Re: [PATCH v2 1/2] cmdline: add function to verify valid commands

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Jun 07, 2022 at 10:08:30AM +0200, Olivier Matz wrote:
> Hi Bruce,
> 
> Just few minor comments below.
> 
> On Fri, May 20, 2022 at 04:12:39PM +0100, Bruce Richardson wrote:
> > The cmdline library cmdline_parse() function parses a command and
> > executes the action automatically too. The cmdline_valid_buffer function
> > also uses this function to validate commands, meaning that there is no
> > function to validate a command as ok without executing it.
> > 
> > To fix this omission, we extract the body of cmdline_parse into a new
> > static inline function with an extra parameter to indicate whether the
> > action should be performed or not. Then we create two wrappers around
> > that - a replacement for the existing cmdline_parse function where the
> > extra parameter is "true" to execute the command, and a new function
> > "cmdline_parse_check" which passes the parameter as "false" to perform
> > cmdline validation only.
> > 
> > Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> > ---
> >  lib/cmdline/cmdline_parse.c | 20 +++++++++++++++++---
> >  lib/cmdline/cmdline_parse.h | 17 +++++++++++++++--
> >  lib/cmdline/version.map     |  3 +++
> >  3 files changed, 35 insertions(+), 5 deletions(-)
> > 
> > diff --git a/lib/cmdline/cmdline_parse.c b/lib/cmdline/cmdline_parse.c
> > index 349ec87bd7..b7fdc67ae5 100644
> > --- a/lib/cmdline/cmdline_parse.c
> > +++ b/lib/cmdline/cmdline_parse.c
> > @@ -7,6 +7,7 @@
> >  #include <stdio.h>
> >  #include <errno.h>
> >  #include <string.h>
> > +#include <stdbool.h>
> >  
> >  #include <rte_string_fns.h>
> >  
> > @@ -182,8 +183,8 @@ match_inst(cmdline_parse_inst_t *inst, const char *buf,
> >  }
> >  
> >  
> > -int
> > -cmdline_parse(struct cmdline *cl, const char * buf)
> > +static inline int
> > +__cmdline_parse(struct cmdline *cl, const char *buf, bool call_fn)
> >  {
> >  	unsigned int inst_num=0;
> >  	cmdline_parse_inst_t *inst;
> > @@ -284,7 +285,8 @@ cmdline_parse(struct cmdline *cl, const char * buf)
> >  
> >  	/* call func */
> >  	if (f) {
> > -		f(result.buf, cl, data);
> > +		if (call_fn)
> > +			f(result.buf, cl, data);
> 
> Maybe nicer to test in one line:
> 
> if (f && call_fn)
> 

If we do so, then we need to also change the "else" leg to "else if
(!call_fn)" because we don't want to have the debug_printf being output in
the case that we have call_fn == false. A better alternative is to slightly
restructure the whole block, to have the error leg first, which removes the
need for two condition checks before calling the function:

        /* no match */
        if (f == NULL) {
                debug_printf("No match err=%d\n", err);
                return err;
        }

        /* call func if requested*/
        if (call_fn)
                f(result.buf, cl, data);

        return linelen;

I think this latter option is better, so will implement in v3.

> 
> >  	}
> >  
> >  	/* no match */
> > @@ -296,6 +298,18 @@ cmdline_parse(struct cmdline *cl, const char * buf)
> >  	return linelen;
> >  }
> >  
> > +int
> > +cmdline_parse(struct cmdline *cl, const char *buf)
> > +{
> > +	return __cmdline_parse(cl, buf, true);
> > +}
> > +
> > +int
> > +cmdline_parse_check(struct cmdline *cl, const char *buf)
> > +{
> > +	return __cmdline_parse(cl, buf, false);
> > +}
> > +
> >  int
> >  cmdline_complete(struct cmdline *cl, const char *buf, int *state,
> >  		 char *dst, unsigned int size)
> > diff --git a/lib/cmdline/cmdline_parse.h b/lib/cmdline/cmdline_parse.h
> > index e4d802fff7..6dd210d843 100644
> > --- a/lib/cmdline/cmdline_parse.h
> > +++ b/lib/cmdline/cmdline_parse.h
> > @@ -7,6 +7,8 @@
> >  #ifndef _CMDLINE_PARSE_H_
> >  #define _CMDLINE_PARSE_H_
> >  
> > +#include <rte_compat.h>
> > +
> >  #ifdef __cplusplus
> >  extern "C" {
> >  #endif
> > @@ -149,11 +151,22 @@ typedef cmdline_parse_inst_t *cmdline_parse_ctx_t;
> >   * argument buf must ends with "\n\0". The function returns
> >   * CMDLINE_PARSE_AMBIGUOUS, CMDLINE_PARSE_NOMATCH or
> >   * CMDLINE_PARSE_BAD_ARGS on error. Else it calls the associated
> > - * function (defined in the context) and returns 0
> > - * (CMDLINE_PARSE_SUCCESS).
> > + * function (defined in the context) and returns the parsed line length (>= 0)
> 
> Can we add a dot at the end?

Ack.

> 
> >   */
> >  int cmdline_parse(struct cmdline *cl, const char *buf);
> >  
> > +/**
> > + * Try to parse a buffer according to the specified context, but do not
> > + * perform any function calls if parse is successful.
> > + *
> > + * The argument buf must ends with "\n\0".
> > + * The function returns CMDLINE_PARSE_AMBIGUOUS, CMDLINE_PARSE_NOMATCH or
> > + * CMDLINE_PARSE_BAD_ARGS on error and returns the parsed line length (>=0).
> > + * on successful parse
> 
> Same here.

Ack.

> 
> > + */
> > +__rte_experimental
> > +int cmdline_parse_check(struct cmdline *cl, const char *buf);
> > +
> >  /**
> >   * complete() must be called with *state==0 (try to complete) or
> >   * with *state==-1 (just display choices), then called without
> > diff --git a/lib/cmdline/version.map b/lib/cmdline/version.map
> > index b9bbb87510..fc7fdd6ea4 100644
> > --- a/lib/cmdline/version.map
> > +++ b/lib/cmdline/version.map
> > @@ -81,5 +81,8 @@ EXPERIMENTAL {
> >  	rdline_get_history_buffer_size;
> >  	rdline_get_opaque;
> >  
> > +	# added in 22.07
> > +	cmdline_parse_check;
> > +
> >  	local: *;
> >  };
> > -- 
> > 2.34.1
> > 
> 
> With these changes:
> Acked-by: Olivier Matz <olivier.matz@6wind.com>
>