* Ensure ssh connection rejection errors are returned
#18302 altered the connection flow which changed the communication
via ssh. Prior to the change an ssh channel was opened first, then
global requests were sent. After the change a global request is sent
prior to opening a channel. This caused users to no longer receive a
human readable rejection message a la: `ssh: rejected: administratively
prohibited (too many concurrent ssh connections for user`, instead only
an `EOF` was returned.
To ensure that the correct message is provided to users two changes are
made, although only the client side change is strictly required.
1) the tracing ssh client now returns any rejected errors cached from
opening the tracing channel
2) the ssh server now processes global requests during it's wait period
waiting for a channel to reject and send the replies to any requests
with said rejection
`TestLockInForce` was updated to include attempting to send a global
request so both scenarios are covered as order should not matter.
Adds a wrapper around `ssh.Session` which injects tracing context
in a similar manner to the `ssh.Client` wrapper. All usages of
`ssh.Session` have now been replaced and have the appropriate
`context.Context` passed along
Part of #12241
* SSH request tracing
Add tracing support for ssh global requests and channels. Wrappers
for `ssh.Client`, `ssh.Channel`, and `ssh.NewChannel` provide a
mechanism for tracing context to be propagated via a `context.Context`.
In order to maintain backwards compatibility the ssh.Client wrapper
tries to open a TracingChannel when constructed. Any servers that
don't support tracing will reject the unknown channel. The client
will only provide tracing context to servers which do NOT reject
the TracingChannel request.
In order to include pass tracing context along all ssh payloads
are wrapped in an Envelope that includes the original payload
AND any tracing context. Servers now try to unmarshal all payloads
into said Envelope when processing messages. If there is an Envelope
provided, a new span will be created and the original payload will
be pass along to handlers.
Part of #12241
rosstimothy