get(sk); + + if (dst == NULL) + goto reset; + + dst_confirm(dst); + + if (dst_metric_locked(dst, RTAX_CWND)) + tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); + if (dst_metric(dst, RTAX_SSTHRESH)) { + tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); + if (tp->snd_ssthresh > tp->snd_cwnd_clamp) + tp->snd_ssthresh = tp->snd_cwnd_clamp; + } + if (dst_metric(dst, RTAX_REORDERING) && + tp->reordering != dst_metric(dst, RTAX_REORDERING)) { + tp->rx_opt.sack_ok &= ~2; + tp->reordering = dst_metric(dst, RTAX_REORDERING); + } + + if (dst_metric(dst, RTAX_RTT) == 0) + goto reset; + + if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) + goto reset; + + /* Initial rtt is determined from SYN,SYN-ACK. + * The segment is small and rtt may appear much + * less than real one. Use per-dst memory + * to make it more realistic. + * + * A bit of theory. RTT is time passed after "normal" sized packet + * is sent until it is ACKed. In normal curcumstances sending small + * packets force peer to delay ACKs and calculation is correct too. + * The algorithm is adaptive and, provided we follow specs, it + * NEVER underestimate RTT. BUT! If peer tries to make some clever + * tricks sort of "quick acks" for time long enough to decrease RTT + * to low value, and then abruptly stops to do it and starts to delay + * ACKs, wait for troubles. + */ + if (dst_metric(dst, RTAX_RTT) > tp->srtt) { + tp->srtt = dst_metric(dst, RTAX_RTT); + tp->rtt_seq = tp->snd_nxt; + } + if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) { + tp->mdev = dst_metric(dst, RTAX_RTTVAR); + tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); + } + tcp_set_rto(tp); + tcp_bound_rto(tp); + if (tp->rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) + goto reset; + tp->snd_cwnd = tcp_init_cwnd(tp, dst); + tp->snd_cwnd_stamp = tcp_time_stamp; + return; + +reset: + /* Play conservative. If timestamps are not + * supported, TCP will fail to recalculate correct + * rtt, if initial rto is too small. FORGET ALL AND RESET! + */ + if (!tp->rx_opt.saw_tstamp && tp->srtt) { + tp->srtt = 0; + tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; + tp->rto = TCP_TIMEOUT_INIT; + } +} + +static void tcp_update_reordering(struct tcp_sock *tp, int metric, int ts) +{ + if (metric > tp->reordering) { + tp->reordering = min(TCP_MAX_REORDERING, metric); + + /* This exciting event is worth to be remembered. 8) */ + if (ts) + NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER); + else if (IsReno(tp)) + NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER); + else if (IsFack(tp)) + NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER); + else + NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER); +#if FASTRETRANS_DEBUG > 1 + printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", + tp->rx_opt.sack_ok, tp->ca_state, + tp->reordering, + tp->fackets_out, + tp->sacked_out, + tp->undo_marker ? tp->undo_retrans : 0); +#endif + /* Disable FACK yet. */ + tp->rx_opt.sack_ok &= ~2; + } +} + +/* This procedure tags the retransmission queue when SACKs arrive. + * + * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). + * Packets in queue with these bits set are counted in variables + * sacked_out, retrans_out and lost_out, correspondingly. + * + * Valid combinations are: + * Tag InFlight Description + * 0 1 - orig segment is in flight. + * S 0 - nothing flies, orig reached receiver. + * L 0 - nothing flies, orig lost by net. + * R 2 - both orig and retransmit are in flight. + * L|R 1 - orig is lost, retransmit is in flight. + * S|R 1 - orig reached receiver, retrans is still in flight. + * (L|S|R is logically valid, it could occur when L|R is sacked, + * but it is equivalent to plain S and code short-curcuits it to S. + * L|S is logically invalid, it would mean -1 packet in flight 8)) + * + * These 6 states form finite state machine, controlled by the following events: + * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) + * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) + * 3. Loss detection event of one of three flavors: + * A. Scoreboard estimator decided the packet is lost. + * A'. Reno "three dupacks" marks head of queue lost. + * A''. Its FACK modfication, head until snd.fack