slirp: Do not allow to remove non-hostfwd sockets

Prevent that the users accidentally shoots down dynamic sockets. This
allows to remove looping for removals as there can now only be one
match.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/net.c b/net.c
index ee321ab..603e77c 100644
--- a/net.c
+++ b/net.c
@@ -880,7 +880,7 @@
     char buf[256] = "";
     const char *p = src_str;
     int is_udp = 0;
-    int n;
+    int err;
 
     if (!slirp_inited) {
         monitor_printf(mon, "user mode network stack not in use\n");
@@ -909,10 +909,10 @@
 
     host_port = atoi(p);
 
-    n = slirp_remove_hostfwd(is_udp, host_addr, host_port);
+    err = slirp_remove_hostfwd(is_udp, host_addr, host_port);
 
-    monitor_printf(mon, "removed %d host forwarding rules for %s\n", n,
-                   src_str);
+    monitor_printf(mon, "host forwarding rule for %s %s\n", src_str,
+                   err ? "removed" : "not found");
     return;
 
  fail_syntax: