Integrated use of netem with testnet scripts (#6746)

automerge

scripts/netem.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+#
+# Start/Stop network emulation
+#
+set -e
+
+[[ $(uname) == Linux ]] || exit 0
+
+cd "$(dirname "$0")"
+
+sudo=
+if sudo true; then
+  sudo="sudo -n"
+fi
+
+set -x
+
+iface="$(ifconfig | grep mtu | grep -iv loopback | grep -i running | awk 'BEGIN { FS = ":" } ; {print $1}')"
+# shellcheck disable=SC2086 # Do not want to quote $2. It has space separated arguments for netem
+$sudo tc qdisc "$1" dev "$iface" root netem $2