Building with Clang 3.5 gave the following warning: error: comparison
of array 'iface_out.sin6_addr.__in6_u.__u6_addr8' equal to a null
pointer is always false [-Werror,-Wtautological-pointer-compare]

This is a problem because as it is written the check will never be
true. A pointer to a structure within a structure will never be null. The
intention was either to null check the pointer or to check if the IP
address itself was not zero.

From context in the code this appeared to be a pointer null check so I
removed it.