ChristianBergerSipgate created an issue (kamailio/kamailio#4281)

### Description

The rtpengine module uses a `cookie` field in the Protocol controlling rtpengines. This field needs to be unique, and is derived from the `server_id` field set in the Kamailio, the `pid` as well as the value of a variable `myseqn`.

In many conditions, this is random enough. However particularly when using docker, the `pid` will be identical across servers, reducing the randomness and causing collisions.

### Expected behavior

The 34 bytes of the cookie should be as unique as possible.

#### Actual observed behavior

We get collisions many times per day, as different kamailio instances randomly choose the same value.

### Possible Solutions

1. Set `myseqn` to a random value during module load. 2. Add an additional random value to the `gencookie` function. 3. Use `%x` instead of `%d` to squeeze more entropy into the 33 characters available, and perhaps use fixed length fields.

The problem probably also exists in the following other modules:

1. rtpproxy 2. lrkproxy

We are not using those modules so we have not yet experienced collisions here.