On 30/06/2024 20:44, Steve Sistare wrote:
Define functions to put/get file descriptors to/from a QEMUFile, for qio
channels that support SCM_RIGHTS. Maintain ordering such that
put(A), put(fd), put(B)
followed by
get(A), get(fd), get(B)
always succeeds. Other get orderings may succeed but are not guaranteed.
Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
---
migration/qemu-file.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++---
migration/qemu-file.h | 2 ++
migration/trace-events | 2 ++
3 files changed, 83 insertions(+), 4 deletions(-)
diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index b6d2f58..424c27d 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -37,6 +37,11 @@
#define IO_BUF_SIZE 32768
#define MAX_IOV_SIZE MIN_CONST(IOV_MAX, 64)
+typedef struct FdEntry {
+ QTAILQ_ENTRY(FdEntry) entry;
+ int fd;
+} FdEntry;
+
struct QEMUFile {
QIOChannel *ioc;
bool is_writable;
@@ -51,6 +56,9 @@ struct QEMUFile {
int last_error;
Error *last_error_obj;
+
+ bool fd_pass;
+ QTAILQ_HEAD(, FdEntry) fds;
};
/*
@@ -109,6 +117,8 @@ static QEMUFile *qemu_file_new_impl(QIOChannel *ioc, bool
is_writable)
object_ref(ioc);
f->ioc = ioc;
f->is_writable = is_writable;
+ f->fd_pass = qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_FD_PASS);
+ QTAILQ_INIT(&f->fds);
return f;
}
@@ -310,6 +320,10 @@ static ssize_t coroutine_mixed_fn
qemu_fill_buffer(QEMUFile *f)
int len;
int pending;
Error *local_error = NULL;
+ g_autofree int *fds = NULL;
+ size_t nfd = 0;
+ int **pfds = f->fd_pass ? &fds : NULL;
+ size_t *pnfd = f->fd_pass ? &nfd : NULL;
assert(!qemu_file_is_writable(f));
@@ -325,10 +339,9 @@ static ssize_t coroutine_mixed_fn qemu_fill_buffer(QEMUFile *f)
}
do {
- len = qio_channel_read(f->ioc,
- (char *)f->buf + pending,
- IO_BUF_SIZE - pending,
- &local_error);
+ struct iovec iov = { f->buf + pending, IO_BUF_SIZE - pending };
+ len = qio_channel_readv_full(f->ioc, &iov, 1, pfds, pnfd, 0,
+ &local_error);
if (len == QIO_CHANNEL_ERR_BLOCK) {
if (qemu_in_coroutine()) {
qio_channel_yield(f->ioc, G_IO_IN);
@@ -348,9 +361,65 @@ static ssize_t coroutine_mixed_fn
qemu_fill_buffer(QEMUFile *f)
qemu_file_set_error_obj(f, len, local_error);
}
+ for (int i = 0; i < nfd; i++) {
+ FdEntry *fde = g_new0(FdEntry, 1);
+ fde->fd = fds[i];
+ QTAILQ_INSERT_TAIL(&f->fds, fde, entry);
+ }
+
return len;
}
+int qemu_file_put_fd(QEMUFile *f, int fd)
+{
+ int ret = 0;
+ QIOChannel *ioc = qemu_file_get_ioc(f);
+ Error *err = NULL;
+ struct iovec iov = { (void *)" ", 1 };
+
+ /*
+ * Send a dummy byte so qemu_fill_buffer on the receiving side does not
+ * fail with a len=0 error. Flush first to maintain ordering wrt other
+ * data.
+ */
+
+ qemu_fflush(f);
+ if (qio_channel_writev_full(ioc, &iov, 1, &fd, 1, 0, &err) < 1) {
+ error_report_err(error_copy(err));
+ qemu_file_set_error_obj(f, -EIO, err);
+ ret = -1;
+ }
+ trace_qemu_file_put_fd(f->ioc->name, fd, ret);
+ return 0;
I think you intended return ret?
+}
+
+int qemu_file_get_fd(QEMUFile *f)
+{
+ int fd = -1;
+ FdEntry *fde;
+
+ if (!f->fd_pass) {
+ Error *err = NULL;
+ error_setg(&err, "%s does not support fd passing", f->ioc->name);
+ error_report_err(error_copy(err));
+ qemu_file_set_error_obj(f, -EIO, err);
+ goto out;
+ }
+
+ /* Force the dummy byte and its fd passenger to appear. */
+ qemu_peek_byte(f, 0);
+
+ fde = QTAILQ_FIRST(&f->fds);
+ if (fde) {
+ qemu_get_byte(f); /* Drop the dummy byte */
+ fd = fde->fd;
+ QTAILQ_REMOVE(&f->fds, fde, entry);
+ }
+out:
+ trace_qemu_file_get_fd(f->ioc->name, fd);
+ return fd;
+}
+
/** Closes the file
*
* Returns negative error value if any error happened on previous operations
or
@@ -361,11 +430,17 @@ static ssize_t coroutine_mixed_fn
qemu_fill_buffer(QEMUFile *f)
*/
int qemu_fclose(QEMUFile *f)
{
+ FdEntry *fde, *next;
int ret = qemu_fflush(f);
int ret2 = qio_channel_close(f->ioc, NULL);
if (ret >= 0) {
ret = ret2;
}
+ QTAILQ_FOREACH_SAFE(fde, &f->fds, entry, next) {
+ warn_report("qemu_fclose: received fd %d was never claimed", fde->fd);
+ close(fde->fd);
+ g_free(fde);
+ }
g_clear_pointer(&f->ioc, object_unref);
error_free(f->last_error_obj);
g_free(f);
diff --git a/migration/qemu-file.h b/migration/qemu-file.h
index 11c2120..3e47a20 100644
--- a/migration/qemu-file.h
+++ b/migration/qemu-file.h
@@ -79,5 +79,7 @@ size_t qemu_get_buffer_at(QEMUFile *f, const uint8_t *buf,
size_t buflen,
off_t pos);
QIOChannel *qemu_file_get_ioc(QEMUFile *file);
+int qemu_file_put_fd(QEMUFile *f, int fd);
+int qemu_file_get_fd(QEMUFile *f);
#endif
diff --git a/migration/trace-events b/migration/trace-events
index 173f2c0..064b22d 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -88,6 +88,8 @@ put_qlist_end(const char *field_name, const char *vmsd_name)
"%s(%s)"
# qemu-file.c
qemu_file_fclose(void) ""
+qemu_file_put_fd(const char *name, int fd, int ret) "ioc %s, fd %d -> status
%d"
+qemu_file_get_fd(const char *name, int fd) "ioc %s -> fd %d"
# ram.c
get_queued_page(const char *block_name, uint64_t tmp_offset, unsigned long page_abs)
"%s/0x%" PRIx64 " page_abs=0x%lx"
