VCL-LDPRELOAD: add sendfile/sendfile64 implementation.

Change-Id: If0c399269238912456d670432d7e953c9d91b9fb
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>

10 files changed, 301 insertions, 53 deletions

diff --git a/src/vcl/sock_test_server.c b/src/vcl/sock_test_server.c
index 728a6a7a14e..ed36c7a6acc 100644
--- a/src/vcl/sock_test_server.c
+++ b/src/vcl/sock_test_server.c
@@ -300,7 +300,7 @@ new_client (void)
     }
 
 #ifdef VCL_TEST
-  client_fd = vppcom_session_accept (ssm->listen_fd, &conn->endpt,
+  client_fd = vppcom_session_accept (ssm->listen_fd, &conn->endpt, 0,
 				     -1.0 /* wait forever */ );
   if (client_fd < 0)
     errno = -client_fd;
diff --git a/src/vcl/vcom.c b/src/vcl/vcom.c
index 624f0247e47..26948d51840 100644
--- a/src/vcl/vcom.c
+++ b/src/vcl/vcom.c
@@ -98,7 +98,7 @@ static int is_vcom_init;
  * RETURN: 0 on success -1 on failure
  * */
 static inline int
-vcom_init ()
+vcom_init (void)
 {
   pid_t pid = getpid ();
 
@@ -2068,6 +2068,46 @@ send (int __fd, const void *__buf, size_t __n, int __flags)
   return libc_send (__fd, __buf, __n, __flags);
 }
 
+ssize_t
+sendfile (int __out_fd, int __in_fd, off_t * __offset, size_t __len)
+{
+  ssize_t size;
+
+  if (VCOM_DEBUG > 2)
+    clib_warning ("[%d] __out_fd %d, __in_fd %d, __offset %p, __len %ld",
+		  getpid (), __out_fd, __in_fd, __offset, __len);
+
+  if (is_vcom_socket_fd (__out_fd))
+    {
+      /* TBD: refactor this check to be part of is_vcom_socket_fd() */
+      if (vcom_init () != 0)
+	return -1;
+
+      size = vcom_socket_sendfile (__out_fd, __in_fd, __offset, __len);
+      if (VCOM_DEBUG > 2)
+	clib_warning ("[%d] vcom_socket_sendfile (out_fd %d, in_fd %d, "
+		      "offset %p (%ld), len %lu) returned %ld",
+		      getpid (), __out_fd, __in_fd, __offset,
+		      __offset ? *__offset : -1, __len, size);
+      if (size < 0)
+	{
+	  errno = -size;
+	  return -1;
+	}
+      return size;
+    }
+  if (VCOM_DEBUG > 2)
+    clib_warning ("[%d] calling libc_sendfile!", getpid ());
+  return libc_sendfile (__out_fd, __in_fd, __offset, __len);
+}
+
+ssize_t
+sendfile64 (int __out_fd, int __in_fd, off_t * __offset, size_t __len)
+{
+  return sendfile (__out_fd, __in_fd, __offset, __len);
+}
+
+
 /*
  * Read N bytes into BUF from socket FD.
  * Returns the number read or -1 for errors.
@@ -2827,7 +2867,7 @@ epoll_wait (int __epfd, struct epoll_event *__events,
 
   rv =
     vcom_socket_epoll_pwait (__epfd, __events, __maxevents, __timeout, NULL);
-  if (VCOM_DEBUG > 1)
+  if (VCOM_DEBUG > 2)
     fprintf (stderr,
 	     "[%d] epoll_wait: "
 	     "'%04d'='%04d', '%p', "
diff --git a/src/vcl/vcom.h b/src/vcl/vcom.h
index 9a78b718f8e..e945c8a5d08 100644
--- a/src/vcl/vcom.h
+++ b/src/vcl/vcom.h
@@ -23,6 +23,8 @@
 #define VCOM_DEBUG 0
 #endif
 
+#include <vppinfra/error.h>
+#include <vppinfra/types.h>
 #include <vcl/vcom_glibc_socket.h>
 
