Peter,
On 5/21/21 3:04 PM, Peter Stuge wrote:
Hi,
rapier wrote:
Is there any documentation (outside of the code) describing the channel
functions?
The channel functions in the OpenSSH codebase? Probably no.
That was my guess but it never hurts to ask.
I'm looking at using a secondary channel to periodically report back
receiver side TCP metrics (via the TCP_INFO struct) to the caller for
flow diagnostics. Alternatively, is there a good place in the code
base I can use as a starting point to understand the process?
Are you familiar with channels in general? RFC 4254 5. Channel Mechanism.
Sort of familiar but only as much as it impacted on HPNSSH. It's been a
while since I read the RFC so thank you for the pointer.
If you want to control exactly when data from (your metric) channels
are sent on the wire I think you have to do quite a deep dive into the code.
While I'm not opposed to deep dives I don't need a specific trigger. I'm
really just going to look for an update every N seconds so a timing loop
would work.
Basically, the idea is on connection two channels are open - one for the
user and one for metrics. Every N seconds read the TCP_INFO data from
the tcp socket and send it down the metric channel which writes it to
stdout, a file, whatever.
If you care less about jitter then you can maybe look at SFTP but
probably much better any of the socket forwarding.
So socket forwarding... I'll take a look at that.
If you want to implement the metric completely in the application layer
you could investigate creating it in a subsystem, which (like SFTP) is
also just a channel.
Can that ride alongside other actions like SFTP or SCP or even just a
tty? Mostly I'm looking to gather metrics from real world usage. Either
way it looks promising.
Thanks for insight,
Chris
_______________________________________________
openssh-unix-dev mailing list
openssh-unix-dev@xxxxxxxxxxx
https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
