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_dev.c b/net/decnet/dn_dev.c
index e65f1be..9017a9a 100644
--- a/net/decnet/dn_dev.c
+++ b/net/decnet/dn_dev.c
@@ -565,7 +565,8 @@ static const struct nla_policy dn_ifa_policy[IFA_MAX+1] = {
 	[IFA_FLAGS]		= { .type = NLA_U32 },
 };
 
-static int dn_nl_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh)
+static int dn_nl_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh,
+			 struct netlink_ext_ack *extack)
 {
 	struct net *net = sock_net(skb->sk);
 	struct nlattr *tb[IFA_MAX+1];
@@ -581,7 +582,8 @@ static int dn_nl_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh)
 	if (!net_eq(net, &init_net))
 		goto errout;
 
-	err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, dn_ifa_policy, NULL);
+	err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, dn_ifa_policy,
+			  extack);
 	if (err < 0)
 		goto errout;
 
@@ -609,7 +611,8 @@ static int dn_nl_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh)
 	return err;
 }
 
-static int dn_nl_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh)
+static int dn_nl_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
+			 struct netlink_ext_ack *extack)
 {
 	struct net *net = sock_net(skb->sk);
 	struct nlattr *tb[IFA_MAX+1];
@@ -625,7 +628,8 @@ static int dn_nl_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh)
 	if (!net_eq(net, &init_net))
 		return -EINVAL;
 
-	err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, dn_ifa_policy, NULL);
+	err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, dn_ifa_policy,
+			  extack);
 	if (err < 0)
 		return err;