net: slirp: add support for CFI-friendly timer API

libslirp 4.7 introduces a CFI-friendly version of the .timer_new callback.
The new callback replaces the function pointer with an enum; invoking the
callback is done with a new function slirp_handle_timer.

Support the new API so that CFI can be made compatible with using a system
libslirp.

Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: Marc-André Lureau <malureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

net/slirp.c

@@ -184,10 +184,43 @@ static int64_t net_slirp_clock_get_ns(void *opaque)
     return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
 }
 
+typedef struct SlirpTimer SlirpTimer;
 struct SlirpTimer {
     QEMUTimer timer;
+#if SLIRP_CHECK_VERSION(4,7,0)
+    Slirp *slirp;
+    SlirpTimerId id;
+    void *cb_opaque;
+#endif
+};
+
+#if SLIRP_CHECK_VERSION(4,7,0)
+static void net_slirp_init_completed(Slirp *slirp, void *opaque)
+{
+    SlirpState *s = opaque;
+    s->slirp = slirp;
 }
 
+static void net_slirp_timer_cb(void *opaque)
+{
+    SlirpTimer *t = opaque;
+    slirp_handle_timer(t->slirp, t->id, t->cb_opaque);
+}
+
+static void *net_slirp_timer_new_opaque(SlirpTimerId id,
+                                        void *cb_opaque, void *opaque)
+{
+    SlirpState *s = opaque;
+    SlirpTimer *t = g_new(SlirpTimer, 1);
+    t->slirp = s->slirp;
+    t->id = id;
+    t->cb_opaque = cb_opaque;
+    timer_init_full(&t->timer, NULL, QEMU_CLOCK_VIRTUAL,
+                    SCALE_MS, QEMU_TIMER_ATTR_EXTERNAL,
+                    net_slirp_timer_cb, t);
+    return t;
+}
+#else
 static void *net_slirp_timer_new(SlirpTimerCb cb,
                                  void *cb_opaque, void *opaque)
 {
@@ -197,6 +230,7 @@ static void *net_slirp_timer_new(SlirpTimerCb cb,
                     cb, cb_opaque);
     return t;
 }
+#endif
 
 static void net_slirp_timer_free(void *timer, void *opaque)
 {
@@ -231,7 +265,12 @@ static const SlirpCb slirp_cb = {
     .send_packet = net_slirp_send_packet,
     .guest_error = net_slirp_guest_error,
     .clock_get_ns = net_slirp_clock_get_ns,
+#if SLIRP_CHECK_VERSION(4,7,0)
+    .init_completed = net_slirp_init_completed,
+    .timer_new_opaque = net_slirp_timer_new_opaque,
+#else
     .timer_new = net_slirp_timer_new,
+#endif
     .timer_free = net_slirp_timer_free,
     .timer_mod = net_slirp_timer_mod,
     .register_poll_fd = net_slirp_register_poll_fd,
@@ -578,7 +617,7 @@ static int net_slirp_init(NetClientState *peer, const char *model,
 
     s = DO_UPCAST(SlirpState, nc, nc);
 
-    cfg.version = 1;
+    cfg.version = SLIRP_CHECK_VERSION(4,7,0) ? 4 : 1;
     cfg.restricted = restricted;
     cfg.in_enabled = ipv4;
     cfg.vnetwork = net;