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Sleep based on fixed point in time to avoid time drift when replaying packets #915

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Sleep based on fixed point in time to avoid time drift when replaying packets #915

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2 changes: 2 additions & 0 deletions src/common/utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,8 @@ typedef struct {
struct timespec end_time;
struct timespec pkt_ts_delta;
struct timespec last_print;
struct timespec first_packet_time;
struct timespec first_packet_wall_time;
COUNTER flow_non_flow_packets;
COUNTER flows;
COUNTER flows_unique;
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37 changes: 13 additions & 24 deletions src/send_packets.c
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Original file line number Diff line number Diff line change
Expand Up @@ -341,6 +341,7 @@ void
send_packets(tcpreplay_t *ctx, pcap_t *pcap, int idx)
{
struct timespec now, print_delta, last_pkt_ts;
bool first_packet = true;
tcpreplay_opt_t *options = ctx->options;
tcpreplay_stats_t *stats = &ctx->stats;
COUNTER packetnum = 0;
Expand Down Expand Up @@ -465,23 +466,25 @@ send_packets(tcpreplay_t *ctx, pcap_t *pcap, int idx)
skip_length = 0;
ctx->skip_packets = 0;

if (!top_speed) {
now_is_now = true;
get_current_time(&now);
}

if (options->speed.mode == speed_multiplier) {
if (!timesisset(&last_pkt_ts)) {
if (first_packet) {
TIMESPEC_SET(&stats->first_packet_time, &pkthdr_ts);
TIMESPEC_SET(&last_pkt_ts, &pkthdr_ts);
TIMESPEC_SET(&stats->first_packet_wall_time, &now);
first_packet = false;
} else if (timescmp(&pkthdr_ts, &last_pkt_ts, >)) {
struct timespec delta;

timessub(&pkthdr_ts, &last_pkt_ts, &delta);
timeradd_timespec(&stats->pkt_ts_delta, &delta, &stats->pkt_ts_delta);
TIMESPEC_SET(&last_pkt_ts, &pkthdr_ts);
timessub(&pkthdr_ts, &stats->first_packet_time, &stats->pkt_ts_delta);
timessub(&now, &stats->first_packet_wall_time, &stats->time_delta);
timesdiv_float(&stats->pkt_ts_delta, options->speed.multiplier);
}
}

if (!top_speed) {
now_is_now = true;
get_current_time(&now);
}

/*
* Only if the current packet is not late.
*
Expand All @@ -498,15 +501,6 @@ send_packets(tcpreplay_t *ctx, pcap_t *pcap, int idx)
TIMESPEC_TO_NANOSEC(&stats->start_time),
&skip_length);

/*
* Track the time of the "last packet sent".
*
* A number of 3rd party tools generate bad timestamps which go backwards
* in time. Hence, don't update the "last" unless pkthdr.ts > last
*/
if (timescmp(&stats->time_delta, &stats->pkt_ts_delta, <))
TIMESPEC_SET(&stats->time_delta, &stats->pkt_ts_delta);

/*
* we know how long to sleep between sends, now do it.
*/
Expand Down Expand Up @@ -807,8 +801,6 @@ send_dual_packets(tcpreplay_t *ctx, pcap_t *pcap1, int cache_file_idx1, pcap_t *
* A number of 3rd party tools generate bad timestamps which go backwards
* in time. Hence, don't update the "last" unless pkthdr_ptr->ts > last
*/
if (timescmp(&stats->time_delta, &stats->pkt_ts_delta, <))
TIMESPEC_SET(&stats->time_delta, &stats->pkt_ts_delta);

/*
* we know how long to sleep between sends, now do it.
Expand Down Expand Up @@ -1062,9 +1054,6 @@ calc_sleep_time(tcpreplay_t *ctx,
/* pkt_time_delta has increased, so handle normally */
timessub(pkt_ts_delta, time_delta, &nap_for);
TIMESPEC_SET(&ctx->nap, &nap_for);
dbgx(3, "original packet delta time: " TIMESPEC_FORMAT, ctx->nap.tv_sec, ctx->nap.tv_nsec);
timesdiv_float(&ctx->nap, options->speed.multiplier);
dbgx(3, "original packet delta/div: " TIMESPEC_FORMAT, ctx->nap.tv_sec, ctx->nap.tv_nsec);
}
break;

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