The eBPF verifier, bounded loops, and you

The verifier is not your enemy. It is a static analyzer with strong opinions. The fastest way to write eBPF is to write code the verifier can reason about, then optimize — not the other way around.

Bounded loops

1/* the verifier needs to know the upper bound */
2#pragma unroll
3for (int i = 0; i < 8; i++) {
4    if (i >= len) break;
5    sum += pkt[i];
6}

Unrolling + an explicit break gives the verifier a finite state space.

Provability is a feature. The verifier rejecting your program at load time is cheaper than the kernel oopsing at runtime.

• Keep scalar ranges tight — the verifier tracks min/max per register.
• Avoid pointer arithmetic the verifier can't follow; use bpf_probe_read.
• Map lookups reset ranges. Use them deliberately.