possible message loss in devp2p implementation

[paulperegud]

(I've just started to learn Rust, so please be gentle)

Commit that contains the implementation of subprotocol and a test program:
paulperegud@6107e98
Branch: https://github.com/paulperegud/parity/tree/buggy-pinger
Code is based on tag v1.4.8

Full instruction on how to run: https://github.com/paulperegud/parity/blob/buggy-pinger/util/network/PINGER

This is a program that implements devp2p subprotocol with rudimentary functionality. On established connection both endpoints send 100 messages with packet_id=1 to each other. When message with packet_id<6 is received, counter corresponding to this packet_id is increased and message with packet_id increased by one is sent back. If all messages are delivered (and pinger is written correctly) counters for all packet_id's in range 1..6 should be set to 100. Total of 1200 messages are being exchanged.

Other notes:

1. Please note that in every 1..N chain of messages only last message, numbered N is sometimes lost.
2. If sleeps are inserted and amount messages per second is small, no messages are being lost.
3. This code has been tested on Linux and OSX. Problem manifests only on Linux.

EDIT: fixed link and typoes

[arkpar]

Thanks for a detailed report. I've reproduced the issue and can confirm that this has been fixed by #4102