Unix domain/FIFOs: Fix a race condition between FIFO buffer operations and the opening and closing of FIFOs which necessary when the FIFOs are used to support Unix domain, datagram sockets. The default policy is the deallocate FIFO buffering when the last client closes the pipe. When when used for datagram communicatinos, packets left in the FIFO will be lost. Some like UDP read-ahead is needed: The buffered data in the FIFO needs to be retained until the reader gets a chance to re-open the FIFO. Added an ioctl (PIPEIOC_POLICY) to control the buffer policy. Default (0) is the legacy behavior; Unix domain datagram logic sets the alternative policy so that the packet data persists after the FIFO is closed.

2 files changed, 98 insertions, 13 deletions

diff --git a/nuttx/net/local/local_fifo.c b/nuttx/net/local/local_fifo.c
index bd9b141d9..071fcdfb2 100644
--- a/nuttx/net/local/local_fifo.c
+++ b/nuttx/net/local/local_fifo.c
@@ -41,6 +41,8 @@
 #if defined(CONFIG_NET) && defined(CONFIG_NET_LOCAL)
 
 #include <sys/stat.h>
+#include <sys/ioctl.h>
+
 #include <stdbool.h>
 #include <stdio.h>
 #include <unistd.h>
@@ -49,6 +51,7 @@
 #include <errno.h>
 #include <assert.h>
 
+
 #include "local/local.h"
 
 /****************************************************************************
@@ -185,8 +188,6 @@ static int local_create_fifo(FAR const char *path)
 
 static int local_release_fifo(FAR const char *path)
 {
-  int ret;
-
   /* Unlink the client-to-server FIFO if it exists. */
 
   if (local_fifo_exists(path))
@@ -197,6 +198,8 @@ static int local_release_fifo(FAR const char *path)
        */
 #warning Missing logic
 #if 0
+      int ret;
+
       ret = unlink(path);
       if (ret < 0)
         {
@@ -222,8 +225,7 @@ static int local_release_fifo(FAR const char *path)
  *
  ****************************************************************************/
 
-static inline int local_rx_open(FAR struct local_conn_s *conn,
-                                FAR const char *path)
+static int local_rx_open(FAR struct local_conn_s *conn, FAR const char *path)
 {
   conn->lc_infd = open(path, O_RDONLY);
   if (conn->lc_infd < 0)
@@ -256,8 +258,7 @@ static inline int local_rx_open(FAR struct local_conn_s *conn,
  *
  ****************************************************************************/
 
-static inline int local_tx_open(FAR struct local_conn_s *conn,
-                                FAR const char *path)
+static int local_tx_open(FAR struct local_conn_s *conn, FAR const char *path)
 {
   conn->lc_outfd = open(path, O_WRONLY);
   if (conn->lc_outfd < 0)
@@ -283,6 +284,36 @@ static inline int local_tx_open(FAR struct local_conn_s *conn,
 }
 
 /****************************************************************************
+ * Name: local_set_policy
+ *
+ * Description:
+ *   Set the FIFO buffer policy:
+ *
+ *     0=Free FIFO resources when the last reference is closed
+ *     1=Free FIFO resources when the buffer is empty.
+ *
+ ****************************************************************************/
+
+static int local_set_policy(int fd, unsigned long policy)
+{
+  int ret;
+
+  /* Set the buffer policy */
+
+  ret = ioctl(fd, PIPEIOC_POLICY, policy);
+  if (ret < 0)
+    {
+      int errcode = get_errno();
+      DEBUGASSERT(errcode > 0);
+
+      ndbg("ERROR: Failed to set FIFO buffer policty: %d\n", errcode);
+      return -errcode;
+    }
+
+  return OK;
+}
+
+/****************************************************************************
  * Public Functions
  ****************************************************************************/
 
@@ -390,6 +421,7 @@ int local_release_halfduplex(FAR struct local_conn_s *conn)
 int local_open_client_rx(FAR struct local_conn_s *client)
 {
   char path[LOCAL_FULLPATH_LEN];
+  int ret;
 
   /* Get the server-to-client path name */
 
@@ -397,7 +429,15 @@ int local_open_client_rx(FAR struct local_conn_s *client)
 
   /* Then open the file for read-only access */
 
-  return local_rx_open(client, path);
+  ret = local_rx_open(client, path);
+  if (ret == OK)
+    {
+      /* Policy: Free FIFO resources when the last reference is closed */
+
+      ret = local_set_policy(client->lc_infd, 0);
+    }
+
+  return ret;
 }
 
