[U-Boot] Setting ipaddr via setenv() - H_INTERACTIVE vs H_PROGRAMMATIC

[U-Boot] Setting ipaddr via setenv() - H_INTERACTIVE vs H_PROGRAMMATIC

[Stefan Roese]

Hi Joe,

I'm currently stumbling over a problem in some board specific code
(not in mainline yet), that sets the "ipaddr" env variable via
setenv(). But as I now noticed, the callback on_ipaddr() doesn't
set net_ip to this new value. As flags has H_PROGRAMMATIC set and
op_ipaddr() skips setting this value in this case.

I fail to see why we need this check in on_ipaddr(). Could you
please explain why this is needed? Why would someone use setenv()
for the "ipaddr" and not want to also update the net_ip value.
This results in the "ipaddr" value being updated but net_ip
still being configured to the old value.

Or if this is really needed, what is the correct way to update
the ipaddr (env variable and net_ip value) from the U-Boot code?

Thanks,
Stefan

[U-Boot] Setting ipaddr via setenv() - H_INTERACTIVE vs H_PROGRAMMATIC

[Joe Hershberger]

Hi Stefan,

On Tue, Mar 1, 2016 at 4:35 AM, Stefan Roese <sr@denx.de> wrote:
> Hi Joe,
>
> I'm currently stumbling over a problem in some board specific code
> (not in mainline yet), that sets the "ipaddr" env variable via
> setenv(). But as I now noticed, the callback on_ipaddr() doesn't
> set net_ip to this new value. As flags has H_PROGRAMMATIC set and
> op_ipaddr() skips setting this value in this case.
>
> I fail to see why we need this check in on_ipaddr(). Could you
> please explain why this is needed? Why would someone use setenv()
> for the "ipaddr" and not want to also update the net_ip value.
> This results in the "ipaddr" value being updated but net_ip
> still being configured to the old value.

The purpose is that programmatic accesses may write directly to the
net_ip variable, but the user on the console cannot. This is because
the "programmatic" accesses to these variables is expected to be
things like the dhcp command and the linklocal command after
successful netloop. You can see this call in the netboot_update_env()
function in cmd/net.c.

> Or if this is really needed, what is the correct way to update
> the ipaddr (env variable and net_ip value) from the U-Boot code?

You can work around it in a similar way to what I did in the initial
change (94b467b14ed908c89a0780256e89b375aa3cf3ef - env: Distinguish
finer between source of env change). The do_env_edit function used to
call setenv, but I changed it to call as though it was interactive.
You could do the same thing in your board driver.

Cheers,
-Joe

[U-Boot] Setting ipaddr via setenv() - H_INTERACTIVE vs H_PROGRAMMATIC

[Stefan Roese]

Hi Joe,

(adding Tom to Cc as this seems to be a fundamental issue)

On 01.03.2016 20:40, Joe Hershberger wrote:
> On Tue, Mar 1, 2016 at 4:35 AM, Stefan Roese <sr@denx.de> wrote:
>> Hi Joe,
>>
>> I'm currently stumbling over a problem in some board specific code
>> (not in mainline yet), that sets the "ipaddr" env variable via
>> setenv(). But as I now noticed, the callback on_ipaddr() doesn't
>> set net_ip to this new value. As flags has H_PROGRAMMATIC set and
>> op_ipaddr() skips setting this value in this case.
>>
>> I fail to see why we need this check in on_ipaddr(). Could you
>> please explain why this is needed? Why would someone use setenv()
>> for the "ipaddr" and not want to also update the net_ip value.
>> This results in the "ipaddr" value being updated but net_ip
>> still being configured to the old value.
> 
> The purpose is that programmatic accesses may write directly to the
> net_ip variable, but the user on the console cannot. This is because
> the "programmatic" accesses to these variables is expected to be
> things like the dhcp command and the linklocal command after
> successful netloop.

Please correct me, but it seems to be implemented the other way around.
If H_PROGRAMMATIC is set (called via setenv()) the net variables
(net_ip...) will *not* be set:

static int on_ipaddr(const char *name, const char *value, enum env_op op,
	int flags)
{
	if (flags & H_PROGRAMMATIC)
		return 0;

	net_ip = string_to_ip(value);

	return 0;
}

> You can see this call in the netboot_update_env()
> function in cmd/net.c.

netboot_update_env() does not update the internal variables. At least
not in my tests. op_ipaddr() returns directly after the "flags" check
(see above).

I've checked how "dhcp" works. And here the variables are updated
in store_net_params() via explicit net_copy_ip() calls.
 
>> Or if this is really needed, what is the correct way to update
>> the ipaddr (env variable and net_ip value) from the U-Boot code?
> 
> You can work around it in a similar way to what I did in the initial
> change (94b467b14ed908c89a0780256e89b375aa3cf3ef - env: Distinguish
> finer between source of env change). The do_env_edit function used to
> call setenv, but I changed it to call as though it was interactive.
> You could do the same thing in your board driver.

