Re: [PATCH net-next v3] netlink: Rightsize IFLA_AF_SPEC size calculation

["Samudrala, Sridhar" <sridhar.samudrala@intel.com>]

On 10/19/2015 9:23 AM, Ronen Arad wrote:
> if_nlmsg_size() overestimates the minimum allocation size of netlink
> dump request (when called from rtnl_calcit()) or the size of the
> message (when called from rtnl_getlink()). This is because
> ext_filter_mask is not supported by rtnl_link_get_af_size() and
> rtnl_link_get_size().
>
> The over-estimation is significant when at least one netdev has many
> VLANs configured (8 bytes for each configured VLAN).
>
> This patch-set "rightsizes" the protocol specific attribute size
> calculation by propagating ext_filter_mask to rtnl_link_get_af_size()
> and adding this a argument to get_link_af_size op in rtnl_af_ops.
>
> Bridge module already used filtering aware sizing for notifications.
> br_get_link_af_size_filtered() is consistent with the modified
> get_link_af_size op so it replaces br_get_link_af_size() in br_af_ops.
> br_get_link_af_size() becomes unused and thus removed.
>
> Signed-off-by: Ronen Arad <ronen.arad@intel.com>
Acked-by: Sridhar Samudrala <sridhar.samudrala@intel.com>

> ---
>   include/net/rtnetlink.h |  3 ++-
>   net/bridge/br_netlink.c | 21 +--------------------
>   net/core/rtnetlink.c    |  8 ++++----
>   net/ipv4/devinet.c      |  4 ++--
>   net/ipv6/addrconf.c     |  3 ++-
>   5 files changed, 11 insertions(+), 28 deletions(-)
>
> diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
> index aff6ceb..2f87c1b 100644
> --- a/include/net/rtnetlink.h
> +++ b/include/net/rtnetlink.h
> @@ -124,7 +124,8 @@ struct rtnl_af_ops {
>   	int			(*fill_link_af)(struct sk_buff *skb,
>   						const struct net_device *dev,
>   						u32 ext_filter_mask);
> -	size_t			(*get_link_af_size)(const struct net_device *dev);
> +	size_t			(*get_link_af_size)(const struct net_device *dev,
> +						    u32 ext_filter_mask);
>   
>   	int			(*validate_link_af)(const struct net_device *dev,
>   						    const struct nlattr *attr);
> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> index 94b4de8..40197ff 100644
> --- a/net/bridge/br_netlink.c
> +++ b/net/bridge/br_netlink.c
> @@ -1214,29 +1214,10 @@ static int br_fill_info(struct sk_buff *skb, const struct net_device *brdev)
>   	return 0;
>   }
>   
> -static size_t br_get_link_af_size(const struct net_device *dev)
> -{
> -	struct net_bridge_port *p;
> -	struct net_bridge *br;
> -	int num_vlans = 0;
> -
> -	if (br_port_exists(dev)) {
> -		p = br_port_get_rtnl(dev);
> -		num_vlans = br_get_num_vlan_infos(nbp_vlan_group(p),
> -						  RTEXT_FILTER_BRVLAN);
> -	} else if (dev->priv_flags & IFF_EBRIDGE) {
> -		br = netdev_priv(dev);
> -		num_vlans = br_get_num_vlan_infos(br_vlan_group(br),
> -						  RTEXT_FILTER_BRVLAN);
> -	}
> -
> -	/* Each VLAN is returned in bridge_vlan_info along with flags */
> -	return num_vlans * nla_total_size(sizeof(struct bridge_vlan_info));
> -}
>   
>   static struct rtnl_af_ops br_af_ops __read_mostly = {
>   	.family			= AF_BRIDGE,
> -	.get_link_af_size	= br_get_link_af_size,
> +	.get_link_af_size	= br_get_link_af_size_filtered,
>   };
>   
>   struct rtnl_link_ops br_link_ops __read_mostly = {
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 2477595..7c78b5a 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -497,7 +497,8 @@ void rtnl_af_unregister(struct rtnl_af_ops *ops)
>   }
>   EXPORT_SYMBOL_GPL(rtnl_af_unregister);
>   
> -static size_t rtnl_link_get_af_size(const struct net_device *dev)
> +static size_t rtnl_link_get_af_size(const struct net_device *dev,
> +				    u32 ext_filter_mask)
>   {
>   	struct rtnl_af_ops *af_ops;
>   	size_t size;
> @@ -509,7 +510,7 @@ static size_t rtnl_link_get_af_size(const struct net_device *dev)
>   		if (af_ops->get_link_af_size) {
>   			/* AF_* + nested data */
>   			size += nla_total_size(sizeof(struct nlattr)) +
> -				af_ops->get_link_af_size(dev);
> +				af_ops->get_link_af_size(dev, ext_filter_mask);
>   		}
>   	}
>   
> @@ -900,7 +901,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
>   	       + rtnl_vfinfo_size(dev, ext_filter_mask) /* IFLA_VFINFO_LIST */
>   	       + rtnl_port_size(dev, ext_filter_mask) /* IFLA_VF_PORTS + IFLA_PORT_SELF */
>   	       + rtnl_link_get_size(dev) /* IFLA_LINKINFO */
> -	       + rtnl_link_get_af_size(dev) /* IFLA_AF_SPEC */
> +	       + rtnl_link_get_af_size(dev, ext_filter_mask) /* IFLA_AF_SPEC */
>   	       + nla_total_size(MAX_PHYS_ITEM_ID_LEN) /* IFLA_PHYS_PORT_ID */
>   	       + nla_total_size(MAX_PHYS_ITEM_ID_LEN) /* IFLA_PHYS_SWITCH_ID */
>   	       + nla_total_size(1); /* IFLA_PROTO_DOWN */
> @@ -3443,4 +3444,3 @@ void __init rtnetlink_init(void)
>   	rtnl_register(PF_BRIDGE, RTM_DELLINK, rtnl_bridge_dellink, NULL, NULL);
>   	rtnl_register(PF_BRIDGE, RTM_SETLINK, rtnl_bridge_setlink, NULL, NULL);
>   }
> -
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index 7350084..cebd9d3 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1644,7 +1644,8 @@ errout:
>   		rtnl_set_sk_err(net, RTNLGRP_IPV4_IFADDR, err);
>   }
>   
> -static size_t inet_get_link_af_size(const struct net_device *dev)
> +static size_t inet_get_link_af_size(const struct net_device *dev,
> +				    u32 ext_filter_mask)
>   {
>   	struct in_device *in_dev = rcu_dereference_rtnl(dev->ip_ptr);
>   
> @@ -2398,4 +2399,3 @@ void __init devinet_init(void)
>   	rtnl_register(PF_INET, RTM_GETNETCONF, inet_netconf_get_devconf,
>   		      inet_netconf_dump_devconf, NULL);
>   }
> -
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index f0326aa..0645fd1 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -4786,7 +4786,8 @@ nla_put_failure:
>   	return -EMSGSIZE;
>   }
>   
> -static size_t inet6_get_link_af_size(const struct net_device *dev)
> +static size_t inet6_get_link_af_size(const struct net_device *dev,
> +				     u32 ext_filter_mask)
>   {
>   	if (!__in6_dev_get(dev))
>   		return 0;