[CRIU] [PATCH 04/12] util-net: Add send_fds and recv_fds

[Cyrill Gorcunov]

We will need these helpers to transfer file
descriptors from dumpee to our space.

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
---
 include/util-net.h |    5 ++-
 util-net.c         |  120 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 124 insertions(+), 1 deletions(-)

diff --git a/include/util-net.h b/include/util-net.h
index 5993778..e96e603 100644
--- a/include/util-net.h
+++ b/include/util-net.h
@@ -26,9 +26,12 @@ struct scm_fdset {
 	struct iovec	iov;
 	char		msg_buf[CR_SCM_MSG_SIZE];
 	int		msg;	/* We are to send at least one byte */
-	int		nr_fds;
 };
 
 extern int send_fd(int sock, struct sockaddr_un *saddr, int len, int fd);
 extern int recv_fd(int sock);
+
+extern int send_fds(int sock, struct sockaddr_un *saddr, int saddr_len, int *fds, int nr_fds);
+extern int recv_fds(int sock, int *fds, int nr_fds);
+
 #endif
diff --git a/util-net.c b/util-net.c
index afd51bd..d4da6cc 100644
--- a/util-net.c
+++ b/util-net.c
@@ -1,8 +1,128 @@
 #include <sys/socket.h>
 #include <sys/un.h>
+#include <errno.h>
 
+#include "compiler.h"
+#include "types.h"
+#include "builtins.h"
 #include "syscall.h"
 
+#include "util-net.h"
+
+static void scm_fdset_init_chunk(struct scm_fdset *fdset, int nr_fds)
+{
+	struct cmsghdr *cmsg;
+	cmsg				= CMSG_FIRSTHDR(&fdset->hdr);
+	fdset->hdr.msg_controllen	= CMSG_LEN(sizeof(int) * nr_fds);
+	cmsg->cmsg_len			= fdset->hdr.msg_controllen;
+}
+
+static int *scm_fdset_init(struct scm_fdset *fdset, struct sockaddr_un *saddr, int saddr_len)
+{
+	struct cmsghdr *cmsg;
+
+	BUILD_BUG_ON(CR_SCM_MAX_FD > SCM_MAX_FD);
+	BUILD_BUG_ON(sizeof(fdset->msg_buf) < (CMSG_SPACE(sizeof(int) * CR_SCM_MAX_FD)));
+
+	fdset->msg			= 0;
+
+	fdset->iov.iov_base		= &fdset->msg;
+	fdset->iov.iov_len		= sizeof(fdset->msg);
+
+	fdset->hdr.msg_iov		= &fdset->iov;
+	fdset->hdr.msg_iovlen		= 1;
+	fdset->hdr.msg_name		= (struct sockaddr *)saddr;
+	fdset->hdr.msg_namelen		= saddr_len;
+
+	fdset->hdr.msg_control		= &fdset->msg_buf;
+	fdset->hdr.msg_controllen	= CMSG_LEN(sizeof(int) * CR_SCM_MAX_FD);
+
+	cmsg				= CMSG_FIRSTHDR(&fdset->hdr);
+	cmsg->cmsg_len			= fdset->hdr.msg_controllen;
+	cmsg->cmsg_level		= SOL_SOCKET;
+	cmsg->cmsg_type			= SCM_RIGHTS;
+
+	return (int *)CMSG_DATA(cmsg);
+}
+
+static int scm_fdset_send(int sock, struct scm_fdset *fdset)
+{
+	int ret = sys_sendmsg(sock, &fdset->hdr, 0);
+	if (ret <= 0)
+		return ret ? : -1;
+	return 0;
+}
+
+static int scm_fdset_recv(int sock, struct scm_fdset *fdset)
+{
+	struct cmsghdr *cmsg;
+	int ret, nr_fds;
+
+	ret = sys_recvmsg(sock, &fdset->hdr, 0);
+	if (ret <= 0)
+		return ret ? : -1;
+
+	cmsg = CMSG_FIRSTHDR(&fdset->hdr);
+	if (!cmsg || cmsg->cmsg_type != SCM_RIGHTS)
+		return -EINVAL;
+
+	nr_fds = (cmsg->cmsg_len - sizeof(struct cmsghdr)) / sizeof(int);
+
+	/*
+	 * In case if kernel screwed the recepient, most probably
+	 * the caller stack frame will be overwriten, just scream
+	 * and exit.
+	 *
+	 * FIXME Need to sanitize util.h to be able to include it
+	 * into files which do not have glibc and a couple of
+	 * sys_write_ helpers. Meawhile opencoded BUG_ON here.
+	 */
+	if (unlikely(nr_fds > CR_SCM_MAX_FD))
+		*(volatile unsigned long *)NULL = 0xdead0000 + __LINE__;
+
+	return nr_fds;
+}
+
+int send_fds(int sock, struct sockaddr_un *saddr, int saddr_len, int *fds, int nr_fds)
+{
+	struct scm_fdset fdset;
+	int *fds_tx, i, min_fd;
+
+	fds_tx = scm_fdset_init(&fdset, saddr, saddr_len);
+
+	for (i = min_fd = 0; i < nr_fds; i += min_fd) {
+		min_fd = min(CR_SCM_MAX_FD, nr_fds - i);
+		scm_fdset_init_chunk(&fdset, min_fd);
+		builtin_memcpy(fds_tx, &fds[i], sizeof(int) * min_fd);
+
+		if (scm_fdset_send(sock, &fdset))
+			return -1;
+	}
+
+	return 0;
+}
+
+int recv_fds(int sock, int *fds, int nr_fds)
+{
+	struct scm_fdset fdset;
+	int *fds_rx, i, min_fd;
+
+	fds_rx = scm_fdset_init(&fdset, NULL, 0);
+
+	for (i = min_fd = 0; i < nr_fds; i += min_fd) {
+		min_fd = min(CR_SCM_MAX_FD, nr_fds - i);
+		scm_fdset_init_chunk(&fdset, min_fd);
+
+		min_fd = scm_fdset_recv(sock, &fdset);
+		if (min_fd < 0)
+			return min_fd;
+
+		builtin_memcpy(&fds[i], fds_rx, sizeof(int) * min_fd);
+	}
+
+	return 0;
+}
+
 int send_fd(int sock, struct sockaddr_un *saddr, int len, int fd)
 {
 	char cmsgbuf[CMSG_SPACE(sizeof(int))];
-- 
1.7.7.6