Add CouchDB netem shim benchmark

test/bench-network/netem-tcp-shim.sh

@@ -0,0 +1,80 @@
+#!/usr/bin/env sh
+set -eu
+
+profile="${NETEM_PROFILE:-home-wifi}"
+iface="${NETEM_INTERFACE:-eth0}"
+delay_ms="${NETEM_DELAY_MS:-20}"
+jitter_ms="${NETEM_JITTER_MS:-5}"
+loss_percent="${NETEM_LOSS_PERCENT:-0.1}"
+bandwidth_mbit="${NETEM_BANDWIDTH_MBIT:-100}"
+mtu="${NETEM_MTU:-1500}"
+listen_port="${SHIM_LISTEN_PORT:-5984}"
+target_host="${SHIM_TARGET_HOST:-couchdb}"
+target_port="${SHIM_TARGET_PORT:-5984}"
+out_root="${NETEM_RESULT_ROOT:-/bench-results}"
+timestamp="$(date -u +%Y%m%d-%H%M%S)"
+out_dir="${out_root}/netem-shim-${profile}-${timestamp}"
+out_file="${out_dir}/summary.json"
+
+json_lines() {
+    awk '
+        {
+            gsub(/\\/, "\\\\");
+            gsub(/"/, "\\\"");
+            printf "%s    \"%s\"", (NR == 1 ? "" : ",\n"), $0;
+        }
+    '
+}
+
+mkdir -p "$out_dir"
+
+if ! ip link show "$iface" >/dev/null 2>&1; then
+    echo "Network interface '$iface' was not found" >&2
+    ip addr >&2
+    exit 2
+fi
+
+ip link set dev "$iface" mtu "$mtu"
+tc qdisc del dev "$iface" root >/dev/null 2>&1 || true
+tc qdisc add dev "$iface" root netem \
+    delay "${delay_ms}ms" "${jitter_ms}ms" \
+    loss "${loss_percent}%" \
+    rate "${bandwidth_mbit}mbit"
+
+ip_addr="$(ip addr show "$iface" | json_lines)"
+ip_route="$(ip route | json_lines)"
+tc_qdisc="$(tc qdisc show dev "$iface" | json_lines)"
+
+cat > "$out_file" <<EOF
+{
+  "simulationTier": 2,
+  "mode": "netem-tcp-shim",
+  "profile": "$profile",
+  "interface": "$iface",
+  "listenPort": $listen_port,
+  "targetHost": "$target_host",
+  "targetPort": $target_port,
+  "netem": {
+    "delayMs": $delay_ms,
+    "jitterMs": $jitter_ms,
+    "lossPercent": $loss_percent,
+    "bandwidthMbit": $bandwidth_mbit,
+    "mtu": $mtu
+  },
+  "ipAddr": [
+$ip_addr
+  ],
+  "ipRoute": [
+$ip_route
+  ],
+  "tcQdisc": [
+$tc_qdisc
+  ]
+}
+EOF
+
+cat "$out_file"
+echo "[netem-shim] forwarding 0.0.0.0:${listen_port} to ${target_host}:${target_port}"
+echo "[netem-shim] result file: $out_file"
+
+exec socat "TCP-LISTEN:${listen_port},fork,reuseaddr" "TCP:${target_host}:${target_port}"