Add DIP=SIP testcase HLD. (#224)

* Added DIP=SIP testcase HLD.
* Extended with additional topologies.

doc/DIP=SIP_HLD.md

@@ -0,0 +1,160 @@
+# DIP=SIP PTF Validation High Level Design
+
+## Overview
+
+The purpose of this test is to validate that SONiC switch supports routing of L3 packets with DIP=SIP.
+
+## Topology
+
+```
+                    |-----------------------|
+                    |                       |
+|--------|          |-------|               |
+|DST HOST|----------|DST RIF|               |
+|--------|          |-------|               |
+                    |                       |
+                    |          DUT          |
+                    |                       |
+|--------|          |-------|               |
+|SRC HOST|----------|SRC RIF|               |
+|--------|          |-------|               |
+                    |                       |
+                    |-----------------------|
+```
+
+_Note_:
+
+> Hosts are emulated using VMs  
+> RIF types are PORT/LAG
+
+## Sources
+
+### Structure
+
+```
+sonic-mgmt
+|
+|-ansible
+  |
+  |-roles
+    |
+    |-test
+      |
+      |-files
+      | |
+      | |-ptftests
+      |   |
+      |   |-dip_sip.py
+      |
+      |-tasks
+      | |
+      | |-dip_sip.yml
+      |
+      |-vars
+        |
+        |-testcases.yml
+```
+
+### testcases.yml
+
+This file defines testcase entry point.
+
+### dip_sip.yml
+
+This file contains logic related to artifacts collection and aggregation.  
+It performs all the necessary prerequisite operations based on provided topology.
+
+Supported topologies:
+
+* t0
+* t0-16
+* t0-56
+* t0-64
+* t0-64-32
+* t0-116
+* t1
+* t1-lag
+* t1-64-lag
+
+Workflow:
+
+1. Gather minigraph info
+2. Gather LLDP info
+3. Get DST/SRC host MAC address
+3. Get DST/SRC router MAC/IPv4/IPv6 address
+4. Get DST/SRC port indices (PTF port numbers)
+5. Run PTF test
+
+_Note_:
+
+> Depending on router type there can be more than one member, thus we need to calculate all the member indices
+
+### dip_sip.py
+
+This file contains core PTF logic.  
+It provides mechanism for UDP packets composing/sending/receiving.
+
+Supported parameters:
+
+| Parameter       | Description                                                   |
+|:--------------- |:------------------------------------------------------------- |
+| testbed_type    | Testbed type                                                  |
+| dst_host_mac    | Destination host MAC address                                  |
+| src_host_mac    | Source host MAC address                                       |
+| dst_router_mac  | Destination router MAC address                                |
+| src_router_mac  | Source router MAC address                                     |
+| dst_router_ipv4 | Destination router IPv4 address                               |
+| src_router_ipv4 | Source router IPv4 address                                    |
+| dst_router_ipv6 | Destination router IPv6 address                               |
+| src_router_ipv6 | Source router IPv6 address                                    |
+| dst_port_ids    | Destination port array of indices (when router has a members) |
+| src_port_ids    | Source port array of indices (when router has a members)      |
+
+## Description
+
+### Testcase summary
+
+Basically, PTF is used to construct two packets: data packet and expected packet.  
+After data packet is sent using source port index, we are waiting expected packet on one of the destination port indices.
+
+Default values:
+
+* pkt_ttl_hlim=64
+
+Values:
+
+* dst_host_ipv4_ipv6=\<dst_router_ipv4_ipv6\>+1
+* src_host_ipv4_ipv6=\<src_router_ipv4_ipv6\>+1
+
+Data packet:
+
+* DST_MAC=\<src_router_mac\>
+* SRC_MAC=\<src_host_mac\>
+* DST_IPv4_IPv6=\<dst_host_ipv4_ipv6\>
+* SRC_IPv4_IPv6=\<dst_host_ipv4_ipv6\>
+* TTL_HL=\<pkt_ttl_hlim\>
+
+Expected packet:
+
+* DST_MAC=\<dst_host_mac\>
+* SRC_MAC=\<dst_router_mac\>
+* DST_IPv4_IPv6=\<dst_host_ipv4_ipv6\>
+* SRC_IPv4_IPv6=\<dst_host_ipv4_ipv6\>
+* TTL_HL=\<pkt_ttl_hlim\>-1
+
+### Expected results
+
+Testcase is considered to be passed successfully if packet is routed between router interfaces, otherwise - failed.
+
+_Note_:
+
+> In case of failure the appropriate error message will be printed (including expected and received packet dumps)
+
+## Examples
+
+```bash
+sudo -H ansible-playbook test_sonic.yml -i inventory --limit arc-switch1025-t0 -e testbed_name=arc-switch1025-t0 -e testbed_type=t0 -e testcase_name=dip_sip -vvvvv
+```
+
+_Note_:
+> Logs are located here: /tmp/dip_sip.DipSipTest.\<timestamp\>.log