Field Report: M1 Ingress Filter

1. Objective

The goal of Milestone M1 was to establish a functional XDP (Express Data Path) hook capable of inspecting packet headers and issuing verdict codes (XDP_DROP / XDP_PASS) before the kernel allocates an sk_buff.

Key Capabilities:

• Attach BPF bytecode to the Loopback interface (lo).
• Parse Ethernet (ethhdr) and IP (iphdr) structures.
• Identify specific traffic patterns (Destination IP).
• Emit debug telemetry via /sys/kernel/debug/tracing/trace_pipe.

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2. Implementation Logic

The core logic resides in src/kern/hyperion_core.c. We utilize direct pointer arithmetic to validate protocol headers against the strict eBPF verifier constraints.

/* Hyperion M1 Logic: Destination Filtering */
if (ip->daddr == 0x04030201) { // Checks for 1.2.3.4 (Big Endian)
    bpf_printk("Hyperion: KILL -> Dest 1.2.3.4 detected!\n");
    return XDP_DROP;
}

This logic executes in the Network Driver Interrupt Context, ensuring minimal latency.

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3. Verification & Evidence

Test Procedure:

1. Loader: sudo ./hyperion_ctrl (Attaches XDP program).
2. Generator: ping -I lo 1.2.3.4 (Generates synthetic traffic).
3. Observer: sudo cat /sys/kernel/debug/tracing/trace_pipe.

Result: The trace pipe confirmed successful interception and dropping of packets destined for 1.2.3.4.

Figure 1: Live capture of the Linux Kernel Trace Pipe showing Hyperion enforcing the drop verdict.

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4. Performance Note

Unlike iptables, which processes packets after memory allocation, Hyperion discarded these packets without traversing the full networking stack. This confirms the “Early Drop” architectural advantage.

Status: M1 COMPLETE