netdev - Re: [RFC PATCH iproute2] link dump filter

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Date:	Mon, 7 Jul 2014 08:49:06 -0700
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	roopa@...ulusnetworks.com
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	shm@...ulusnetworks.com, nolan@...ulusnetworks.com,
	sfeldma@...ulusnetworks.com, jhs@...atatu.com
Subject: Re: [RFC PATCH iproute2] link dump filter

On Thu,  3 Jul 2014 16:07:15 -0700
roopa@...ulusnetworks.com wrote:

> From: Roopa Prabhu <roopa@...ulusnetworks.com>
> 
> This patch avoids a full link wildump request when the user has specified
> a single link. Uses RTM_GETLINK without the NLM_F_DUMP flag.
> 
> This helps on a system with large number of interfaces.
> 
> This patch currently only uses the link ifindex in the filter.
> Hoping to provide a subsequent kernel patch to do link dump filtering on
> other attributes in the kernel.
> 
> In iplink_get, to be safe, this patch currently sets the answer buffer
> size to the max size that libnetlink rtnl_talk can copy. The current api
> does not seem to provide a way to indicate the answer buf size.

Good, should be same size as all the other buffers.

> 
> Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>
> ---
>  ip/ip_common.h |    1 +
>  ip/ipaddress.c |   20 +++++++++++++++++---
>  ip/iplink.c    |   32 ++++++++++++++++++++++++++++++++
>  3 files changed, 50 insertions(+), 3 deletions(-)
> 
> diff --git a/ip/ip_common.h b/ip/ip_common.h
> index ac1e4c1..e56d1ac 100644
> --- a/ip/ip_common.h
> +++ b/ip/ip_common.h
> @@ -51,6 +51,7 @@ extern int do_ipl2tp(int argc, char **argv);
>  extern int do_tcp_metrics(int argc, char **argv);
>  extern int do_ipnetconf(int argc, char **argv);
>  extern int do_iptoken(int argc, char **argv);
> +extern int iplink_get(unsigned int flags, char *name, __u32 filt_mask);
>  
>  static inline int rtm_get_table(struct rtmsg *r, struct rtattr **tb)
>  {
> diff --git a/ip/ipaddress.c b/ip/ipaddress.c
> index 8138e86..d111fab 100644
> --- a/ip/ipaddress.c
> +++ b/ip/ipaddress.c
> @@ -1241,9 +1241,23 @@ static int ipaddr_list_flush_or_save(int argc, char **argv, int action)
>  		exit(0);
>  	}
>  
> -	if (rtnl_wilddump_request(&rth, preferred_family, RTM_GETLINK) < 0) {
> -		perror("Cannot send dump request");
> -		exit(1);
> +	if (filter_dev && filter.group == -1 && do_link == 1) {
> +		/*
> +		 * If only filter_dev present and none of the other
> +		 * link filters are present, use RTM_GETLINK to get
> +		 * the link device
> +		 */
move comment before if

> +		if (iplink_get(0, filter_dev, RTEXT_FILTER_VF) < 0) {
> +			perror("Cannot send link get request");
> +			exit(1);
> +		}
> +		exit(0);
> +	} else {

Since code always does exit, the else is redundant.

> +		if (rtnl_wilddump_request(&rth, preferred_family,
> +					RTM_GETLINK) < 0) {
> +			perror("Cannot send dump request");
> +			exit(1);
> +		}
>  	}
>  
>  	if (rtnl_dump_filter(&rth, store_nlmsg, &linfo) < 0) {
> diff --git a/ip/iplink.c b/ip/iplink.c
> index 0d020ef..7ac2813 100644
> --- a/ip/iplink.c
> +++ b/ip/iplink.c
> @@ -703,6 +703,38 @@ static int iplink_modify(int cmd, unsigned int flags, int argc, char **argv)
>  	return 0;
>  }
>  
> +int iplink_get(unsigned int flags, char *name, __u32 filt_mask)
> +{
> +	int len;
> +	struct iplink_req req;
> +	char answer[16384];
> +
> +	memset(&req, 0, sizeof(req));
> +
> +	req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
> +	req.n.nlmsg_flags = NLM_F_REQUEST|flags;
> +	req.n.nlmsg_type = RTM_GETLINK;
> +	req.i.ifi_family = preferred_family;
> +
> +	if (name) {
> +		len = strlen(name) + 1;
> +		if (len == 1)
> +			invarg("\"\" is not a valid device identifier\n",
> +				   "name");
> +		if (len > IFNAMSIZ)
> +			invarg("\"name\" too long\n", name);
> +		addattr_l(&req.n, sizeof(req), IFLA_IFNAME, name, len);
> +	}
> +	addattr32(&req.n, sizeof(req), IFLA_EXT_MASK, filt_mask);
> +
> +	if (rtnl_talk(&rth, &req.n, 0, 0, (struct nlmsghdr *)answer) < 0)
> +		return -2;
> +
> +	print_linkinfo(NULL, (struct nlmsghdr *)answer, stdout);
> +
> +	return 0;
> +}
> +
>  #if IPLINK_IOCTL_COMPAT
>  static int get_ctl_fd(void)
>  {

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