netlink: extended ACK reporting

Add the base infrastructure and UAPI for netlink extended ACK
reporting. All "manual" calls to netlink_ack() pass NULL for now and
thus don't get extended ACK reporting.

Big thanks goes to Pablo Neira Ayuso for not only bringing up the
whole topic at netconf (again) but also coming up with the nlattr
passing trick and various other ideas.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index c138b6b75e59..3cc4a627a537 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -4046,7 +4046,8 @@ out:
 
 /* Process one rtnetlink message. */
 
-static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
+static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
+                             struct netlink_ext_ack *extack)
 {
         struct net *net = sock_net(skb->sk);
         rtnl_doit_func doit;