nquic_pmtud (nquic v1.0.0)

Datagram Packetization Layer PMTU Discovery (DPLPMTUD) per RFC 8899.

Pure functional state machine for path MTU discovery. The caller (nquic_protocol or nquic_conn_statem) drives transitions by calling on_probe_acked/1, on_probe_lost/1, on_timeout/1, etc.

States: disabled, base, searching, search_complete, error.

Summary

Functions

disable(S)

Disable PMTUD. Resets to BASE_PLPMTU.

enable/1

Enable PMTUD. Transitions from disabled to searching.

generate_probe/1

Generate a probe frame list (PING + PADDING to target size). Returns {ok, Frames, Size, State} where Size is the target probe size and State has probe_pending cleared, or {error, no_probe_needed}.

get_current_mtu/1

Get the current effective MTU.

get_probe_size/1

Get the size of the next probe packet.

get_state/1

Get the current DPLPMTUD state.

get_timer_ms/1

Get the timer interval in milliseconds, or infinity if no timer needed.

needs_probe/1

Whether a probe packet should be sent now.

new()

Create a new PMTUD state (disabled).

new(MaxMTU)

Create a new PMTUD state with a custom max MTU.

on_black_hole(S)

Called when black hole is detected (sustained loss after MTU increase).

on_probe_acked/1

Called when a probe packet was acknowledged.

on_probe_lost/1

Called when a probe packet was lost (not acked within timeout).

on_timeout/1

Called on reprobe timer expiry. Triggers a new search from current MTU.

Types

pmtud_state()

-type pmtud_state() ::
          #pmtud{state :: disabled | base | searching | search_complete | error,
                 current_mtu :: pos_integer(),
                 probe_size :: non_neg_integer(),
                 probe_count :: non_neg_integer(),
                 search_low :: pos_integer(),
                 search_high :: pos_integer(),
                 probe_pending :: boolean(),
                 last_probe_time :: non_neg_integer()}.