Re: [PROPOSAL]: Alias names for network interfaces

[Patrick McHardy <kaber@trash.net>]

Narendra K wrote:
>>>>>> ifconfig would show Embedded_NIC_N instead of ethN.
>>>>> Renaming away from ethN causes some applications like net-snmp to
>>> get
>>>>> confused,
>>>>> and others have special sorting rules based on existing model
>> (like
>>>>> quagga).
>>>>>
>>>>> I would argue that the "ethN" convention is part of existing
>> system
>>>>> ABI and should not get changed in a visible way to applications.
>>>> Stephen,
>>>>
>>>> Thanks. What are your views on the current proposal we are making
>>> where
>>>> ethN names are not changed (or renamed) and libnetdevname would
>>> suggest
>>>> alias names for the ethN names ( and also alias to ethN names) in
>>> user
>>>> space. Applications like ip, ethtool etc can use these aliases, make
>>>> calls to libnetdevname and get the ethN name.
>>>>
>>>> Libnetdevname would read from sysfs the smbios names of the network
>>>> interface devices as Jordan mentioned
>>>> (/sys/class/net/ethX/device/smbiosname). Would this be acceptable ?
>>> I have no need or use for them, but if it doesn't break other things
>>> then sure.
>> Jeff / netfilter-devel,
>>
>> It would greatly help to know your views on this proposal.
> 
> The proposal is to enhance iptables (and other tools which might fail if
> integrated port 1 does not get named as eth0) to support something like
> 
> iptables -A INPUT -i Embedded_NIC_1 -j ACCEPT 
> 
> in addition to what it already supports 
> 
> iptables -A INPUT -i eth0 -j ACCEPT.
> 
> Below is how the iptables code that handles the "-i ethN" would look
> like (Only a part of the code to demonstrate the idea shown here) -
> 
> diff -Naru iptables-1.4.5/xtables.c iptables-1.4.5-new/xtables.c
> --- iptables-1.4.5/xtables.c	2010-01-12 02:47:16.293249537 +0530
> +++ iptables-1.4.5-new/xtables.c	2010-01-13 06:14:12.130185117 +0530
> @@ -455,8 +455,8 @@
>  void xtables_parse_interface(const char *arg, char *vianame,
>  			     unsigned char *mask)
>  {
> -	int vialen = strlen(arg);
>  	unsigned int i;
> +	static char kernel_name[IFNAMSIZ];
>  
>  	memset(mask, 0, IFNAMSIZ);
>  	memset(vianame, 0, IFNAMSIZ);
> @@ -466,7 +466,11 @@
>  			   "interface name `%s' must be shorter than IFNAMSIZ"
>  			   " (%i)", arg, IFNAMSIZ-1);
>  
> -	strcpy(vianame, arg);
> +	if (netdev_alias_to_kernel_name(arg, kernel_name) < 0)
> +		show_alias_name_usage();

Is this able to deal with non-existant devices?

> +	
> +	strcpy(vianame, kernel_name);
> +	int vialen = strlen(kernel_name);
>  	if ((vialen == 0) || (vialen == 1 && vianame[0] == '+'))
>  		memset(mask, 0, IFNAMSIZ);
>  	else if (vianame[vialen - 1] == '+') {
> 
> 
> where kernel_name is the ethN name that will be returned by a library
> like libnetdevname which will map the user supplied "Embedded_NIC_1"
> name to the corresponding ethN name, thus bringing in determinism while
> referring to the network interfaces.
> 
> Netfilter-devel, would this be acceptable ?

What I don't like very much is that you can't decide whether to
map the interface names back in order to display a rule the same
way it was specified. Anyone looking at the output will have to
know the alias mapping, which seems to defeat the purpose of
this patch.