close(fd);
return;
}
+ /*
+ * Disable IP (*not* TCP) options. In particular, this makes it impossible
+ * to use source routing to connect to the server. If we didn't do this
+ * (and if intermediate networks didn't drop source-routed packets), an
+ * attacker could successfully IP spoof us...and even return the anti-spoof
+ * ping, because the options would cause the packet to be routed back to
+ * the spoofer's machine. When we disable the IP options, we delete the
+ * source route, and the normal routing takes over.
+ */
+ os_disable_options(fd);
/*
* Add this local client to the IPcheck registry.