XS(XS_Net__LibnetRaw_libnet_init_packet)
                [...]
                        u_char *        buf = (u_char *)SvPV(ST(1),PL_na);
                [...]
                        RETVAL = libnet_init_packet(p_size, &buf);
                        sv_setpv((SV*)ST(1), buf);

##</code><code>##

int libnet_init_packet(size_t p_size, u_char **buf);

##</code><code>##

int libnet_build_ip([...], u_char *buf);

##</code><code>##

u_char *buf;

libnet_init_packet(IP_H + TCP_H, &buf); /* This calls malloc() and sets buf as a pointer to that new memory */
[...]
libnet_build_ip([...], buf); /* The pointer value is the same, but data pointed to is altered */