[NET]: Calculate RTATTR_MAX at run time.

This also solved a problem noticed by Thomas Graf
in that RTATTR_MAX had become incorrect recently
due to IFLA_MAX increasing and thus becomming the
largest one.
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/rtnetlink.h

@@ -660,10 +660,6 @@ enum
 #define TCA_PAYLOAD(n) NLMSG_PAYLOAD(n,sizeof(struct tcmsg))
 
 
-/* SUMMARY: maximal rtattr understood by kernel */
-
-#define RTATTR_MAX		RTA_MAX
-
 /* RTnetlink multicast groups */
 
 #define RTMGRP_LINK		1

net/core/rtnetlink.c

@@ -401,6 +401,10 @@ static int rtnetlink_done(struct netlink_callback *cb)
 	return 0;
 }
 
+/* Protected by RTNL sempahore.  */
+static struct rtattr **rta_buf;
+static int rtattr_max;
+
 /* Process one rtnetlink message. */
 
 static __inline__ int
@@ -408,8 +412,6 @@ rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, int *errp)
 {
 	struct rtnetlink_link *link;
 	struct rtnetlink_link *link_tab;
-	struct rtattr	*rta[RTATTR_MAX];
-
 	int sz_idx, kind;
 	int min_len;
 	int family;
@@ -476,7 +478,7 @@ rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, int *errp)
 		return -1;
 	}
 
-	memset(&rta, 0, sizeof(rta));
+	memset(rta_buf, 0, (rtattr_max * sizeof(struct rtattr *)));
 
 	min_len = rtm_min[sz_idx];
 	if (nlh->nlmsg_len < min_len)
@@ -491,7 +493,7 @@ rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, int *errp)
 			if (flavor) {
 				if (flavor > rta_max[sz_idx])
 					goto err_inval;
-				rta[flavor-1] = attr;
+				rta_buf[flavor-1] = attr;
 			}
 			attr = RTA_NEXT(attr, attrlen);
 		}
@@ -501,7 +503,7 @@ rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, int *errp)
 		link = &(rtnetlink_links[PF_UNSPEC][type]);
 	if (link->doit == NULL)
 		goto err_inval;
-	err = link->doit(skb, nlh, (void *)&rta);
+	err = link->doit(skb, nlh, (void *)&rta_buf[0]);
 
 	*errp = err;
 	return err;
@@ -621,6 +623,16 @@ static struct notifier_block rtnetlink_dev_notifier = {
 
 void __init rtnetlink_init(void)
 {
+	int i;
+
+	rtattr_max = 0;
+	for (i = 0; i < ARRAY_SIZE(rta_max); i++)
+		if (rta_max[i] > rtattr_max)
+			rtattr_max = rta_max[i];
+	rta_buf = kmalloc(rtattr_max * sizeof(struct rtattr *), GFP_KERNEL);
+	if (!rta_buf)
+		panic("rtnetlink_init: cannot allocate rta_buf\n");
+
 	rtnl = netlink_kernel_create(NETLINK_ROUTE, rtnetlink_rcv);
 	if (rtnl == NULL)
 		panic("rtnetlink_init: cannot initialize rtnetlink\n");