X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/mLib/blobdiff_plain/dd3c57bc8cac59e0d657ee665ce462988d27d714..18c831dcd0ae4d660c70ccac69d27ed2a97851be:/sys/fdpass.c

diff --git a/sys/fdpass.c b/sys/fdpass.c
new file mode 100644
index 0000000..e860ec3
--- /dev/null
+++ b/sys/fdpass.c
@@ -0,0 +1,154 @@
+/* -*-c-*-
+ *
+ * File descriptor passing
+ *
+ * (c) 2003 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of the mLib utilities library.
+ *
+ * mLib is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * mLib 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 Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with mLib; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "config.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <sys/types.h>
+#include <sys/time.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#include <sys/un.h>
+
+#include "fdpass.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @fdpass_send@ --- *
+ *
+ * Arguments:	@int sock@ = socket to send over
+ *		@int fd@ = file descriptor to send
+ *		@const void *p@ = pointer to data to send
+ *		@size_t sz@ = size of buffer to send
+ *
+ * Returns:	On error, @-1@, otherwise number of bytes transferred from
+ *		@p@.
+ *
+ * Use:		Sends a copy of file descriptor @fd@ to the other end of
+ *		@sock@.
+ */
+
+ssize_t fdpass_send(int sock, int fd, const void *p, size_t sz)
+{
+  struct iovec iov;
+  struct msghdr msg;
+#ifndef HAVE_MSG_ACCRIGHTS
+  char buf[CMSG_SPACE(sizeof(fd))];
+  struct cmsghdr *cmsg;
+#endif
+
+  iov.iov_base = (/*unconst*/ void *)p;
+  iov.iov_len = sz;
+  msg.msg_name = 0;
+  msg.msg_namelen = 0;
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+#ifdef HAVE_MSG_ACCRIGHTS
+  msg.msg_accrights = &fd;
+  msg.msg_accrightslen = sizeof(fd);
+#else
+  msg.msg_flags = 0;
+  msg.msg_control = buf;
+  msg.msg_controllen = sizeof(buf);
+  cmsg = CMSG_FIRSTHDR(&msg);
+  cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
+  cmsg->cmsg_level = SOL_SOCKET;
+  cmsg->cmsg_type = SCM_RIGHTS;
+  memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
+#endif
+  return (sendmsg(sock, &msg, 0));
+}
+
+/* --- @fdpass_recv@ --- *
+ *
+ * Arguments:	@int sock@ = socket to send over
+ *		@int *fd@ = where to put received descriptor
+ *		@void *p@ = pointer to where to put data
+ *		@size_t sz@ = size of buffer
+ *
+ * Returns:	On error, @-1@, otherwise number of bytes transferred.
+ *
+ * Use:		Receives a file descriptor.  If the call succeeds, and there
+ *		was a file descriptor, then @fd@ won't be @-1@ on exit;
+ *		otherwise it will.  At most one descriptor will be collected.
+ */
+
+ssize_t fdpass_recv(int sock, int *fd, void *p, size_t sz)
+{
+  struct iovec iov;
+  struct msghdr msg;
+  ssize_t rc;
+#ifndef HAVE_MSG_ACCRIGHTS
+  char buf[CMSG_SPACE(sizeof(fd))];
+  struct cmsghdr *cmsg;
+  int fdtmp;
+#endif
+
+  *fd = -1;
+  iov.iov_base = p;
+  iov.iov_len = sz;
+  msg.msg_name = 0;
+  msg.msg_namelen = 0;
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+#ifdef HAVE_MSG_ACCRIGHTS
+  msg.msg_accrights = fd;
+  msg.msg_accrightslen = sizeof(*fd);
+#else
+  msg.msg_flags = 0;
+  msg.msg_control = buf;
+  msg.msg_controllen = sizeof(buf);
+#endif
+  if ((rc = recvmsg(sock, &msg, 0)) < 0)
+    return (rc);
+#ifdef HAVE_MSG_ACCRIGHTS
+  if (msg.msg_accrightslen < sizeof(*fd))
+    *fd = -1;
+#else
+  for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+    if (cmsg->cmsg_level == SOL_SOCKET &&
+	cmsg->cmsg_type == SCM_RIGHTS &&
+	cmsg->cmsg_len >= CMSG_LEN(sizeof(fd))) {
+      memcpy(&fdtmp, CMSG_DATA(cmsg), sizeof(fdtmp));
+      if (*fd == -1)
+	*fd = fdtmp;
+      else
+	close(fdtmp);
+    }
+  }
+#endif
+  return (rc);
+}
+
+/*----- That's all, folks -------------------------------------------------*/