x/crypto/ssh: investigate support for ping@openssh.com protocol extension

[drakkan]

Maybe we can just advertise server side support for this extension and reply to ping requests

see section 1.9

https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL?rev=HEAD

This extension will be added to OpenSSH 9.5

[gopherbot]

Change https://go.dev/cl/524775 mentions this issue: ssh: add server side support for ping@openssh.com protocol extension

[dmitshur]

CC @FiloSottile.

[djmdjm]

FYI I've started an I-D to get this extension standardised but that would be at least a year away.

https://github.com/djmdjm/drafts/blob/master/draft-miller-ssh-ping.txt

[hanwen]

@djmdjm

Is this RFC final already?

A single byte keystroke looks like 10 bytes (uint8 packet type, uint32 channel ID, uint32 data length, data), but in response the other side will send a 9 byte window adjust message (uint8 packet type, uint32 channel ID, uint32 byte count.)

wouldn't it be better if the ping message contained the number of bytes to send in the return pong?