[PATCH net 2/2] mptcp: subflows garbage collection

[Paolo Abeni]

The msk can close MP_JOIN subflows if the initial handshake
fails. Currently such subflows are kept alive in the
conn_list until the msk itself is closed.

Beyond the wasted memory, we could end-up sending the
DATA_FIN and the DATA_FIN ack on such socket, even after a
reset.

Fixes: 43b54c6ee382 ("mptcp: Use full MPTCP-level disconnect state machine")
Reviewed-by: Mat Martineau <mathew.j.martin...@linux.intel.com>
Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
 net/mptcp/protocol.c | 17 +++++++++++++++++
 net/mptcp/protocol.h |  1 +
 net/mptcp/subflow.c  |  6 ++++++
 3 files changed, 24 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 5d747c6a610e..b295eb6e9580 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1383,6 +1383,20 @@ static void pm_work(struct mptcp_sock *msk)
        spin_unlock_bh(&msk->pm.lock);
 }
 
+static void __mptcp_close_subflow(struct mptcp_sock *msk)
+{
+       struct mptcp_subflow_context *subflow, *tmp;
+
+       list_for_each_entry_safe(subflow, tmp, &msk->conn_list, node) {
+               struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+               if (inet_sk_state_load(ssk) != TCP_CLOSE)
+                       continue;
+
+               __mptcp_close_ssk((struct sock *)msk, ssk, subflow, 0);
+       }
+}
+
 static void mptcp_worker(struct work_struct *work)
 {
        struct mptcp_sock *msk = container_of(work, struct mptcp_sock, work);
@@ -1400,6 +1414,9 @@ static void mptcp_worker(struct work_struct *work)
        mptcp_clean_una(sk);
        mptcp_check_data_fin_ack(sk);
        __mptcp_flush_join_list(msk);
+       if (test_and_clear_bit(MPTCP_WORK_CLOSE_SUBFLOW, &msk->flags))
+               __mptcp_close_subflow(msk);
+
        __mptcp_move_skbs(msk);
 
        if (msk->pm.status)
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 0a6e5b3f6ae8..0c4b8cc64dbc 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -90,6 +90,7 @@
 #define MPTCP_WORK_RTX         2
 #define MPTCP_WORK_EOF         3
 #define MPTCP_FALLBACK_DONE    4
+#define MPTCP_WORK_CLOSE_SUBFLOW 5
 
 struct mptcp_options_received {
        u64     sndr_key;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index b1b8028730bf..80f67cb56631 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -272,9 +272,15 @@ static bool subflow_thmac_valid(struct 
mptcp_subflow_context *subflow)
 
 void mptcp_subflow_reset(struct sock *ssk)
 {
+       struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+       struct sock *sk = subflow->conn;
+
        tcp_set_state(ssk, TCP_CLOSE);
        tcp_send_active_reset(ssk, GFP_ATOMIC);
        tcp_done(ssk);
+       if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags) &&
+           schedule_work(&mptcp_sk(sk)->work))
+               sock_hold(sk);
 }
 
 static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
-- 
2.26.2