mptcp: implement and use MPTCP-level retransmission

On timeout event, schedule a work queue to do the retransmission.
Retransmission code closely resembles the sendmsg() implementation and
re-uses mptcp_sendmsg_frag, providing a dummy msghdr - for flags'
sake - and peeking the relevant dfrag from the rtx head.

Signed-off-by: Paolo Abeni <pabeni@redhat.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 b785d4a..8d27770 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -283,6 +283,10 @@ static void mptcp_reset_timer(struct sock *sk)
 void mptcp_data_acked(struct sock *sk)
 {
        mptcp_reset_timer(sk);
+
+       if (!sk_stream_is_writeable(sk) &&
+           schedule_work(&mptcp_sk(sk)->work))
+               sock_hold(sk);
 }
 
 static void mptcp_stop_timer(struct sock *sk)
@@ -900,10 +904,13 @@ static void mptcp_retransmit_handler(struct sock *sk)
 {
        struct mptcp_sock *msk = mptcp_sk(sk);
 
-       if (atomic64_read(&msk->snd_una) == msk->write_seq)
+       if (atomic64_read(&msk->snd_una) == msk->write_seq) {
                mptcp_stop_timer(sk);
-       else
-               mptcp_reset_timer(sk);
+       } else {
+               set_bit(MPTCP_WORK_RTX, &msk->flags);
+               if (schedule_work(&msk->work))
+                       sock_hold(sk);
+       }
 }
 
 static void mptcp_retransmit_timer(struct timer_list *t)
@@ -925,6 +932,37 @@ static void mptcp_retransmit_timer(struct timer_list *t)
        sock_put(sk);
 }
 
+/* Find an idle subflow.  Return NULL if there is unacked data at tcp
+ * level.
+ *
+ * A backup subflow is returned only if that is the only kind available.
+ */
+static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk)
+{
+       struct mptcp_subflow_context *subflow;
+       struct sock *backup = NULL;
+
+       sock_owned_by_me((const struct sock *)msk);
+
+       mptcp_for_each_subflow(msk, subflow) {
+               struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+               /* still data outstanding at TCP level?  Don't retransmit. */
+               if (!tcp_write_queue_empty(ssk))
+                       return NULL;
+
+               if (subflow->backup) {
+                       if (!backup)
+                               backup = ssk;
+                       continue;
+               }
+
+               return ssk;
+       }
+
+       return backup;
+}
+
 /* subflow sockets can be either outgoing (connect) or incoming
  * (accept).
  *
@@ -958,11 +996,62 @@ static unsigned int mptcp_sync_mss(struct sock *sk, u32 pmtu)
 static void mptcp_worker(struct work_struct *work)
 {
        struct mptcp_sock *msk = container_of(work, struct mptcp_sock, work);
-       struct sock *sk = &msk->sk.icsk_inet.sk;
+       struct sock *ssk, *sk = &msk->sk.icsk_inet.sk;
+       int orig_len, orig_offset, ret, mss_now = 0, size_goal = 0;
+       struct mptcp_data_frag *dfrag;
+       u64 orig_write_seq;
+       size_t copied = 0;
+       struct msghdr msg;
+       long timeo = 0;
 
        lock_sock(sk);
+       mptcp_clean_una(sk);
        __mptcp_flush_join_list(msk);
        __mptcp_move_skbs(msk);
+
+       if (!test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
+               goto unlock;
+
+       dfrag = mptcp_rtx_head(sk);
+       if (!dfrag)
+               goto unlock;
+
+       ssk = mptcp_subflow_get_retrans(msk);
+       if (!ssk)
+               goto reset_unlock;
+
+       lock_sock(ssk);
+
+       msg.msg_flags = MSG_DONTWAIT;
+       orig_len = dfrag->data_len;
+       orig_offset = dfrag->offset;
+       orig_write_seq = dfrag->data_seq;
+       while (dfrag->data_len > 0) {
+               ret = mptcp_sendmsg_frag(sk, ssk, &msg, dfrag, &timeo, &mss_now,
+                                        &size_goal);
+               if (ret < 0)
+                       break;
+
+               copied += ret;
+               dfrag->data_len -= ret;
+               dfrag->offset += ret;
+       }
+       if (copied)
+               tcp_push(ssk, msg.msg_flags, mss_now, tcp_sk(ssk)->nonagle,
+                        size_goal);
+
+       dfrag->data_seq = orig_write_seq;
+       dfrag->offset = orig_offset;
+       dfrag->data_len = orig_len;
+
+       mptcp_set_timeout(sk, ssk);
+       release_sock(ssk);
+
+reset_unlock:
+       if (!mptcp_timer_pending(sk))
+               mptcp_reset_timer(sk);
+
+unlock:
        release_sock(sk);
        sock_put(sk);
 }
@@ -1124,6 +1213,7 @@ static int mptcp_disconnect(struct sock *sk, int flags)
        lock_sock(sk);
        __mptcp_clear_xmit(sk);
        release_sock(sk);
+       mptcp_cancel_work(sk);
        return tcp_disconnect(sk, flags);
 }
 

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index f855c95..e9d4a85 100644 (file)
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -88,6 +88,7 @@
 /* MPTCP socket flags */
 #define MPTCP_DATA_READY       0
 #define MPTCP_SEND_SPACE       1
+#define MPTCP_WORK_RTX         2
 
 static inline __be32 mptcp_option(u8 subopt, u8 len, u8 nib, u8 field)
 {