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* Answer a link's packet from the address it came toeunhhu2026-09-291-14/+59
| | | | | | | | | | | | | | The listener's socket takes packets to any address of the node, and its answers went out from whichever address the system chose for the way back. A sender whose socket is connected to another of the node's addresses (a node with many, or a name that points at a second one) takes answers only from the address it sent to: it heard none, and its records went on arriving unacknowledged. Now the listener asks for the address each packet came to (IP_PKTINFO; IPv4 as ::ffff:a.b.c.d on a socket of both) and answers from it. The path a receiver keeps for a run is both addresses (48 bytes, not 28): a packet that comes to another of the node's addresses moves it, and is checked, as one from elsewhere is. Found by a receiver moved to 127.0.0.2 (the check that follows).
* Find how large a packet the path carries: 1,452 bytes once a probe is ↵eunhhu2026-09-291-13/+50
| | | | | | | | | | | | | | | acknowledged A link starts at 1,200 bytes; once an RTT is known it sends a PING padded to 1,452 (DPLPMTUD, RFC 8899), alone and with the don't-fragment bit, and uses that size once it is acknowledged. A probe lost is no congestion; it is tried again a second on, three times, then ten minutes on. GSO is asked for each burst (a control message), not the socket, so a packet sent alone is never cut. CUBIC counts in the datagram. On loopback packets fall by 19-27%; the CPU a record falls 13% at 1 KiB and 7% at 16 KiB; in the simulator of a 50 Mbit/s path with 1% loss the goodput rises from 6.1 to 7.0 Mbit/s (5%: 2.3 to 3.0).
* Measure a link on a path of loss, reordering and a bottleneck (M6 harness)eunhhu2026-09-291-2/+4
| | | | | | | | | 020-lossy-paths/run.py runs each case in an unprivileged namespace: a 50 Mbit/s tbf bottleneck under netem's delay, jitter and loss, both ways. A link may send without UDP GSO (pure_link_gso), as netem takes a burst as one packet; quinn the same (QUIC_GSO=0). transport.c and the quinn harness give the records handed over in each 100 ms, and at a steady rate the time each took; TCP CUBIC flows run beside them.
* Keep a link's two sides as state alone, the sockets and threads aparteunhhu2026-09-291-1446/+68
| | | | | | | | | | | | link/link-protocol.h is the protocol with no socket, thread or clock of its own: packets and time in, packets out. link/link.h carries it over UDP as before. A sender starts small (8 flights, 16 records, a 4 KiB ring) so one thread can hold many. The transport's CPU a record is the same within 2% (five rounds each way, 61 B to 16 KiB). test-link runs both sides through a network of its own: loss, packets held back and doubled, failed saves, an idle sweep, and both sides starting again, every record applied once as sent.
* Let links know nothing of the core: the host names inputs and shapeseunhhu2026-09-291-70/+40
| | | | | | A sender takes its messages' shape, and a listener asks its host which input a stream goes to. The core gives the shape (pure_module_shape); link/ now builds without the core's headers.
* Put the links and the crypto they use in link/, a part of their owneunhhu2026-09-291-0/+1862
libpure-link.a holds them; pure-serve and the M5 harness link it instead of naming its source files.