Initial checkin from CRI-O repo

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

1 files changed, 149 insertions, 0 deletions

diff --git a/conmon/cmsg.c b/conmon/cmsg.c
new file mode 100644
index 000000000..c44db2ef1
--- /dev/null
+++ b/conmon/cmsg.c
@@ -0,0 +1,149 @@
+/*
+ * Copyright 2016 SUSE LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* NOTE: This code comes directly from runc/libcontainer/utils/cmsg.c. */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "cmsg.h"
+
+#define error(fmt, ...)							\
+	({								\
+		fprintf(stderr, "nsenter: " fmt ": %m\n", ##__VA_ARGS__); \
+		errno = ECOMM;						\
+		goto err; /* return value */				\
+	})
+
+/*
+ * Sends a file descriptor along the sockfd provided. Returns the return
+ * value of sendmsg(2). Any synchronisation and preparation of state
+ * should be done external to this (we expect the other side to be in
+ * recvfd() in the code).
+ */
+ssize_t sendfd(int sockfd, struct file_t file)
+{
+	struct msghdr msg = {0};
+	struct iovec iov[1] = {0};
+	struct cmsghdr *cmsg;
+	int *fdptr;
+
+	union {
+		char buf[CMSG_SPACE(sizeof(file.fd))];
+		struct cmsghdr align;
+	} u;
+
+	/*
+	 * We need to send some other data along with the ancillary data,
+	 * otherwise the other side won't recieve any data. This is very
+	 * well-hidden in the documentation (and only applies to
+	 * SOCK_STREAM). See the bottom part of unix(7).
+	 */
+	iov[0].iov_base = file.name;
+	iov[0].iov_len = strlen(file.name) + 1;
+
+	msg.msg_name = NULL;
+	msg.msg_namelen = 0;
+	msg.msg_iov = iov;
+	msg.msg_iovlen = 1;
+	msg.msg_control = u.buf;
+	msg.msg_controllen = sizeof(u.buf);
+
+	cmsg = CMSG_FIRSTHDR(&msg);
+	cmsg->cmsg_level = SOL_SOCKET;
+	cmsg->cmsg_type = SCM_RIGHTS;
+	cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+
+	fdptr = (int *) CMSG_DATA(cmsg);
+	memcpy(fdptr, &file.fd, sizeof(int));
+
+	return sendmsg(sockfd, &msg, 0);
+}
+
+/*
+ * Receives a file descriptor from the sockfd provided. Returns the file
+ * descriptor as sent from sendfd(). It will return the file descriptor
+ * or die (literally) trying. Any synchronisation and preparation of
+ * state should be done external to this (we expect the other side to be
+ * in sendfd() in the code).
+ */
+struct file_t recvfd(int sockfd)
+{
+	struct msghdr msg = {0};
+	struct iovec iov[1] = {0};
+	struct cmsghdr *cmsg;
+	struct file_t file = {0};
+	int *fdptr;
+	int olderrno;
+
+	union {
+		char buf[CMSG_SPACE(sizeof(file.fd))];
+		struct cmsghdr align;
+	} u;
+
+	/* Allocate a buffer. */
+	/* TODO: Make this dynamic with MSG_PEEK. */
+	file.name = malloc(TAG_BUFFER);
+	if (!file.name)
+		error("recvfd: failed to allocate file.tag buffer\n");
+
+	/*
+	 * We need to "recieve" the non-ancillary data even though we don't
+	 * plan to use it at all. Otherwise, things won't work as expected.
+	 * See unix(7) and other well-hidden documentation.
+	 */
+	iov[0].iov_base = file.name;
+	iov[0].iov_len = TAG_BUFFER;
+
+	msg.msg_name = NULL;
+	msg.msg_namelen = 0;
+	msg.msg_iov = iov;
+	msg.msg_iovlen = 1;
+	msg.msg_control = u.buf;
+	msg.msg_controllen = sizeof(u.buf);
+
+	ssize_t ret = recvmsg(sockfd, &msg, 0);
+	if (ret < 0)
+		goto err;
+
+	cmsg = CMSG_FIRSTHDR(&msg);
+	if (!cmsg)
+		error("recvfd: got NULL from CMSG_FIRSTHDR");
+	if (cmsg->cmsg_level != SOL_SOCKET)
+		error("recvfd: expected SOL_SOCKET in cmsg: %d", cmsg->cmsg_level);
+	if (cmsg->cmsg_type != SCM_RIGHTS)
+		error("recvfd: expected SCM_RIGHTS in cmsg: %d", cmsg->cmsg_type);
+	if (cmsg->cmsg_len != CMSG_LEN(sizeof(int)))
+		error("recvfd: expected correct CMSG_LEN in cmsg: %lu", cmsg->cmsg_len);
+
+	fdptr = (int *) CMSG_DATA(cmsg);
+	if (!fdptr || *fdptr < 0)
+		error("recvfd: recieved invalid pointer");
+
+	file.fd = *fdptr;
+	return file;
+
+err:
+	olderrno = errno;
+	free(file.name);
+	errno = olderrno;
+	return (struct file_t){0};
+}