slirp: use libslirp migration code

slirp migration code uses QEMU vmstate so far, when building WITH_QEMU.

Introduce slirp_state_{load,save,version}() functions to move the
state saving handling to libslirp side.

So far, the bitstream compatibility should remain equal with current
QEMU, as this is effectively using the same code, with the same format
etc. When libslirp is made standalone, we will need some mechanism to
ensure bitstream compatibility regardless of the libslirp version
installed. See the FIXME note in the code.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20190212162524.31504-3-marcandre.lureau@redhat.com>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

include/migration/qemu-file-types.h

@@ -25,6 +25,8 @@
 #ifndef QEMU_FILE_H
 #define QEMU_FILE_H
 
+int qemu_file_get_error(QEMUFile *f);
+
 void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, size_t size);
 void qemu_put_byte(QEMUFile *f, int v);
 

migration/qemu-file.h

@@ -149,7 +149,6 @@ void qemu_update_position(QEMUFile *f, size_t size);
 void qemu_file_reset_rate_limit(QEMUFile *f);
 void qemu_file_set_rate_limit(QEMUFile *f, int64_t new_rate);
 int64_t qemu_file_get_rate_limit(QEMUFile *f);
-int qemu_file_get_error(QEMUFile *f);
 void qemu_file_set_error(QEMUFile *f, int ret);
 int qemu_file_shutdown(QEMUFile *f);
 QEMUFile *qemu_file_get_return_path(QEMUFile *f);

net/slirp.c

@@ -44,6 +44,8 @@
 #include "qapi/error.h"
 #include "qapi/qmp/qdict.h"
 #include "util.h"
+#include "migration/register.h"
+#include "migration/qemu-file-types.h"
 
 static int get_str_sep(char *buf, int buf_size, const char **pp, int sep)
 {
@@ -146,6 +148,7 @@ static void net_slirp_cleanup(NetClientState *nc)
 
     g_slist_free_full(s->fwd, slirp_free_fwd);
     main_loop_poll_remove_notifier(&s->poll_notifier);
+    unregister_savevm(NULL, "slirp", s->slirp);
     slirp_cleanup(s->slirp);
     if (s->exit_notifier.notify) {
         qemu_remove_exit_notifier(&s->exit_notifier);
@@ -303,6 +306,46 @@ static void net_slirp_poll_notify(Notifier *notifier, void *data)
     }
 }
 
+static ssize_t
+net_slirp_stream_read(void *buf, size_t size, void *opaque)
+{
+    QEMUFile *f = opaque;
+
+    return qemu_get_buffer(f, buf, size);
+}
+
+static ssize_t
+net_slirp_stream_write(const void *buf, size_t size, void *opaque)
+{
+    QEMUFile *f = opaque;
+
+    qemu_put_buffer(f, buf, size);
+    if (qemu_file_get_error(f)) {
+        return -1;
+    }
+
+    return size;
+}
+
+static int net_slirp_state_load(QEMUFile *f, void *opaque, int version_id)
+{
+    Slirp *slirp = opaque;
+
+    return slirp_state_load(slirp, version_id, net_slirp_stream_read, f);
+}
+
+static void net_slirp_state_save(QEMUFile *f, void *opaque)
+{
+    Slirp *slirp = opaque;
+
+    slirp_state_save(slirp, net_slirp_stream_write, f);
+}
+
+static SaveVMHandlers savevm_slirp_state = {
+    .save_state = net_slirp_state_save,
+    .load_state = net_slirp_state_load,
+};
+
 static int net_slirp_init(NetClientState *peer, const char *model,
                           const char *name, int restricted,
                           bool ipv4, const char *vnetwork, const char *vhost,
@@ -523,6 +566,18 @@ static int net_slirp_init(NetClientState *peer, const char *model,
                           &slirp_cb, s);
     QTAILQ_INSERT_TAIL(&slirp_stacks, s, entry);
 
+    /*
+     * Make sure the current bitstream version of slirp is 4, to avoid
+     * QEMU migration incompatibilities, if upstream slirp bumped the
+     * version.
+     *
+     * FIXME: use bitfields of features? teach libslirp to save with
+     * specific version?
+     */
+    g_assert(slirp_state_version() == 4);
+    register_savevm_live(NULL, "slirp", 0, slirp_state_version(),
+                         &savevm_slirp_state, s->slirp);
+
     s->poll_notifier.notify = net_slirp_poll_notify;
     main_loop_poll_add_notifier(&s->poll_notifier);
 

slirp/libslirp.h

@@ -102,6 +102,14 @@ void slirp_socket_recv(Slirp *slirp, struct in_addr guest_addr,
                        int guest_port, const uint8_t *buf, int size);
 size_t slirp_socket_can_recv(Slirp *slirp, struct in_addr guest_addr,
                              int guest_port);
+
+void slirp_state_save(Slirp *s, SlirpWriteCb write_cb, void *opaque);
+
+int slirp_state_load(Slirp *s, int version_id,
+                     SlirpReadCb read_cb, void *opaque);
+
+int slirp_state_version(void);
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif

slirp/slirp.c

@@ -23,9 +23,6 @@
  */
 #include "slirp.h"
 
