[PATCH net-next v2 2/3] netfilter: nfnetlink: Handle ACK flags for batch messages

[Donald Hunter <donald.hunter@gmail.com>]

The NLM_F_ACK flag is not processed for nfnetlink batch messages. This
is a problem for ynl which wants to receive an ack for every message it
sends. Add processing for ACK and provide responses when requested.

I have checked that iproute2, pyroute2 and systemd are unaffected by
this change since none of them use NLM_F_ACK for batch begin/end. I also
ran a search on github and did not spot any usage that would break.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
---
 net/netfilter/nfnetlink.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index c9fbe0f707b5..37762941c288 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -427,6 +427,9 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	nfnl_unlock(subsys_id);
 
+	if (nlh->nlmsg_flags & NLM_F_ACK)
+		nfnl_err_add(&err_list, nlh, 0, &extack);
+
 	while (skb->len >= nlmsg_total_size(0)) {
 		int msglen, type;
 
@@ -463,6 +466,8 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 			goto done;
 		} else if (type == NFNL_MSG_BATCH_END) {
 			status |= NFNL_BATCH_DONE;
+			if (nlh->nlmsg_flags & NLM_F_ACK)
+				nfnl_err_add(&err_list, nlh, 0, &extack);
 			goto done;
 		} else if (type < NLMSG_MIN_TYPE) {
 			err = -EINVAL;
-- 
2.43.0