 /****************************************************************************
@@ -411,6 +451,7 @@ int local_open_client_rx(FAR struct local_conn_s *client)
 int local_open_client_tx(FAR struct local_conn_s *client)
 {
   char path[LOCAL_FULLPATH_LEN];
+  int ret;
 
   /* Get the client-to-server path name */
 
@@ -418,7 +459,15 @@ int local_open_client_tx(FAR struct local_conn_s *client)
 
   /* Then open the file for write-only access */
 
-  return local_tx_open(client, path);
+  ret = local_tx_open(client, path);
+  if (ret == OK)
+    {
+      /* Policy: Free FIFO resources when the last reference is closed */
+
+      ret = local_set_policy(client->lc_outfd, 0);
+    }
+
+  return ret;
 }
 
 /****************************************************************************
@@ -432,6 +481,7 @@ int local_open_client_tx(FAR struct local_conn_s *client)
 int local_open_server_rx(FAR struct local_conn_s *server)
 {
   char path[LOCAL_FULLPATH_LEN];
+  int ret;
 
   /* Get the client-to-server path name */
 
@@ -439,7 +489,15 @@ int local_open_server_rx(FAR struct local_conn_s *server)
 
   /* Then open the file for write-only access */
 
-  return local_rx_open(server, path);
+  ret = local_rx_open(server, path);
+  if (ret == OK)
+    {
+      /* Policy: Free FIFO resources when the last reference is closed */
+
+      ret = local_set_policy(server->lc_infd, 0);
+    }
+
+  return ret;
 }
 
 /****************************************************************************
@@ -453,6 +511,7 @@ int local_open_server_rx(FAR struct local_conn_s *server)
 int local_open_server_tx(FAR struct local_conn_s *server)
 {
   char path[LOCAL_FULLPATH_LEN];
+  int ret;
 
   /* Get the server-to-client path name */
 
@@ -460,7 +519,15 @@ int local_open_server_tx(FAR struct local_conn_s *server)
 
   /* Then open the file for read-only access */
 
-  return local_tx_open(server, path);
+  ret = local_tx_open(server, path);
+  if (ret == OK)
+    {
+      /* Policy: Free FIFO resources when the last reference is closed */
+
+      ret = local_set_policy(server->lc_outfd, 0);
+    }
+
+  return ret;
 }
 
 /****************************************************************************
@@ -474,6 +541,7 @@ int local_open_server_tx(FAR struct local_conn_s *server)
 int local_open_receiver(FAR struct local_conn_s *conn)
 {
   char path[LOCAL_FULLPATH_LEN];
+  int ret;
 
   /* Get the server-to-client path name */
 
@@ -481,7 +549,15 @@ int local_open_receiver(FAR struct local_conn_s *conn)
 
   /* Then open the file for read-only access */
 
-  return local_rx_open(conn, path);
+  ret = local_rx_open(conn, path);
+  if (ret == OK)
+    {
+      /* Policy: Free FIFO resources when the buffer is empty. */
+
+      ret = local_set_policy(conn->lc_infd, 1);
+    }
+
+  return ret;
 }
 
 /****************************************************************************
@@ -495,6 +571,7 @@ int local_open_receiver(FAR struct local_conn_s *conn)
 int local_open_sender(FAR struct local_conn_s *conn, FAR const char *path)
 {
   char fullpath[LOCAL_FULLPATH_LEN];
+  int ret;
 
   /* Get the server-to-client path name */
 
@@ -502,7 +579,15 @@ int local_open_sender(FAR struct local_conn_s *conn, FAR const char *path)
 
   /* Then open the file for read-only access */
 
-  return local_tx_open(conn, fullpath);
+  ret = local_tx_open(conn, fullpath);
+  if (ret == OK)
+    {
+      /* Policy: Free FIFO resources when the buffer is empty. */
+
+      ret = local_set_policy(conn->lc_outfd, 1);
+    }
+
+  return ret;
 }
 
 #endif /* CONFIG_NET && CONFIG_NET_LOCAL */
diff --git a/nuttx/net/local/local_recvfrom.c b/nuttx/net/local/local_recvfrom.c
index 97109ea1a..b3346b7f7 100644
--- a/nuttx/net/local/local_recvfrom.c
+++ b/nuttx/net/local/local_recvfrom.c
@@ -337,7 +337,7 @@ psock_dgram_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
 
           /* Adjust the number of bytes remaining to be read from the packet */
 
-          DEBUGASSERT(tmplen <= remain);
+          DEBUGASSERT(tmplen <= remaining);
           remaining -= tmplen;
         }
       while (remaining > 0);