lsquic_sfcw.c revision 5392f7a3 
1/* Copyright (c) 2017 - 2019 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_varint.h"
16#include "lsquic_hq.h"
17#include "lsquic_hash.h"
18#include "lsquic_stream.h"
19#include "lsquic_conn_public.h"
20#include "lsquic_mm.h"
21#include "lsquic_engine_public.h"
22#include "lsquic_util.h"
23#include "lsquic_conn.h"
24#include "lsquic_ev_log.h"
25
26#define LSQUIC_LOGGER_MODULE LSQLM_SFCW
27#define LSQUIC_LOG_CONN_ID lsquic_conn_log_cid(fc->sf_conn_pub->lconn)
28#define LSQUIC_LOG_STREAM_ID fc->sf_stream_id
29#include "lsquic_logger.h"
30
31void
32lsquic_sfcw_init (struct lsquic_sfcw *fc, unsigned max_recv_window,
33                  struct lsquic_cfcw *cfcw, struct lsquic_conn_public *cpub,
34                  lsquic_stream_id_t stream_id)
35{
36    memset(fc, 0, sizeof(*fc));
37    fc->sf_max_recv_win = max_recv_window;
38    fc->sf_cfcw = cfcw;
39    fc->sf_conn_pub = cpub;
40    fc->sf_stream_id = stream_id;
41    (void) lsquic_sfcw_fc_offsets_changed(fc);
42}
43
44
45static void
46sfcw_maybe_increase_max_window (struct lsquic_sfcw *fc)
47{
48    unsigned new_max_window, max_conn_window;
49
50    new_max_window = fc->sf_max_recv_win * 2;
51
52    /* Do not increase past explicitly specified maximum */
53    if (new_max_window > fc->sf_conn_pub->enpub->enp_settings.es_max_sfcw)
54        new_max_window = fc->sf_conn_pub->enpub->enp_settings.es_max_sfcw;
55
56    if (fc->sf_cfcw)
57    {
58        /* Do not increase past the connection's maximum window size.  The
59         * connection's window will be increased separately, if possible.
60         *
61         * The reference implementation has the logic backwards:  Imagine
62         * several concurrent streams that are not being read from fast
63         * enough by the user code.  Each of them uses only a fraction
64         * of bandwidth.  Does it mean that the connection window must
65         * increase?  No.
66         */
67        max_conn_window = lsquic_cfcw_get_max_recv_window(fc->sf_cfcw);
68        if (new_max_window > max_conn_window)
69            new_max_window = max_conn_window;
70    }
71    else
72    {
73        /* This means that this stream is not affected by connection flow
74         * controller.  No need to adjust under connection window.
75         */
76    }
77
78    if (new_max_window > fc->sf_max_recv_win)
79    {
80        LSQ_DEBUG("max window increase %u -> %u",
81            fc->sf_max_recv_win, new_max_window);
82        EV_LOG_CONN_EVENT(LSQUIC_LOG_CONN_ID,
83            "max SFCW increase %u -> %u", fc->sf_max_recv_win,
84                                                            new_max_window);
85        fc->sf_max_recv_win = new_max_window;
86    }
87    else
88        LSQ_DEBUG("max window could use an increase, but we're stuck "
89            "at %u", fc->sf_max_recv_win);
90}
91
92
93int
94lsquic_sfcw_fc_offsets_changed (struct lsquic_sfcw *fc)
95{
96    lsquic_time_t since_last_update, srtt, now;
97
98    if (fc->sf_recv_off - fc->sf_read_off >= fc->sf_max_recv_win / 2)
99    {
100        LSQ_DEBUG("recv_off has not changed, still at %"PRIu64,
101                                                            fc->sf_recv_off);
102        return 0;
103    }
104
105    now = lsquic_time_now();
106    since_last_update = now - fc->sf_last_updated;
107    fc->sf_last_updated = now;
108
109    srtt = lsquic_rtt_stats_get_srtt(&fc->sf_conn_pub->rtt_stats);
110    if (since_last_update < srtt * 2)
111        sfcw_maybe_increase_max_window(fc);
112
113    fc->sf_recv_off = fc->sf_read_off + fc->sf_max_recv_win;
114    LSQ_DEBUG("recv_off changed: read_off: %"PRIu64"; "
115        "recv_off: %"PRIu64, fc->sf_read_off, fc->sf_recv_off);
116    return 1;
117}
118
119
120int
121lsquic_sfcw_set_max_recv_off (struct lsquic_sfcw *fc, uint64_t max_recv_off)
122{
123    if (max_recv_off <= fc->sf_recv_off)
124    {
125        if (!fc->sf_cfcw || lsquic_cfcw_incr_max_recv_off(fc->sf_cfcw,
126                                        max_recv_off - fc->sf_max_recv_off))
127        {
128            LSQ_DEBUG("max_recv_off goes from %"PRIu64" to %"PRIu64,
129                                            fc->sf_max_recv_off, max_recv_off);
130            fc->sf_max_recv_off = max_recv_off;
131            return 1;
132        }
133        else
134        {
135            /* cfcw prints its own warning */
136            return 0;
137        }
138    }
139    else
140    {
141        LSQ_WARN("flow control violation: received at offset %"PRIu64", "
142            "while flow control receive offset is %"PRIu64,
143            max_recv_off, fc->sf_recv_off);
144        return 0;
145    }
146}
147
148
149void
150lsquic_sfcw_set_read_off (struct lsquic_sfcw *fc, uint64_t off)
151{
152    if (fc->sf_cfcw)
153        lsquic_cfcw_incr_read_off(fc->sf_cfcw, off - fc->sf_read_off);
154    LSQ_DEBUG("read_off goes from %"PRIu64" to %"PRIu64,
155                                                fc->sf_read_off, off);
156    fc->sf_read_off = off;
157}
158