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

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Date:   Tue, 19 Dec 2017 18:05:02 +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 23:37:09 +0200
> Serhey Popovich <serhe.popovych@...il.com> wrote:
> 
>> 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.
>>
> 
> The legacy BSD ABI for interfaces uses int, so that sets the upper
> bound for kernel.
> 
> The netlink ABI limit is u32 for ifindex so technically 1..UINT32_MAX are
> possible values but kernel is bound by BSD mistake.
Thank you for in depth explanation!

> 
> I will take the original patch.
> 
> 




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