net: rtnetlink: plumb extended ack to doit function

Add netlink_ext_ack arg to rtnl_doit_func. Pass extack arg to nlmsg_parse
for doit functions that call it directly.

This is the first step to using extended error reporting in rtnetlink.
>From here individual subsystems can be updated to set netlink_ext_ack as
needed.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/decnet/dn_fib.c b/net/decnet/dn_fib.c
index 34663bf..f9058eb 100644
--- a/net/decnet/dn_fib.c
+++ b/net/decnet/dn_fib.c
@@ -501,7 +501,8 @@ static inline u32 rtm_get_table(struct nlattr *attrs[], u8 table)
 	return table;
 }
 
-static int dn_fib_rtm_delroute(struct sk_buff *skb, struct nlmsghdr *nlh)
+static int dn_fib_rtm_delroute(struct sk_buff *skb, struct nlmsghdr *nlh,
+			       struct netlink_ext_ack *extack)
 {
 	struct net *net = sock_net(skb->sk);
 	struct dn_fib_table *tb;
@@ -516,7 +517,7 @@ static int dn_fib_rtm_delroute(struct sk_buff *skb, struct nlmsghdr *nlh)
 		return -EINVAL;
 
 	err = nlmsg_parse(nlh, sizeof(*r), attrs, RTA_MAX, rtm_dn_policy,
-			  NULL);
+			  extack);
 	if (err < 0)
 		return err;
 
@@ -527,7 +528,8 @@ static int dn_fib_rtm_delroute(struct sk_buff *skb, struct nlmsghdr *nlh)
 	return tb->delete(tb, r, attrs, nlh, &NETLINK_CB(skb));
 }
 
-static int dn_fib_rtm_newroute(struct sk_buff *skb, struct nlmsghdr *nlh)
+static int dn_fib_rtm_newroute(struct sk_buff *skb, struct nlmsghdr *nlh,
+			       struct netlink_ext_ack *extack)
 {
 	struct net *net = sock_net(skb->sk);
 	struct dn_fib_table *tb;
@@ -542,7 +544,7 @@ static int dn_fib_rtm_newroute(struct sk_buff *skb, struct nlmsghdr *nlh)
 		return -EINVAL;
 
 	err = nlmsg_parse(nlh, sizeof(*r), attrs, RTA_MAX, rtm_dn_policy,
-			  NULL);
+			  extack);
 	if (err < 0)
 		return err;