 #define MAX_VCOM_APP_NAME  256
@@ -107,7 +109,7 @@ vcom_getpeername (int __fd, __SOCKADDR_ARG __addr,
 		  socklen_t * __restrict __len);
 
 extern ssize_t
-vcom_send (int __fd, const void *__buf, size_t __n, int __flags);
+vcom_sendfile (int __out_fd, int __in_fd, off_t * __offset, int __len);
 
 extern ssize_t vcom_recv (int __fd, void *__buf, size_t __n, int __flags);
 
diff --git a/src/vcl/vcom_glibc_socket.h b/src/vcl/vcom_glibc_socket.h
index 969029f3e63..bf18473de85 100644
--- a/src/vcl/vcom_glibc_socket.h
+++ b/src/vcl/vcom_glibc_socket.h
@@ -153,6 +153,9 @@ getpeername (int __fd, __SOCKADDR_ARG __addr, socklen_t * __restrict __len);
    __THROW.  */
 extern ssize_t send (int __fd, const void *__buf, size_t __n, int __flags);
 
+extern ssize_t sendfile (int __out_fd, int __in_fd, off_t * __offset,
+			 size_t __len);
+
 /* Read N bytes into BUF from socket FD.
    Returns the number read or -1 for errors.
 
diff --git a/src/vcl/vcom_socket.c b/src/vcl/vcom_socket.c
index a84359e8417..6450eddc895 100644
--- a/src/vcl/vcom_socket.c
+++ b/src/vcl/vcom_socket.c
@@ -70,6 +70,7 @@ typedef struct vcom_socket_main_t_
   /* Hash table - key:fd, value:vec of epitemidx */
   uword *epitemidxs_by_fd;
 
+  u8 *io_buffer;
 } vcom_socket_main_t;
 
 vcom_socket_main_t vcom_socket_main;
@@ -1493,6 +1494,156 @@ vcom_socket_send (int __fd, const void *__buf, size_t __n, int __flags)
   return vcom_socket_sendto (__fd, __buf, __n, __flags, NULL, 0);
 }
 
