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Handle bi-directional communication for fd migration

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libvirt prefers opening the TCP connection itself, for two reasons.
First, connection failed errors can be detected easier, without having
to parse qemu's error output.
Second, libvirt might be asked to secure the transfer by tunnelling the
communication through an TLS layer.
Therefore, libvirt opens the TCP connection itself and passes an FD to qemu
using QMP and a POSIX-specific mechanism.

Hence, in order to make the reverse-path work in such cases, qemu needs to
distinguish if the transmitted FD is a socket (reverse-path available)
or not (reverse-path might not be available) and use the corresponding
abstraction.

Signed-off-by: Cristian Klein <cristian.klein@cs.umu.se>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
This commit is contained in:
Cristian Klein 2015-01-08 11:11:31 +00:00 committed by Amit Shah
parent e1a8c9b67f
commit 131fe9b843
1 changed files with 22 additions and 2 deletions
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24
migration/fd.c
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@ -31,13 +31,29 @@
do { } while (0)
#endif
static bool fd_is_socket(int fd)
{
struct stat stat;
int ret = fstat(fd, &stat);
if (ret == -1) {
/* When in doubt say no */
return false;
}
return S_ISSOCK(stat.st_mode);
}
void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **errp)
{
int fd = monitor_get_fd(cur_mon, fdname, errp);
if (fd == -1) {
return;
}
s->file = qemu_fdopen(fd, "wb");
if (fd_is_socket(fd)) {
s->file = qemu_fopen_socket(fd, "wb");
} else {
s->file = qemu_fdopen(fd, "wb");
}
migrate_fd_connect(s);
}
@ -58,7 +74,11 @@ void fd_start_incoming_migration(const char *infd, Error **errp)
DPRINTF("Attempting to start an incoming migration via fd\n");
fd = strtol(infd, NULL, 0);
f = qemu_fdopen(fd, "rb");
if (fd_is_socket(fd)) {
f = qemu_fopen_socket(fd, "rb");
} else {
f = qemu_fdopen(fd, "rb");
}
if(f == NULL) {
error_setg_errno(errp, errno, "failed to open the source descriptor");
return;