mptcp: Allow DATA_FIN in headers without TCP FIN

RFC 8684-compliant DATA_FIN needs to be sent and ack'd before subflows
are closed with TCP FIN, so write DATA_FIN DSS headers whenever their
transmission has been enabled by the MPTCP connection-level socket.

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 3bc56eb..0b122b2 100644 (file)
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -482,17 +482,10 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
        struct mptcp_sock *msk;
        unsigned int ack_size;
        bool ret = false;
-       u8 tcp_fin;
 
-       if (skb) {
-               mpext = mptcp_get_ext(skb);
-               tcp_fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
-       } else {
-               mpext = NULL;
-               tcp_fin = 0;
-       }
+       mpext = skb ? mptcp_get_ext(skb) : NULL;
 
-       if (!skb || (mpext && mpext->use_map) || tcp_fin) {
+       if (!skb || (mpext && mpext->use_map) || subflow->data_fin_tx_enable) {
                unsigned int map_size;
 
                map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
@@ -502,7 +495,7 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
                if (mpext)
                        opts->ext_copy = *mpext;
 
-               if (skb && tcp_fin && subflow->data_fin_tx_enable)
+               if (skb && subflow->data_fin_tx_enable)
                        mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
                ret = true;
        }