The Practice:
=============
wget darkircop.org/profile.tgz
cd profile
make
insmod ccid2.ko ccid2_profile=1
./profiler log
LD_PRELOAD=./libintr.so iperf -X DCCP -i1 -l 1400 -c 1.2.3.5 -t 60
cat log | grep "^pid.* 0 " | awk '{print $3 " " $4}' > log.cwnd
cat log | grep "^pid.* 1 " | awk '{print $3 " " $4}' > log.rtt
cat log | grep "^pid.* 2 " | awk '{print $3 " " $4}' > log.pipe
cat log | grep "^pid.* 3 " | awk '{print $3 " " $4}' > log.rate
The Theory:
===========
* If the module is loaded with profiling information, changes in CCID2's state
will be recorded.
* Use getsockopt on the socket to obtain all profiling info.
* To simplify the process, I coded profiler.c which will poll getsockopt() on a
socket and log info on a file.
* profiler.c needs a DCCP socket to monitor. You can pass one to it via UNIX
sockets.
* libintr will intercept library calls which create DCCP sockets. When a DCCP
socket is created, it will be sent to the profiler so that it can monitor it.
This allows you to monitor the sockets created by a program [such as iperf]
without having to screw with its code.
Details:
========
* RTT is initialized to -1, hence the giant number on the first sample.
* Pipe is only recorded if it varies > 3 I think. Otherwise, you would get huge
amounts of data [pipe normally varies +-1].
* X amount is allocated in the kernel for storing profiling information. It is
a ring buffer. If there is an overflow, profiler.c will tell you. Try either
increasing allocated size in kernel or polling frequency.
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