Re: SSHv2 doesn't actually have compression levels

[Ludovic Courtès]

Hello,

Tobias Geerinckx-Rice <address@hidden> skribis:

> While reading (guix scripts offload) in a (failed) attempt to get
> offloading working, the following comment caught my eye:
>
>  ;; We rely on protocol-level compression from libssh to optimize
> large data
>  ;; transfers.  Warn if it's missing.
>
> which means that we're not currently doing our own compression inside
> the tunnel.
>
> This is significant, because it means that the COMPRESS-LEVEL field of
> BUILD-MACHINE is completely bogus[0], and probably always was - unless

[...]

> [0]: Take a look at OpenSSH's readconf.c, packet.c, and all calls to
> start_compression_out().

I don’t get it: the ‘compression-level’ field defaults to 3, and OpenSSH
does:

  static int
  start_compression_out(struct ssh *ssh, int level)
  {
          if (level < 1 || level > 9)
                  return SSH_ERR_INVALID_ARGUMENT;
          debug("Enabling compression at level %d.", level);

  [...]

  }

What’s wrong?

Ludo’.