mptcp: track and update contiguous data status

This patch adds a new member allow_infinite_fallback in mptcp_sock,
which is initialized to 'true' when the connection begins and is set
to 'false' on any retransmit or successful MP_JOIN. Only do infinite
mapping fallback if there is a single subflow AND there have been no
retransmissions AND there have never been any MP_JOINs.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
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/protocol.c b/net/mptcp/protocol.c
index 0492aa9..6d65391 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2465,6 +2465,7 @@ static void __mptcp_retrans(struct sock *sk)
                dfrag->already_sent = max(dfrag->already_sent, info.sent);
                tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
                         info.size_goal);
+               WRITE_ONCE(msk->allow_infinite_fallback, false);
        }
 
        release_sock(ssk);
@@ -2539,6 +2540,7 @@ static int __mptcp_init_sock(struct sock *sk)
        msk->first = NULL;
        inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss;
        WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));
+       WRITE_ONCE(msk->allow_infinite_fallback, true);
        msk->recovery = false;
 
        mptcp_pm_data_init(msk);
@@ -3275,6 +3277,7 @@ err_prohibited:
        }
 
        subflow->map_seq = READ_ONCE(msk->ack_seq);
+       WRITE_ONCE(msk->allow_infinite_fallback, false);
 
 out:
        mptcp_event(MPTCP_EVENT_SUB_ESTABLISHED, msk, ssk, GFP_ATOMIC);

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index aca1fb5..88d2923 100644 (file)
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -263,6 +263,7 @@ struct mptcp_sock {
        bool            rcv_fastclose;
        bool            use_64bit_ack; /* Set when we received a 64-bit DSN */
        bool            csum_enabled;
+       bool            allow_infinite_fallback;
        u8              recvmsg_inq:1,
                        cork:1,
                        nodelay:1;

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 7f26a5b..31dcb55 100644 (file)
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1206,7 +1206,8 @@ fallback:
        if (!__mptcp_check_fallback(msk)) {
                /* RFC 8684 section 3.7. */
                if (subflow->send_mp_fail) {
-                       if (mptcp_has_another_subflow(ssk)) {
+                       if (mptcp_has_another_subflow(ssk) ||
+                           !READ_ONCE(msk->allow_infinite_fallback)) {
                                ssk->sk_err = EBADMSG;
                                tcp_set_state(ssk, TCP_CLOSE);
                                subflow->reset_transient = 0;
@@ -1486,6 +1487,7 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
        /* discard the subflow socket */
        mptcp_sock_graft(ssk, sk->sk_socket);
        iput(SOCK_INODE(sf));
+       WRITE_ONCE(msk->allow_infinite_fallback, false);
        return err;
 
 failed_unlink: