1 files changed, 122 insertions, 0 deletions
diff --git a/fdpass.c b/fdpass.c
new file mode 100644
index 0000000..6e2e0c7
--- /dev/null
+++ b/fdpass.c
@@ -0,0 +1,122 @@
+/*
+ * Copyright © 2012 Keith Packard <keithp@keithp.com>
+ *
+ * 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; version 2 of the License.
+ *
+ * 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.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "fdpass.h"
+
+ssize_t
+sock_fd_read(int sock, void *buf, ssize_t bufsize, int *fd)
+{
+	ssize_t		size;
+
+	if (fd) {
+		struct msghdr	msg;
+		struct iovec	iov;
+		union {
+			struct cmsghdr	cmsghdr;
+			char		control[CMSG_SPACE(sizeof (int))];
+		} cmsgu;
+		struct cmsghdr	*cmsg;
+
+		iov.iov_base = buf;
+		iov.iov_len = bufsize;
+
+		msg.msg_name = NULL;
+		msg.msg_namelen = 0;
+		msg.msg_iov = &iov;
+		msg.msg_iovlen = 1;
+		msg.msg_control = cmsgu.control;
+		msg.msg_controllen = sizeof(cmsgu.control);
+		size = recvmsg (sock, &msg, 0);
+		if (size < 0) {
+			perror ("recvmsg");
+			exit(1);
+		}
+		if ((msg.msg_flags & MSG_TRUNC) ||
+		    (msg.msg_flags & MSG_CTRUNC)) {
+			fprintf (stderr, "control message truncated");
+			exit(1);
+		}
+		cmsg = CMSG_FIRSTHDR(&msg);
+		if (cmsg && cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
+			if (cmsg->cmsg_level != SOL_SOCKET) {
+				fprintf (stderr, "invalid cmsg_level %d\n",
+					 cmsg->cmsg_level);
+				exit(1);
+			}
+			if (cmsg->cmsg_type != SCM_RIGHTS) {
+				fprintf (stderr, "invalid cmsg_type %d\n",
+					 cmsg->cmsg_type);
+				exit(1);
+			}
+
+			*fd = *((int *) CMSG_DATA(cmsg));
+			printf ("received fd %d\n", *fd);
+		} else
+			*fd = -1;
+	} else {
+		size = read (sock, buf, bufsize);
+		if (size < 0) {
+			perror("read");
+			exit(1);
+		}
+	}
+	return size;
+}
+
+ssize_t
+sock_fd_write(int sock, void *buf, ssize_t buflen, int fd)
+{
+	ssize_t		size;
+	struct msghdr	msg;
+	struct iovec	iov;
+	union {
+		struct cmsghdr	cmsghdr;
+		char		control[CMSG_SPACE(sizeof (int))];
+	} cmsgu;
+	struct cmsghdr	*cmsg;
+
+	iov.iov_base = buf;
+	iov.iov_len = buflen;
+
+	msg.msg_name = NULL;
+	msg.msg_namelen = 0;
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	if (fd != -1) {
+		msg.msg_control = cmsgu.control;
+		msg.msg_controllen = sizeof(cmsgu.control);
+
+		cmsg = CMSG_FIRSTHDR(&msg);
+		cmsg->cmsg_len = CMSG_LEN(sizeof (int));
+		cmsg->cmsg_level = SOL_SOCKET;
+		cmsg->cmsg_type = SCM_RIGHTS;
+
+		printf ("passing fd %d\n", fd);
+		*((int *) CMSG_DATA(cmsg)) = fd;
+	} else {
+		msg.msg_control = NULL;
+		msg.msg_controllen = 0;
+		printf ("not passing fd\n");
+	}
+
+	size = sendmsg(sock, &msg, 0);
+
+	if (size < 0)
+		perror ("sendmsg");
+	return size;
+}