Module probe 

SWIM direct and indirect liveness probe packets.

SWIM probes use standard NDN Interest/Data so they traverse the normal forwarding pipeline. The PIT handles rendezvous for indirect probes — no special routing is needed.

Packet formats

Direct probe (node A → node B):

Interest: /ndn/local/nd/probe/direct/<B-name>/<nonce-u32>

Indirect probe (node A asks node C to probe node B):

Interest: /ndn/local/nd/probe/via/<C-name>/<B-name>/<nonce-u32>

Probe ACK (node B or C → node A via PIT reverse path):

Data: same name as the Interest
      Content: empty (the ACK is the Data itself)

Usage pattern

1. A detects B is STALE; sends build_direct_probe(b, nonce) on B’s face.
2. If no ACK within probe_timeout, A sends build_indirect_probe(c, b, nonce) for K randomly chosen intermediaries.
3. Only if all K indirect probes time out does A declare B ABSENT.

The SWIM fanout K is set by DiscoveryConfig::swim_indirect_fanout. K = 0 disables indirect probing entirely (use BackoffScheduler instead).

Structs

DirectProbe

Parsed fields from a direct probe Interest.

IndirectProbe

Parsed fields from an indirect probe Interest.

Functions

build_direct_probe

Build a direct probe Interest.

build_indirect_probe

Build an indirect probe Interest.

build_indirect_probe_encoded

Build an indirect probe with the length-prefix encoding.

build_probe_ack

Build a probe ACK Data packet.

is_probe_ack

Check whether the raw packet is a probe ACK Data (empty-content reply).

parse_direct_probe

Parse a direct probe Interest name.

parse_indirect_probe

Parse an indirect probe Interest name.