Are you planning on piecing the individual packets together first, doing your substitution, and then re-splitting the packets?

If not, I think you will run into complications on the splitting points of the packets. How will you know that the entire URL of your image is contained in one single packet, all of the time? Do packets always respect URLs in such a way as to make sure that they will not get chopped in two? I don't think so.

As one website put it:

TCP/IP implementations differ in the approach they take to deciding on packet size. It is fairly common for implementations to use 576-byte packets whenever they can't verify that the entire path is able to handle larger packets. The problem is that many implementations have bugs in the code to reassemble pieces. So many implementors try to avoid ever having splits occur. Different implementors take different approaches to deciding when it is safe to use large packets. Some use them only for the local network. Others will use them for any network on the same campus. 576 bytes is a safe size, which every implementation must support.

So, what are the odds of your URL always landing somewhere in the middle of that packet, and never on the joint between two packets?

Blessings,

~Polyglot~

In reply to Re: Packet editing by Polyglot
in thread Packet editing by p0c

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