Update to scripts to better handle netem

scripts/bench-loss.sh

@@ -16,6 +16,10 @@ RATE_HZ="${RATE_HZ:-100}"
 BUILD="${BUILD:-release}"
 IFACE="${IFACE:-eth0}"
 RUN_SIMULATOR="${RUN_SIMULATOR:-1}"
+# Bidirectional loss via ifb (ingress redirect). Set BIDI=0 to disable and fall
+# back to egress-only shaping on $IFACE.
+BIDI="${BIDI:-1}"
+IFB_DEV="${IFB_DEV:-ifb0}"
 
 OUT_CSV="${OUT_CSV:-data/loopback/final_table.csv}"
 
@@ -45,6 +49,67 @@ for port in 9000 9100; do
 done
 [[ -f certs/server.crt ]] || make certs >/dev/null
 
+# --- netem helpers -----------------------------------------------------------
+# tc qdiscs are egress-only. To shape ingress (traffic arriving on $IFACE) we
+# install an ingress qdisc that redirects every packet to an ifb device, then
+# put the netem qdisc on the ifb's egress. Net effect: both directions of
+# $IFACE see the configured loss percentage.
+#
+# Egress-only fallback (BIDI=0) keeps the historical behaviour: shape outgoing
+# CM5 → peer traffic only.
+
+netem_init() {
+    [[ "$HAS_TC" -eq 1 && "$BIDI" -eq 1 ]] || return 0
+    # Load the ifb module (idempotent on modern kernels; ignored if built in).
+    sudo modprobe ifb numifbs=1 2>/dev/null || true
+    if ! ip link show "$IFB_DEV" >/dev/null 2>&1; then
+        fail "ifb device $IFB_DEV not present after modprobe; BIDI mode unavailable"
+        echo "  - check 'modprobe ifb' on this kernel, or run with BIDI=0"
+        return 1
+    fi
+    sudo ip link set "$IFB_DEV" up
+}
+
+netem_clear() {
+    [[ "$HAS_TC" -eq 1 ]] || return 0
+    sudo tc qdisc del dev "$IFACE" root 2>/dev/null || true
+    sudo tc qdisc del dev "$IFACE" ingress 2>/dev/null || true
+    if [[ "$BIDI" -eq 1 ]]; then
+        sudo tc qdisc del dev "$IFB_DEV" root 2>/dev/null || true
+    fi
+}
+
+# Apply $1% loss in both directions (or egress-only when BIDI=0).
+netem_apply() {
+    local pct="$1"
+    [[ "$HAS_TC" -eq 1 ]] || return 0
+    netem_clear
+    [[ "$pct" -gt 0 ]] || return 0
+    # Egress: outgoing from $IFACE.
+    sudo tc qdisc add dev "$IFACE" root netem loss "${pct}%" 2>/dev/null || {
+        echo "Warning: failed to apply egress netem loss on $IFACE."
+        return 1
+    }
+    if [[ "$BIDI" -eq 1 ]]; then
+        # Ingress: incoming on $IFACE, redirected to $IFB_DEV egress and shaped there.
+        sudo tc qdisc add dev "$IFACE" handle ffff: ingress 2>/dev/null || {
+            echo "Warning: failed to add ingress qdisc on $IFACE."
+            return 1
+        }
+        sudo tc filter add dev "$IFACE" parent ffff: protocol all u32 \
+            match u32 0 0 action mirred egress redirect dev "$IFB_DEV" 2>/dev/null || {
+            echo "Warning: failed to install ingress redirect filter."
+            return 1
+        }
+        sudo tc qdisc add dev "$IFB_DEV" root netem loss "${pct}%" 2>/dev/null || {
+            echo "Warning: failed to apply netem on $IFB_DEV."
+            return 1
+        }
+    fi
+}
+
+netem_init || true
+
 step "Building ($BUILD)"
 if [[ "$BUILD" == "release" ]]; then
     if [[ "$RUN_SIMULATOR" -eq 1 ]]; then
@@ -84,9 +149,7 @@ done
 cleanup() {
     [[ -n "${SIM_PID:-}" ]] && kill -TERM "$SIM_PID" 2>/dev/null || true
     [[ -n "${SUBSTRATE_PID:-}" ]] && kill -TERM "$SUBSTRATE_PID" 2>/dev/null || true
-    if [[ "$HAS_TC" -eq 1 ]]; then
-        sudo tc qdisc del dev $IFACE root 2>/dev/null || true
-    fi
+    netem_clear
     wait 2>/dev/null || true
 }
 trap cleanup EXIT INT TERM
@@ -115,15 +178,8 @@ for entities in "${ENTITIES_LIST[@]}"; do
     devices=$(( entities / 7 ))
     
     for loss in "${LOSS_LIST[@]}"; do
-        # Apply tc netem loss
-        if [[ "$HAS_TC" -eq 1 ]]; then
-            sudo tc qdisc del dev $IFACE root 2>/dev/null || true
-            if [[ "$loss" -gt 0 ]]; then
-                sudo tc qdisc add dev $IFACE root netem loss ${loss}% 2>/dev/null || {
-                    echo "Warning: failed to apply tc netem loss on interface $IFACE."
-                }
-            fi
-        fi
+        # Apply tc-netem loss in both directions (or egress-only when BIDI=0).
+        netem_apply "$loss"
 
         if [[ "$RUN_SIMULATOR" -eq 1 ]]; then
             sim_args=(
@@ -178,8 +234,6 @@ for entities in "${ENTITIES_LIST[@]}"; do
     done
 done
 
-if [[ "$HAS_TC" -eq 1 ]]; then
-    sudo tc qdisc del dev $IFACE root 2>/dev/null || true
-fi
+netem_clear
 
 printf '\n%sCSV written to:%s %s\n' "$DIM" "$RESET" "$OUT_CSV"