netdev - Re: [patch iproute2-next v2 2/2] ip: allow to use alternative names as handle

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Date:   Wed, 9 Oct 2019 14:41:41 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     David Ahern <dsahern@...il.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        jakub.kicinski@...ronome.com, roopa@...ulusnetworks.com,
        dcbw@...hat.com, nikolay@...ulusnetworks.com, mkubecek@...e.cz,
        andrew@...n.ch, parav@...lanox.com, saeedm@...lanox.com,
        f.fainelli@...il.com, stephen@...workplumber.org,
        sd@...asysnail.net, sbrivio@...hat.com, pabeni@...hat.com,
        mlxsw@...lanox.com
Subject: Re: [patch iproute2-next v2 2/2] ip: allow to use alternative names
 as handle

Mon, Oct 07, 2019 at 11:52:46PM CEST, dsahern@...il.com wrote:
>On 10/2/19 4:56 AM, Jiri Pirko wrote:
>> @@ -1106,7 +1106,8 @@ int iplink_get(char *name, __u32 filt_mask)
>>  
>>  	if (name) {
>>  		addattr_l(&req.n, sizeof(req),
>> -			  IFLA_IFNAME, name, strlen(name) + 1);
>> +			  !check_ifname(name) ? IFLA_IFNAME : IFLA_ALT_IFNAME,
>
>If this trick works here ...
>
>> +			  name, strlen(name) + 1);
>>  	}
>>  	addattr32(&req.n, sizeof(req), IFLA_EXT_MASK, filt_mask);
>>  
>> diff --git a/lib/ll_map.c b/lib/ll_map.c
>> index e0ed54bf77c9..04dfb0f2320b 100644
>> --- a/lib/ll_map.c
>> +++ b/lib/ll_map.c
>> @@ -70,7 +70,7 @@ static struct ll_cache *ll_get_by_name(const char *name)
>>  		struct ll_cache *im
>>  			= container_of(n, struct ll_cache, name_hash);
>>  
>> -		if (strncmp(im->name, name, IFNAMSIZ) == 0)
>> +		if (strcmp(im->name, name) == 0)
>>  			return im;
>>  	}
>>  
>> @@ -240,6 +240,43 @@ int ll_index_to_flags(unsigned idx)
>>  	return im ? im->flags : -1;
>>  }
>>  
>> +static int altnametoindex(const char *name)
>> +{
>> +	struct {
>> +		struct nlmsghdr		n;
>> +		struct ifinfomsg	ifm;
>> +		char			buf[1024];
>> +	} req = {
>> +		.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
>> +		.n.nlmsg_flags = NLM_F_REQUEST,
>> +		.n.nlmsg_type = RTM_GETLINK,
>> +	};
>> +	struct rtnl_handle rth = {};
>> +	struct nlmsghdr *answer;
>> +	struct ifinfomsg *ifm;
>> +	int rc = 0;
>> +
>> +	if (rtnl_open(&rth, 0) < 0)
>> +		return 0;
>> +
>> +	addattr32(&req.n, sizeof(req), IFLA_EXT_MASK,
>> +		  RTEXT_FILTER_VF | RTEXT_FILTER_SKIP_STATS);
>> +	addattr_l(&req.n, sizeof(req), IFLA_ALT_IFNAME, name, strlen(name) + 1);
>
>then why is altnametoindex even needed? why not just use the same check
>in the current ll_link_get?

Good point. Reworked. Thanks!


>
>> +
>> +	if (rtnl_talk_suppress_rtnl_errmsg(&rth, &req.n, &answer) < 0)
>> +		goto out;
>> +
>> +	ifm = NLMSG_DATA(answer);
>> +	rc = ifm->ifi_index;
>> +
>> +	free(answer);
>> +
>> +	rtnl_close(&rth);
>> +out:
>> +	return rc;
>> +}
>> +
>> +
>>  unsigned ll_name_to_index(const char *name)
>>  {
>>  	const struct ll_cache *im;
>> @@ -257,6 +294,8 @@ unsigned ll_name_to_index(const char *name)
>>  		idx = if_nametoindex(name);
>>  	if (idx == 0)
>>  		idx = ll_idx_a2n(name);
>> +	if (idx == 0)
>> +		idx = altnametoindex(name);
>
>And then this ordering does not need to be fixed (altname check should
>come before if_nametoindex.
>
>>  	return idx;
>>  }
>>  
>> 
>