beginning of mds-vt

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 371 insertions, 0 deletions

diff --git a/src/mds-vt.c b/src/mds-vt.c
new file mode 100644
index 0000000..2167fb1
--- /dev/null
+++ b/src/mds-vt.c
@@ -0,0 +1,371 @@
+/**
+ * mds — A micro-display server
+ * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "mds-vt.h"
+
+#include <libmdsserver/macros.h>
+#include <libmdsserver/util.h>
+#include <libmdsserver/mds-message.h>
+
+#include <errno.h>
+#include <inttypes.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <linux/kd.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <signal.h>
+#define reconnect_to_display() -1 /* TODO */
+
+
+
+#define MDS_VT_VARS_VERSION  0
+
+
+
+/**
+ * This variable should declared by the actual server implementation.
+ * It must be configured before `main` is invoked.
+ * 
+ * This tells the server-base how to behave
+ */
+server_characteristics_t server_characteristics =
+  {
+    .require_privileges = 1, /* we want to open the new tty (the rest is fine without root for some reason) */
+    .require_display = 1,
+    .require_respawn_info = 0,
+    .sanity_check_argc = 1,
+    .fork_for_safety = 0,
+    .danger_is_deadly = 0
+  };
+
+
+
+/**
+ * Value of the ‘Message ID’ header for the next message
+ */
+static int32_t message_id = 1;
+
+/**
+ * Buffer for received messages
+ */
+static mds_message_t received;
+
+/**
+ * Whether the server is connected to the display
+ */
+static int connected = 1;
+
+
+
+/**
+ * This function will be invoked before `initialise_server` (if not re-exec:ing)
+ * or before `unmarshal_server` (if re-exec:ing)
+ * 
+ * @return  Non-zero on error
+ */
+int __attribute__((const)) preinitialise_server(void)
+{
+  return 0;
+}
+
+
+/**
+ * This function should initialise the server,
+ * and it not invoked after a re-exec.
+ * 
+ * @return  Non-zero on error
+ */
+int initialise_server(void)
+{
+  const char* const message =
+    "Command: intercept\n"
+    "Message ID: 0\n"
+    "Length: 14\n"
+    "\n"
+    "Command: echo\n";
+  
+  if (full_send(message, strlen(message)))
+    return 1;
+  fail_if (server_initialised() < 0);
+  fail_if (mds_message_initialise(&received));
+  
+  return 0;
+ pfail:
+  xperror(*argv);
+  mds_message_destroy(&received);
+  return 1;
+}
+
+
+/**
+ * This function will be invoked after `initialise_server` (if not re-exec:ing)
+ * or after `unmarshal_server` (if re-exec:ing)
+ * 
+ * @return  Non-zero on error
+ */
+int postinitialise_server(void)
+{
+  if (connected)
+    return 0;
+  
+  if (reconnect_to_display())
+    {
+      mds_message_destroy(&received);
+      return 1;
+    }
+  connected = 1;
+  return 0;
+}
+
+
+/**
+ * Calculate the number of bytes that will be stored by `marshal_server`
+ * 
+ * On failure the program should `abort()` or exit by other means.
+ * However it should not be possible for this function to fail.
+ * 
+ * @return  The number of bytes that will be stored by `marshal_server`
+ */
+size_t marshal_server_size(void)
+{
+  return 2 * sizeof(int) + sizeof(int32_t) + mds_message_marshal_size(&received);
+}
+
+
+/**
+ * Marshal server implementation specific data into a buffer
+ * 
+ * @param   state_buf  The buffer for the marshalled data
+ * @return             Non-zero on error
+ */
+int marshal_server(char* state_buf)
+{
+  buf_set_next(state_buf, int, MDS_VT_VARS_VERSION);
+  buf_set_next(state_buf, int, connected);
+  buf_set_next(state_buf, int32_t, message_id);
+  mds_message_marshal(&received, state_buf);
+  
+  mds_message_destroy(&received);
+  return 0;
+}
+
+
+/**
+ * Unmarshal server implementation specific data and update the servers state accordingly
+ * 
+ * On critical failure the program should `abort()` or exit by other means.
+ * That is, do not let `reexec_failure_recover` run successfully, if it unrecoverable
+ * error has occurred or one severe enough that it is better to simply respawn.
