lsquic_sfcw.c revision 06b2a236 
1/* Copyright (c) 2017 - 2021 LiteSpeed Technologies Inc.  See LICENSE. */
2#include <inttypes.h>
3#include <stdint.h>
4#include <stdlib.h>
5#include <string.h>
6#include <sys/queue.h>
7
8#include "lsquic.h"
9#include "lsquic_int_types.h"
10#include "lsquic_conn_flow.h"
11#include "lsquic_types.h"
12#include "lsquic_rtt.h"
13#include "lsquic_varint.h"
14#include "lsquic_sfcw.h"
15#include "lsquic_hq.h"
16#include "lsquic_hash.h"
17#include "lsquic_stream.h"
18#include "lsquic_conn_public.h"
19#include "lsquic_mm.h"
20#include "lsquic_engine_public.h"
21#include "lsquic_util.h"
22#include "lsquic_conn.h"
23#include "lsquic_ev_log.h"
24
25#define LSQUIC_LOGGER_MODULE LSQLM_SFCW
26#define LSQUIC_LOG_CONN_ID lsquic_conn_log_cid(fc->sf_conn_pub->lconn)
27#define LSQUIC_LOG_STREAM_ID fc->sf_stream_id
28#include "lsquic_logger.h"
29
30void
31lsquic_sfcw_init (struct lsquic_sfcw *fc, unsigned max_recv_window,
32                  struct lsquic_cfcw *cfcw, struct lsquic_conn_public *cpub,
33                  lsquic_stream_id_t stream_id)
34{
35    memset(fc, 0, sizeof(*fc));
36    fc->sf_max_recv_win = max_recv_window;
37    fc->sf_cfcw = cfcw;
38    fc->sf_conn_pub = cpub;
39    fc->sf_stream_id = stream_id;
40    (void) lsquic_sfcw_fc_offsets_changed(fc);
41}
42
43
44static void
45sfcw_maybe_increase_max_window (struct lsquic_sfcw *fc)
46{
47    unsigned new_max_window, max_conn_window;
48
49    new_max_window = fc->sf_max_recv_win * 2;
50
51    /* Do not increase past explicitly specified maximum */
52    if (new_max_window > fc->sf_conn_pub->enpub->enp_settings.es_max_sfcw)
53        new_max_window = fc->sf_conn_pub->enpub->enp_settings.es_max_sfcw;
54
55    if (fc->sf_cfcw)
56    {
57        /* Do not increase past the connection's maximum window size.  The
58         * connection's window will be increased separately, if possible.
59         *
60         * The reference implementation has the logic backwards:  Imagine
61         * several concurrent streams that are not being read from fast
62         * enough by the user code.  Each of them uses only a fraction
63         * of bandwidth.  Does it mean that the connection window must
64         * increase?  No.
65         */
66        max_conn_window = lsquic_cfcw_get_max_recv_window(fc->sf_cfcw);
67        if (new_max_window > max_conn_window)
68            new_max_window = max_conn_window;
69    }
70    else
71    {
72        /* This means that this stream is not affected by connection flow
73         * controller.  No need to adjust under connection window.
74         */
75    }
76
77    if (new_max_window > fc->sf_max_recv_win)
78    {
79        LSQ_DEBUG("max window increase %u -> %u",
80            fc->sf_max_recv_win, new_max_window);
81        EV_LOG_CONN_EVENT(LSQUIC_LOG_CONN_ID,
82            "max SFCW increase %u -> %u", fc->sf_max_recv_win,
83                                                            new_max_window);
84        fc->sf_max_recv_win = new_max_window;
85    }
86    else
87        LSQ_DEBUG("max window could use an increase, but we're stuck "
88            "at %u", fc->sf_max_recv_win);
89}
90
91
92int
93lsquic_sfcw_fc_offsets_changed (struct lsquic_sfcw *fc)
94{
95    lsquic_time_t since_last_update, srtt, now;
96
97    if (fc->sf_recv_off - fc->sf_read_off >= fc->sf_max_recv_win / 2)
98    {
99        LSQ_DEBUG("recv_off has not changed, still at %"PRIu64,
100                                                            fc->sf_recv_off);
101        return 0;
102    }
103
104    now = lsquic_time_now();
105    since_last_update = now - fc->sf_last_updated;
106    fc->sf_last_updated = now;
107
108    srtt = lsquic_rtt_stats_get_srtt(&fc->sf_conn_pub->rtt_stats);
109    if (since_last_update < srtt * 2)
110        sfcw_maybe_increase_max_window(fc);
111
112    fc->sf_recv_off = fc->sf_read_off + fc->sf_max_recv_win;
113    LSQ_DEBUG("recv_off changed: read_off: %"PRIu64"; "
114        "recv_off: %"PRIu64, fc->sf_read_off, fc->sf_recv_off);
115    return 1;
116}
117
118
119int
120lsquic_sfcw_set_max_recv_off (struct lsquic_sfcw *fc, uint64_t max_recv_off)
121{
122    if (max_recv_off <= fc->sf_recv_off)
123    {
124        if (!fc->sf_cfcw || lsquic_cfcw_incr_max_recv_off(fc->sf_cfcw,
125                                        max_recv_off - fc->sf_max_recv_off))
126        {
127            LSQ_DEBUG("max_recv_off goes from %"PRIu64" to %"PRIu64,
128                                            fc->sf_max_recv_off, max_recv_off);
129            fc->sf_max_recv_off = max_recv_off;
130            return 1;
131        }
132        else
133        {
134            /* cfcw prints its own warning */
135            return 0;
136        }
137    }
138    else
139    {
140        LSQ_INFO("flow control violation: received at offset %"PRIu64", "
141            "while flow control receive offset is %"PRIu64,
142            max_recv_off, fc->sf_recv_off);
143        return 0;
144    }
145}
146
147
148void
149lsquic_sfcw_set_read_off (struct lsquic_sfcw *fc, uint64_t off)
150{
151    if (fc->sf_cfcw)
152        lsquic_cfcw_incr_read_off(fc->sf_cfcw, off - fc->sf_read_off);
153    LSQ_DEBUG("read_off goes from %"PRIu64" to %"PRIu64,
154                                                fc->sf_read_off, off);
155    fc->sf_read_off = off;
156}
157