TCP Retransmissions

Ordinarily, you're a terrible place to get code, /prog/, but I must yield.

I'm having trouble with AES encryption increasing on packet retransmissions, so I obviously must detect and discard retransmissions for encryption purposes. Since I'm using WinPcap, I figured that Ethereal would be a good place to go to see how it detects these events. I was wrong.

Example: http://pastebin.com/d165a8f15 ^[1]

I can't tell what the shit is going on with such ugly C code. Any of you have an enterprise-level solution to retransmission detection? Thanks for your time.

¹: As accessed on 4 JAN 09 at 10 PM CST. It will evaporate within 24 hours.

>>40
So fucking what? The target will be inlined in Jcc just as in JMP.  No fucking target prediction.

There is difference:
example JMP :
"This instruction is used to deviate the flow of a program without taking into account the actual conditions of the flags or of the data."
exmaple JA Label
"This means that the jump is only done if the CF flag is deactivated or if the ZF flag is deactivated, that is that one of the two be equal to zero."

Which one is faster?

>>42
With branch prediction, none is faster.

>>43
Its faster to inline direct JMPs then predict what conditional/boolean JMP will do.

>>42
Also what the fuck does that have to do with gotos being faster than regular control structures anyway? You must be talking about using goto to leave inner loops or shit like that. That doesn't have anything to do with JMP being faster than Jcc. Just fucking die already, you fucking /g/-dwelling troll.

>>18 says "Both goto and if/else becomes jcc in ASM anyway"
Which is plain wrong. Goto can compile to direct JMPs
in QBasic:
goto "end"
goto 20;

"You must be talking about using goto to leave inner loops or shit like that." Thats just like >>18 thinks

>>44
Why the fuck would you even make that comparison? What the fuck is your fucking point anyway? Also why don't you fucking write clearly, you fucking asspie? Is Enlish not your 1st language or something? God damn...

>>47
English is my third language, however due constant practice i write very well.

>>46
My god, you fucking robot. What the fuck do you mean by gotos being faster than control structures then?

>>48
Oh, believe me, you don't. Not even close.

>>49
I'm not sure if its worth explaining if you can't understand what i say.see http://en.wikipedia.org/wiki/Goto
this post quoted:
http://kerneltrap.org/node/553/2131

"Used over short distances with well-documented labels, a "goto" can be more
effective, faster, and cleaner than a series of complex flags or other
constructs. The "goto" may also be safer and more intuitive than the
alternative. A "break" is a goto; a "continue" is a "goto" -- these are
statements that move the point of execution explicitly.
"

>>51
That's what I said in >>45, you cunt.

another quote from above:
That said, I have used exactly two "goto" statements in all the lines of C,
C++, Fortran 95, and (yes) COBOL I've written since leaving BASIC and
Fortran IV behind. In one case, a single "goto" doubled the speed of a
time-critical application; in the other case, "goto" shortens a segment of
code by half and makes the algorithm much clearer. I would not use a goto
willy-nilly for the fun of it -- unless I was entering an obfuscated code
contest ;)

We keep lowering the bar for technical prowess, it seems; if something has
the potential to be used "wrong", high-minded designers remove the offending
syntax rather than find or train competent programmers. This is why Java
removes pointers (among other things) -- it's not that pointers aren't
useful or efficient, it's that they require discipline from programmers.

Just because something is dogma doesn't mean it is absolute truth. If
anything, dogma should be sniffed quite carefully, since it tends to be
rather rank if you get close enough. Removing goto is a religious choice,
not a technical one.

I could draw parallels with idiotic laws in general society, but this
message is already marginal for this list.

STOP. TALKING. TO. HIM. YOU. STUPID. FUCKERS.

STOP SEEING HIS POSTS YOU STUPID FUCKERS

    STOP SEEING MY POSTS YOU STUPID FUCKERS

STOP PEEING MY GHOSTS YOU STUPID FUCKERS

Why don't you use a JAVASCRIPT-based solution if you want to stop seeing them?

Meanwhile, back on the farm
>>1
Trying to read and understand code can often be difficult for large or complicated projects (I tried to read through parts of ffmpeg once open source? more like why the fuck do I need to document anything?).

Try running the project through Doxygen to make it easier to to cross-reference. of course that didn't make ffmpeg any easier to understand

There's also a program I ran across once whose sole purpose was for reading, browsing, and cross-referencing C/C++ code. Don't have the link on my atm.

>>59
learn c, problem solved.

This thread has been closed and replaced with the following thread:

Subject: Discharges
Name: Leah Culver
Email: leah@vox.com

Body:

Hi guys, I know that you are mostly guys, but I hope there is at least one girl here that is able to help me. I have been having vaginal discharges recently. The discharge is a green-ish color and smells like cottage cheese mixed with coffee. Any help appreciated.

>>60
Brilliant, I managed to learn C in the last hour and can now read this <http://cekirdek.pardus.org.tr/~ismail/ffmpeg-docs/mdec_8c-source.html>; with perfect clarity. My understanding of the code is deep and insightful. Why, I already identified dozens of bugs and can see the purpose of meaning within the delimiters.

0/10

It doesn't matter anyway because reconstructing a tcp data stream is fucking trivial.  You don't ``detect retransmissions'', you just copy down the byte ranges you see and consume everything up to the first hole.

>>64
Not really debug, just maintain the integrity of.

Currently, I check the current packet in any given direction for being exactly the same as the previous packet in the same directional sequence, but this does not seem to be enough.

>>66
I tried creating a class that contains 20 sequence numbers (arbitrary number that I figured was "good enough") and each time I receive a packet, I assign the sequence number to this array.

When I receive the 20th packet, it resets the index so it should be a rolling window.

However, when I check for matches of the current sequence number, it would seem that either it fails or somehow the code skips that if.

I've had it check to see if there's a match for the direction of the packet and I've had a single unit for sequence testing. Neither works. It's supposed to be: If a sequence number matches, then nothing happens until it gets the next packet.

What does happen is the encryption breaks nearly immediately. So either sequence numbers are matching when they aren't supposed to or they aren't matching when they are.

Logically, it's structured in the way that <capture device> <-> <session encryption/decryption/distribution> <-> <data interfacing>.

This means that it doesn't account for packets that don't get fed into the session. Ideas?

>>67
First line may be a bit ambiguous. I only assign sequence numbers if no matches are found first.

Not really. Testing on my home network connecting to an enterprise network at the moment. Interestingly enough, the stream that goes from here to there breaks first 100% of the time with my last version.

I moved the code to the dispatch spot instead of a higher scope and it seems to be faring much better. I also increased the number to 200.

However, I still have increased issues with just plain not dispatching any more packets period. On a positive note, it doesn't seem like the encryption is falsely increasing .. in my limited testing.

>>70
Still yields broken streams. I don't think this particular implementation of sequence checking is going to work out.

>>68
Are you assigning your own sequence numbers? You need to use the TCP sequence number from the TCP header to detect retransmissions.

>>73
I was using the TCP sequence numbers.

>>74
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