Again, my findings are that this is implemented the other way around.
setenv from the user via the command "setenv ipaddr ..." will update
the net_ip variable. And code that calls setenv() will not.

I still fails to see why one of both should not update the net_ip
(and others) variable. From my understanding setenv() from code and
"setenv ipaddr ..." from the prompt should update the internal
variables.

Thanks,
Stefan

[U-Boot] Setting ipaddr via setenv() - H_INTERACTIVE vs H_PROGRAMMATIC

[Joe Hershberger]

Hi Stefan,

On Wed, Mar 2, 2016 at 12:21 AM, Stefan Roese <sr@denx.de> wrote:
> Hi Joe,
>
> (adding Tom to Cc as this seems to be a fundamental issue)
>
> On 01.03.2016 20:40, Joe Hershberger wrote:
>> On Tue, Mar 1, 2016 at 4:35 AM, Stefan Roese <sr@denx.de> wrote:
>>> Hi Joe,
>>>
>>> I'm currently stumbling over a problem in some board specific code
>>> (not in mainline yet), that sets the "ipaddr" env variable via
>>> setenv(). But as I now noticed, the callback on_ipaddr() doesn't
>>> set net_ip to this new value. As flags has H_PROGRAMMATIC set and
>>> op_ipaddr() skips setting this value in this case.
>>>
>>> I fail to see why we need this check in on_ipaddr(). Could you
>>> please explain why this is needed? Why would someone use setenv()
>>> for the "ipaddr" and not want to also update the net_ip value.
>>> This results in the "ipaddr" value being updated but net_ip
>>> still being configured to the old value.
>>
>> The purpose is that programmatic accesses may write directly to the
>> net_ip variable, but the user on the console cannot. This is because
>> the "programmatic" accesses to these variables is expected to be
>> things like the dhcp command and the linklocal command after
>> successful netloop.
>
> Please correct me, but it seems to be implemented the other way around.
> If H_PROGRAMMATIC is set (called via setenv()) the net variables
> (net_ip...) will *not* be set:
>
> static int on_ipaddr(const char *name, const char *value, enum env_op op,
>         int flags)
> {
>         if (flags & H_PROGRAMMATIC)
>                 return 0;
>
>         net_ip = string_to_ip(value);
>
>         return 0;
> }
>
>> You can see this call in the netboot_update_env()
>> function in cmd/net.c.
>
> netboot_update_env() does not update the internal variables. At least
> not in my tests. op_ipaddr() returns directly after the "flags" check
> (see above).

That's exactly the point. It doesn't set the internal variables
because the source *is* the internal variables.

> I've checked how "dhcp" works. And here the variables are updated
> in store_net_params() via explicit net_copy_ip() calls.
>
>>> Or if this is really needed, what is the correct way to update
>>> the ipaddr (env variable and net_ip value) from the U-Boot code?
>>
>> You can work around it in a similar way to what I did in the initial
>> change (94b467b14ed908c89a0780256e89b375aa3cf3ef - env: Distinguish
>> finer between source of env change). The do_env_edit function used to
>> call setenv, but I changed it to call as though it was interactive.
>> You could do the same thing in your board driver.
>
> Again, my findings are that this is implemented the other way around.
> setenv from the user via the command "setenv ipaddr ..." will update
> the net_ip variable. And code that calls setenv() will not.
>
> I still fails to see why one of both should not update the net_ip
> (and others) variable. From my understanding setenv() from code and
> "setenv ipaddr ..." from the prompt should update the internal
> variables.
>
> Thanks,
> Stefan
>

[U-Boot] Setting ipaddr via setenv() - H_INTERACTIVE vs H_PROGRAMMATIC

[Stefan Roese]

