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

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Date:   Mon, 7 Oct 2019 15:52:46 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org
Cc:     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

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?

> +
> +	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;
>  }
>  
>