* Build udhcpc binary from source.

[grml-terminalserver.git] / udhcp / signalpipe.c

diff --git a/udhcp/signalpipe.c b/udhcp/signalpipe.c
new file mode 100644 (file)
index 0000000..074c8a6
--- /dev/null
+++ b/udhcp/signalpipe.c
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+/* signalpipe.c
+ *
+ * Signal pipe infrastructure. A reliable way of delivering signals.
+ *
+ * Russ Dill <Russ.Dill@asu.edu> December 2003
+ *
+ * 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 2 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, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <unistd.h>
+#include <signal.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/select.h>
+
+
+#include "signalpipe.h"
+#include "common.h"
+
+static int signal_pipe[2];
+
+static void signal_handler(int sig)
+{
+       if (send(signal_pipe[1], &sig, sizeof(sig), MSG_DONTWAIT) < 0)
+               DEBUG(LOG_ERR, "Could not send signal: %m");
+}
+
+
+/* Call this before doing anything else. Sets up the socket pair
+ * and installs the signal handler */
+void udhcp_sp_setup(void)
+{
+       socketpair(AF_UNIX, SOCK_STREAM, 0, signal_pipe);
+       signal(SIGUSR1, signal_handler);
+       signal(SIGUSR2, signal_handler);
+       signal(SIGTERM, signal_handler);
+}
+
+
+/* Quick little function to setup the rfds. Will return the
+ * max_fd for use with select. Limited in that you can only pass
+ * one extra fd */
+int udhcp_sp_fd_set(fd_set *rfds, int extra_fd)
+{
+       FD_ZERO(rfds);
+       FD_SET(signal_pipe[0], rfds);
+       if (extra_fd >= 0) FD_SET(extra_fd, rfds);
+       return signal_pipe[0] > extra_fd ? signal_pipe[0] : extra_fd;
+}
+
+
+/* Read a signal from the signal pipe. Returns 0 if there is
+ * no signal, -1 on error (and sets errno appropriately), and
+ * your signal on success */
+int udhcp_sp_read(fd_set *rfds)
+{
+       int sig;
+
+       if (!FD_ISSET(signal_pipe[0], rfds))
+               return 0;
+
+       if (read(signal_pipe[0], &sig, sizeof(sig)) < 0)
+               return -1;
+
+       return sig;
+}