Hi Joe,

On 02.03.2016 07:46, Joe Hershberger wrote:
> On Wed, Mar 2, 2016 at 12:21 AM, Stefan Roese <sr@denx.de> wrote:
>> Hi Joe,
>>
>> (adding Tom to Cc as this seems to be a fundamental issue)
>>
>> On 01.03.2016 20:40, Joe Hershberger wrote:
>>> On Tue, Mar 1, 2016 at 4:35 AM, Stefan Roese <sr@denx.de> wrote:
>>>> Hi Joe,
>>>>
>>>> I'm currently stumbling over a problem in some board specific code
>>>> (not in mainline yet), that sets the "ipaddr" env variable via
>>>> setenv(). But as I now noticed, the callback on_ipaddr() doesn't
>>>> set net_ip to this new value. As flags has H_PROGRAMMATIC set and
>>>> op_ipaddr() skips setting this value in this case.
>>>>
>>>> I fail to see why we need this check in on_ipaddr(). Could you
>>>> please explain why this is needed? Why would someone use setenv()
>>>> for the "ipaddr" and not want to also update the net_ip value.
>>>> This results in the "ipaddr" value being updated but net_ip
>>>> still being configured to the old value.
>>>
>>> The purpose is that programmatic accesses may write directly to the
>>> net_ip variable, but the user on the console cannot. This is because
>>> the "programmatic" accesses to these variables is expected to be
>>> things like the dhcp command and the linklocal command after
>>> successful netloop.
>>
>> Please correct me, but it seems to be implemented the other way around.
>> If H_PROGRAMMATIC is set (called via setenv()) the net variables
>> (net_ip...) will *not* be set:
>>
>> static int on_ipaddr(const char *name, const char *value, enum env_op op,
>>          int flags)
>> {
>>          if (flags & H_PROGRAMMATIC)
>>                  return 0;
>>
>>          net_ip = string_to_ip(value);
>>
>>          return 0;
>> }
>>
>>> You can see this call in the netboot_update_env()
>>> function in cmd/net.c.
>>
>> netboot_update_env() does not update the internal variables. At least
>> not in my tests. op_ipaddr() returns directly after the "flags" check
>> (see above).
>
> That's exactly the point. It doesn't set the internal variables
> because the source *is* the internal variables.

Now I understand what you mean. The PROGRAMMATIC approach should set
the variables directly. I'll set the net_ip variable directly from
the board specific code then.

But again, why exactly do we need to distinguish between this
interactive and programmatic access? Why not set the internal variables
every time the special env variables are set (interactively and
programmatically)?

Thanks,
Stefan

[U-Boot] Setting ipaddr via setenv() - H_INTERACTIVE vs H_PROGRAMMATIC

[Joe Hershberger]

On Wed, Mar 2, 2016 at 1:01 AM, Stefan Roese <sr@denx.de> wrote:
> Hi Joe,
>
>
> On 02.03.2016 07:46, Joe Hershberger wrote:
>>
>> On Wed, Mar 2, 2016 at 12:21 AM, Stefan Roese <sr@denx.de> wrote:
>>>
>>> Hi Joe,
>>>
>>> (adding Tom to Cc as this seems to be a fundamental issue)
>>>
>>> On 01.03.2016 20:40, Joe Hershberger wrote:
>>>>
>>>> On Tue, Mar 1, 2016 at 4:35 AM, Stefan Roese <sr@denx.de> wrote:
>>>>>
>>>>> Hi Joe,
>>>>>
>>>>> I'm currently stumbling over a problem in some board specific code
>>>>> (not in mainline yet), that sets the "ipaddr" env variable via
>>>>> setenv(). But as I now noticed, the callback on_ipaddr() doesn't
>>>>> set net_ip to this new value. As flags has H_PROGRAMMATIC set and
>>>>> op_ipaddr() skips setting this value in this case.
>>>>>
>>>>> I fail to see why we need this check in on_ipaddr(). Could you
>>>>> please explain why this is needed? Why would someone use setenv()
>>>>> for the "ipaddr" and not want to also update the net_ip value.
>>>>> This results in the "ipaddr" value being updated but net_ip
>>>>> still being configured to the old value.
>>>>
>>>>
>>>> The purpose is that programmatic accesses may write directly to the
>>>> net_ip variable, but the user on the console cannot. This is because
>>>> the "programmatic" accesses to these variables is expected to be
>>>> things like the dhcp command and the linklocal command after
>>>> successful netloop.
>>>
>>>
>>> Please correct me, but it seems to be implemented the other way around.
>>> If H_PROGRAMMATIC is set (called via setenv()) the net variables
>>> (net_ip...) will *not* be set:
>>>
>>> static int on_ipaddr(const char *name, const char *value, enum env_op op,
>>>          int flags)
>>> {
>>>          if (flags & H_PROGRAMMATIC)
>>>                  return 0;
>>>
>>>          net_ip = string_to_ip(value);
>>>
>>>          return 0;
>>> }
>>>
>>>> You can see this call in the netboot_update_env()
>>>> function in cmd/net.c.
>>>
>>>
>>> netboot_update_env() does not update the internal variables. At least
>>> not in my tests. op_ipaddr() returns directly after the "flags" check
>>> (see above).
>>
>>
>> That's exactly the point. It doesn't set the internal variables
>> because the source *is* the internal variables.
>
>
> Now I understand what you mean. The PROGRAMMATIC approach should set
> the variables directly. I'll set the net_ip variable directly from
> the board specific code then.
>
> But again, why exactly do we need to distinguish between this
> interactive and programmatic access? Why not set the internal variables
> every time the special env variables are set (interactively and
> programmatically)?

It was simply for the reason above. I think in this case, it is
writing the variable with the previous value and would be harmless. In
general it is to be able to avoid infinite loops if the on_blah
handler is calling a helper that updates the env, etc.

-Joe