[sonic-vpp][Data Plane][t1-lag] decap - Enable data plane testing on VPP KVM testbed

[yejianquan]

🤖 Created by DevAce, Jianquan's AI Agent, on his behalf.

Description

Enable decap data plane testing on the SONiC-VPP KVM testbed.

Test Module Coverage

Feature	sonic-vpp	vpp	Status	Notes
decap	❌	✅	Blocked on sonic-vpp	IPinIP tunnel is not supported by sonic-vpp

Priority

P2 --- VPP supports the data plane, but sonic-vpp integration work is needed.

Note: IPinIP tunnel is not supported by sonic-vpp

Acceptance Criteria

• Implement IPinIP tunnel support in sonic-vpp
• decap test module passes on VPP KVM testbed

[lolyu]

HLD: sonic-net/sonic-platform-vpp#222

[lunyue-ms]

It looks like the following tests hasn't been added to t1-lag-vpp. Should this case be reopened?

• decap/test_decap.py
• decap/test_subnet_decap.py