Re: [dpdk-dev] [PATCH v3] examples/qos_meter: fix unchecked return value

["Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>]

> -----Original Message-----
> From: Dumitrescu, Cristian
> Sent: Thursday, May 12, 2016 10:41 AM
> To: Mrozowicz, SlawomirX <slawomirx.mrozowicz@intel.com>
> Cc: dev@dpdk.org; Singh, Jasvinder <jasvinder.singh@intel.com>
> Subject: RE: [PATCH v3] examples/qos_meter: fix unchecked return value
> 
> 
> 
> > -----Original Message-----
> > From: Mrozowicz, SlawomirX
> > Sent: Thursday, May 12, 2016 8:06 AM
> > To: Dumitrescu, Cristian <cristian.dumitrescu@intel.com>
> > Cc: dev@dpdk.org; Singh, Jasvinder <jasvinder.singh@intel.com>
> > Subject: RE: [PATCH v3] examples/qos_meter: fix unchecked return value
> >
> >
> >
> > >-----Original Message-----
> > >From: Dumitrescu, Cristian
> > >Sent: Wednesday, May 11, 2016 7:57 PM
> > >To: Mrozowicz, SlawomirX <slawomirx.mrozowicz@intel.com>
> > >Cc: dev@dpdk.org; Singh, Jasvinder <jasvinder.singh@intel.com>
> > >Subject: RE: [PATCH v3] examples/qos_meter: fix unchecked return value
> > >
> > >
> > >
> > >> -----Original Message-----
> > >> From: Mrozowicz, SlawomirX
> > >> Sent: Wednesday, May 11, 2016 10:15 AM
> > >> To: Dumitrescu, Cristian <cristian.dumitrescu@intel.com>
> > >> Cc: dev@dpdk.org; Singh, Jasvinder <jasvinder.singh@intel.com>
> > >> Subject: RE: [PATCH v3] examples/qos_meter: fix unchecked return
> value
> > >>
> > >>
> > >>
> > >> >-----Original Message-----
> > >> >From: Dumitrescu, Cristian
> > >> >Sent: Tuesday, May 10, 2016 7:42 PM
> > >> >To: Mrozowicz, SlawomirX <slawomirx.mrozowicz@intel.com>
> > >> >Cc: dev@dpdk.org; Singh, Jasvinder <jasvinder.singh@intel.com>
> > >> >Subject: RE: [PATCH v3] examples/qos_meter: fix unchecked return
> > >> >value
> > >> >
> > >> >
> > >> >
> > >> >> -----Original Message-----
> > >> >> From: Mrozowicz, SlawomirX
> > >> >> Sent: Monday, May 9, 2016 9:38 AM
> > >> >> To: Dumitrescu, Cristian <cristian.dumitrescu@intel.com>
> > >> >> Cc: dev@dpdk.org; Singh, Jasvinder <jasvinder.singh@intel.com>;
> > >> >> Mrozowicz, SlawomirX <slawomirx.mrozowicz@intel.com>
> > >> >> Subject: [PATCH v3] examples/qos_meter: fix unchecked return
> value
> > >> >>
> > >> >> Fix issue reported by Coverity.
> > >> >>
> > >> >> Coverity ID 30693: Unchecked return value
> > >> >> check_return: Calling rte_meter_srtcm_config without checking
> > >> >> return value.
> > >> >>
> > >> >> Fixes: e6541fdec8b2 ("meter: initial import")
> > >> >>
> > >> >> Signed-off-by: Slawomir Mrozowicz
> > <slawomirx.mrozowicz@intel.com>
> > >> >> ---
> > >> >>  examples/qos_meter/main.c | 15 ++++++++++-----
> > >> >> examples/qos_meter/main.h |  2 +-
> > >> >>  2 files changed, 11 insertions(+), 6 deletions(-)
> > >> >>
> > >> >> diff --git a/examples/qos_meter/main.c
> > b/examples/qos_meter/main.c
> > >> >> index b968b00..7c69606 100644
> > >> >> --- a/examples/qos_meter/main.c
> > >> >> +++ b/examples/qos_meter/main.c
> > >> >> @@ -133,14 +133,17 @@ struct rte_meter_trtcm_params
> > >> >app_trtcm_params[]
> > >> >> = {
> > >> >>
> > >> >>  FLOW_METER app_flows[APP_FLOWS_MAX];
> > >> >>
> > >> >> -static void
> > >> >> +static int
> > >> >>  app_configure_flow_table(void)
> > >> >>  {
> > >> >>  	uint32_t i, j;
> > >> >> +	int ret = 0;
> > >> >>
> > >> >> -	for (i = 0, j = 0; i < APP_FLOWS_MAX; i ++, j = (j + 1) %
> > >> >> RTE_DIM(PARAMS)){
> > >> >> -		FUNC_CONFIG(&app_flows[i], &PARAMS[j]);
> > >> >> -	}
> > >> >> +	for (i = 0, j = 0; i < APP_FLOWS_MAX && ret == 0;
> > >> >> +			i ++, j = (j + 1) % RTE_DIM(PARAMS))
> > >> >> +		ret = FUNC_CONFIG(&app_flows[i], &PARAMS[j]);
> > >> >> +
> > >> >> +	return ret;
> > >> >>  }
> > >> >
> > >> >This is only returns the configuration status for the last flow and
> > >> >leaves undetected an error for any other flow. Why not check the
> > >> >status for each flow and return an error on first occurrence?
> > >> >For (...){ret = FUNC_CONFIG(...); if (ret) return ret;}
> > >> >
> > >>
> > >> This code check status of the function FUNC_CONFIG for each flow and
> > >> return an error on first occurrence. Rest of functions FUNC_CONFIG are
> > >> not called. See terminate condition of the loop.
> > >>
> > >
> > >Where is the status of FUNC_CONFIG checked exactly? I cannot see any
> > check
> > >in your code. I can only see returning the status code for the last call of
> this
> > >function in the for loop. I was expecting a check such as: if (ret) return ret.
> > >
> >
> > Look at the loop terminate conditions:
> > i < APP_FLOWS_MAX && ret == 0
> > Program terminate the loop if the ret variable is differ then zero.
> > It means that program terminate if the last status of FUNC_CONFIG is an
> > error.
> 
> Yes, you're right, my bad, sorry.
> 

