Bug 219674

Summary:	rpcbind -h breaks broadcast functionality
Product:	Base System	Reporter:	Andriy Gapon <avg>
Component:	bin	Assignee:	freebsd-net (Nobody) <net>
Status:	New ---
Severity:	Affects Only Me	CC:	michael.osipov
Priority:	---
Version:	CURRENT
Hardware:	Any
OS:	Any

Description Andriy Gapon freebsd_committer

2017-05-31 08:34:12 UTC

If rpcbind is started with -h <ip-addr> option, then it does not receive any broadcast traffic.  This is because the FreeBSD UDP stack passes an incoming broadcast packet to a socket only if the socket is bound to either the INADDR_ANY or to the same broadcast IP address as in the packet's destination.

Thus, any RPC services depending on the broadcast functionality stop working.
For example, ypbind is no longer able to discover ypserv(-s).

This behaviour is not documented at all neither in man pages nor in the handbook (https://www.freebsd.org/doc/handbook/network-nis.html).  At minimum, the issue deserves a big warning, at maximum there should be an example of the configuration tweaks required to work around the problem (e.g. using ypset, etc).

Ideally, though, rpcbind should bind to each broadcast address matching any IP address passed via -h.
Alternatively, we could add a socket option to allow a UDP socket to see the matching [the interface] broadcast traffic in addition to the traffic destined to the bound IP address.