VTY errors

[Neels Hofmeyr]

I have a problem with VTY validation. When there is wrong command formatting,
we exit VTY parsing in error, which leads to a program exit in error.

However, if the format matches but the value is wrong in a way that the VTY
format description is unable to detect, the way to escalate an error up
the VTY call chain is a bit weird.

The concrete item in question is the SCCP address point code. The format is
like A.B.C, while ranges are variable depending on configuration.

  point-code 0.0.1

If I write 'point-code 0.0.99', it exceeds the range and I want to immediately
abort the program, indicating the VTY config error.

If I return CMD_WARNING, it is merely ignored.

There are various CMD_ERR_* values to return, but there is no plain error like
CMD_ERR_INVALID_VALUE.

I can for example return CMD_ERR_AMBIGUOUS; then the code will try to parse the
same line a second time, to see whether the command succeeds on a child of the
parent node (we had this before, about implicit node 'exit').

  DLSS7 <002d> ../../src/osmo_ss7.c:244 1: Error parsing Pointcode '0.42.99'
  DLSS7 <002d> ../../src/osmo_ss7.c:244 1: Error parsing Pointcode '0.42.99'
  There is no such command.
  Error occurred during reading below line:
    point-code 0.42.99
  
  % Power 21 dB is not an even value
  Invalid point code (0.42.99)
  Invalid point code (0.42.99)

This result is rather curious.

I would like to have a CMD_ERROR return value that immediately exits VTY
parsing with a clear error return code.

(We can't abort with an assertion, because that would cause the program to exit
in case someone enters a wrong value on the telnet VTY.)

This is the function in question:

int config_from_file(struct vty *vty, FILE * fp)
{
        int ret;
        vector vline;

        while (fgets(vty->buf, VTY_BUFSIZ, fp)) {
                vline = cmd_make_strvec(vty->buf);

                /* In case of comment line */
                if (vline == NULL)
                        continue;
                /* Execute configuration command : this is strict match */
                ret = cmd_execute_command_strict(vline, vty, NULL);

                // I would insert something like this:
                // if (ret == CMD_ERROR)
                //         return ret;

                /* Try again with setting node to CONFIG_NODE */
                while (ret != CMD_SUCCESS && ret != CMD_WARNING
                       && ret != CMD_ERR_NOTHING_TODO
                       && is_config_child(vty)) {
                        vty_go_parent(vty);
                        ret = cmd_execute_command_strict(vline, vty, NULL);
                        // same here
                }

                cmd_free_strvec(vline);

                if (ret != CMD_SUCCESS && ret != CMD_WARNING
                    && ret != CMD_ERR_NOTHING_TODO)
                        return ret;
        }
        return CMD_SUCCESS;
}


Am I on the right track here, have I missed something?

~N
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