mptcp: recvmsg() can drain data from multiple subflows

With the previous patch in place, the msk can detect which subflow
has the current map with a simple walk, let's update the main
loop to always select the 'current' subflow. The exit conditions now
closely mirror tcp_recvmsg() to get expected timeout and signal
behavior.

Co-developed-by: Peter Krystad <peter.krystad@linux.intel.com>
Signed-off-by: Peter Krystad <peter.krystad@linux.intel.com>
Co-developed-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Co-developed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Co-developed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 408efbe3475346a50ca88f2a2422325365a5423c..ad9c73cc20e18b0b714effd735e38dd9788129d7 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -9,6 +9,8 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/netdevice.h>
+#include <linux/sched/signal.h>
+#include <linux/atomic.h>
 #include <net/sock.h>
 #include <net/inet_common.h>
 #include <net/inet_hashtables.h>
@@ -105,6 +107,21 @@ static bool mptcp_ext_cache_refill(struct mptcp_sock *msk)
        return !!msk->cached_ext;
 }
 
+static struct sock *mptcp_subflow_recv_lookup(const struct mptcp_sock *msk)
+{
+       struct mptcp_subflow_context *subflow;
+       struct sock *sk = (struct sock *)msk;
+
+       sock_owned_by_me(sk);
+
+       mptcp_for_each_subflow(msk, subflow) {
+               if (subflow->data_avail)
+                       return mptcp_subflow_tcp_sock(subflow);
+       }
+
+       return NULL;
+}
+
 static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
                              struct msghdr *msg, long *timeo)
 {
@@ -269,13 +286,37 @@ int mptcp_read_actor(read_descriptor_t *desc, struct sk_buff *skb,
        return copy_len;
 }
 
+static void mptcp_wait_data(struct sock *sk, long *timeo)
+{
+       DEFINE_WAIT_FUNC(wait, woken_wake_function);
+       struct mptcp_sock *msk = mptcp_sk(sk);
+
+       add_wait_queue(sk_sleep(sk), &wait);
+       sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
+
+       sk_wait_event(sk, timeo,
+                     test_and_clear_bit(MPTCP_DATA_READY, &msk->flags), &wait);
+
+       sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
+       remove_wait_queue(sk_sleep(sk), &wait);
+}
+
 static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
                         int nonblock, int flags, int *addr_len)
 {
        struct mptcp_sock *msk = mptcp_sk(sk);
+       struct mptcp_subflow_context *subflow;
+       bool more_data_avail = false;
+       struct mptcp_read_arg arg;
+       read_descriptor_t desc;
+       bool wait_data = false;
        struct socket *ssock;
+       struct tcp_sock *tp;
+       bool done = false;
        struct sock *ssk;
        int copied = 0;
+       int target;
+       long timeo;
 
        if (msg->msg_flags & ~(MSG_WAITALL | MSG_DONTWAIT))
                return -EOPNOTSUPP;
@@ -290,16 +331,124 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
                return copied;
        }
 
