begin on base for servers

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

3 files changed, 237 insertions, 1 deletions

diff --git a/src/mds-base.c b/src/mds-base.c
new file mode 100644
index 0000000..433564e
--- /dev/null
+++ b/src/mds-base.c
@@ -0,0 +1,159 @@
+/**
+ * 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-base.h"
+
+#include <libmdsserver/config.h>
+#include <libmdsserver/macros.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+
+#define  try(INSTRUCTION)  if ((r = INSTRUCTION))  return r
+
+
+int argc;
+char** argv;
+int is_respawn = 0;
+int is_reexec = 0;
+
+int socket_fd = -1;
+
+
+
+/**
+ * Parse command line arguments
+ * 
+ * @return  Non-zero on error
+ */
+static int parse_cmdline(void)
+{
+  int i;
+  for (i = 1; i < argc; i++)
+    {
+      char* arg = argv[i];
+      int v;
+      if ((v = strequals(arg, "--initial-spawn")) || /* Initial spawn? */
+	  strequals(arg, "--respawn"))               /* Respawning after crash? */
+	{
+	  exit_if (is_respawn == v,
+		   eprintf("conflicting arguments %s and %s cannot be combined.",
+			   "--initial-spawn", "--respawn"););
+	  is_respawn = !v;
+	}
+      else if (strequals(arg, "--re-exec")) /* Re-exec state-marshal. */
+	is_reexec = 1;
+    }
+  if (is_reexec)
+    {
+      is_respawn = 1;
+      eprint("re-exec performed.");
+    }
+  return 0;
+}
+
+
+/**
+ * Connect to the display
+ * 
+ * @return  Non-zero on error
+ */
+static int connect_to_display(void)
+{
+  char* display;
+  char pathname[PATH_MAX];
+  struct sockaddr_un address;
+  
+  display = getenv("MDS_DISPLAY");
+  exit_if ((display == NULL) || (strchr(display, ':') == NULL),
+	   eprint("MDS_DISPLAY has not set."););
+  exit_if (display[0] != ':',
+	   eprint("Remote mds sessions are not supported."););
+  xsnprintf(pathname, "%s/%s.socket", MDS_RUNTIME_ROOT_DIRECTORY, display + 1);
+  address.sun_family = AF_UNIX;
+  strcpy(address.sun_path, pathname);
+  fail_if ((socket_fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0);
+  fail_if (connect(socket_fd, (struct sockaddr*)(&address), sizeof(address)) < 0);
+  
+  return 0;
+  
+ pfail:
+  perror(*argv);
+  if (socket_fd >= 0)
+    close(socket_fd);
+  return 1;
+}
+
+
+/**
+ * Entry point of the server
+ * 
+ * @param   argc_  Number of elements in `argv_`
+ * @param   argv_  Command line arguments
+ * @return         Non-zero on error
+ */
+int main(int argc_, char** argv_)
+{
+  int r;
+  
+#if (LIBEXEC_ARGC_EXTRA_LIMIT < 2)
+# error LIBEXEC_ARGC_EXTRA_LIMIT is too small, need at least 2.
+#endif
+  
+  
+  argc = argc_;
+  argv = argv_;
+  
+  
+  if (server_characteristics.require_privileges == 0)
+    /* Drop privileges like it's hot. */
+    fail_if (drop_privileges());
+  
+  
+  /* Sanity check the number of command line arguments. */
+  exit_if (argc > ARGC_LIMIT + LIBEXEC_ARGC_EXTRA_LIMIT,
+	   eprint("that number of arguments is ridiculous, I will not allow it."););
+  
+  
+  /* Parse command line arguments. */
+  try (parse_cmdline());
+  
+  /* Connect to the display. */
+  if (is_reexec == 0)
+    try (connect_to_display());
+  
+  
+  close(socket_fd);
+  return 0;
+  
+ pfail:
+  perror(*argv);
+  if (socket_fd >= 0)
+    close(socket_fd);
+  return 1;
+}
+
+
+#undef try
+
diff --git a/src/mds-base.h b/src/mds-base.h
new file mode 100644
index 0000000..26b9c17
--- /dev/null
+++ b/src/mds-base.h
@@ -0,0 +1,77 @@
+/**
+ * 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/>.
+ */
+#ifndef MDS_MDS_BASE_H
+#define MDS_MDS_BASE_H
+
+
+/**
+ * Characteristics of the server
+ */
+typedef struct server_characteristics
+{
+  /**
+   * Setting this to zero will cause the server to drop privileges as a security precaution
+   */
+  int require_privileges;
+  
+} server_characteristics_t;
+
+
+/**
+ * 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.
+ */
+extern server_characteristics_t server_characteristics;
+
+
+/**
+ * Number of elements in `argv`
+ */
+extern int argc;
+
+/**
+ * Command line arguments
+ */
+extern char** argv;
+
+/**
+ * Whether the server has been respawn
+ * rather than this being the initial spawn.
+ * This will be at least as true as `is_reexec`.
+ */
+extern int is_respawn;
+
+/**
+ * Whether the server is continuing
+ * from a self-reexecution
+ */
+extern int is_reexec;
+
+
+/**
+ * The file descriptor of the socket
+ * that is connected to the server
+ */
+extern int socket_fd;
+
+
+
+#endif
+
diff --git a/src/mds.c b/src/mds.c
index 8651cdf..c86b08a 100644
--- a/src/mds.c
+++ b/src/mds.c
@@ -167,7 +167,7 @@ int main(int argc_, char** argv_)
   address.sun_family = AF_UNIX;
   strcpy(address.sun_path, pathname);
   unlink(pathname);
-  fd = socket(AF_UNIX, SOCK_STREAM, 0);
+  fail_if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0);
   fail_if (fchmod(fd, S_IRWXU) < 0);
   fail_if (bind(fd, (struct sockaddr*)(&address), sizeof(address)) < 0);
   fail_if (chown(pathname, getuid(), NOBODY_GROUP_GID) < 0);