slirp: Fix guestfwd for incoming data

Unless a virtual server address was explicitly defined (which is
impossible with the legacy -net channel format), guestfwd did not
properly forwarded host->guest packets. This patch fixes it.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/slirp/libslirp.h b/slirp/libslirp.h
index 3bcc392..93087ed 100644
--- a/slirp/libslirp.h
+++ b/slirp/libslirp.h
@@ -33,7 +33,7 @@
 int slirp_remove_hostfwd(Slirp *slirp, int is_udp,
                          struct in_addr host_addr, int host_port);
 int slirp_add_exec(Slirp *slirp, int do_pty, const void *args,
-                   struct in_addr guest_addr, int guest_port);
+                   struct in_addr *guest_addr, int guest_port);
 
 void slirp_connection_info(Slirp *slirp, Monitor *mon);