+operating systems. In that case, B<ping_setopt> sets the error to
+C<operation not supported>.
+
+=item B<PING_OPT_QOS>
+
+Sets the I<Quality of Service> flags that should be used when crafting ICMP and
+ICMPv6 packets. The memory pointed to by I<val> is interpreted as a C<uint8_t>.
+The byte is passed to L<setsockopt(2)> without modification, using the
+C<IP_TOS> (IPv4) or C<IPV6_TCLASS> (IPv6) option. It is the caller's
+responsibility to chose a valid bit combination. For details, read the L<ip(7)>
+and L<ipv6(7)> manual pages, as well as I<RFCE<nbsp>2474>.