+/* NOTE: this function is not thread safe or 32-bit friendly */
+ssize_t
+vcom_socket_sendfile (int __out_fd, int __in_fd, off_t * __offset,
+		      size_t __len)
+{
+  vcom_socket_main_t *vsm = &vcom_socket_main;
+  uword *p;
+  vcom_socket_t *vsock;
+  size_t n_bytes_left = __len;
+  u32 out_sockidx, out_sid = ~0;
+  size_t bytes_to_read;
+  int nbytes;
+  int rv, errno_val;
+  ssize_t results = 0;
+  u8 eagain = 0;
+
+  if (VCOM_DEBUG > 2)
+    clib_warning ("[%d] __out_fd %d, __in_fd %d, __offset %p, __len %lu",
+		  getpid (), __out_fd, __in_fd, __offset, __len);
+
+  p = hash_get (vsm->sockidx_by_fd, __out_fd);
+  if (!p)
+    {
+      clib_warning ("[%d] ERROR: invalid __out_fd (%d), fd lookup failed!",
+		    getpid (), __len);
+      return -EBADF;
+    }
+  out_sockidx = p[0];
+  vsock = pool_elt_at_index (vsm->vsockets, out_sockidx);
+  if (!vsock)
+    {
+      clib_warning ("[%d] ERROR: invalid __out_fd (%d) / out_sockidx %u, "
+		    "missing vsock pool element!",
+		    getpid (), __len, out_sockidx);
+      return -ENOTSOCK;
+    }
+  out_sid = vsock->sid;
+  if (vsock->type != SOCKET_TYPE_VPPCOM_BOUND)
+    {
+      clib_warning ("[%d] ERROR: __out_fd (%d), socket (sid %u) "
+		    "is not VCL bound!", getpid (), __out_fd, out_sid);
+      return -EINVAL;
+    }
+
+  if (__offset)
+    {
+      off_t offset = lseek (__in_fd, *__offset, SEEK_SET);
+      if (offset == -1)
+	{
+	  errno_val = errno;
+	  perror ("lseek()");
+	  clib_warning ("[%d] ERROR: lseek SEEK_SET failed: "
+			"in_fd %d, offset %p (%ld), rv %ld, errno %d",
+			getpid (), __in_fd, __offset, *__offset, offset,
+			errno_val);
+	  return -errno_val;
+	}
+
+      ASSERT (offset == *__offset);
+    }
+
+  do
+    {
+      bytes_to_read = vppcom_session_attr (out_sid,
+					   VPPCOM_ATTR_GET_NWRITE, 0, 0);
+      if (VCOM_DEBUG > 2)
+	clib_warning ("[%d] results %ld, n_bytes_left %lu, "
+		      "bytes_to_read %lu", getpid (), results,
+		      n_bytes_left, bytes_to_read);
+      if (bytes_to_read == 0)
+	{
+	  u32 flags, flags_len = sizeof (flags);
+	  rv = vppcom_session_attr (out_sid, VPPCOM_ATTR_GET_FLAGS, &flags,
+				    &flags_len);
+	  ASSERT (rv == VPPCOM_OK);
+
+	  if (flags & O_NONBLOCK)
+	    {
+	      if (!results)
+		{
+		  if (VCOM_DEBUG > 2)
+		    clib_warning ("[%d] EAGAIN", getpid ());
+		  eagain = 1;
+		}
+	      goto update_offset;
+	    }
+	  else
+	    continue;
+	}
+      bytes_to_read = clib_min (n_bytes_left, bytes_to_read);
+      vec_validate (vsm->io_buffer, bytes_to_read);
+      nbytes = libc_read (__in_fd, vsm->io_buffer, bytes_to_read);
+      if (nbytes < 0)
+	{
+	  errno_val = errno;
+	  perror ("read()");
+	  clib_warning ("[%d] ERROR: libc_read (__in_fd (%d), "
+			"io_buffer %p, bytes_to_read %lu) returned "
+			"errno %d",
+			getpid (), __in_fd, vsm->io_buffer,
+			bytes_to_read, errno_val);
+	  if (results == 0)
+	    {
+	      vec_reset_length (vsm->io_buffer);
+	      return -errno_val;
+	    }
+	  goto update_offset;
+	}
+      rv = vppcom_session_write (out_sid, vsm->io_buffer, nbytes);
+      if (rv < 0)
+	{
+	  clib_warning ("[%d] ERROR: vppcom_session_write ("
+			"out_sid %u, io_buffer %p, nbytes %d) returned %d",
+			getpid (), out_sid, vsm->io_buffer, nbytes, rv);
+	  if (results == 0)
+	    {
+	      vec_reset_length (vsm->io_buffer);
+	      return rv;
+	    }
+	  goto update_offset;
+	}
+
+      results += nbytes;
+      ASSERT (n_bytes_left >= nbytes);
+      n_bytes_left = n_bytes_left - nbytes;
+    }
+  while (n_bytes_left > 0);
+
+update_offset:
+  if (__offset)
+    {
+      off_t offset = lseek (__in_fd, *__offset, SEEK_SET);
+      if (offset == -1)
+	{
+	  errno_val = errno;
+	  perror ("lseek()");
+	  clib_warning ("[%d] ERROR: lseek (__in_fd %d, __offset %p "
+			"(%ld), SEEK_SET) returned errno %d",
+			getpid (), __in_fd, __offset, *__offset, errno_val);
+	  vec_reset_length (vsm->io_buffer);
+	  return -errno_val;
+	}
+
+      *__offset += results + 1;
+    }
+
+  vec_reset_length (vsm->io_buffer);
+  return eagain ? -EAGAIN : results;
+}
+
 ssize_t
 vcom_socket_recv (int __fd, void *__buf, size_t __n, int __flags)
 {
@@ -2327,7 +2478,7 @@ vcom_socket_accept_flags (int __fd, __SOCKADDR_ARG __addr,
 	   * on the queue, accept () blocks the caller
 	   * until a connection is present.
 	   */
-	  rv = vppcom_session_accept (vsock->sid, &ep,
+	  rv = vppcom_session_accept (vsock->sid, &ep, flags,
 				      -1.0 /* wait forever */ );
 	}
       else
@@ -2337,7 +2488,7 @@ vcom_socket_accept_flags (int __fd, __SOCKADDR_ARG __addr,
 	   * block.
 	   * */
 	  /* is non blocking */
-	  rv = vppcom_session_accept (vsock->sid, &ep, 0);
+	  rv = vppcom_session_accept (vsock->sid, &ep, flags, 0);
 	  /* If the socket is marked nonblocking and
 	   * no pending connections are present on the
 	   * queue, accept fails with the error
diff --git a/src/vcl/vcom_socket.h b/src/vcl/vcom_socket.h
index 0a5335fab9c..2ce11c021a1 100644
--- a/src/vcl/vcom_socket.h
+++ b/src/vcl/vcom_socket.h
@@ -383,6 +383,10 @@ vcom_socket_send (int __fd, const void *__buf, size_t __n, int __flags);
 
