c_chksum
arcn->crc = asc_ul(hd->c_chksum, sizeof(hd->c_chksum), HEX);
ul_asc((u_long)arcn->crc,hd->c_chksum,sizeof(hd->c_chksum),
ul_asc((u_long)0L, hd->c_chksum, sizeof(hd->c_chksum),HEX))
char c_chksum[8]; /* 0 OR CRC of bytes of FILE data */
udp->uh_sum = c_chksum((u_short *)udp, (u_int)ntohs(iptmp.ip_len), sum);
tcp->th_sum = c_chksum((u_short *)tcp, (u_int)ntohs(iptmp.ip_len), sum);
u_short c_chksum(u_short *, u_int, u_long);