Bad Packets

[Klaus_1250]

I'm having problems downloading from an Azureus 2.3.0.6 client. It gives me "Bad Packets":

[23:15:15] **.**.**.*** : [Azureus/2306 ]: Got PieceRequest i don't have: 625:131072->16384

[23:15:15] **.**.**.*** : [Azureus/2306 ]: Disconnect: Bad packet

The client is on a fast connection and the torrent is on a private tracker. The client in question send me a few 100 MB of data and I send about 30MB back, without any errors. But now it ALWAYS goes wrong after a few requests. E.g. Upon every reconnection, good data is send/received for a few seconds, and than the above message/request and disconnect. (happend tens of times)

What is that bad packet? Can't µTorrent ignore the packet?

[Edit]

Sometimes upon handshake:

[23:23:56] **.**.**.*** : [Azureus/2306 ]: Handshake completed

[23:25:01] **.**.**.*** : [Azureus/2306 ]: Disconnect: Peer EOF.

[1c3d0g]

Is it a legal torrent? If not, it could be an RIAA/MPAA zombie... :/

[Firon]

Could be a problem on his end. Perhaps his router has DMZ mode on and is mangling the packet.

[splintax]

How does DMZ mangle the packet? Doesn't that just let everything through without interference? :S

[abbad0n]

Probably ment game mode.

[Firon]

Yeah, game mode DMZ. D-Link routers have this mode.

[MoJo]

I don't know what's been happening lately ... but I've been getting more and more Bad Packets with uTorrent/ and Azureus. Sometimes even on legal files, could there be a bug ... like BitComet's PHE polluting torrents, or a DHT trouble where somewhere incorrect data is finding it's way onto the downloads? Maybe an Azureus <-> uTorrent <-> BitComet <-> Mainline interaction, where when one of these clients interacts with another, Bad Data is sent. Maybe our ISP's are intentionally polluting torrents ... wouldn't that just waste there precious bandwidth. Like on my Ubuntu box, Azureus has been running and to now it has 252 MB's of Bad Data, that consists of only one piece thats is 1 MB in size. It bans people who have consistently sent Bad Data ... but somehow Bad Data is still being sent. This is suspicious ... I have never had this much hasfails, most I had a month ago was 3, now on 1 file that doesn't fall under MPAA or RIAA jurisdiction is giving me problems?

[1c3d0g]

Your RAM could be getting corrupted (slowly), so you might want to run a RAM stress-test tool at least 24 hours to rule out any inconsistencies... :/

[Firon]

Run SpinRite too.

[Klaus_1250]

Yeah, game mode DMZ. D-Link routers have this mode.

What exactly does this do? (game mode DMZ). I'm only familiar with normal DMZ's :-)

The torrent isn't legal (I think) but it is not something the RIAA/MPAA will look at / interfere with either :-p I received well over 150MB of good data, so there seems to be a genuine problem somewhere. No zombie or anything (checked the stats on the private tracker).

I do have an Ethereal trace, which include the bad-packets, but does Ludde have the time for that?

[Firon]

Some routers employ a trick called game mode, rewriting internal and external IP address bytes within incoming and outgoing packets. This allows older games that hard-code IP addresses to function behind a NAT setup. However, when such an address-byte sequence is coincidentally present within a file being sent via the BitTorrent protocol, the router mistakenly rewrites the data. This changes the content of the packet, which fails hash-checking. Any incoming packet that has a byte sequence that happens to match the address byte sequence is susceptible to mangling, an event estimated to happen once for about every 4GB of data transferred.

[1c3d0g]

Looks like there's a lot of packet mangling (either intentional or not) going on... :mad:

[Klaus_1250]

@Firon: I don't understand that part. Whenever you're NAT'ted, e.g. you internal IP is something like 192.168.1.100 and your external IP is a regular IP-address, routers rewrite the IP-addresses for incoming and outgoing addresses in the IP-header and recalculate the checksum?

Or does game-mode DMZ actually look inside the contents of the packet and rewrite data there? Once in every 4GB doesn't sound like a lot, but I can't even exchange 4MB without the error :-(

[Moody]

@Klaus_1250: as someone advised earlier in the thread check your ram. Download a ram checker that runs from a bootable floppy disk. (Microsoft do one). Bad ram is often the culprit, with corrupt data in bit torrents.

[Klaus_1250]

@moody: I think the RAM-checking comment was ment for MoJo. I can easily fill/use my RAM without problems, and the bad packets I was talking about were from 1 user only.

[Firon]

Klaus_1250: it's designed for old games that were for LAN only or something, the problem is that it mangles any packet with the string matching your local IP, which is often just a normal packet. And it happens over and over. It's the 99.9% bug some people get on Azureus.