Messages to SSH Client #77
Description
It would be good to have feedback to the SSH client so the user can have a better understanding of issues.
Pre SSH authorisation we will need to use SSH return values/exit codes to inform the client why the connection failed.
These may not be displayed by most SSH clients so another way could be useful.
https://www.iana.org/assignments/ssh-parameters/ssh-parameters.xhtml#ssh-parameters-3
https://datatracker.ietf.org/doc/html/rfc4253
Symbolic name reason code
------------- -----------
SSH_DISCONNECT_HOST_NOT_ALLOWED_TO_CONNECT 1
SSH_DISCONNECT_PROTOCOL_ERROR 2
SSH_DISCONNECT_KEY_EXCHANGE_FAILED 3
SSH_DISCONNECT_RESERVED 4
SSH_DISCONNECT_MAC_ERROR 5
SSH_DISCONNECT_COMPRESSION_ERROR 6
SSH_DISCONNECT_SERVICE_NOT_AVAILABLE 7
SSH_DISCONNECT_PROTOCOL_VERSION_NOT_SUPPORTED 8
SSH_DISCONNECT_HOST_KEY_NOT_VERIFIABLE 9
SSH_DISCONNECT_CONNECTION_LOST 10
SSH_DISCONNECT_BY_APPLICATION 11
SSH_DISCONNECT_TOO_MANY_CONNECTIONS 12
SSH_DISCONNECT_AUTH_CANCELLED_BY_USER 13
SSH_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE 14
SSH_DISCONNECT_ILLEGAL_USER_NAME 15
Post SSH authorisation we could send characters over the SSH channel but with a flag to determine if the client wants to receive these characters or not, as it could cause issues with the bridge creating an 'invisible' UART connection.
Some useful responses could be:
- Existing UART pins so user can confirm pin usage.
- Printing out all config values
- Informing user when the config has been updated and to/from what values.
- When bridge is connected / disconnected