I would like to control the remote communication port

[Lorac]

Bugzilla Link	45669
Version	unspecified
OS	All
CC	@JDevlieghere,@labath

Extended Description

Hello!

I would like to debug my target (which is at home), from my remote work computer while being at home through a VPN.

From home I connect to my workstation through the VPN and create an ssh tunnel
(ssh config: RemoteForward localhost:10000 TARGET_LAN_IP:10000).

But when I try to attach to the running application on the target it dynamically allocates a port and tries to reach the server to that port. Unfortunately, this is not possible because of the ssh tunnel. I can however do : platform connect connect://localhost:10000, but I cannot go into debugging.

SSH tunnelling doesn't support, as far as I know, ranges of RemoteForward ports.

Is there a way to control the port that is dynamically allocated? I found a "similar" issue of 4 years ago: (I'm not inside a container, but the idea is the same)

http://lists.llvm.org/pipermail/lldb-dev/2016-June/010616.html

I'm wondering if the situation is still the same and the port cannot be set manually?

[labath]

SSH tunnelling doesn't support, as far as I know, ranges of RemoteForward
ports.

Is there a way to control the port that is dynamically allocated? I found a
"similar" issue of 4 years ago: (I'm not inside a container, but the idea is
the same)

http://lists.llvm.org/pipermail/lldb-dev/2016-June/010616.html

I'm wondering if the situation is still the same and the port cannot be set
manually?

The usual "solution" to that is to restrict the gdb port "range" to a single value using the --min-gdbserver-port/--max-gdbserver-port arguments. Then you just need to forward that additional port over ssh.

One day I'd like to see a solution that does not require multiple ports a'la ftp. A relatively simple way to achieve that would be to have the "platform" lldb-server instance pass on its socket connection to the "gdbserver" instance when it launches (execs ?) it.

If you're interested in trying to implement that, I can provide more details.

[DavidSpickett]

@labath did the recent changes to lldb-server port handling implement what you suggested here?

https://releases.llvm.org/20.1.0/docs/ReleaseNotes.html#changes-to-lldb

lldb-server now listens to a single port for gdbserver connections and provides that port to the connection handler processes. This means that only 2 ports need to be opened in the firewall (one for the lldb-server platform, one for gdbserver connections). In addition, due to this work, lldb-server now works on Windows in the server mode.

2 is still "multiple ports", so I assume it did not.

The usual "solution" to that is to restrict the gdb port "range" to a single value using the --min-gdbserver-port/--max-gdbserver-port arguments. Then you just need to forward that additional port over ssh.

These options still exist but afaict do nothing since the port map removal. I'll see if we can remove them.

[labath]

Not exactly, but it comes pretty close. We currently use two ports, while the solution I outline here would have used one. Two is more than one, but it's definitely less than ~infinity.

I still like the one port solution better, but I think the need for it is greatly diminished now, and I think the two port solution should solve the original problem, so I think we can close this.

These options still exist but afaict do nothing since the port map removal. I'll see if we can remove them.

👍