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Re: Apr 17 10:49:49 teks kernel: TCP: Treason uncloaked! Peer

On Thu, 18 Apr 2002 01:43, Jason Lim wrote:
> Hi all,
> can anyone make sense of the following?
> Apr 17 10:49:49 teks kernel: TCP: Treason uncloaked! Peer
> 80 shrinks window 2321430930:2321431630. Repaired.
> What is this "Treason uncloaked"?

>From /usr/src/linux/net/ipv4/tcp_timer.c:

        if (tp->snd_wnd == 0 && !sk->dead &&
            !((1<<sk->state)&(TCPF_SYN_SENT|TCPF_SYN_RECV))) {
                /* Receiver dastardly shrinks window. Our retransmits
                 * become zero probes, but we should not timeout this
                 * connection. If the socket is an orphan, time it out,
                 * we cannot allow such beasts to hang infinitely.
#ifdef TCP_DEBUG
                if (net_ratelimit())
                        printk(KERN_DEBUG "TCP: Treason uncloaked! Peer 
%u.%u.%u.%u:%u/%u shrinks window %u:%u. Repaired.\n",
                               NIPQUAD(sk->daddr), htons(sk->dport), sk->num,
                               tp->snd_una, tp->snd_nxt);

So it appears that someone is running some sort of "tar-pit" system that is 
designed to keep sockets in a bad state and run you out of kernel memory.

I suspect that this ties in with the spam blocking things we recently 
discussed.  Maybe you should tell your ISP that they are to blame for such 
actions being done to you and that they should "give you face" (I think that 
was the term you used) by closing their open relays.

> I think the following is unrelated, but I also found a lot of them (50+)
> in the logs:
> Apr 16 19:52:54 teks kernel: UDP: bad checksum. From
> to xxx.194.146.xxx:33618 ulen 20
> Apr 16 19:53:00 teks kernel: UDP: bad checksum. From
> to xxx.194.146.xxx:33561 ulen 20

UDP and TCP, no direct relation.  But if someone's trying something nasty on 
one protocol they might be trying something nasty on another, the IPs are 
different, but faking the source of UDP is no great challenge.

> About 6 hours later, the box crashed (not sure if it could be related to
> the above attacks).

Someone who's doing the tar-pit attack would probably like your box to crash, 
but I'd hope that Linux can withstand such things, and there is special-case 
code in there to deal with it.  My guess is that your posting to the 
ide-arrays list about 3ware driver problems is a more likely explanation of 
the crash.

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