 ssize_t vcom_socket_recv (int __fd, void *__buf, size_t __n, int __flags);
 
+ssize_t
+vcom_socket_sendfile (int __out_fd, int __in_fd, off_t * __offset,
+		      size_t __len);
+
 /*
  * RETURN   1 if __fd is (SOCK_STREAM, SOCK_SEQPACKET),
  * 0 otherwise
diff --git a/src/vcl/vcom_socket_wrapper.c b/src/vcl/vcom_socket_wrapper.c
index d73f4b20562..de633d1cc7b 100644
--- a/src/vcl/vcom_socket_wrapper.c
+++ b/src/vcl/vcom_socket_wrapper.c
@@ -212,6 +212,8 @@ typedef int (*__libc_recvmsg) (int sockfd, const struct msghdr * msg,
 			       int flags);
 typedef int (*__libc_send) (int sockfd, const void *buf, size_t len,
 			    int flags);
+typedef ssize_t (*__libc_sendfile) (int out_fd, int in_fd, off_t * offset,
+				    size_t len);
 typedef int (*__libc_sendmsg) (int sockfd, const struct msghdr * msg,
 			       int flags);
 typedef int (*__libc_sendto) (int sockfd, const void *buf, size_t len,
@@ -314,6 +316,7 @@ struct swrap_libc_symbols
   SWRAP_SYMBOL_ENTRY (recvfrom);
   SWRAP_SYMBOL_ENTRY (recvmsg);
   SWRAP_SYMBOL_ENTRY (send);
+  SWRAP_SYMBOL_ENTRY (sendfile);
   SWRAP_SYMBOL_ENTRY (sendmsg);
   SWRAP_SYMBOL_ENTRY (sendto);
   SWRAP_SYMBOL_ENTRY (setsockopt);
@@ -615,6 +618,7 @@ libc_listen (int sockfd, int backlog)
   return swrap.libc.symbols._libc_listen.f (sockfd, backlog);
 }
 
+/* TBD: libc_read() should return ssize_t not an int */
 int
 libc_read (int fd, void *buf, size_t count)
 {
@@ -668,6 +672,14 @@ libc_send (int sockfd, const void *buf, size_t len, int flags)
   return swrap.libc.symbols._libc_send.f (sockfd, buf, len, flags);
 }
 
