Ideas:

strlcpy(3)
<p>
The strlcpy() and strlcat() functions copy and concatenate strings re-
     spectively.  They are designed to be safer, more consistent,
and less error prone replacements for strncpy(3) and strncat(3).
It only copies as
much as needed, up to a limit (with a guarantee of NUL termination to
boot, unlike strncpy()).  strncpy will continue to write 0's after the
end of the string, up to the limit, so strncpy(a,"b",1048576) will
write almost 1MB of zeroes
while strlcpy does the minimum memory traffic needed.

<pre>
-    strncpy(z_suffix, Z_SUFFIX, sizeof(z_suffix)-1);
+    strlcpy(z_suffix, Z_SUFFIX, sizeof(z_suffix));

-        strcat(ifname, ".");
+        strlcat(ifname, ".", sizeof(ifname));
</pre>