is lost. + * B. SACK arrives sacking data transmitted after never retransmitted + * hole was sent out. + * C. SACK arrives sacking SND.NXT at the moment, when the + * segment was retransmitted. + * 4. D-SACK added new rule: D-SACK changes any tag to S. + * + * It is pleasant to note, that state diagram turns out to be commutative, + * so that we are allowed not to be bothered by order of our actions, + * when multiple events arrive simultaneously. (see the function below). + * + * Reordering detection. + * -------------------- + * Reordering metric is maximal distance, which a packet can be displaced + * in packet stream. With SACKs we can estimate it: + * + * 1. SACK fills old hole and the corresponding segment was not + * ever retransmitted -> reordering. Alas, we cannot use it + * when segment was retransmitted. + * 2. The last flaw is solved with D-SACK. D-SACK arrives + * for retransmitted and already SACKed segment -> reordering.. + * Both of these heuristics are not used in Loss state, when we cannot + * account for retransmits accurately. + */ +static int +tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una) +{ + struct tcp_sock *tp = tcp_sk(sk); + unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked; + struct tcp_sack_block *sp = (struct tcp_sack_block *)(ptr+2); + int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3; + int reord = tp->packets_out; + int prior_fackets; + u32 lost_retrans = 0; + int flag = 0; + int i; + + /* So, SACKs for already sent large segments will be lost. + * Not good, but alternative is to resegment the queue. */ + if (sk->sk_route_caps & NETIF_F_TSO) { + sk->sk_route_caps &= ~NETIF_F_TSO; + sock_set_flag(sk, SOCK_NO_LARGESEND); + tp->mss_cache = tp->mss_cache_std; + } + + if (!tp->sacked_out) + tp->fackets_out = 0; + prior_fackets = tp->fackets_out; + + for (i=0; i<num_sacks; i++, sp++) { + struct sk_buff *skb; + __u32 start_seq = ntohl(sp->start_seq); + __u32 end_seq = ntohl(sp->end_seq); + int fack_count = 0; + int dup_sack = 0; + + /* Check for D-SACK. */ + if (i == 0) { + u32 ack = TCP_SKB_CB(ack_skb)->ack_seq; + + if (before(start_seq, ack)) { + dup_sack = 1; + tp->rx_opt.sack_ok |= 4; + NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV); + } else if (num_sacks > 1 && + !after(end_seq, ntohl(sp[1].end_seq)) && + !before(start_seq, ntohl(sp[1].start_seq))) { + dup_sack = 1; + tp->rx_opt.sack_ok |= 4; + NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV); + } + + /* D-SACK for already forgotten data... + * Do dumb counting. */ + if (dup_sack && + !after(end_seq, prior_snd_una) && + after(end_seq, tp->undo_marker)) + tp->undo_retrans--; + + /* Eliminate too old ACKs, but take into + * account more or less fresh ones, they can + * contain valid SACK info. + */ + if (before(ack, prior_snd_una - tp->max_window)) + return 0; + } + + /* Event "B" in the comment above. */ + if (after(end_seq, tp->high_seq)) + flag |= FLAG_DATA_LOST; + + sk_stream_for_retrans_queue(skb, sk) { + u8 sacked = TCP_SKB_CB(skb)->sacked; + int in_sack; + + /* The retransmission queue is always in order, so + * we can short-circuit the walk early. + */ + if(!before(TCP_SKB_CB(skb)->seq, end_seq)) + break; + + fack_count += tcp_skb_pcount(skb); + + in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && + !before(end_seq, TCP_SKB_CB(skb)->end_seq); + + /* Account D-SACK for retransmitted packet. */ + if ((dup_sack && in_sack) && + (sacked & TCPCB_RETRANS) && + after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) + tp->undo_retrans--; + + /* The frame is ACKed. */ + if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) { + if (sacked&TCPCB_RETRANS) { + if ((dup_sack && in_sack) && + (sacked&TCPCB_SACKED_ACKED)) + reord = min(fack_count, reord); + } else { + /* If it was in a hole, we detected reordering. */ + if (fack_count < prior_fackets && + !(sacked&TCPCB_SACKED_ACKED)) + reord = min(fack_count, reord); + } + + /* Nothing to do; acked frame is about to be dropped. */ + continue; + } + + if ((sacked&TCPCB_SACKED_RETRANS) && + after(end_seq, TCP_SKB_CB(skb)->ack_seq) && + (!lost_retrans || after(end_seq, lost_retrans))) + lost_retrans = end_seq; + + if (!in_sack) + continue; + + if (!(sacked&TCPCB_SACKED_ACKED)) { |