[Qemu-devel] [PATCH 3/8] migration-local: add send_pipefd()

[Lei Li]

This patch adds send_pipefd() to pass the pipe file descriptor
to destination process.

Signed-off-by: Lei Li <address@hidden>
---
 include/migration/qemu-file.h |    1 +
 migration-local.c             |   57 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 0 deletions(-)

diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index 39ad0bd..5fad65f 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -101,6 +101,7 @@ QEMUFile *qemu_fopen_socket(int fd, const char *mode);
 QEMUFile *qemu_popen_cmd(const char *command, const char *mode);
 QEMUFile *qemu_fopen_pipe(int sockfd, const char *mode);
 
+int send_pipefd(int sockfd, int pipefd);
 int qemu_get_fd(QEMUFile *f);
 int qemu_fclose(QEMUFile *f);
 int64_t qemu_ftell(QEMUFile *f);
diff --git a/migration-local.c b/migration-local.c
index d90b2ff..3875b27 100644
--- a/migration-local.c
+++ b/migration-local.c
@@ -132,3 +132,60 @@ QEMUFile *qemu_fopen_pipe(int pipefd, const char *mode)
 
     return s->file;
 }
+
+union MsgControl {
+    struct cmsghdr cmsg;
+    char control[CMSG_SPACE(sizeof(int))];
+};
+
+/*
+ * Pass a pipe file descriptor to another process.
+ *
+ * Return negative value If pipefd < 0. Return 0 on
+ * success.
+ *
+ */
+
+int send_pipefd(int sockfd, int pipefd)
+{
+    struct cmsghdr *cmsg;
+    struct iovec iov[1];
+    struct msghdr msg;
+    union MsgControl msg_control;
+
+    char msbuf[1] = { 0x01 };
+    int ret;
+
+    iov[0].iov_base = msbuf;
+    iov[0].iov_len = sizeof(msbuf);
+
+    msg.msg_iov = iov;
+    msg.msg_iovlen = 1;
+
+    if (pipefd < 0) {
+        msg.msg_control = NULL;
+        msg.msg_controllen = 0;
+        /* Negative status means error */
+        msbuf[0] = pipefd;
+    } else {
+        msg.msg_control = &msg_control;
+        msg.msg_controllen = sizeof(msg_control);
+
+        cmsg = &msg_control.cmsg;
+        cmsg->cmsg_level = SOL_SOCKET;
+        cmsg->cmsg_type = SCM_RIGHTS;
+        cmsg->cmsg_len = CMSG_LEN(sizeof(pipefd));
+
+        /* The pipefd to be passed */
+        memcpy(CMSG_DATA(cmsg), &pipefd, sizeof(pipefd));
+    }
+
+    do {
+        ret = sendmsg(sockfd, &msg, 0);
+    } while (ret < 0 && errno == EINTR);
+
+    if (ret < 0) {
+        return ret;
+    }
+    return 0;
+}
-- 
1.7.7.6