usrsock: Avoid frequent POLLIN when remote close during accept.

Clear USRSOCK_EVENT_RECVFROM_AVAIL flag when remote closes connection during accept to prevent repeated POLLIN events and EPIPE loop.

Signed-off-by: daichuan <daichuan@xiaomi.com>

net/usrsock/usrsock_accept.c

@@ -297,6 +297,7 @@ int usrsock_accept(FAR struct socket *psock, FAR struct sockaddr *addr,
         {
           ninfo("usockid=%d; remote closed (EOF).\n", conn->usockid);
 
+          conn->flags &= ~USRSOCK_EVENT_RECVFROM_AVAIL;
           ret = -EPIPE;
           goto errout_free_conn;
         }

net/usrsock/usrsock_poll.c

@@ -83,7 +83,13 @@ static uint32_t poll_event(FAR struct net_driver_s *dev,
 
       /* Remote closed. */
 
-      eventset |= (POLLHUP | POLLIN);
+      eventset |= POLLHUP;
+      if (flags & USRSOCK_EVENT_RECVFROM_AVAIL)
+        {
+          ninfo("socket recv avail.\n");
+
+          eventset |= POLLIN;
+        }
     }
   else
     {