[Qemu-devel] [PATCH 1/6] qemu-fd-exchange: provide common methods for exchange fd

[Lei Li <lilei@linux.vnet.ibm.com>]

Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
---
 include/qemu/fd-exchange.h |   25 +++++++++++
 util/Makefile.objs         |    1 +
 util/qemu-fd-exchange.c    |   97 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 123 insertions(+), 0 deletions(-)
 create mode 100644 include/qemu/fd-exchange.h
 create mode 100644 util/qemu-fd-exchange.c

diff --git a/include/qemu/fd-exchange.h b/include/qemu/fd-exchange.h
new file mode 100644
index 0000000..6929026
--- /dev/null
+++ b/include/qemu/fd-exchange.h
@@ -0,0 +1,25 @@
+/*
+ * Internel common methods for exchange of FD
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef FD_EXCHANGE_H
+#define FD_EXCHANGE_H
+
+#include <sys/socket.h>
+
+union MsgControl {
+    struct cmsghdr cmsg;
+    char control[CMSG_SPACE(sizeof(int))];
+};
+
+ssize_t qemu_send_with_fd(int sockfd, int passed_fd,
+                          const void *buf, size_t len);
+
+ssize_t qemu_recv_with_fd(int sockfd, int *passed_fd,
+                          void *buf, size_t len);
+
+#endif
diff --git a/util/Makefile.objs b/util/Makefile.objs
index af3e5cb..2fb42bf 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -13,3 +13,4 @@ util-obj-y += hexdump.o
 util-obj-y += crc32c.o
 util-obj-y += throttle.o
 util-obj-y += getauxval.o
+util-obj-y += qemu-fd-exchange.o
diff --git a/util/qemu-fd-exchange.c b/util/qemu-fd-exchange.c
new file mode 100644
index 0000000..70a3206
--- /dev/null
+++ b/util/qemu-fd-exchange.c
@@ -0,0 +1,97 @@
+/*
+ * Internel common methods for exchange of FD
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/fd-exchange.h"
+#include "qemu-common.h"
+
+
+ssize_t qemu_send_with_fd(int sockfd, int passed_fd,
+                          const void *buf, size_t len)
+{
+    struct msghdr msg;
+    struct iovec iov;
+    struct cmsghdr *cmsg;
+    union MsgControl msg_control;
+    int retval;
+
+    iov.iov_base = (int *)buf;
+    iov.iov_len = len;
+
+    memset(&msg, 0, sizeof(msg));
+    msg.msg_iov = &iov;
+    msg.msg_iovlen = len;
+    msg.msg_control = &msg_control;
+    msg.msg_controllen = sizeof(msg_control);
+
+    if (passed_fd < 0) {
+        *(int *)buf = passed_fd;
+    } else {
+        msg.msg_control = &msg_control;
+        msg.msg_controllen = sizeof(msg_control);
+
+        cmsg = &msg_control.cmsg;
+        cmsg->cmsg_len = CMSG_LEN(sizeof(passed_fd));
+        cmsg->cmsg_level = SOL_SOCKET;
+        cmsg->cmsg_type = SCM_RIGHTS;
+        memcpy(CMSG_DATA(cmsg), &passed_fd, sizeof(passed_fd));
+
+    }
+
+    do {
+        retval = sendmsg(sockfd, &msg, 0);
+    } while (retval < 0 && errno == EINTR);
+
+    return retval;
+}
+
+ssize_t qemu_recv_with_fd(int sockfd, int *passed_fd,
+                          void *buf, size_t len)
+{
+    struct iovec iov;
+    struct msghdr msg;
+    struct cmsghdr *cmsg;
+    union MsgControl msg_control;
+    int retval;
+    int data = *(int *)buf;
+
+    iov.iov_base = buf;
+    iov.iov_len = len;
+
+    memset(&msg, 0, sizeof(msg));
+    msg.msg_iov = &iov;
+    msg.msg_iovlen = 1;
+    msg.msg_control = &msg_control;
+    msg.msg_controllen = sizeof(msg_control);
+
+    do {
+        retval = recvmsg(sockfd, &msg, 0);
+    } while (retval < 0 && errno == EINTR);
+
+    if (retval <= 0) {
+        return retval;
+    }
+
+    if (data != *(int *)buf) {
+        *passed_fd = data;
+        return 0;
+    }
+
+    for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+        if (cmsg->cmsg_len != CMSG_LEN(sizeof(int)) ||
+            cmsg->cmsg_level != SOL_SOCKET ||
+            cmsg->cmsg_type != SCM_RIGHTS) {
+            continue;
+        }
+
+        memcpy(passed_fd, CMSG_DATA(cmsg), sizeof(*passed_fd));
+        return 0;
+    }
+
+    *passed_fd = -ENFILE;
+    return retval;
+}
-- 
1.7.7.6