+ * 
+ * @param   state_buf  The marshalled data that as not been read already
+ * @return             Non-zero on error
+ */
+int unmarshal_server(char* state_buf)
+{
+  int r;
+  /* buf_get_next(state_buf, int, MDS_VT_VARS_VERSION); */
+  buf_next(state_buf, int, 1);
+  buf_get_next(state_buf, int, connected);
+  buf_get_next(state_buf, int32_t, message_id);
+  r = mds_message_unmarshal(&received, state_buf);
+  if (r)
+    {
+      xperror(*argv);
+      mds_message_destroy(&received);
+    }
+  return r;
+}
+
+
+/**
+ * Attempt to recover from a re-exec failure that has been
+ * detected after the server successfully updated it execution image
+ * 
+ * @return  Non-zero on error
+ */
+int __attribute__((const)) reexec_failure_recover(void)
+{
+  return -1;
+}
+
+
+/**
+ * Perform the server's mission
+ * 
+ * @return  Non-zero on error
+ */
+int master_loop(void)
+{
+  int rc = 1;
+  
+  while (!reexecing && !terminating)
+    {
+      int r = mds_message_read(&received, socket_fd);
+      if (r == 0)
+	{
+	  r = 0; /* FIXME */
+	  if (r == 0)
+	    continue;
+	}
+      
+      if (r == -2)
+	{
+	  eprint("corrupt message received, aborting.");
+	  goto fail;
+	}
+      else if (errno == EINTR)
+	continue;
+      else if (errno != ECONNRESET)
+	goto pfail;
+      
+      eprint("lost connection to server.");
+      mds_message_destroy(&received);
+      mds_message_initialise(&received);
+      connected = 0;
+      if (reconnect_to_display())
+	goto fail;
+      connected = 1;
+    }
+  
+  rc = 0;
+  goto fail;
+ pfail:
+  xperror(*argv);
+ fail:
+  if (rc || !reexecing)
+    mds_message_destroy(&received);
+  return rc;
+}
+
+
+/**
+ * Send a full message even if interrupted
+ * 
+ * @param   message  The message to send
+ * @param   length   The length of the message
+ * @return           Non-zero on success
+ */
+int full_send(const char* message, size_t length)
+{
+  size_t sent;
+  
+  while (length > 0)
+    {
+      sent = send_message(socket_fd, message, length);
+      if (sent > length)
+	{
+	  eprint("Sent more of a message than exists in the message, aborting.");
+	  return -1;
+	}
+      else if ((sent < length) && (errno != EINTR))
+	{
+	  xperror(*argv);
+	  return -1;
+	}
+      message += sent;
+      length -= sent;
+    }
+  return 0;
+}
+
+
+/**
+ * Get the index of the next available virtual terminal
+ * 
+ * @return  -1 on error, 0 if the terminals are exhausted, otherwise the next terminal
+ */
+int vt_get_next_available(void)
+{
+  int next_vt = -1;
+  int r = ioctl(STDIN_FILENO, VT_OPENQRY, &next_vt);
+  if (r < 0)
+    return r;
+  return ((next_vt < 0) || (MAX_NR_CONSOLES < next_vt)) ? 0 : next_vt;
+}
+
+
+/**
+ * Get the currently active virtual terminal
+ * 
+ * @return  -1 on error, otherwise the current terminal
+ */
+int vt_get_active(void)
+{
+  struct vt_stat state;
+  if (ioctl(STDIN_FILENO, VT_GETSTATE, &state) < 0)
+    return -1;
+  return state.v_active;
+}
+
+
+/**
+ * Change currently active virtual terminal and wait for it to complete the switch
+ * 
+ * @param   vt  The index of the terminal
+ * @return      Zero on success, -1 on error
+ */
+int vt_set_active(int vt)
+{
+  if (ioctl(STDIN_FILENO, VT_ACTIVATE, vt) < 0)
+    return -1;
+  
+  if (ioctl(STDIN_FILENO, VT_WAITACTIVE, vt) < 0)
+    xperror(*argv);
+  
+  return 0;
+}
+
+
+/**
+ * Open a virtual terminal
+ * 
+ * @param   vt  The index of the terminal
+ * @return      The file descriptor for the terminal, -1 on error
+ */
+int vt_open(int vt)
+{
+  char vtpath[64]; /* Should be small enought and large enought for any
+		      lunatic alternative to /dev/ttyNNN, if not you
+		      will need to apply a patch (or fix your system.) */
+  sprintf(vtpath, VT_PATH_PATTERN, vt);
+  return open(vtpath, O_RDWR);
+}
+
+
+/**
+ * Construct a virtual terminal mode that can be used in `vt_get_set_mode`
+ * 
+ * @param  vt_switch_control  Whether we want to be able to block and delay VT switches
+ * @param  vt_leave_signal    The signal that should be send to us we a process is trying
+ *                            to switch terminal to another terminal
+ * @param  vt_enter_signal    The signal that should be send to us we a process is trying
+ *                            to switch terminal to our terminal
+ * @param  mode               Output parameter
+ */
+void vt_construct_mode(int vt_switch_control, int vt_leave_signal,
+		       int vt_enter_signal, struct vt_mode* restrict mode)
+{
+  mode->mode = vt_switch_control ? VT_PROCESS : VT_AUTO;
+  mode->waitv = 0;
+  mode->relsig = (short int)vt_leave_signal;
+  mode->acqsig = (short int)vt_enter_signal;
+}
+