Implement two new functions for sending descriptor and receving descriptor

over UNIX domain sockets and socket pairs.
This is in preparation for capsicum.

MFC after:	1 week

1 files changed, 69 insertions, 6 deletions

diff --git a/sbin/hastd/proto_common.c b/sbin/hastd/proto_common.c
index 89c637d..d638d3b 100644
--- a/sbin/hastd/proto_common.c
+++ b/sbin/hastd/proto_common.c
@@ -46,18 +46,18 @@ __FBSDID("$FreeBSD$");
 #endif
 
 int
-proto_common_send(int fd, const unsigned char *data, size_t size)
+proto_common_send(int sock, const unsigned char *data, size_t size)
 {
 	ssize_t done;
 	size_t sendsize;
 
-	PJDLOG_ASSERT(fd >= 0);
+	PJDLOG_ASSERT(sock >= 0);
 	PJDLOG_ASSERT(data != NULL);
 	PJDLOG_ASSERT(size > 0);
 
 	do {
 		sendsize = size < MAX_SEND_SIZE ? size : MAX_SEND_SIZE;
-		done = send(fd, data, sendsize, MSG_NOSIGNAL);
+		done = send(sock, data, sendsize, MSG_NOSIGNAL);
 		if (done == 0)
 			return (ENOTCONN);
 		else if (done < 0) {
@@ -73,16 +73,16 @@ proto_common_send(int fd, const unsigned char *data, size_t size)
 }
 
 int
-proto_common_recv(int fd, unsigned char *data, size_t size)
+proto_common_recv(int sock, unsigned char *data, size_t size)
 {
 	ssize_t done;
 
-	PJDLOG_ASSERT(fd >= 0);
+	PJDLOG_ASSERT(sock >= 0);
 	PJDLOG_ASSERT(data != NULL);
 	PJDLOG_ASSERT(size > 0);
 
 	do {
-		done = recv(fd, data, size, MSG_WAITALL);
+		done = recv(sock, data, size, MSG_WAITALL);
 	} while (done == -1 && errno == EINTR);
 	if (done == 0)
 		return (ENOTCONN);
@@ -90,3 +90,66 @@ proto_common_recv(int fd, unsigned char *data, size_t size)
 		return (errno);
 	return (0);
 }
+
+int
+proto_common_descriptor_send(int sock, int fd)
+{
+	unsigned char ctrl[CMSG_SPACE(sizeof(fd))];
+	struct msghdr msg;
+	struct cmsghdr *cmsg;
+
+	PJDLOG_ASSERT(sock >= 0);
+	PJDLOG_ASSERT(fd >= 0);
+
+	bzero(&msg, sizeof(msg));
+	bzero(&ctrl, sizeof(ctrl));
+
+	msg.msg_iov = NULL;
+	msg.msg_iovlen = 0;
+	msg.msg_control = ctrl;
+	msg.msg_controllen = sizeof(ctrl);
+
+	cmsg = CMSG_FIRSTHDR(&msg);
+	cmsg->cmsg_level = SOL_SOCKET;
+	cmsg->cmsg_type = SCM_RIGHTS;
+	cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
+	*((int *)CMSG_DATA(cmsg)) = fd;
+
+	if (sendmsg(sock, &msg, 0) == -1)
+		return (errno);
+
+	return (0);
+}
+
+int
+proto_common_descriptor_recv(int sock, int *fdp)
+{
+	unsigned char ctrl[CMSG_SPACE(sizeof(*fdp))];
+	struct msghdr msg;
+	struct cmsghdr *cmsg;
+
+	PJDLOG_ASSERT(sock >= 0);
+	PJDLOG_ASSERT(fdp != NULL);
+
+	bzero(&msg, sizeof(msg));
+	bzero(&ctrl, sizeof(ctrl));
+
+	msg.msg_iov = NULL;
+	msg.msg_iovlen = 0;
+	msg.msg_control = ctrl;
+	msg.msg_controllen = sizeof(ctrl);
+
+	if (recvmsg(sock, &msg, 0) == -1)
+		return (errno);
+
+	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
+	    cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+		if (cmsg->cmsg_level == SOL_SOCKET &&
+		    cmsg->cmsg_type == SCM_RIGHTS) {
+			*fdp = *((int *)CMSG_DATA(cmsg));
+			return (0);
+		}
+	}
+
+	return (ENOENT);
+}