I'm sorry but you're making things up at this point. Feel free to read the first paragraph of RFC 767 [0], most notably the last sentence:
"This User Datagram Protocol (UDP) is defined to make available a
datagram mode of packet-switched computer communication in the
environment of an interconnected set of computer networks. This
protocol assumes that the Internet Protocol (IP) is used as the
underlying protocol."
As for your code, again, you make a lot of assumptions. As I mentioned before opening a socket as IPv6 does not guarantee backwards compatibility with IPv4 addressing. So, again, my point is that you do have to care about the version of IP. In your original example you conveniently skipped the socket call and claimed "See, I can just consume any IP!". Now you're just glossing over the glaring assumption, as I stated in the last post, that not every platform guarantees backward compatibility with IPv4 on an IPv6 socket.
Also... Your pigeon analogy makes zero sense to the argument you're attempting to make because it's highly irrelevant to the protocols and how they actually work in computing environments.
If you care to read the OSI layer 3 protocols state that they are concerned with deciding which physical path data will take. UDP and TCP have no routing facilities I'm aware of because port numbers don't define path. So, again, UDP is not a layer 3 protocol just because you feel like it is.
I understand and agree with you that IPv4 and IPv6 are OSI layer 3 protocols and UDP and TCP are layer 4. At the same time, the OSI model above the fourth layer has been widely considered mostly useless, and some have called into question the whole thing. Yes, RFCs exist that point to what you are saying. But again, I can 100% implement TCP on top of UDP without ever thinking about IP packets. And no, I don't care which layer 3 protocol TCP is using underneath, so long as I can initialize the socket properly and get the local/remote addresses. Take a look at a complete example of a TCP server: https://www.cs.cmu.edu/afs/cs/academic/class/15213-f99/www/c...
Where in there do you see anything about ARP or ND? Or hops vs TTL? Or IP packet header sizes? Or header checksums? Or priority flags? You can take this code, add a couple of macros for getting the correct AF_ value and structs and the code would be 100% abstracted away from any mention of the underlying layer 3 protocol.
Google has been developing transport layer protocols on top of UDP for years now. Why? Because getting a new layer 4 protocol to work is nearly impossible. Yet, if we all agreed that it was something we wanted, they could easily do so, which makes these new protocols functionally transport layer. If it helps you sleep at night, you can say that they are temporarily exiled to be encapsulated in UDP, but really they'll return some day to their proper place in the OSI model.
"This User Datagram Protocol (UDP) is defined to make available a datagram mode of packet-switched computer communication in the environment of an interconnected set of computer networks. This protocol assumes that the Internet Protocol (IP) is used as the underlying protocol."
As for your code, again, you make a lot of assumptions. As I mentioned before opening a socket as IPv6 does not guarantee backwards compatibility with IPv4 addressing. So, again, my point is that you do have to care about the version of IP. In your original example you conveniently skipped the socket call and claimed "See, I can just consume any IP!". Now you're just glossing over the glaring assumption, as I stated in the last post, that not every platform guarantees backward compatibility with IPv4 on an IPv6 socket.
Also... Your pigeon analogy makes zero sense to the argument you're attempting to make because it's highly irrelevant to the protocols and how they actually work in computing environments.
If you care to read the OSI layer 3 protocols state that they are concerned with deciding which physical path data will take. UDP and TCP have no routing facilities I'm aware of because port numbers don't define path. So, again, UDP is not a layer 3 protocol just because you feel like it is.
[0] https://tools.ietf.org/html/rfc768