[swss]: Update the ipinip.j2 template to specify the IPv4 loopback address (#998)

Use ipv4_loopback_addresses variable to store all IPv4 loopback addresses.
The source IP for encapsulation is chosen from one of the addresses.
The destination IPs for decapsulation is the list of the addresses.

Signed-off-by: Shu0T1an ChenG <[email protected]>

Author: Shuotian Cheng

dockers/docker-orchagent/ipinip.json.j2

@@ -1,9 +1,16 @@
+{# only IPv4 decapsulation is supported #}
+{% set ipv4_loopback_addresses = [] %}
+{% for (name, prefix) in LOOPBACK_INTERFACE %}
+    {%- if prefix | ipv4 %}
+        {%- set ipv4_loopback_addresses = ipv4_loopback_addresses.append(prefix) %}
+    {%- endif %}
+{% endfor %}
 [
     {
         "TUNNEL_DECAP_TABLE:IPINIP_TUNNEL" : {
             "tunnel_type":"IPINIP",
-            "src_ip":"{{ LOOPBACK_INTERFACE.keys()[0][1] | ip }}",
-            "dst_ip":"{{ LOOPBACK_INTERFACE.keys()[0][1] | ip }}",
+            "src_ip":"{{ ipv4_loopback_addresses | first | ip }}",
+            "dst_ip":"{% for prefix in ipv4_loopback_addresses %}{{ prefix | ip }}{% if not loop.last %},{% endif %}{% endfor %}",
 {% if onie_switch_asic == "mlnx" %}
             "dscp_mode":"uniform",
             "ecn_mode":"standard",
@@ -16,4 +23,3 @@
         "OP": "SET"
     }
 ]
-

src/sonic-config-engine/tests/sample_output/ipinip.json

@@ -11,4 +11,3 @@
         "OP": "SET"
     }
 ]
-