All,
Before I post a patch I thought I'd see if there was any interest.
As part of some work I'm doing I have implemented a method to have an
SSH client report on both the local and remote TCP instrument metrics
via the TCP_INFO struct. The goal is to provide network engineers and
knowledgeable users a means to profile and diagnose their SSH connections.
Currently I have this working under Linux, FreeBSD, and NetBSD. OpenBSD
doesn't seem to have the tcp_info struct (if I'm mistaken please let me
know). Apple is just being annoying and redefined that struct in their
own very special way that doesn't correspond that well.
Quick run down of the method. Every N seconds (default of 5) the client
sends a SSH2_MSG_GLOBAL_REQUEST to the server with a custom type. If the
server supports it then it dumps the TCP_INFO for the SSH TCP socket
into a serialized object. The client receives this, extracts the
information, and writes it to a file (default of
ssh_stack_metrics.remote). The client then queries the socket on it's
end and extracts the same information and write that to a different file
(default of ssh_stack_metrics.local).
It handles different versions of the TCP_INFO struct, cases where the
server doesn't understand the message request, and where TCP_INFO isn't
available.
Upside: More information for diagnostics and performance metrics.
Doesn't impact performance when not being used. Doesn't seem to impact
performance when in use.
Downside: 1) The serialization is handled by the binn object
serialization library from https://github.com/liteserver/binn. It's not
an external dependency but it is code that needs to be included in the
repo. 2) The timer is in main loop of client_loop in clientloop.c. In an
interactive session where it's waiting for input the timer doesn't
necessarily fire every N seconds as the loop pauses waiting for input.
In most cases where people would use this that won't be a problem.
Anyway, if people want to see the patch, have any interest, or questions
please let me know.
Chris
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