conn_build_hdr_template
extern int conn_build_hdr_template(conn_t *, uint_t, uint_t,
error = conn_build_hdr_template(connp, 0, 0, v6src, v6dst, flowinfo);
error = conn_build_hdr_template(connp, ulplen, extralen,
error = conn_build_hdr_template(connp, UDPH_SIZE, 0, v6src, v6dst,