+ssize_t
+libc_sendfile (int out_fd, int in_fd, off_t * offset, size_t len)
+{
+  swrap_bind_symbol_libc (sendfile);
+
+  return swrap.libc.symbols._libc_sendfile.f (out_fd, in_fd, offset, len);
+}
+
 int
 libc_sendmsg (int sockfd, const struct msghdr *msg, int flags)
 {
diff --git a/src/vcl/vcom_socket_wrapper.h b/src/vcl/vcom_socket_wrapper.h
index f44b5a8ef3b..ce03ebe83da 100644
--- a/src/vcl/vcom_socket_wrapper.h
+++ b/src/vcl/vcom_socket_wrapper.h
@@ -159,6 +159,8 @@ int libc_recvmsg (int sockfd, struct msghdr *msg, int flags);
 
 int libc_send (int sockfd, const void *buf, size_t len, int flags);
 
+ssize_t libc_sendfile (int out_fd, int in_fd, off_t * offset, size_t len);
+
 int libc_sendmsg (int sockfd, const struct msghdr *msg, int flags);
 
 int
diff --git a/src/vcl/vppcom.c b/src/vcl/vppcom.c
index 09ebe26813f..2f62b81d864 100644
--- a/src/vcl/vppcom.c
+++ b/src/vcl/vppcom.c
@@ -691,7 +691,7 @@ vl_api_disconnect_session_t_handler (vl_api_disconnect_session_t * mp)
     }
   else
     {
-      clib_warning ("[%d] couldn't find session: unknonwn vpp handle 0x%llx",
+      clib_warning ("[%d] couldn't find session: unknown vpp handle 0x%llx",
 		    getpid (), mp->handle);
       rv = -11;
     }
@@ -1020,6 +1020,7 @@ vl_api_accept_session_t_handler (vl_api_accept_session_t * mp)
   svm_fifo_t *rx_fifo, *tx_fifo;
   session_t *session;
   u32 session_index;
+  uword *p;
 
   clib_spinlock_lock (&vcm->sessions_lockp);
   if (!clib_fifo_free_elts (vcm->client_session_index_fifo))
@@ -1057,6 +1058,34 @@ vl_api_accept_session_t_handler (vl_api_accept_session_t * mp)
   /* Add it to lookup table */
   hash_set (vcm->session_index_by_vpp_handles, mp->handle, session_index);
 
+  p = hash_get (vcm->session_index_by_vpp_handles, mp->listener_handle);
+  if (p)
+    {
+      int rval;
+      session_t *listen_session;
+
+      rval = vppcom_session_at_index (p[0], &listen_session);
+      if (PREDICT_FALSE (rval))
+	{
+	  if (VPPCOM_DEBUG > 1)
+	    clib_warning ("[%d] invalid listen session, sid (%u) "
+			  "has been closed!", getpid (), p[0]);
+	}
+      else
+	{
+	  session->lcl_port = listen_session->lcl_port;
+	  session->lcl_addr = listen_session->lcl_addr;
+	}
+      clib_spinlock_unlock (&vcm->sessions_lockp);
+      hash_unset (vcm->session_index_by_vpp_handles, mp->handle);
+    }
+  else
+    {
+      clib_warning ("[%d] couldn't find listen session: unknown vpp "
+		    "listener handle %llx", getpid (), mp->listener_handle);
+    }
+
+  /* TBD: move client_session_index_fifo into listener session */
   clib_fifo_add1 (vcm->client_session_index_fifo, session_index);
   clib_spinlock_unlock (&vcm->sessions_lockp);
 
@@ -1071,8 +1100,7 @@ vl_api_accept_session_t_handler (vl_api_accept_session_t * mp)
 }
 
 static void
-vppcom_send_connect_session_reply (session_t * session, u32 context,
-				   int retval, int handle)
+vppcom_send_connect_session_reply (session_t * session, int retval)
 {
   vl_api_connect_session_reply_t *rmp;
   u32 len;
@@ -1082,26 +1110,20 @@ vppcom_send_connect_session_reply (session_t * session, u32 context,
   memset (rmp, 0, sizeof (*rmp));
 
