TCP: How are the seq / ack numbers generated?

Question

I am currently working on a program which sniffs TCP packets being sent and received to and from a particular address. What I am trying to accomplish is replying with custom tai

Answer 1

If I understand you correctly - you're trying to mount a TCP SEQ prediction attack. If that's the case, you'll want to study the specifics of your target OS's Initial Sequence Number generator.

There were widely publicized vulnerabilties in pretty much all the major OS's wrt their ISN generators being predictable. I haven't followed the fallout closely, but my understanding is that most vendors released patches to randomize their ISN increments.

Answer 2

Seems that the rest of the answers explained pretty much all about where to find detailed and official information about ACK's, namely TCP RFC

Here's a more practical and "easy understood" page that I found when I was doing similar implementations that may also help TCP Analysis - Section 2: Sequence & Acknowledgement Numbers