-#ifdef WITH_QEMU
-#include "state.h"
-#endif
 
 #ifndef _WIN32
 #include <net/if.h>
@@ -326,9 +323,6 @@ Slirp *slirp_init(int restricted, bool in_enabled, struct in_addr vnetwork,
         translate_dnssearch(slirp, vdnssearch);
     }
 
-#ifdef WITH_QEMU
-    slirp_state_register(slirp);
-#endif
     return slirp;
 }
 
@@ -342,9 +336,6 @@ void slirp_cleanup(Slirp *slirp)
         g_free(e);
     }
 
-#ifdef WITH_QEMU
-    slirp_state_unregister(slirp);
-#endif
     ip_cleanup(slirp);
     ip6_cleanup(slirp);
     m_cleanup(slirp);

slirp/state.c

@@ -21,13 +21,10 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-#include "qemu/osdep.h"
-
 #include "slirp.h"
+#include "vmstate.h"
 #include "state.h"
-#include "migration/vmstate.h"
-#include "migration/qemu-file-types.h"
-#include "migration/register.h"
+#include "stream.h"
 
 static int slirp_tcp_post_load(void *opaque, int version)
 {
@@ -180,7 +177,7 @@ static int slirp_socket_pre_load(void *opaque)
 #else
 /* Win uses u_long rather than uint32_t - but it's still 32bits long */
 #define VMSTATE_SIN4_ADDR(f, s, t) VMSTATE_SINGLE_TEST(f, s, t, 0, \
-                                       vmstate_info_uint32, u_long)
+                                       slirp_vmstate_info_uint32, u_long)
 #endif
 
 /* The OS provided ss_family field isn't that portable; it's size
@@ -322,10 +319,13 @@ static const VMStateDescription vmstate_slirp = {
     }
 };
 
-static void slirp_state_save(QEMUFile *f, void *opaque)
+void slirp_state_save(Slirp *slirp, SlirpWriteCb write_cb, void *opaque)
 {
-    Slirp *slirp = opaque;
     struct gfwd_list *ex_ptr;
+    SlirpOStream f = {
+        .write_cb = write_cb,
+        .opaque = opaque,
+    };
 
     for (ex_ptr = slirp->guestfwd_list; ex_ptr; ex_ptr = ex_ptr->ex_next)
         if (ex_ptr->write_cb) {
@@ -336,25 +336,29 @@ static void slirp_state_save(QEMUFile *f, void *opaque)
                 continue;
             }
 
-            qemu_put_byte(f, 42);
-            vmstate_save_state(f, &vmstate_slirp_socket, so, NULL);
+            slirp_ostream_write_u8(&f, 42);
+            slirp_vmstate_save_state(&f, &vmstate_slirp_socket, so);
         }
-    qemu_put_byte(f, 0);
+    slirp_ostream_write_u8(&f, 0);
 
-    vmstate_save_state(f, &vmstate_slirp, slirp, NULL);
+    slirp_vmstate_save_state(&f, &vmstate_slirp, slirp);
 }
 
 
-static int slirp_state_load(QEMUFile *f, void *opaque, int version_id)
+int slirp_state_load(Slirp *slirp, int version_id,
+                     SlirpReadCb read_cb, void *opaque)
 {
-    Slirp *slirp = opaque;
     struct gfwd_list *ex_ptr;
+    SlirpIStream f = {
+        .read_cb = read_cb,
+        .opaque = opaque,
+    };
 
-    while (qemu_get_byte(f)) {
+    while (slirp_istream_read_u8(&f)) {
         int ret;
         struct socket *so = socreate(slirp);
 
-        ret = vmstate_load_state(f, &vmstate_slirp_socket, so, version_id);
+        ret = slirp_vmstate_load_state(&f, &vmstate_slirp_socket, so, version_id);
         if (ret < 0) {
             return ret;
         }
@@ -375,20 +379,10 @@ static int slirp_state_load(QEMUFile *f, void *opaque, int version_id)
         }
     }
 
-    return vmstate_load_state(f, &vmstate_slirp, slirp, version_id);
+    return slirp_vmstate_load_state(&f, &vmstate_slirp, slirp, version_id);
 }
 
-void slirp_state_register(Slirp *slirp)
+int slirp_state_version(void)
 {
-    static SaveVMHandlers savevm_slirp_state = {
-        .save_state = slirp_state_save,
-        .load_state = slirp_state_load,
-    };
-
-    register_savevm_live(NULL, "slirp", 0, 4, &savevm_slirp_state, slirp);
-}
-
-void slirp_state_unregister(Slirp *slirp)
-{
-    unregister_savevm(NULL, "slirp", slirp);
+    return 4;
 }

slirp/state.h

@@ -1,9 +0,0 @@
-#ifndef SLIRP_STATE_H_
-#define SLIRP_STATE_H_
-
-#include "libslirp.h"
-
-void slirp_state_register(Slirp *slirp);
-void slirp_state_unregister(Slirp *slirp);
-
-#endif /* SLIRP_STATE_H_ */