From: Geliang Tang <geliang.tang@suse.com>

MP_FAIL can be sent with RST or DSS, and FASTCLOSE can be sent with
RST too. So we should use a similar xmit logic for FASTCLOSE and
MP_FAIL in both mptcp_write_options() and mptcp_established_options*().

Cc: Paolo Abeni <pabeni@redhat.com>
Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---

Notes:
    v8:
     - 'ptr += 2;' was missing for FastClose (Geliang)
     - moving the MP_FAIL option is now in a dedicated patch
       ("mptcp: reduce branching when writing MP_FAIL option")

 net/mptcp/options.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index c6726e8389ec..aa3ed37bc59a 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -829,8 +829,12 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 
 	if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
 		if (mptcp_established_options_fastclose(sk, &opt_size, remaining, opts) ||
-		    mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts) ||
-		    mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
+		    mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
+			*size += opt_size;
+			remaining -= opt_size;
+		}
+		/* MP_RST can be used with MP_FASTCLOSE and MP_FAIL if there is room */
+		if (mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts)) {
 			*size += opt_size;
 			remaining -= opt_size;
 		}
@@ -1460,19 +1464,23 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
 				ptr += 1;
 			}
 		}
-	} else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
-		/* RST is mutually exclusive with everything else */
-		*ptr++ = mptcp_option(MPTCPOPT_RST,
-				      TCPOLEN_MPTCP_RST,
-				      opts->reset_transient,
-				      opts->reset_reason);
-		return;
 	} else if (unlikely(OPTION_MPTCP_FASTCLOSE & opts->suboptions)) {
-		/* FASTCLOSE is mutually exclusive with everything else */
+		/* FASTCLOSE is mutually exclusive with others except RST */
 		*ptr++ = mptcp_option(MPTCPOPT_MP_FASTCLOSE,
 				      TCPOLEN_MPTCP_FASTCLOSE,
 				      0, 0);
 		put_unaligned_be64(opts->rcvr_key, ptr);
+		ptr += 2;
+
+		if (OPTION_MPTCP_RST & opts->suboptions)
+			goto mp_rst;
+		return;
+	} else if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
+mp_rst:
+		*ptr++ = mptcp_option(MPTCPOPT_RST,
+				      TCPOLEN_MPTCP_RST,
+				      opts->reset_transient,
+				      opts->reset_reason);
 		return;
 	}
 
-- 
2.33.1