On Fri, 5 Jan 2001, Steven Vacca wrote:
> Here's my problem,
>
> The Unit Under Test (UUT) has Redhat's embedded Linux kernel (based on Linux/PPC
> kernel 2.2.13), from the Redhat EDK 1.0, running on an embedded PowerPC
> processor with 8M of RAM, and is connected to a LAN.
>
> For my test, I have a TCP Client (Microsoft) on a PC, also connected to the LAN,
>connect
> to a TCP Server (linux) on the UUT at the following intervals (1/5s = "once every 5
>secs"):
> 1/5s, 1/20s, 1/30s, and 1/60s.
>
> For 1/5s, 1/20s, and 1/30s, approx. 10 minutes is the constant time when the TCP
> Client fails to connect to the Server.
>
> But, whenever the connect frequency = 1/60s, or longer, then the problem goes away
>and
> the TCP Client can connect forever at this rate.
>
> Test Results:
>
> 1/5s: stopped connecting on next try @ 10:05
>
> 1/20s: stopped connecting on nex try @ 9:40
>
> 1/30s: stopped connecting on next try @ 10:30
>
> 1/60s: connects forever (several hours in test)
>
> The fact that regardless of whether the connects occur at a very high frequency
>(100/s) or
> low frequency (1/30s), the TCP Client fails to connect after 10 mins. I think 10
>min is the key).
> So it appears that something happens once a minute, and if that goes on for 10
>times, then
> connects are denied. As long as at least 1 min is allowed to go by without
>accepting a connect
> from a client, then there is no problem.
>
> This is very repeatable. Note that if I pause the Client from connecting just
>before the 10 minute
> time period connect() failure is to occur, and wait at least 1 minute (can't be
>less), and then allow
> the Client to continue connecting, then the Client is able to connect for another 10
>minutes before
> the connect() failure occurs.
>
> So, it appears that something must be scheduled to run once per minute, and it
>somehow does
> something to the TCP Server. There aren't any background activities running tha I
>know of in this
> small-sized embedded environment.
>
> Thanks a million for anybody's help or suggestions,
>
> ShutEye Thinkin
> Roanoke, Virginia USA
>
>
Is the program you are connecting to launched by inetd? If so you may be
running into its limits on how often you can spawn a process. This limit
is settable, but you are exceding the default limit with your tests. You
will want to check the logs on the Linux machine in any case to see what
is going on. If inetd is shutting down the service, it will say so. If
it is some other DOS detection, it should also show up in the logs.
Mikkel
--
Do not meddle in the affairs of dragons,
for you are crunchy and taste good with ketchup.
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