[Icecast] Source throttling bug, windows->linux

Dan Merillat
2005-11-24T16:36:56Z

I'm getting a weird source throttling bug that I just don't know how to
track down.

Source is windows shoutcast 1.9.0 winamp plugin (XP up to date, and possibly
others)
Server is 2.3.0

It works fine for quite a while, then I get the following wierdness on
tcpdump and it goes to hell:

21:03:54.601871 IP (tos 0x0, ttl 64, id 27852, offset 0, flags [DF], length:
40) server.8001 > source.2225: . [tcp sum ok] 25:25(0) ack 426502 win 62780
21:03:54.644783 IP (tos 0x0, ttl 118, id 6813, offset 0, flags [DF], length:
1500) source.2225 > server.8001: P 426502:427962(1460) ack 25 win 65511
21:03:54.644813 IP (tos 0x0, ttl 64, id 27853, offset 0, flags [DF], length:
40) server.8001 > source.2225: . [tcp sum ok] 25:25(0) ack 427962 win 164
21:03:54.648512 IP (tos 0x0, ttl 118, id 6814, offset 0, flags [DF], length:
144) source.2225 > server.8001: P 427962:428066(104) ack 25 win 65511
21:03:54.648595 IP (tos 0x0, ttl 64, id 27854, offset 0, flags [DF], length:
40) server.8001 > source.2225: . [tcp sum ok] 25:25(0) ack 428066 win 164
21:03:59.651984 IP (tos 0x0, ttl 118, id 7095, offset 0, flags [DF], length:
204) source.2225 > server.8001: . 428066:428230(164) ack 25 win 65511

So the server goes from a windowsize of 62k to 164 bytes. Once this happens,
the XP stack only tries sending one packet every 5 seconds.

What would cause that kind of throttling behavior? If I restart icecast it
works for a while, then locks up again.

I've had reports that it happens with windows icecast2 sources as well, but
I wasn't able to get a tcpdump of it happening for them.

I tried turning off tcp_window_scaling on linux, in case it was hitting a
bug in XP, but no luck there either.

Oddities: I tried setting the server to the lowest priority in linux, then
running a few CPU hogging programs. That didn't cause
a noticible difference.

Ideas where to look?
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