Networking: Fix a race condition. The accept() operation is performed with the network locked. However, the network is unlocked BEFORE the connected state is set. Therefore, a context switch may occur and the socket may no longer be connected when it is marked so. Noted by Pascal Speck.

net/ieee802154/ieee802154_sockif.c

@@ -313,6 +313,9 @@ static int ieee802154_connect(FAR struct socket *psock,
  *   Returns 0 (OK) on success.  On failure, it returns a negated errno
  *   value.  See accept() for a desrciption of the approriate error value.
  *
+ * Assumptions:
+ *   The network is locked.
+ *
  ****************************************************************************/
 
 static int ieee802154_accept(FAR struct socket *psock,

net/inet/inet_sockif.c

@@ -741,6 +741,9 @@ static int inet_connect(FAR struct socket *psock,
  *   Returns 0 (OK) on success.  On failure, it returns a negated errno
  *   value.  See accept() for a desrciption of the approriate error value.
  *
+ * Assumptions:
+ *   The network is locked.
+ *
  ****************************************************************************/
 
 static int inet_accept(FAR struct socket *psock, FAR struct sockaddr *addr,
@@ -810,9 +813,8 @@ static int inet_accept(FAR struct socket *psock, FAR struct sockaddr *addr,
 
 #ifdef CONFIG_NET_TCP
 #ifdef NET_TCP_HAVE_STACK
-  /* Perform the local accept operation (with the network locked) */
+  /* Perform the local accept operation (the network locked must be locked) */
 
-  net_lock();
   ret = psock_tcp_accept(psock, addr, addrlen, &newsock->s_conn);
   if (ret < 0)
     {
@@ -835,7 +837,6 @@ static int inet_accept(FAR struct socket *psock, FAR struct sockaddr *addr,
       goto errout_after_accept;
     }
 
-  net_unlock();
   return OK;
 
 errout_after_accept:

net/local/local_sockif.c

@@ -567,6 +567,9 @@ static int local_connect(FAR struct socket *psock,
  *   Returns 0 (OK) on success.  On failure, it returns a negated errno
  *   value.  See accept() for a desrciption of the approriate error value.
  *
+ * Assumptions:
+ *   The network is locked.
+ *
  ****************************************************************************/
 
 #ifndef CONFIG_NET_LOCAL_STREAM

net/pkt/pkt_sockif.c

@@ -308,6 +308,9 @@ static int pkt_connect(FAR struct socket *psock,
  *   Returns 0 (OK) on success.  On failure, it returns a negated errno
  *   value.  See accept() for a desrciption of the approriate error value.
  *
+ * Assumptions:
+ *   The network is locked.
+ *
  ****************************************************************************/
 
 static int pkt_accept(FAR struct socket *psock, FAR struct sockaddr *addr,

net/socket/accept.c

@@ -153,6 +153,8 @@ int psock_accept(FAR struct socket *psock, FAR struct sockaddr *addr,
   /* Let the address family's accept() method handle the operation */
 
   DEBUGASSERT(psock->s_sockif != NULL && psock->s_sockif->si_accept != NULL);
+
+  net_lock();
   ret = psock->s_sockif->si_accept(psock, addr, addrlen, newsock);
   if (ret < 0)
     {
@@ -165,6 +167,7 @@ int psock_accept(FAR struct socket *psock, FAR struct sockaddr *addr,
 
   newsock->s_flags |= _SF_CONNECTED;
   newsock->s_flags &= ~_SF_CLOSED;
+  net_unlock();
 
   leave_cancellation_point();
   return OK;

net/tcp/tcp.h

@@ -1074,7 +1074,7 @@ uint16_t tcp_datahandler(FAR struct tcp_conn_s *conn, FAR uint8_t *buffer,
  *   the listen arguments.
  *
  * Assumptions:
- *   Called from normal user code. Interrupts may be disabled.
+ *   Called from network socket logic.  The network may or may not be locked.
  *
  ****************************************************************************/
 
@@ -1095,7 +1095,7 @@ int tcp_backlogcreate(FAR struct tcp_conn_s *conn, int nblg);
  *   is freed that has pending connections.
  *
  * Assumptions:
- *   Called from network stack logic with the network stack locked
+ *   Called from network socket logic with the network stack locked
  *
  ****************************************************************************/
 

net/tcp/tcp_backlog.c

@@ -64,7 +64,7 @@
  *   the listen arguments.
  *
  * Assumptions:
- *   Called from normal user code. Interrupts may be disabled.
+ *   Called from normal task logic.  The network may or may not be locked.
  *
  ****************************************************************************/
 
@@ -129,7 +129,7 @@ int tcp_backlogcreate(FAR struct tcp_conn_s *conn, int nblg)
 
   /* Now install the backlog tear-off in the connection.  NOTE that bls may
    * actually be NULL if nblg is <= 0;  In that case, we are disabling backlog
-   * support.  Since interrupts are disabled, destroying the old backlog and
+   * support.  Since the network is locked, destroying the old backlog and
    * replace it with the new is an atomic operation
    */
 
@@ -149,8 +149,7 @@ int tcp_backlogcreate(FAR struct tcp_conn_s *conn, int nblg)
  *   is freed that has pending connections.
  *
  * Assumptions:
- *   The caller has disabled interrupts so that there can be no conflict
- *   with ongoing, interrupt driven activity
+ *   Called from network socket logic with the network locked
  *
  ****************************************************************************/
 
@@ -211,7 +210,7 @@ int tcp_backlogdestroy(FAR struct tcp_conn_s *conn)
  *  function adds the new connection to the backlog.
  *
  * Assumptions:
- *   Called from the interrupt level with interrupts disabled
+ *   Called from network socket logic with the network locked
  *
  ****************************************************************************/
 
@@ -264,7 +263,7 @@ int tcp_backlogadd(FAR struct tcp_conn_s *conn, FAR struct tcp_conn_s *blconn)
  *  call this API to see if there are pending connections in the backlog.
  *
  * Assumptions:
- *   Called from normal user code, but with interrupts disabled,
+ *   Called from network socket logic with the network locked
  *
  ****************************************************************************/
 
@@ -283,7 +282,7 @@ bool tcp_backlogavailable(FAR struct tcp_conn_s *conn)
  *  call this API to see if there are pending connections in the backlog.
  *
  * Assumptions:
- *   Called from normal user code, but with interrupts disabled,
+ *   Called from network socket logic with the network locked
  *
  ****************************************************************************/
 
@@ -333,7 +332,7 @@ FAR struct tcp_conn_s *tcp_backlogremove(FAR struct tcp_conn_s *conn)
  *  to remove the defunct connection from the list.
  *
  * Assumptions:
- *   Called from the interrupt level with interrupts disabled
+ *   Called from network socket logic with the network locked
  *
  ****************************************************************************/
 

net/usrsock/usrsock_sockif.c

@@ -297,6 +297,9 @@ int usrsock_sockif_listen(FAR struct socket *psock, int backlog)
  *   Returns 0 (OK) on success.  On failure, it returns a negated errno
  *   value.  See accept() for a desrciption of the approriate error value.
  *
+ * Assumptions:
+ *   The network is locked.
+ *
  ****************************************************************************/
 
 static int usrsock_sockif_accept(FAR struct socket *psock,