T6456: Convert "monitor traffic" to modern op-mode wrapper

The old "monitor traffic" definition had misaligned arguments under the verbose node
and manually offered the same parameter keyword in multiple positions to emulate
flexible parameters.

I've wrapped tcpdump for op-mode and replicated the "varargs" style from mtr.py/mtr.xml.in
to present a few more parameters in a more flexible manner.

Changes to the Makefile were required for recursive varargs lookup.

3 files changed, 175 insertions, 48 deletions

diff --git a/Makefile b/Makefile
index 3b26273d6..cc382e206 100644
--- a/Makefile
+++ b/Makefile
@@ -61,12 +61,13 @@ op_mode_definitions: $(op_xml_obj)
 	rm -f $(OP_TMPL_DIR)/clear/node.def
 	rm -f $(OP_TMPL_DIR)/delete/node.def
 
-	# XXX: ping, traceroute and mtr must be able to recursivly call themselves as the
+	# XXX: tcpdump, ping, traceroute and mtr must be able to recursivly call themselves as the
 	# options are provided from the scripts themselves
 	ln -s ../node.tag $(OP_TMPL_DIR)/ping/node.tag/node.tag/
 	ln -s ../node.tag $(OP_TMPL_DIR)/traceroute/node.tag/node.tag/
 	ln -s ../node.tag $(OP_TMPL_DIR)/mtr/node.tag/node.tag/
 	ln -s ../node.tag $(OP_TMPL_DIR)/monitor/traceroute/node.tag/node.tag/
+	ln -s ../node.tag $(OP_TMPL_DIR)/monitor/traffic/interface/node.tag/node.tag/
 
