[IPV4]: Add fib rule netlink notifications

To really make sense of route notifications in the presence of
multiple tables, userspace also needs to be notified about routing
rule updates.  Notifications are sent to the so far unused
RTNLGRP_NOP1 (now RTNLGRP_RULE) group.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/rtnetlink.h

@@ -839,6 +839,7 @@ enum
 #define RTMGRP_IPV4_IFADDR	0x10
 #define RTMGRP_IPV4_MROUTE	0x20
 #define RTMGRP_IPV4_ROUTE	0x40
+#define RTMGRP_IPV4_RULE	0x80
 
 #define RTMGRP_IPV6_IFADDR	0x100
 #define RTMGRP_IPV6_MROUTE	0x200
@@ -869,7 +870,8 @@ enum rtnetlink_groups {
 #define	RTNLGRP_IPV4_MROUTE	RTNLGRP_IPV4_MROUTE
 	RTNLGRP_IPV4_ROUTE,
 #define RTNLGRP_IPV4_ROUTE	RTNLGRP_IPV4_ROUTE
-	RTNLGRP_NOP1,
+	RTNLGRP_IPV4_RULE,
+#define RTNLGRP_IPV4_RULE	RTNLGRP_IPV4_RULE
 	RTNLGRP_IPV6_IFADDR,
 #define RTNLGRP_IPV6_IFADDR	RTNLGRP_IPV6_IFADDR
 	RTNLGRP_IPV6_MROUTE,

net/ipv4/fib_rules.c

@@ -104,6 +104,8 @@ static struct hlist_head fib_rules;
 
 /* writer func called from netlink -- rtnl_sem hold*/
 
+static void rtmsg_rule(int, struct fib_rule *);
+
 int inet_rtm_delrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 {
 	struct rtattr **rta = arg;
@@ -131,6 +133,7 @@ int inet_rtm_delrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 
 			hlist_del_rcu(&r->hlist);
 			r->r_dead = 1;
+			rtmsg_rule(RTM_DELRULE, r);
 			fib_rule_put(r);
 			err = 0;
 			break;
@@ -253,6 +256,7 @@ int inet_rtm_newrule(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 	else
 		hlist_add_before_rcu(&new_r->hlist, &r->hlist);
 
+	rtmsg_rule(RTM_NEWRULE, new_r);
 	return 0;
 }
 
@@ -382,14 +386,14 @@ static struct notifier_block fib_rules_notifier = {
 
 static __inline__ int inet_fill_rule(struct sk_buff *skb,
 				     struct fib_rule *r,
-				     struct netlink_callback *cb,
+				     u32 pid, u32 seq, int event,
 				     unsigned int flags)
 {
 	struct rtmsg *rtm;
 	struct nlmsghdr  *nlh;
 	unsigned char	 *b = skb->tail;
 
-	nlh = NLMSG_NEW_ANSWER(skb, cb, RTM_NEWRULE, sizeof(*rtm), flags);
+	nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*rtm), flags);
 	rtm = NLMSG_DATA(nlh);
 	rtm->rtm_family = AF_INET;
 	rtm->rtm_dst_len = r->r_dst_len;
@@ -430,6 +434,21 @@ static __inline__ int inet_fill_rule(struct sk_buff *skb,
 
 /* callers should hold rtnl semaphore */
 
+static void rtmsg_rule(int event, struct fib_rule *r)
+{
+	int size = NLMSG_SPACE(sizeof(struct rtmsg) + 128);
+	struct sk_buff *skb = alloc_skb(size, GFP_KERNEL);
+
+	if (!skb)
+		netlink_set_err(rtnl, 0, RTNLGRP_IPV4_RULE, ENOBUFS);
+	else if (inet_fill_rule(skb, r, 0, 0, event, 0) < 0) {
+		kfree_skb(skb);
+		netlink_set_err(rtnl, 0, RTNLGRP_IPV4_RULE, EINVAL);
+	} else {
+		netlink_broadcast(rtnl, skb, 0, RTNLGRP_IPV4_RULE, GFP_KERNEL);
+	}
+}
+
 int inet_dump_rules(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	int idx = 0;
@@ -442,7 +461,9 @@ int inet_dump_rules(struct sk_buff *skb, struct netlink_callback *cb)
 
 		if (idx < s_idx)
 			continue;
-		if (inet_fill_rule(skb, r, cb, NLM_F_MULTI) < 0)
+		if (inet_fill_rule(skb, r, NETLINK_CB(cb->skb).pid,
+				   cb->nlh->nlmsg_seq,
+				   RTM_NEWRULE, NLM_F_MULTI) < 0)
 			break;
 		idx++;
 	}