Add lacp-rate option to portchannel add command

config/main.py

@@ -1720,8 +1720,11 @@ def portchannel(ctx, namespace):
 @click.argument('portchannel_name', metavar='<portchannel_name>', required=True)
 @click.option('--min-links', default=1, type=click.IntRange(1,1024))
 @click.option('--fallback', default='false')
+@click.option('--fast-rate', default='false',
+              type=click.Choice(['true', 'false'],
+                                case_sensitive=False))
 @click.pass_context
-def add_portchannel(ctx, portchannel_name, min_links, fallback):
+def add_portchannel(ctx, portchannel_name, min_links, fallback, fast_rate):
     """Add port channel"""
     if is_portchannel_name_valid(portchannel_name) != True:
         ctx.fail("{} is invalid!, name should have prefix '{}' and suffix '{}'"
@@ -1732,9 +1735,12 @@ def add_portchannel(ctx, portchannel_name, min_links, fallback):
     if is_portchannel_present_in_db(db, portchannel_name):
         ctx.fail("{} already exists!".format(portchannel_name))
 
-    fvs = {'admin_status': 'up',
-           'mtu': '9100',
-           'lacp_key': 'auto'}
+    fvs = {
+        'admin_status': 'up',
+        'mtu': '9100',
+        'lacp_key': 'auto',
+        'fast_rate': fast_rate.lower(),
+    }
     if min_links != 0:
         fvs['min_links'] = str(min_links)
     if fallback != 'false':

doc/Command-Reference.md

@@ -6738,12 +6738,13 @@ When any port is already member of any other portchannel and if user tries to ad
 Command takes two optional arguements given below.
 1) min-links  - minimum number of links required to bring up the portchannel
 2) fallback - true/false. LACP fallback feature can be enabled / disabled.  When it is set to true, only one member port will be selected as active per portchannel during fallback mode. Refer https://github.com/Azure/SONiC/blob/master/doc/lag/LACP%20Fallback%20Feature%20for%20SONiC_v0.5.md for more details about fallback feature.
+3) fast-rate - true/false, default is flase (slow). Option specifying the rate in which we'll ask our link partner to transmit LACPDU packets in 802.3ad mode. slow - request partner to transmit LACPDUs every 30 seconds, fast - request partner to transmit LACPDUs every 1 second. In slow mode 60-90 seconds needed to detect linkdown, in fast mode only 2-3 seconds.
 
 A port channel can be deleted only if it does not have any members or the members are already deleted. When a user tries to delete a port channel and the port channel still has one or more members that exist, the deletion of port channel is blocked. 
 
 - Usage:
   ```
-  config portchannel (add | del) <portchannel_name> [min-links <num_min_links>] [fallback (true | false)]
+  config portchannel (add | del) <portchannel_name> [min-links <num_min_links>] [fallback (true | false)] [fast-rate (true | false)]
   ```
 
 - Example (Create the portchannel with name "PortChannel0011"):