   rmp->_vl_msg_id = ntohs (VL_API_CONNECT_SESSION_REPLY);
-  rmp->context = session ? session->client_context : context;
+  rmp->context = session->client_context;
   rmp->retval = htonl (retval);
-  rmp->handle = session ? session->vpp_handle : handle;
-
-  if (session)
-    {
-      rmp->server_rx_fifo = pointer_to_uword (session->server_rx_fifo);
-      rmp->server_tx_fifo = pointer_to_uword (session->server_tx_fifo);
-      rmp->vpp_event_queue_address =
-	pointer_to_uword (session->vpp_event_queue);
-      rmp->segment_size = vcm->cfg.segment_size;
-      len = vec_len (session->segment_name);
-      rmp->segment_name_length = clib_min (len, sizeof (rmp->segment_name));
-      clib_memcpy (rmp->segment_name, session->segment_name,
-		   rmp->segment_name_length - 1);
-      clib_memcpy (rmp->lcl_ip, session->lcl_addr.ip46.as_u8,
-		   sizeof (rmp->lcl_ip));
-      rmp->is_ip4 = session->lcl_addr.is_ip4;
-    }
-
+  rmp->handle = session->vpp_handle;
+  rmp->server_rx_fifo = pointer_to_uword (session->server_rx_fifo);
+  rmp->server_tx_fifo = pointer_to_uword (session->server_tx_fifo);
+  rmp->vpp_event_queue_address = pointer_to_uword (session->vpp_event_queue);
+  rmp->segment_size = vcm->cfg.segment_size;
+  len = vec_len (session->segment_name);
+  rmp->segment_name_length = clib_min (len, sizeof (rmp->segment_name));
+  clib_memcpy (rmp->segment_name, session->segment_name,
+	       rmp->segment_name_length - 1);
+  clib_memcpy (rmp->lcl_ip, session->lcl_addr.ip46.as_u8,
+	       sizeof (rmp->lcl_ip));
+  rmp->is_ip4 = session->lcl_addr.is_ip4;
   client_q = uword_to_pointer (session->client_queue_address,
 			       unix_shared_memory_queue_t *);
   ASSERT (client_q);
@@ -1281,12 +1303,18 @@ vppcom_session_disconnect (u32 session_index)
 
       rv = vppcom_wait_for_session_state_change (session_index,
 						 STATE_DISCONNECT, 1.0);
+      /* TBD: Force clean up on error/timeout since there is no other
+       *      way to recover from a failed disconnect.
+       */
       if ((VPPCOM_DEBUG > 0) && (rv < 0))
 	clib_warning ("[%d] disconnect (session %d) failed, rv = %s (%d)",
 		      getpid (), session_index, vppcom_retval_str (rv), rv);
     }
   else
-    clib_spinlock_unlock (&vcm->sessions_lockp);
+    {
+      /* TBD: Handle cut-thru disconnect */
+      clib_spinlock_unlock (&vcm->sessions_lockp);
+    }
 
   return VPPCOM_OK;
 }
@@ -2212,11 +2240,11 @@ vppcom_session_listen (uint32_t listen_session_index, uint32_t q_len)
 
 int
 vppcom_session_accept (uint32_t listen_session_index, vppcom_endpt_t * ep,
-		       double wait_for_time)
+		       uint32_t flags, double wait_for_time)
 {
   session_t *listen_session = 0;
   session_t *client_session = 0;
-  u32 client_session_index;
+  u32 client_session_index = ~0;
   int rv;
   f64 wait_for;
   char *cut_thru_str;
@@ -2283,9 +2311,11 @@ vppcom_session_accept (uint32_t listen_session_index, vppcom_endpt_t * ep,
   ASSERT (client_session->peer_addr.is_ip4 ==
 	  listen_session->lcl_addr.is_ip4);
 
