mirror of
https://github.com/livekit/livekit.git
synced 2026-06-28 23:58:45 -04:00
David Chen
113 lines
3.5 KiB
Bash
Executable File
113 lines
3.5 KiB
Bash
Executable File
#!/usr/bin/env bash
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# Traffic shaper for the FlexFEC test harness (Linux, tc/netem).
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#
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# Applies packet loss to UDP traffic destined to the SFU's pinned media port on
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# loopback, simulating a robot uplink over cellular: continuous low base loss
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# (Gilbert-Elliott model for realistic loss correlation) plus periodic
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# high-loss bursts. Burst on/off transitions are appended to an events file
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# (wall-clock microseconds) so plots can shade the burst windows.
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#
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# Usage:
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# sudo ./shape_linux.sh start --port 7882 --base-loss 0.02 \
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# --burst-loss 0.25 --burst-every 15 --burst-len 3 --events events.csv
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# sudo ./shape_linux.sh stop
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#
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# `start` runs in the foreground until terminated, cleaning up on exit.
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# `stop` force-cleans shaping state from a previous run.
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set -u
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DEV="lo"
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PORT=7882
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BASE_LOSS=0.02
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BURST_LOSS=0.25
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BURST_EVERY=15
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BURST_LEN=3
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EVENTS_FILE=""
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log() { echo "[shape_linux] $*" >&2; }
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now_us() { python3 -c 'import time; print(int(time.time() * 1e6))'; }
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record_event() {
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if [ -n "$EVENTS_FILE" ]; then
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echo "$(now_us),$1" >> "$EVENTS_FILE"
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fi
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}
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pct() { python3 -c "print($1 * 100)"; }
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apply_base_loss() {
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# Gilbert-Elliott: p = chance of entering the bad state, r = chance of
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# leaving it. p derived from the target average loss with r fixed at 30%
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# gives short correlated loss runs typical for radio links.
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local p
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p=$(pct "$BASE_LOSS")
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tc qdisc change dev $DEV parent 1:4 handle 40: netem loss gemodel "${p}%" 30%
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}
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cleanup() {
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trap - EXIT INT TERM
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log "cleaning up"
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tc qdisc del dev $DEV root 2>/dev/null
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record_event "shaper_stopped"
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log "done"
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}
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start() {
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trap cleanup EXIT INT TERM
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# 4-band prio qdisc: default TOS mapping never selects band 4, so only the
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# filtered SFU-bound UDP flow passes through the netem child
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tc qdisc add dev $DEV root handle 1: prio bands 4 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1 || {
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log "failed to add root qdisc (already shaped? try '$0 stop')"
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exit 1
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}
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tc qdisc add dev $DEV parent 1:4 handle 40: netem loss gemodel "$(pct "$BASE_LOSS")%" 30%
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tc filter add dev $DEV parent 1: protocol ip prio 1 u32 \
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match ip protocol 17 0xff \
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match ip dport "$PORT" 0xffff \
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flowid 1:4
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log "shaping active: udp dport $PORT, base loss $BASE_LOSS (gemodel), burst $BURST_LOSS for ${BURST_LEN}s every ${BURST_EVERY}s"
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record_event "shaper_started base=$BASE_LOSS burst=$BURST_LOSS"
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# periodic burst loop
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while true; do
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sleep "$BURST_EVERY"
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tc qdisc change dev $DEV parent 1:4 handle 40: netem loss "$(pct "$BURST_LOSS")%"
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record_event "burst_on"
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log "burst on ($BURST_LOSS)"
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sleep "$BURST_LEN"
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apply_base_loss
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record_event "burst_off"
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log "burst off ($BASE_LOSS)"
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done
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}
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CMD="${1:-}"
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shift || true
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while [ $# -gt 0 ]; do
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case "$1" in
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--port) PORT="$2"; shift 2 ;;
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--base-loss) BASE_LOSS="$2"; shift 2 ;;
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--burst-loss) BURST_LOSS="$2"; shift 2 ;;
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--burst-every) BURST_EVERY="$2"; shift 2 ;;
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--burst-len) BURST_LEN="$2"; shift 2 ;;
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--events) EVENTS_FILE="$2"; shift 2 ;;
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*) log "unknown argument: $1"; exit 1 ;;
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esac
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done
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if [ "$(id -u)" -ne 0 ]; then
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log "ERROR: must run as root (sudo)"
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exit 1
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fi
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case "$CMD" in
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start) start ;;
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stop) cleanup ;;
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*) echo "usage: $0 {start|stop} [--port N] [--base-loss F] [--burst-loss F] [--burst-every S] [--burst-len S] [--events FILE]" >&2; exit 1 ;;
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esac
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