Actually, although the logic is correct, personally I find this code very cryptic / hard to read and more difficult to extend later if need be, can we please make it a bit more readable:

for (i = 0, j = 0; i < APP_FLOWS_MAX; i ++, j = (j + 1) % RTE_DIM(PARAMS)) {
	ret = FUNC_CONFIG(&app_flows[i], &PARAMS[j]);
	if (ret)
		return ret;
}

return ret;

Thanks, Slawomir!

> >
> > >> >>
> > >> >>  static inline void
> > >> >> @@ -381,7 +384,9 @@ main(int argc, char **argv)
> > >> >>  	rte_eth_promiscuous_enable(port_tx);
> > >> >>
> > >> >>  	/* App configuration */
> > >> >> -	app_configure_flow_table();
> > >> >> +	ret = app_configure_flow_table();
> > >> >> +	if (ret < 0)
> > >> >> +		rte_exit(EXIT_FAILURE, "Invalid configure flow
> table\n");
> > >> >>
> > >> >>  	/* Launch per-lcore init on every lcore */
> > >> >>  	rte_eal_mp_remote_launch(main_loop, NULL,
> CALL_MASTER); diff -
> > >> -
> > >> >git
> > >> >> a/examples/qos_meter/main.h b/examples/qos_meter/main.h
> index
> > >> >> 530bf69..54867dc 100644
> > >> >> --- a/examples/qos_meter/main.h
> > >> >> +++ b/examples/qos_meter/main.h
> > >> >> @@ -51,7 +51,7 @@ enum policer_action
> > >> >> policer_table[e_RTE_METER_COLORS][e_RTE_METER_COLORS] =
> #if
> > >> >APP_MODE
> > >> >> == APP_MODE_FWD
> > >> >>
> > >> >>  #define FUNC_METER(a,b,c,d) color, flow_id=flow_id,
> > >> >> pkt_len=pkt_len, time=time -#define FUNC_CONFIG(a,b)
> > >> >> +#define FUNC_CONFIG(a, b) 0
> > >> >>  #define PARAMS	app_srtcm_params
> > >> >>  #define FLOW_METER int
> > >> >>
> > >> >> --
> > >> >> 1.9.1