net/ipv6: move metrics from dst to rt6_info

Similar to IPv4, add fib metrics to the fib struct, which at the moment
is rt6_info. Will be moved to fib6_info in a later patch. Copy metrics
into dst by reference using refcount.

To make the transition:
- add dst_metrics to rt6_info. Default to dst_default_metrics if no
  metrics are passed during route add. No need for a separate pmtu
  entry; it can reference the MTU slot in fib6_metrics

- ip6_convert_metrics allocates memory in the FIB entry and uses
  ip_metrics_convert to copy from netlink attribute to metrics entry

- the convert metrics call is done in ip6_route_info_create simplifying
  the route add path
  + fib6_commit_metrics and fib6_copy_metrics and the temporary
    mx6_config are no longer needed

- add fib6_metric_set helper to change the value of a metric in the
  fib entry since dst_metric_set can no longer be used

- cow_metrics for IPv6 can drop to dst_cow_metrics_generic

- rt6_dst_from_metrics_check is no longer needed

- rt6_fill_node needs the FIB entry and dst as separate arguments to
  keep compatibility with existing output. Current dst address is
  renamed to dest.
  (to be consistent with IPv4 rt6_fill_node really should be split
  into 2 functions similar to fib_dump_info and rt_fill_info)

- rt6_fill_node no longer needs the temporary metrics variable

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_fib.c

@@ -578,6 +578,24 @@ out:
 	return res;
 }
 
+void fib6_metric_set(struct rt6_info *f6i, int metric, u32 val)
+{
+	if (!f6i)
+		return;
+
+	if (f6i->fib6_metrics == &dst_default_metrics) {
+		struct dst_metrics *p = kzalloc(sizeof(*p), GFP_ATOMIC);
+
+		if (!p)
+			return;
+
+		refcount_set(&p->refcnt, 1);
+		f6i->fib6_metrics = p;
+	}
+
+	f6i->fib6_metrics->metrics[metric - 1] = val;
+}
+
 /*
  *	Routing Table
  *
@@ -801,38 +819,6 @@ insert_above:
 	return ln;
 }
 
-static void fib6_copy_metrics(u32 *mp, const struct mx6_config *mxc)
-{
-	int i;
-
-	for (i = 0; i < RTAX_MAX; i++) {
-		if (test_bit(i, mxc->mx_valid))
-			mp[i] = mxc->mx[i];
-	}
-}
-
-static int fib6_commit_metrics(struct dst_entry *dst, struct mx6_config *mxc)
-{
-	if (!mxc->mx)
-		return 0;
-
-	if (dst->flags & DST_HOST) {
-		u32 *mp = dst_metrics_write_ptr(dst);
-
-		if (unlikely(!mp))
-			return -ENOMEM;
-
-		fib6_copy_metrics(mp, mxc);
-	} else {
-		dst_init_metrics(dst, mxc->mx, false);
-
-		/* We've stolen mx now. */
-		mxc->mx = NULL;
-	}
-
-	return 0;
-}
-
 static void fib6_purge_rt(struct rt6_info *rt, struct fib6_node *fn,
 			  struct net *net)
 {
@@ -866,7 +852,7 @@ static void fib6_purge_rt(struct rt6_info *rt, struct fib6_node *fn,
  */
 
 static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
-			    struct nl_info *info, struct mx6_config *mxc,
+			    struct nl_info *info,
 			    struct netlink_ext_ack *extack)
 {
 	struct rt6_info *leaf = rcu_dereference_protected(fn->leaf,
@@ -923,7 +909,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
 					rt6_clean_expires(iter);
 				else
 					rt6_set_expires(iter, rt->dst.expires);
-				iter->rt6i_pmtu = rt->rt6i_pmtu;
+				fib6_metric_set(iter, RTAX_MTU, rt->fib6_pmtu);
 				return -EEXIST;
 			}
 			/* If we have the same destination and the same metric,
@@ -1002,9 +988,6 @@ next_iter:
 
 add:
 		nlflags |= NLM_F_CREATE;
-		err = fib6_commit_metrics(&rt->dst, mxc);
-		if (err)
-			return err;
 
 		err = call_fib6_entry_notifiers(info->nl_net,
 						FIB_EVENT_ENTRY_ADD,
@@ -1035,10 +1018,6 @@ add:
 			return -ENOENT;
 		}
 
-		err = fib6_commit_metrics(&rt->dst, mxc);
-		if (err)
-			return err;
-
 		err = call_fib6_entry_notifiers(info->nl_net,
 						FIB_EVENT_ENTRY_REPLACE,
 						rt, extack);
@@ -1135,8 +1114,7 @@ void fib6_update_sernum_upto_root(struct net *net, struct rt6_info *rt)
  */
 
 int fib6_add(struct fib6_node *root, struct rt6_info *rt,
-	     struct nl_info *info, struct mx6_config *mxc,
-	     struct netlink_ext_ack *extack)
+	     struct nl_info *info, struct netlink_ext_ack *extack)
 {
 	struct fib6_table *table = rt->rt6i_table;
 	struct fib6_node *fn, *pn = NULL;
@@ -1244,7 +1222,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
 	}
 #endif
 
-	err = fib6_add_rt2node(fn, rt, info, mxc, extack);
+	err = fib6_add_rt2node(fn, rt, info, extack);
 	if (!err) {
 		__fib6_update_sernum_upto_root(rt, sernum);
 		fib6_start_gc(info->nl_net, rt);