Use iftop to collect network bandwidth usage (#6560)

* Use iftop to collect network bandwidth usage

* fix shellcheck

* more shellchecks

* review comments

scripts/iftop.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+#
+# Reports network bandwidth usage
+#
+set -e
+
+[[ $(uname) == Linux ]] || exit 0
+
+cd "$(dirname "$0")"
+
+sudo iftop -i "$(ifconfig | grep mtu | grep -iv loopback | grep -i running | awk 'BEGIN { FS = ":" } ; {print $1}')" -nNbBP  -t \
+	| awk '{ if ($3 ~ "=>") { print $2, $7 } else if ($2 ~ "<=") { print $1, $6 }} ' \
+	| awk 'NR%2{printf "%s ",$0;next;}1' \
+	| awk '{ print $1, "<=>", $3, ":",  $2, $4 }'
+
+exit 1