Network bad packets
 

In writing my client, I have had to identify what constitutes a bad packet...
From the information I have attained so far I know that the following are bad
packets:

1. TTL = 0
2 Function = ping, with payload
3. Query, with payload[size-1] != NULL
4. Function ID not valid
5. TTL > MAX_TTL (predefined to 25), same for hop count

Anything I'm missing? I seem to be forwarding a few bad packets, can't figure
out what the are...