I added a safety check for sipping_from with the commit referenced above, to be
protected better in the future.
The sending of SIP request NAT pings for ping_nated_only=0 seems to be a side
effect of commit b34cf58a3a88e5ed2b2aa6aa9e5df0e5bb1808f9, I guess it was
designed only for the 4-bytes
### Description
We upgraded from Kamailio 4.4.5 to 5.1.4 today. We have a IPv6-to-v4
loadbalancer which sends out NAT pings to keep the connection through routers
alive. So it is not a real NAT scenario.
Kamailio 4.4.5 sent out dummy 4-byte UDP packets. Kamailio 5.1.4 sends out SIP
OPTIONS
