I don't think you understand, and based on your reply it doesn't sound like I'm mistaken.
With this CLI I am able to listen for external packets to port 80 from userspace without any elevated permissions and intercept traffic that's going to an application that's bound to that port on the OS?
Edit: I think I understand what you're trying to do, but if I do then traffic is going from the kernel UDP stack to the userland TCP stack, back to the UDP kernel stack. Not sure how that avoids sending the packet to the kernel. If it's to get around the port restrictions, why can you not just use unprivileged ports?
I'm not sure I can make this any simpler for you or easier to get your head around. If it helps: the idea here is giving an invocation of your program its own IP address. It can then do whatever it likes with TCP/IP for that address; its own routing, arbitrary protocols, whatever. The Go standard library makes it extremely easy to integrate. To the OS, it's all just ordinary socket code.
> the idea here is giving an invocation of your program its own IP address
I understand that, I just don't understand any case where that's desirable...
We have 2^32 ports available to applications(and a special `0` port that can be used to request any port) on a single IP(which is usually shared between multiple machines). I have never heard of a case where 2^32 ports is not enough ports for the number of applications that need to be listening.
> To the OS, it's all just ordinary socket code.
Which is what I don't understand. Why not just use ordinary socket code without all of these additional LoC in between that open you up to more bugs(security and functionality).
"Unprivileged ports" is just a case in point for everything you would need privileges to do, from binding arbitrary ports to adding arbitrary addresses and running local servers on them, etc, etc, etc. The point is: turning "complicated" network features that require privilege into simple unprivileged socket code.
Right, per my other thread below, my understanding was the "privileged" ports were mainly ones that were allowed for off machine communication by standard policy/convention long time ago. As such, using higher number ports should be just as easy in the code as using lower ports, outside of the discovery that was implied by following the other conventions. But, introducing new network addresses seems to have already side stepped the discovery affordances?
I'll offer the same caveat here, btw, I am not trying to torpedo the idea of trying this. I'm genuinely curious why you would need to do this. Not necessarily why you would want to.
We did it because we run WireGuard gateways to the public cloud we operate, and our CLI wants to talk to things on customer networks (like remote Docker server instances to build new versions of apps). Our options were:
* Do user-mode WireGuard (and thus TCP/IP) and talk "natively" to the infrastructure deployed on our platform.
* Write case-by-case application gateways for each of those pieces of infrastructure tunneled somehow through HTTP.
Granted, my old recollection was largely that the "privileged" ports were that way because they were blessed by the routing tables, at the time. The entire point was that the lower ports were expected to be connectable to external machines. Not shocking if I am out of date there.
I know this is subtle but if you take a step back, user-mode TCP/IP moots the policies we're talking about; it doesn't subvert them. There are no security or policy implications to e.g. binding a low-numbered port on an IP address unrelated to your physical computer that is allocated directly to a running instance of your program. There are (archaic) implications to binding that port on an actual interface of your machine, because that binding (archaically) stood in for an assertion of identity/authority back in the 1990s.
Sorta? If it renders them moot, why not attack the policies? For that matter, if there are no implications to the number of the port, I'm again forced to ask why not just use the higher numbers? Wouldn't that have let you use the "simplicity of standard socket code" with no extra effort?
(This is also a new use of "moot" to me? You seem to be offering it as a synonym of obsolete? But a "moot" debate is one that is closer to "overcome by events" than one that is not relevant. Right?)
You get that these are just people shipping a program that random people are going to run on random computers, right? If your go-to-market involves "reversing longstanding Unix network policy rules", you have problems.
Respectfully, if at this point the situation hasn't been made clear to you, I don't think there's much more to productively discuss.
Amusingly, I would do an appeal to a word you already used. :D I was treating this as a bit of a moot debate. Discussing it as much for interests in the general discussion.
My impression from something said elsewhere was that this was largely for internal tools. I'm not sure why I got that impression, though.
I think it is fair, btw, that I would be pushing for both paths, at this point? If a long standing network policy rule has become obsolete from advance, it is worth considering dropping it? Is that not something people are looking at?
(I will also note that I will not be at all offended if you drop out from lack of interest here. Apologies if you feel I was wasting your time!)
Doesn't this program need to bind a UDP port on your machine? If policies prevent you binding ports I don't see how you'd be able to use this software...
I have no idea what you're talking about. We're talking about essentially fictitious IP addresses on synthetic machines. I think everyone's talking past each other here.
I don't really think people are talking past eachother, I think we're all trying to understand the point of this, and the article(and marketing on the website) doesn't make it clear at all.
Some potential options for "what is it for" come up, and others bring up reasons why they don't make sense.
It seems this is a solution to a very specific problem that nobody seems to have, which is why when people are trying to figure out what problem it solves they're coming up with 10 better solutions.
With this CLI I am able to listen for external packets to port 80 from userspace without any elevated permissions and intercept traffic that's going to an application that's bound to that port on the OS?
Edit: I think I understand what you're trying to do, but if I do then traffic is going from the kernel UDP stack to the userland TCP stack, back to the UDP kernel stack. Not sure how that avoids sending the packet to the kernel. If it's to get around the port restrictions, why can you not just use unprivileged ports?