+  client_session->is_nonblocking = (flags & O_NONBLOCK) ? 1 : 0;
   if (VPPCOM_DEBUG > 0)
-    clib_warning ("[%d] Got a request: client sid %d", getpid (),
-		  client_session_index);
+    clib_warning ("[%d] Got a request: client sid %d, flags %d, "
+		  " is_nonblocking %u", getpid (), client_session_index,
+		  flags, client_session->is_nonblocking);
 
   ep->vrf = client_session->vrf;
   ep->is_cut_thru = client_session->is_cut_thru;
@@ -2324,7 +2354,7 @@ vppcom_session_accept (uint32_t listen_session_index, vppcom_endpt_t * ep,
 			  getpid (), a->segment_name);
 	  vec_reset_length (a->new_segment_indices);
 	  rv = VNET_API_ERROR_URI_FIFO_CREATE_FAILED;
-	  vppcom_send_connect_session_reply (client_session, 0, rv, 0);
+	  vppcom_send_connect_session_reply (client_session, rv);
 	  clib_spinlock_unlock (&vcm->sessions_lockp);
 	  return VPPCOM_ENOMEM;
 	}
@@ -2344,7 +2374,7 @@ vppcom_session_accept (uint32_t listen_session_index, vppcom_endpt_t * ep,
 			getpid (), vcm->cfg.rx_fifo_size,
 			vcm->cfg.rx_fifo_size);
 	  rv = VNET_API_ERROR_URI_FIFO_CREATE_FAILED;
-	  vppcom_send_connect_session_reply (client_session, 0, rv, 0);
+	  vppcom_send_connect_session_reply (client_session, rv);
 	  clib_spinlock_unlock (&vcm->sessions_lockp);
 	  return VPPCOM_ENOMEM;
 	}
@@ -2362,7 +2392,7 @@ vppcom_session_accept (uint32_t listen_session_index, vppcom_endpt_t * ep,
 			  getpid (), vcm->cfg.tx_fifo_size,
 			  vcm->cfg.tx_fifo_size);
 	  rv = VNET_API_ERROR_URI_FIFO_CREATE_FAILED;
-	  vppcom_send_connect_session_reply (client_session, 0, rv, 0);
+	  vppcom_send_connect_session_reply (client_session, rv);
 	  clib_spinlock_unlock (&vcm->sessions_lockp);
 	  return VPPCOM_ENOMEM;
 	}
@@ -2390,7 +2420,7 @@ vppcom_session_accept (uint32_t listen_session_index, vppcom_endpt_t * ep,
 	ssvm_unlock_non_recursive (sh);
       }
 #endif
-      vppcom_send_connect_session_reply (client_session, 0, 0, 0);
+      vppcom_send_connect_session_reply (client_session, 0);
     }
   else
     {
@@ -3419,14 +3449,18 @@ vppcom_session_attr (uint32_t session_index, uint32_t op,
     {
     case VPPCOM_ATTR_GET_NREAD:
       rv = vppcom_session_read_ready (session, session_index);
-      if (VPPCOM_DEBUG > 1)
-	clib_warning ("[%d] VPPCOM_ATTR_GET_NREAD: nread = %d",
+      if (VPPCOM_DEBUG > 2)
+	clib_warning ("[%d] VPPCOM_ATTR_GET_NREAD: sid %u, nread = %d",
 		      getpid (), rv);
 
       break;
 
-    case VPPCOM_ATTR_PEEK_NREAD:
-      /* TBD */
+    case VPPCOM_ATTR_GET_NWRITE:
+      rv = vppcom_session_write_ready (session, session_index);
+      if (VPPCOM_DEBUG > 2)
+	clib_warning ("[%d] VPPCOM_ATTR_GET_NWRITE: sid %u, nwrite = %d",
+		      getpid (), session_index, rv);
+
       break;
 
