+ struct net *net = sock_net(skb->sk);
+ struct net_device *dev;
+ struct nlattr *tb[IFLA_MAX+1];
+ u32 ext_filter_mask = 0;
+ u16 min_ifinfo_dump_size = 0;
+ int hdrlen;
+
+ /* Same kernel<->userspace interface hack as in rtnl_dump_ifinfo. */
+ hdrlen = nlmsg_len(nlh) < sizeof(struct ifinfomsg) ?
+ sizeof(struct rtgenmsg) : sizeof(struct ifinfomsg);
+
+ if (nlmsg_parse(nlh, hdrlen, tb, IFLA_MAX, ifla_policy) >= 0) {
+ if (tb[IFLA_EXT_MASK])
+ ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]);
+ }
+
+ if (!ext_filter_mask)
+ return NLMSG_GOODSIZE;
+ /*
+ * traverse the list of net devices and compute the minimum
+ * buffer size based upon the filter mask.
+ */
+ list_for_each_entry(dev, &net->dev_base_head, dev_list) {
+ min_ifinfo_dump_size = max_t(u16, min_ifinfo_dump_size,
+ if_nlmsg_size(dev,
+ ext_filter_mask));
+ }
+