I would like to create a TCP proxy that supports multiple hosts. The example I saw was where a DNS server was used to point a specific host to a TCP proxy which had the host hardcoded in it. The TCP proxy can not handle multiple hosts because if all hosts were routed to the TCP proxy, the proxy would not know where to send the data to. Are there any ways to get around this issue?
3
-
How could the proxy possibly know where to proxy to?– Michael HamptonJul 26, 2021 at 23:50
-
Yes that is the question. I want to be able to use the TCP proxy like an HTTP proxy supporting all hosts and ports without knowing what they are beforehand. I was thinking of something like creating new servers on the fly on DNS lookup but I don't know if that is feasible.– comctimertJul 27, 2021 at 0:06
-
You have to have some way to distinguish them!– Michael HamptonJul 27, 2021 at 0:29
Add a comment
|
1 Answer
TCP works over IP and IP has no notion of host(names) but only of IP addresses.
As such, TCP knows also only about IP addresses, not hostnames.
If you want to have something handling hostnames you need a protocol on top of TCP (ex: HTTP, SSH, etc.) or translate names to IP addresses before using TCP, as the DNS is typically providing.
Or you need your "TCP" proxy to listen on separate ports and proxy things depending on which port is accessed. However you still have the problem of mapping names to now not only an IP address (of the proxy) but its port too, which is possible but more difficult with DNS (if you control the client, you can do that using SRV records or in the future SVCB ones).
answered Jul 27, 2021 at 0:41