     case VPPCOM_ATTR_GET_FLAGS:
@@ -3434,10 +3468,10 @@ vppcom_session_attr (uint32_t session_index, uint32_t op,
 	{
 	  *flags = O_RDWR | ((session->is_nonblocking) ? O_NONBLOCK : 0);
 	  *buflen = sizeof (*flags);
-	  if (VPPCOM_DEBUG > 1)
-	    clib_warning ("[%d] VPPCOM_ATTR_GET_FLAGS: flags = 0x%08x, "
-			  "is_nonblocking = %u", getpid (), *flags,
-			  session->is_nonblocking);
+	  if (VPPCOM_DEBUG > 2)
+	    clib_warning ("[%d] VPPCOM_ATTR_GET_FLAGS: sid %u, "
+			  "flags = 0x%08x, is_nonblocking = %u", getpid (),
+			  session_index, *flags, session->is_nonblocking);
 	}
       else
 	rv = VPPCOM_EINVAL;
@@ -3447,10 +3481,10 @@ vppcom_session_attr (uint32_t session_index, uint32_t op,
       if (buffer && buflen && (*buflen >= sizeof (*flags)))
 	{
 	  session->is_nonblocking = (*flags & O_NONBLOCK) ? 1 : 0;
-	  if (VPPCOM_DEBUG > 1)
-	    clib_warning ("[%d] VPPCOM_ATTR_SET_FLAGS: flags = 0x%08x, "
-			  "is_nonblocking = %u", getpid (), *flags,
-			  session->is_nonblocking);
+	  if (VPPCOM_DEBUG > 2)
+	    clib_warning ("[%d] VPPCOM_ATTR_SET_FLAGS: sid %u, "
+			  "flags = 0x%08x, is_nonblocking = %u",
+			  getpid (), *flags, session->is_nonblocking);
 	}
       else
 	rv = VPPCOM_EINVAL;
@@ -3470,7 +3504,7 @@ vppcom_session_attr (uint32_t session_index, uint32_t op,
 			 sizeof (ip6_address_t));
 	  *buflen = sizeof (*ep);
 	  if (VPPCOM_DEBUG > 1)
-	    clib_warning ("[%d] VPPCOM_ATTR_GET_PEER_ADDR: sid %u is_ip4 = "
+	    clib_warning ("[%d] VPPCOM_ATTR_GET_PEER_ADDR: sid %u, is_ip4 = "
 			  "%u, addr = %U, port %u", getpid (),
 			  session_index, ep->is_ip4, format_ip46_address,
 			  &session->peer_addr.ip46, ep->is_ip4,
@@ -3494,7 +3528,7 @@ vppcom_session_attr (uint32_t session_index, uint32_t op,
 			 sizeof (ip6_address_t));
 	  *buflen = sizeof (*ep);
 	  if (VPPCOM_DEBUG > 1)
-	    clib_warning ("[%d] VPPCOM_ATTR_GET_LCL_ADDR: sid %u is_ip4 = "
+	    clib_warning ("[%d] VPPCOM_ATTR_GET_LCL_ADDR: sid %u, is_ip4 = "
 			  "%u, addr = %U port %d", getpid (),
 			  session_index, ep->is_ip4, format_ip46_address,
 			  &session->lcl_addr.ip46, ep->is_ip4,
diff --git a/src/vcl/vppcom.h b/src/vcl/vppcom.h
index 6260bdc82e4..93b7173550e 100644
--- a/src/vcl/vppcom.h
+++ b/src/vcl/vppcom.h
@@ -72,7 +72,7 @@ typedef enum
 typedef enum
 {
   VPPCOM_ATTR_GET_NREAD,
-  VPPCOM_ATTR_PEEK_NREAD,
+  VPPCOM_ATTR_GET_NWRITE,
   VPPCOM_ATTR_GET_FLAGS,
   VPPCOM_ATTR_SET_FLAGS,
   VPPCOM_ATTR_GET_LCL_ADDR,
@@ -147,7 +147,7 @@ extern int vppcom_session_bind (uint32_t session_index, vppcom_endpt_t * ep);
 extern int vppcom_session_listen (uint32_t session_index, uint32_t q_len);
 extern int vppcom_session_accept (uint32_t session_index,
 				  vppcom_endpt_t * client_ep,
-				  double wait_for_time);
+				  uint32_t flags, double wait_for_time);
 
 extern int vppcom_session_connect (uint32_t session_index,
 				   vppcom_endpt_t * server_ep);