Let's say I'm writing a simple SOCKS4/4a server(yes, obsolete, but still does it's job), no authorization(although it wouldn't matter). So I need to read some data from the client: ip and port and maybe domain if it's 4A. Then I connect to the ip/domain:port and send a success response. Meanwhile the IP/Domain:port I connected to, before sending success to the client might send some data, like if the target was an SSH server, it sends a version string right away if you connect to it. So it could be missed if I then put client and target socket into a sockmap/hash and tell them to redirect traffic to each other. I've tried very hard to figure out a way to use eBPF stream_verdict or sk_msg_verdict to redirect traffic right when I need it, but I think it is impossible. Do I have to do SOCKS4/4A parsing inside stream_parser and communicate with my userspace program via a ring buffer about the results? But I'm not sure how that could help with missing bytes. I guess I got interested after I read that article on cloudflare blog about sockmap https://blog.cloudflare.com/sockmap-tcp-splicing-of-the-future/ , but their example of an echo server is plagued with the same problem, if you put a delay, before socket addition to a sockmap.
