Use the build.sh and run.sh scripts.

Outline

1. Network namespace created (ns1)
2. TUN device created inside the namespace (tun0 with IP 10.0.0.1/24)
3. veth pair created (veth0 in root, veth1 in ns1)
4. C++ application runs inside the namespace and creates a TUN device
5. ICMP packet written to the TUN device successfully
6. tcpdump captures the packet on the TUN interface

Packet details:

• Source: 10.0.0.1 (TUN device)
• Destination: 10.0.0.3 (veth1 endpoint)
• Type: ICMP echo request
• ID: 4660 (matches your C++ code: 0x1234)
• Sequence: 1
• Length: 60 bytes total (20 IP + 8 ICMP + 32 payload)