Red Hat Bugzilla – Bug 71538
libwrap causes unexpected failures / denial of service
Last modified: 2007-04-18 12:45:31 EDT
From Bugzilla Helper: User-Agent: Mozilla/5.0 Galeon/1.2.5 (X11; Linux i686; U;) Gecko/0 Description of problem: I worked with tftp but this seems general. If a client's ip does not resolve, then tftp does not start. Error text is "libwrap refused connection to tftp from ...." If "instances = UNLIMITED" and/or "per_source = UNLIMITED" are ineffective (and they are in xinetd from 7.2 but seem correct in xinetd-2.3.7-1), then the tftp service is lost. Error text is "tftp service was deactivated because of looping". If they ARE effective, then still no joy, and you pound syslogd. Removing "only_from" expressions did not help. Version-Release number of selected component (if applicable): How reproducible: Always Steps to Reproduce: 1.have on hand a tftp client whose ip does not resolve. 2.arrange for a dhcpd.conf entry for it, so that it will then attempt a tftp from linux box. 3.activate tftp on linux 4.connect the client machine to the net let it boot. Actual Results: tftp service is disrupted. Additional info: This likely of high interest to LTSP project.
As a workaround (tested in xinetd-2.3.7-1) say flags = NOLIBWRAP which I suppose makes your "only_from" lines useless, and access control becomes an ipchains problem.
No, NOLIBWRAP deals with /etc/hosts.{allow,deny}, not only_from. Anyway, 2.3.7 is what is in rawhide currently..