-       ssk = mptcp_subflow_get(msk);
-       if (!ssk) {
-               release_sock(sk);
-               return -ENOTCONN;
+       arg.msg = msg;
+       desc.arg.data = &arg;
+       desc.error = 0;
+
+       timeo = sock_rcvtimeo(sk, nonblock);
+
+       len = min_t(size_t, len, INT_MAX);
+       target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
+
+       while (!done) {
+               u32 map_remaining;
+               int bytes_read;
+
+               ssk = mptcp_subflow_recv_lookup(msk);
+               pr_debug("msk=%p ssk=%p", msk, ssk);
+               if (!ssk)
+                       goto wait_for_data;
+
+               subflow = mptcp_subflow_ctx(ssk);
+               tp = tcp_sk(ssk);
+
+               lock_sock(ssk);
+               do {
+                       /* try to read as much data as available */
+                       map_remaining = subflow->map_data_len -
+                                       mptcp_subflow_get_map_offset(subflow);
+                       desc.count = min_t(size_t, len - copied, map_remaining);
+                       pr_debug("reading %zu bytes, copied %d", desc.count,
+                                copied);
+                       bytes_read = tcp_read_sock(ssk, &desc,
+                                                  mptcp_read_actor);
+                       if (bytes_read < 0) {
+                               if (!copied)
+                                       copied = bytes_read;
+                               done = true;
+                               goto next;
+                       }
+
+                       pr_debug("msk ack_seq=%llx -> %llx", msk->ack_seq,
+                                msk->ack_seq + bytes_read);
+                       msk->ack_seq += bytes_read;
+                       copied += bytes_read;
+                       if (copied >= len) {
+                               done = true;
+                               goto next;
+                       }
+                       if (tp->urg_data && tp->urg_seq == tp->copied_seq) {
+                               pr_err("Urgent data present, cannot proceed");
+                               done = true;
+                               goto next;
+                       }
+next:
+                       more_data_avail = mptcp_subflow_data_available(ssk);
+               } while (more_data_avail && !done);
+               release_sock(ssk);
+               continue;
+
+wait_for_data:
+               more_data_avail = false;
+
+               /* only the master socket status is relevant here. The exit
+                * conditions mirror closely tcp_recvmsg()
+                */
+               if (copied >= target)
+                       break;
+
+               if (copied) {
+                       if (sk->sk_err ||
+                           sk->sk_state == TCP_CLOSE ||
+                           (sk->sk_shutdown & RCV_SHUTDOWN) ||
+                           !timeo ||
+                           signal_pending(current))
+                               break;
+               } else {
+                       if (sk->sk_err) {
+                               copied = sock_error(sk);
+                               break;
+                       }
+
+                       if (sk->sk_shutdown & RCV_SHUTDOWN)
+                               break;
+
+                       if (sk->sk_state == TCP_CLOSE) {
+                               copied = -ENOTCONN;
+                               break;
+                       }
+
+                       if (!timeo) {
+                               copied = -EAGAIN;
+                               break;
+                       }
+
+                       if (signal_pending(current)) {
+                               copied = sock_intr_errno(timeo);
+                               break;
+                       }
+               }
+
+               pr_debug("block timeout %ld", timeo);
+               wait_data = true;
+               mptcp_wait_data(sk, &timeo);
        }
 
-       copied = sock_recvmsg(ssk->sk_socket, msg, flags);
+       if (more_data_avail) {
+               if (!test_bit(MPTCP_DATA_READY, &msk->flags))
+                       set_bit(MPTCP_DATA_READY, &msk->flags);
+       } else if (!wait_data) {
+               clear_bit(MPTCP_DATA_READY, &msk->flags);
 
-       release_sock(sk);
+               /* .. race-breaker: ssk might get new data after last
+                * data_available() returns false.
+                */
+               ssk = mptcp_subflow_recv_lookup(msk);
+               if (unlikely(ssk))
+                       set_bit(MPTCP_DATA_READY, &msk->flags);
+       }
 
+       release_sock(sk);
        return copied;
 }
 
@@ -460,10 +609,6 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
                msk->write_seq = subflow->idsn + 1;
                ack_seq++;
                msk->ack_seq = ack_seq;
-               subflow->map_seq = ack_seq;
-               subflow->map_subflow_seq = 1;
-               subflow->rel_write_seq = 1;
-               subflow->tcp_sock = ssk;
                newsk = new_mptcp_sock;
                mptcp_copy_inaddrs(newsk, ssk);
                list_add(&subflow->node, &msk->conn_list);
@@ -475,6 +620,19 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
                bh_unlock_sock(new_mptcp_sock);
                local_bh_enable();
                release_sock(sk);
+
+               /* the subflow can already receive packet, avoid racing with
+                * the receive path and process the pending ones
+                */
+               lock_sock(ssk);
+               subflow->map_seq = ack_seq;
+               subflow->map_subflow_seq = 1;
+               subflow->rel_write_seq = 1;
+               subflow->tcp_sock = ssk;
+               subflow->conn = new_mptcp_sock;
+               if (unlikely(!skb_queue_empty(&ssk->sk_receive_queue)))
+                       mptcp_subflow_data_available(ssk);
+               release_sock(ssk);
        }
 
        return newsk;