-c sets a corruption rate in % of the packets.
-o sets the start offset of the area to be corrupted.
-w sets the length of the area to be corrupted.
A single byte within that area will then be randomly XORed with a
random value.
In order to ease addition of new types of perturbations to udp-perturb,
let's first switch to getopt() and get rid of the positional arguments.
The random seed was already a conditional option of the rate which was
a conditional option as well. We add -r and -s for the rate and the
seed, and new options will follow.
By passing a 3rd argument it's now possible to set a randomness level
according to which received packets will be replaced by one of the 20
previous ones. This happens in both directions and the buffer is common
so that it's possible to receive responses on requests and conversely,
which adds to the perturbation. E.g:
./dev/udp/udp-perturb 127.0.0.4:9443 127.0.0.4:8443 10
This will add 10% randomness on forwarded packets between these two
ports.
QUIC really needs more traffic perturbation for the tests. Let's have
a tiny UDP proxy for this, mostly derived from the 'connect' test suite.
For now it only supports a single "connection" at once, but the code is
here to support more. A new "connection" will simply replace the previous
one. It doesn't yet cause traffic perturbations, this is still to be added.
Some of the setsockopt() are possibly unneeded. The error handling is
almost inexistent, and polling for sends is not implemented at all (will
cause losses). No stats are collected.
