s3: If sendfile returns 0 bytes read, fall back to the normal read path

This allows sendfile implementations that are atomic to avoid having
to send zeros or kill the client connection on a short read (usually
the file was truncated).

diff --git a/source3/smbd/reply.c b/source3/smbd/reply.c
index 457f9412a91d0bbe771c56437c0868c38061f825..b30ef23c0ead08adbfd294a453ce6fe1e8a50e8d 100644 (file)
--- a/source3/smbd/reply.c
+++ b/source3/smbd/reply.c
@@ -2788,6 +2788,18 @@ static void send_file_readbraw(connection_struct *conn,
                        DEBUG(0,("send_file_readbraw: sendfile failed for file %s (%s). Terminating\n",
                                fsp->fsp_name, strerror(errno) ));
                        exit_server_cleanly("send_file_readbraw sendfile failed");
+               } else if (sendfile_read == 0) {
+                       /*
+                        * Some sendfile implementations return 0 to indicate
+                        * that there was a short read, but nothing was
+                        * actually written to the socket.  In this case,
+                        * fallback to the normal read path so the header gets
+                        * the correct byte count.
+                        */
+                       DEBUG(3, ("send_file_readbraw: sendfile sent zero "
+                                 "bytes falling back to the normal read: "
+                                 "%s\n", fsp->fsp_name));
+                       goto normal_readbraw;
                }
 
                /* Deal with possible short send. */
@@ -3284,6 +3296,18 @@ static void send_file_readX(connection_struct *conn, struct smb_request *req,
                        DEBUG(0,("send_file_readX: sendfile failed for file %s (%s). Terminating\n",
                                fsp->fsp_name, strerror(errno) ));
                        exit_server_cleanly("send_file_readX sendfile failed");
+               } else if (nread == 0) {
+                       /*
+                        * Some sendfile implementations return 0 to indicate
+                        * that there was a short read, but nothing was
+                        * actually written to the socket.  In this case,
+                        * fallback to the normal read path so the header gets
+                        * the correct byte count.
+                        */
+                       DEBUG(3, ("send_file_readX: sendfile sent zero bytes "
+                                 "falling back to the normal read: %s\n",
+                                 fsp->fsp_name));
+                       goto normal_read;
                }
 
                DEBUG( 3, ( "send_file_readX: sendfile fnum=%d max=%d nread=%d\n",