UDP broke

[totaam]

Reported on the mailing list: UDP connection issues.

Original ticket: #639, see also #1669.

Bisecting:

• 3.0.6 bad
• r24990 bad, python3
• r18000 OK, python2
• r21000 OK, python2
• 23000 OK, python2
• r23820 (3.0.0) OK, python2 - bad with python3

So the bug comes from the switch to python3.

[totaam]

First, debugging the 3.0 branch with python2 (different regression..):

• r23820 OK
• r24990 bad (different regression...)
• 24500 OK
• 24750 OK
• r24850 OK
• r24900 OK
• r24950 OK
• r24975 OK
• r24980 bad
• r24976 OK
• 24977 bad

24977 is reverted in 24991.

---

Now, for the python3 bug.

[totaam]

Lots of network debug improvements:

• r25001 log all packet types with XPRA_LOG_PACKET_TYPE=1
• r25003 log both in and out
• r24998 + r25000 make it possible to skip sending (very large) xdg menu data without disabling start-new-commands
• r24999 use repr for ellipsized byte data
  And UDP improvements:
• r24995 + r24992: send control packets more slowly, simplify, warnings, etc
• r25004 + r25005: better debug logging
• r25006: better re-send request heuristics

---

With a python3 server and packet logging:

• we receive the hello packet in about ~46 chunks:

process_udp_data: packet sequence     0 : 25159 bytes added to read queue (got final chunk 45, synchronous=True)

and switch to async mode:

accept() enabling asynchronous packet reception

• we send: hello, setting-change, new-window, startup-complete, server-event
• we receive: clipboard-enable-selections, set-clipboard-enabled, clipboard-enable-selections (?), set_deflate
• ping and we send ping_echo
• we receive server-settings (twice?), set-keyboard-sync-enabled, udp-control, configure-window
• we send cursor, set_deflate
• we receive info-request, configure-window, map-window, focus
• we send window-icon, window-metadata, info-response, draw, ping, udp-control

On the client side it sometimes failed to receive anything at all, but if it does get something, it always fails when trying to parse the udp-control packet, with an error like this one:

Error: received uninterpretable nonsense: invalid packet header byte 801000001919913911710011245991111101161141111080672727102192: '3830313030303030' read buffer='801000001919913911710011245991111101161141111080672727102192' (60 bytes)
 packet no 69 data: '801000001919913911710011245991111101161141111080672727102192'

(not sending the udp-control packet "fixes" things)

[totaam]

2020-01-19 13:33:11: antoine uploaded file udp-badfix.patch (1.9 KiB)

this "fixes" things but is not correct

[totaam]

Fixed in r25007: the code that forces the synchronous flag to False for udp-control packets was duplicating the logic slightly wrong.

Backport to v3.0.x in 25008.