 	# XXX: test if there are empty node.def files - this is not allowed as these
 	# could mask help strings or mandatory priority statements
diff --git a/op-mode-definitions/traffic-dump.xml.in b/op-mode-definitions/traffic-dump.xml.in
index 76e3ddce5..e86e69736 100644
--- a/op-mode-definitions/traffic-dump.xml.in
+++ b/op-mode-definitions/traffic-dump.xml.in
@@ -8,7 +8,7 @@
         </properties>
         <children>
           <tagNode name="interface">
-            <command>sudo tcpdump -i $4</command>
+            <command>${vyos_op_scripts_dir}/tcpdump.py $4</command>
             <properties>
               <help>Monitor traffic dump from an interface</help>
               <completionHelp>
@@ -16,54 +16,15 @@
               </completionHelp>
             </properties>
             <children>
-              <node name="verbose">
-                <command>sudo tcpdump -vvv -ne -i $4</command>
+              <leafNode name="node.tag">
                 <properties>
-                  <help>Provide more detailed packets for each monitored traffic</help>
+                  <help>Traffic capture options</help>
+                  <completionHelp>
+                    <script>${vyos_op_scripts_dir}/tcpdump.py --get-options-nested "${COMP_WORDS[@]}"</script>
+                  </completionHelp>
                 </properties>
-                <children>
-                  <tagNode name="filter">
-                    <command>sudo tcpdump -vvv -ne -i $4 "${@:6}"</command>
-                    <properties>
-                      <help>Monitor traffic matching filter conditions</help>
-                    </properties>
-                  </tagNode>
-                  <tagNode name="save">
-                    <command>sudo tcpdump -vvv -ne -i $4 -w $6</command>
-                    <properties>
-                      <help>Save traffic dump from an interface to a file</help>
-                    </properties>
-                    <children>
-                      <tagNode name="filter">
-                        <command>sudo tcpdump -vvv -ne -i $4 -w $6 "${@:8}"</command>
-                        <properties>
-                          <help>Save a dump of traffic matching filter conditions to a file</help>
-                        </properties>
-                      </tagNode>
-                    </children>
-                  </tagNode>
-                </children>
-              </node>
-              <tagNode name="filter">
-                <command>sudo tcpdump -n -i $4 "${@:6}"</command>
-                <properties>
-                  <help>Monitor traffic matching filter conditions</help>
-                </properties>
-              </tagNode>
-              <tagNode name="save">
-                <command>sudo tcpdump -n -i $4 -w $6</command>
-                <properties>
-                  <help>Save traffic dump from an interface to a file</help>
-                </properties>
-                <children>
-                  <tagNode name="filter">
-                    <command>sudo tcpdump -n -i $4 -w $6 "${@:8}"</command>
-                    <properties>
-                      <help>Save a dump of traffic matching filter conditions to a file</help>
-                    </properties>
-                  </tagNode>
-                </children>
-              </tagNode>
+                <command>${vyos_op_scripts_dir}/tcpdump.py "${@:4}"</command>
+              </leafNode>
             </children>
           </tagNode>
         </children>
diff --git a/src/op_mode/tcpdump.py b/src/op_mode/tcpdump.py
new file mode 100644
index 000000000..607b59603
--- /dev/null
+++ b/src/op_mode/tcpdump.py
@@ -0,0 +1,165 @@
+#! /usr/bin/env python3
+
+# Copyright (C) 2024 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import sys
+
+from vyos.utils.process import call
+
+options = {
+    'dump': {
+        'cmd': '{command} -A',
+        'type': 'noarg',
+        'help': 'Print each packet (minus its link level header) in ASCII.'
+    },
+    'hexdump': {
+        'cmd': '{command} -X',
+        'type': 'noarg',
+        'help': 'Print each packet (minus its link level header) in both hex and ASCII.'
+    },
+    'filter': {
+        'cmd': '{command} \'{value}\'',
+        'type': '<pcap-filter>',
+        'help': 'Match traffic for capture and display with a pcap-filter expression.'
+    },
+    'numeric': {
+        'cmd': '{command} -nn',
+        'type': 'noarg',
+        'help': 'Do not attempt to resolve addresses, protocols or services to names.'
+    },
+    'save': {
+        'cmd': '{command} -w {value}',
+        'type': '<file>',
+        'help': 'Write captured raw packets to <file> rather than parsing or printing them out.'
+    },
+    'verbose': {
+        'cmd': '{command} -vvv -ne',
+        'type': 'noarg',
+        'help': 'Parse packets with increased detail output, including link-level headers and extended decoding protocol sanity checks.'
+    },
+}
+
+tcpdump = 'sudo /usr/bin/tcpdump'
+
+class List(list):
+    def first(self):
+        return self.pop(0) if self else ''
+
+    def last(self):
+        return self.pop() if self else ''
+
+    def prepend(self, value):
+        self.insert(0, value)
+
+
+def completion_failure(option: str) -> None:
+    """
+    Shows failure message after TAB when option is wrong
+    :param option: failure option
+    :type str:
+    """
+    sys.stderr.write('\n\n Invalid option: {}\n\n'.format(option))
+    sys.stdout.write('<nocomps>')
+    sys.exit(1)
+
+
+def expansion_failure(option, completions):
+    reason = 'Ambiguous' if completions else 'Invalid'
+    sys.stderr.write(
+        '\n\n  {} command: {} [{}]\n\n'.format(reason, ' '.join(sys.argv),
+                                               option))
+    if completions:
+        sys.stderr.write('  Possible completions:\n   ')
+        sys.stderr.write('\n   '.join(completions))
+        sys.stderr.write('\n')
+    sys.stdout.write('<nocomps>')
+    sys.exit(1)
+
+
+def complete(prefix):
+    return [o for o in options if o.startswith(prefix)]
+
+
+def convert(command, args):
+    while args:
+        shortname = args.first()
+        longnames = complete(shortname)
+        if len(longnames) != 1:
+            expansion_failure(shortname, longnames)
+        longname = longnames[0]
+        if options[longname]['type'] == 'noarg':
+            command = options[longname]['cmd'].format(
+                command=command, value='')
+        elif not args:
+            sys.exit(f'monitor traffic: missing argument for {longname} option')
+        else:
+            command = options[longname]['cmd'].format(
+                command=command, value=args.first())
+    return command
+
+
+if __name__ == '__main__':
+    args = List(sys.argv[1:])
+    ifname = args.first()
+
+    # Slightly simplified & tweaked version of the code from mtr.py - it may be 
+    # worthwhile to combine and centralise this in a common module. 
+    if ifname == '--get-options-nested':
+        args.first()  # pop monitor
+        args.first()  # pop traffic
+        args.first()  # pop interface
+        args.first()  # pop <ifname>
+        usedoptionslist = []
+        while args:
+            option = args.first()  # pop option
+            matched = complete(option)  # get option parameters
+            usedoptionslist.append(option)  # list of used options
+            # Select options
+            if not args:
+                # remove from Possible completions used options
+                for o in usedoptionslist:
+                    if o in matched:
+                        matched.remove(o)
+                if not matched:
+                    sys.stdout.write('<nocomps>')
+                else:
+                    sys.stdout.write(' '.join(matched))
+                sys.exit(0)
+
+            if len(matched) > 1:
+                sys.stdout.write(' '.join(matched))
+                sys.exit(0)
+            # If option doesn't have value
+            if matched:
+                if options[matched[0]]['type'] == 'noarg':
+                    continue
+            else:
+                # Unexpected option
+                completion_failure(option)
+
+            value = args.first()  # pop option's value
+            if not args:
+                matched = complete(option)
+                helplines = options[matched[0]]['type']
+                # Run helpfunction to get list of possible values
+                if 'helpfunction' in options[matched[0]]:
+                    result = options[matched[0]]['helpfunction']()
+                    if result:
+                        helplines = '\n' + ' '.join(result)
+                sys.stdout.write(helplines)
+                sys.exit(0)
+
+    command = convert(tcpdump, args)
+    call(f'{command} -i {ifname}')