[PATCH 5.15.y 3/6] mptcp: introduce MAPPING_BAD_CSUM

["Matthieu Baerts (NGI0)" <matttbe@kernel.org>]

From: Paolo Abeni <pabeni@redhat.com>

commit 31bf11de146c3f8892093ff39f8f9b3069d6a852 upstream.

This allow moving a couple of conditional out of the fast path,
making the code more easy to follow and will simplify the next
patch.

Fixes: ae66fb2ba6c3 ("mptcp: Do TCP fallback on early DSS checksum failure")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Conflicts in subflow.c, because commit 0348c690ed37 ("mptcp: add the
  fallback check") is not in this version. This commit is linked to a
  new feature, changing the context around. The new condition can still
  be added at the same place. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/subflow.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 6a7c48397e3d..6bc36132d490 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -848,7 +848,8 @@ enum mapping_status {
 	MAPPING_INVALID,
 	MAPPING_EMPTY,
 	MAPPING_DATA_FIN,
-	MAPPING_DUMMY
+	MAPPING_DUMMY,
+	MAPPING_BAD_CSUM
 };
 
 static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
@@ -963,9 +964,7 @@ static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *
 				 subflow->map_data_csum);
 	if (unlikely(csum)) {
 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
-		if (subflow->mp_join || subflow->valid_csum_seen)
-			subflow->send_mp_fail = 1;
-		return subflow->mp_join ? MAPPING_INVALID : MAPPING_DUMMY;
+		return MAPPING_BAD_CSUM;
 	}
 
 	subflow->valid_csum_seen = 1;
@@ -1188,10 +1187,8 @@ static bool subflow_check_data_avail(struct sock *ssk)
 
 		status = get_mapping_status(ssk, msk);
 		trace_subflow_check_data_avail(status, skb_peek(&ssk->sk_receive_queue));
-		if (unlikely(status == MAPPING_INVALID))
-			goto fallback;
-
-		if (unlikely(status == MAPPING_DUMMY))
+		if (unlikely(status == MAPPING_INVALID || status == MAPPING_DUMMY ||
+			     status == MAPPING_BAD_CSUM))
 			goto fallback;
 
 		if (status != MAPPING_OK)
@@ -1232,7 +1229,10 @@ static bool subflow_check_data_avail(struct sock *ssk)
 
 fallback:
 	/* RFC 8684 section 3.7. */
-	if (subflow->send_mp_fail) {
+	if (status == MAPPING_BAD_CSUM &&
+	    (subflow->mp_join || subflow->valid_csum_seen)) {
+		subflow->send_mp_fail = 1;
+
 		if (mptcp_has_another_subflow(ssk) ||
 		    !READ_ONCE(msk->allow_infinite_fallback)) {
 			while ((skb = skb_peek(&ssk->sk_receive_queue)))
-- 
2.50.0