mxsnoop: Add prototype

Use to monitor network traffic on site.

mxsnoop/mxsnoop.sh

@@ -0,0 +1,117 @@
+#!/bin/bash
+
+#
+#  +--------------+   (!)   +----------------------+        +---****
+#  |              |         |        br01          |        |
+#  | THE SUSPECT  O]===X===[O   SCHNUEFFELSTUECK   O]======[O  WIS-NET
+#  |              |         |INLET           OUTLET|        |
+#  +--------------+         +----------------------+        +---****
+#                                        (MX_NETDEV)
+
+#  Basics: https://wiki.archlinux.org/title/Network_bridge
+
+# GATEWAY=10.0.3.1
+# BROADCAST=10.0.3.255
+# NETMASK=255.255.255.0
+# NIDL=24
+
+GATEWAY=141.14.16.128
+BROADCAST=141.14.31.255
+NETMASK=255.255.240.0
+NIDL=20
+
+INLET=${INLET:-}
+OUTLET=${OUTLET:-}
+BRIDGE=br01
+
+TRANSPARENT=${TRANSPARENT:-}
+STP=${STP:-}
+
+function die() { echo $1; exit 1; }
+
+type ip > /dev/null || \
+  die 'Error: Tools not available, check for ip command.'
+
+MXHOSTCONF=${MXHOSTCONF:-/etc/local/mxhost.conf}
+source $MXHOSTCONF || die "# Error: No 'mxhost.conf' ?"
+test -n "$MX_IPADDR" || die '# Error: MX_IPADDR missing.'
+
+if [ -z "$OUTLET" ]; then
+  test -n "$MX_NETDEV" || die '# Error: MX_NETDEV missing?'
+  test -e /sys/class/net/$MX_NETDEV || die "# Error: $MX_NETDEV missing."
+  OUTLET=$MX_NETDEV
+fi
+
+
+# inlet was present at boot time -> netXY, or plugged later -> Search for ethX
+if [ -z "$INLET" ]; then # find the (sole) inlet
+  for D in net{00..09} eth{0..9}; do
+    test -e /sys/class/net/$D || continue
+    test $D = $OUTLET && continue
+    test -n "$INLET" && \
+      die 'Error: Too many network devices (netXY) present, use INLET=dev (OUTLET=dev ?).'
+    INLET=$D
+  done
+fi
+
+test -z "$INLET" && die '# Error: no second network device found.'
+
+echo "# Note: about to setup/destroy $BRIDGE between $INLET (INLET) and $OUTLET (OUTLET), IP: $MX_IPADDR"
+
+cmd="$1"
+
+case "$cmd" in
+
+  start)
+
+    if [ -z "$STP" ]; then
+      ip link add dev $BRIDGE type bridge
+    else
+      ip link add dev $BRIDGE type bridge stp_state 1
+    fi
+
+    ip address flush dev $INLET
+    ip address flush dev $OUTLET
+
+    ip link set $INLET master $BRIDGE
+    ip link set $OUTLET master $BRIDGE
+
+    if [ -z "$TRANSPARENT" ] ; then
+      ip addr add $MX_IPADDR/$NIDL broadcast $BROADCAST dev $BRIDGE
+      ip link set up dev $BRIDGE
+      ip route add default via $GATEWAY dev $BRIDGE
+    fi
+
+    ip link set dev $INLET up
+    ip link set dev $OUTLET up
+
+    ;;
+
+  stop)
+
+    ip link set $INLET nomaster
+    ip link set $OUTLET nomaster
+    ip link delete $BRIDGE type bridge
+
+    ip addr add $MX_IPADDR/$NIDL broadcast $BROADCAST dev $OUTLET
+    ip link set dev $OUTLET up
+    ip route add default via $GATEWAY
+
+    ;;
+
+  restart)
+
+    $0 stop
+    sleep 1
+    $0 start
+    ;;
+
+  *)
+
+    echo "#   usage:     [INLET=dev] [OUTLET=dev] $0 [start|stop|restart]"
+    echo "# options:     TRANSPARENT=1 doesn't bind IP on the bridge"
+    echo "#              STP=1 enables Spanning Tree"
+    ;;
+
+esac
+