+ Modified buffer config template to include internal ASIC with 5m ca… (#4959)

+ Modified buffer config template to include internal ASIC with 5m cable length
+ added unit test to verify the changes.

files/build_templates/buffers_config.j2

@@ -34,6 +34,7 @@ def
 {%- else %}
     {%- set ports2cable = {
             'torrouter_server'       : '5m',
+            'internal'               : '5m',
             'leafrouter_torrouter'   : '40m',
             'spinerouter_leafrouter' : '300m'
             }
@@ -47,10 +48,14 @@ def
             {%- if DEVICE_NEIGHBOR_METADATA is defined and DEVICE_NEIGHBOR_METADATA[DEVICE_NEIGHBOR[local_port].name] %}
                 {%- set neighbor = DEVICE_NEIGHBOR_METADATA[DEVICE_NEIGHBOR[local_port].name] %}
                 {%- set neighbor_role = neighbor.type %}
-                {%- set roles1 = switch_role + '_' + neighbor_role %}
+                {%- if 'asic' == neighbor_role | lower %}
-                {%- set roles2 = neighbor_role + '_' + switch_role %}
+                         {%- set roles1 = 'internal' %}
-                {%- set roles1 = roles1 | lower %}
+                {%- else %}
-                {%- set roles2 = roles2 | lower %}
+                         {%- set roles1 = switch_role + '_' + neighbor_role %}
+                         {%- set roles2 = neighbor_role + '_' + switch_role %}
+                         {%- set roles1 = roles1 | lower %}
+                         {%- set roles2 = roles2 | lower %}
+                {%- endif %}
                 {%- if roles1 in ports2cable %}
                     {%- if cable_len.append(ports2cable[roles1]) %}{% endif %}
                 {%- elif roles2 in ports2cable %}

src/sonic-config-engine/sonic-cfggen

@@ -57,7 +57,11 @@ def sort_by_port_index(value):
     if not value:
         return
     if isinstance(value, list):
-        value.sort(key = lambda k: int(k[8:]))
+        # In multi-ASIC platforms backend ethernet ports are identified as 
+        # 'Ethernet-BPxy'. Add 1024 to sort backend ports to the end.
+        value.sort(
+            key = lambda k: int(k[8:]) if "BP" not in k else int(k[11:]) + 1024
+        )
 
 def is_ipv4(value):
     if not value:

src/sonic-config-engine/tests/test_multinpu_cfggen.py

@@ -4,6 +4,7 @@ import subprocess
 import os
 import json
 import yaml
+import shutil
 
 SKU = 'multi-npu-01'
 ASIC_SKU = 'multi-npu-asic'
@@ -274,3 +275,47 @@ class TestMultiNpuCfgGen(TestCase):
                                       "Loopback0|FC00:1::32/128": {},
                                       "Loopback4096|8.0.0.5/32": {},
                                       "Loopback4096|FD00:4::32/128": {}})
+
+    def test_buffers_multi_asic_template(self):
+        build_root_dir = os.path.join(
+            self.test_dir, "..", "..", ".."
+        )
+        # using Trident2 buffer configuration
+        device_config_dir = os.path.join(
+            build_root_dir,
+            "device",
+            "arista",
+            "x86_64-arista_7050_qx32",
+            "Arista-7050-QX32"
+        )
+        device_buffer_template = os.path.join(
+            device_config_dir, "buffers.json.j2"
+        )
+        buffer_template = os.path.join(
+            build_root_dir, "files", "build_templates", "buffers_config.j2"
+        )
+        port_config_ini_asic0 = os.path.join(
+            self.test_data_dir, "sample_port_config-0.ini"
+        )
+        # asic0 - mix of front end and back end ports
+        shutil.copy2(buffer_template, device_config_dir)
+        argument = "-m {} -p {} -n asic0 -t {}".format(
+            self.sample_graph, port_config_ini_asic0, device_buffer_template
+        )
+        output = json.loads(self.run_script(argument))
+        os.remove(os.path.join(device_config_dir, "buffers_config.j2"))
+        self.assertDictEqual(
+            output['CABLE_LENGTH'],
+            {
+                'AZURE': {
+                    'Ethernet8': '300m',
+                    'Ethernet0': '300m',
+                    'Ethernet4': '300m',
+                    'Ethernet-BP4': '5m',
+                    'Ethernet-BP0': '5m',
+                    'Ethernet-BP12': '5m',
+                    'Ethernet-BP8': '5m',
+                    'Ethernet12': '300m'
+                }
+            }
+        )