[MPTCP][PATCH v2 mptcp-next 3/5] mptcp: send out MP_FAIL when data checksum fail

[Geliang Tang <geliangtang@gmail.com>]

When a bad checksum is detected, send out the MP_FAIL suboption.

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
---
 net/mptcp/subflow.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 0b5d4a3eadcd..13e53a6bd3a1 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -913,6 +913,7 @@ static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *
 	csum = csum_partial(&header, sizeof(header), subflow->map_data_csum);
 	if (unlikely(csum_fold(csum))) {
 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
+		subflow->send_mp_fail = 1;
 		return subflow->mp_join ? MAPPING_INVALID : MAPPING_DUMMY;
 	}
 
@@ -1159,6 +1160,20 @@ static bool subflow_check_data_avail(struct sock *ssk)
 	return false;
 
 fallback:
+	if (subflow->send_mp_fail) {
+		if (mptcp_has_another_subflow_established(ssk)) {
+			mptcp_subflow_reset(ssk);
+			while ((skb = skb_peek(&ssk->sk_receive_queue)))
+				sk_eat_skb(ssk, skb);
+		} else {
+			pr_fallback(msk);
+			__mptcp_do_fallback(msk);
+		}
+
+		WRITE_ONCE(subflow->data_avail, 0);
+		return true;
+	}
+
 	/* RFC 8684 section 3.7. */
 	if (subflow->mp_join || subflow->fully_established) {
 		/* fatal protocol error, close the socket.
-- 
2.31.1