netdev - Re: [PATCH iproute2 1/3] iplink: Improve index parameter handling

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Date:   Mon, 18 Dec 2017 23:37:09 +0200
From:   Serhey Popovich <serhe.popovych@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH iproute2 1/3] iplink: Improve index parameter handling

Stephen Hemminger wrote:
> On Mon, 18 Dec 2017 23:02:07 +0200
> Serhey Popovich <serhe.popovych@...il.com> wrote:
> 
>> Stephen Hemminger wrote:
>>> On Mon, 18 Dec 2017 20:54:06 +0200
>>> Serhey Popovych <serhe.popovych@...il.com> wrote:
>>>   
>>>> diff --git a/ip/iplink.c b/ip/iplink.c
>>>> index 1e685cc..4f9c169 100644
>>>> --- a/ip/iplink.c
>>>> +++ b/ip/iplink.c
>>>> @@ -586,8 +586,10 @@ int iplink_parse(int argc, char **argv, struct iplink_req *req,
>>>>  			*name = *argv;
>>>>  		} else if (strcmp(*argv, "index") == 0) {
>>>>  			NEXT_ARG();
>>>> +			if (*index)
>>>> +				duparg("index", *argv);
>>>>  			*index = atoi(*argv);
>>>> -			if (*index < 0)
>>>> +			if (*index <= 0)  
>>>
>>> Why not use strtoul instead of atoi?  
>> Do not see reason for strtoul() instead atoi():
>>
>>   1) main arg: indexes in kernel represented as "int", which is
>>      signed. <= 0 values are reserved for various special purposes
>>      (see net/core/fib_rules.c on how device matching implemented).
>>
>>      Configuring network device manually with index <= 0 is not correct
>>      (however possible). Kernel itself never chooses ifindex <= 0.
>>
>>      Having unsigned int > 0x7fffffff actually means index <= 0.
>>
>>   2) this is not single place in iproute2 where it is used: not
>>      going to remove last user.
>>
>>   3) make changes clear and transparent for review.
> 
> I would rather all of iproute2 correctly handles unsigned values.
> Too much code is old K&R style C "the world is an int" and "who needs
> to check for negative".

You are right :(. I'm just trying to improve things a bit.

> 
> There already is get_unsigned() in iproute2 util functions.
This is good one based on strtoul(). But do we want to submit say
index = (unsigned int)2147483648(0x7fffffff) to the kernel that is
illegal from it's perspective?

Or do you mean I can prepare treewide change to replace atoi() with
get_unsigned()/get_integer() where appropriate?

We already check if (*index < 0) since commit 3c682146aeff
(iplink: forbid negative ifindex and modifying ifindex), and I just
put index == 0 in the same range of invalid indexes.

> Why not use that?
> 




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