add plugin and rsyslog changes to change sonic_name to alias

files/image_config/rsyslog/rsyslog.conf.j2

@@ -33,6 +33,9 @@ $ModLoad imudp
 $UDPServerAddress {{udp_server_ip}}  #bind to localhost before udp server run
 $UDPServerRun 514
 
+# provides support to use external plugins
+$ModLoad mmexternal
+
 # provides TCP syslog reception
 #$ModLoad imtcp
 #$InputTCPServerRun 514

files/image_config/rsyslog/rsyslog.d/00-sonic.conf

@@ -37,3 +37,9 @@ if $msg startswith  " telemetry" or ($msg startswith  " dialout" )then {
     /var/log/telemetry.log
     stop
 }
+
+if $msg contains "Ethernet"  then {
+    action(type="mmexternal"
+        binary="/etc/rsyslog.d/port_name_mod.py"
+        interface.input="msg")
+}

files/image_config/rsyslog/rsyslog.d/port_name_mod.py

@@ -0,0 +1,69 @@
+#!/usr/bin/python3
+import sys
+import re
+import json
+
+from sonic_py_common import multi_asic
+from swsscommon import swsscommon
+
+def onInit():
+    global pattern
+    global port_alias_mapping
+    num_asics = multi_asic.get_namespaces_from_linux()
+    port_alias_mapping  = {}
+    swsscommon.SonicDBConfig.load_sonic_global_db_config()
+    for asic in num_asics:
+        cfg_db = multi_asic.connect_config_db_for_ns(asic)
+        port_table = cfg_db.get_table('PORT')
+        for port, values in port_table.items():
+            port_alias_mapping[port] = values['alias']
+
+    pattern = 'Ethernet[\d]+'
+
+def onReceive(msg):
+    global pattern
+    global port_alias_mapping
+
+    matches = re.findall(pattern, msg)
+    found_match = False
+    for match in matches:
+        if match in port_alias_mapping.keys():
+            new_log= re.sub(match, port_alias_mapping[match],msg)
+            msg = new_log
+            found_match = True
+    if found_match:
+        print(json.dumps({'msg': new_log}))
+    else:
+        print(json.dumps({}))
+
+def onExit():
+    pass
+
+
+## source https://github.com/rsyslog/rsyslog/blob/master/plugins/external/messagemod/anon_cc_nbrs/anon_cc_nbrs.py
+
+"""
+-------------------------------------------------------
+This is plumbing that DOES NOT need to be CHANGED
+-------------------------------------------------------
+Implementor's note: Python seems to very agressively
+buffer stdouot. The end result was that rsyslog does not
+receive the script's messages in a timely manner (sometimes
+even never, probably due to races). To prevent this, we
+flush stdout after we have done processing. This is especially
+important once we get to the point where the plugin does
+two-way conversations with rsyslog. Do NOT change this!
+See also: https://github.com/rsyslog/rsyslog/issues/22
+"""
+onInit()
+keepRunning = 1
+while keepRunning == 1:
+    msg = sys.stdin.readline()
+    if msg:
+        msg = msg[:-1] # remove LF
+        onReceive(msg)
+        sys.stdout.flush() # very important, Python buffers far too much!
+    else: # an empty line means stdin has been closed
+        keepRunning = 0
+onExit()
+sys.stdout.flush() # very important, Python buffers far too much!