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/*
* ip-util.c
*
* Copyright (c) 2002 Dug Song <dugsong@monkey.org>
*
* $Id: ip-util.c 595 2005-02-17 02:55:56Z dugsong $
*/
#include "config.h"
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include "dnet.h"
ssize_t
ip_add_option(void *buf, size_t len, int proto,
const void *optbuf, size_t optlen)
{
struct ip_hdr *ip;
struct tcp_hdr *tcp = NULL;
u_char *p;
int hl, datalen, padlen;
if (proto != IP_PROTO_IP && proto != IP_PROTO_TCP) {
errno = EINVAL;
return (-1);
}
ip = (struct ip_hdr *)buf;
hl = ip->ip_hl << 2;
p = (u_char *)buf + hl;
if (proto == IP_PROTO_TCP) {
tcp = (struct tcp_hdr *)p;
hl = tcp->th_off << 2;
p = (u_char *)tcp + hl;
}
datalen = ntohs(ip->ip_len) - (p - (u_char *)buf);
/* Compute padding to next word boundary. */
if ((padlen = 4 - (optlen % 4)) == 4)
padlen = 0;
/* XXX - IP_HDR_LEN_MAX == TCP_HDR_LEN_MAX */
if (hl + optlen + padlen > IP_HDR_LEN_MAX ||
ntohs(ip->ip_len) + optlen + padlen > len) {
errno = EINVAL;
return (-1);
}
/* XXX - IP_OPT_TYPEONLY() == TCP_OPT_TYPEONLY */
if (IP_OPT_TYPEONLY(((struct ip_opt *)optbuf)->opt_type))
optlen = 1;
/* Shift any existing data. */
if (datalen) {
memmove(p + optlen + padlen, p, datalen);
}
/* XXX - IP_OPT_NOP == TCP_OPT_NOP */
if (padlen) {
memset(p, IP_OPT_NOP, padlen);
p += padlen;
}
memmove(p, optbuf, optlen);
p += optlen;
optlen += padlen;
if (proto == IP_PROTO_IP)
ip->ip_hl = (p - (u_char *)ip) >> 2;
else if (proto == IP_PROTO_TCP)
tcp->th_off = (p - (u_char *)tcp) >> 2;
ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
return (optlen);
}
void
ip_checksum(void *buf, size_t len)
{
struct ip_hdr *ip;
int hl, off, sum;
if (len < IP_HDR_LEN)
return;
ip = (struct ip_hdr *)buf;
hl = ip->ip_hl << 2;
ip->ip_sum = 0;
sum = ip_cksum_add(ip, hl, 0);
ip->ip_sum = ip_cksum_carry(sum);
off = htons(ip->ip_off);
if ((off & IP_OFFMASK) != 0 || (off & IP_MF) != 0)
return;
len -= hl;
if (ip->ip_p == IP_PROTO_TCP) {
struct tcp_hdr *tcp = (struct tcp_hdr *)((u_char *)ip + hl);
if (len >= TCP_HDR_LEN) {
tcp->th_sum = 0;
sum = ip_cksum_add(tcp, len, 0) +
htons(ip->ip_p + len);
sum = ip_cksum_add(&ip->ip_src, 8, sum);
tcp->th_sum = ip_cksum_carry(sum);
}
} else if (ip->ip_p == IP_PROTO_UDP) {
struct udp_hdr *udp = (struct udp_hdr *)((u_char *)ip + hl);
if (len >= UDP_HDR_LEN) {
udp->uh_sum = 0;
sum = ip_cksum_add(udp, len, 0) +
htons(ip->ip_p + len);
sum = ip_cksum_add(&ip->ip_src, 8, sum);
udp->uh_sum = ip_cksum_carry(sum);
if (!udp->uh_sum)
udp->uh_sum = 0xffff; /* RFC 768 */
}
} else if (ip->ip_p == IP_PROTO_ICMP || ip->ip_p == IP_PROTO_IGMP) {
struct icmp_hdr *icmp = (struct icmp_hdr *)((u_char *)ip + hl);
if (len >= ICMP_HDR_LEN) {
icmp->icmp_cksum = 0;
sum = ip_cksum_add(icmp, len, 0);
icmp->icmp_cksum = ip_cksum_carry(sum);
}
}
}
int
ip_cksum_add(const void *buf, size_t len, int cksum)
{
uint16_t *sp = (uint16_t *)buf;
int n, sn;
sn = len / 2;
n = (sn + 15) / 16;
/* XXX - unroll loop using Duff's device. */
switch (sn % 16) {
case 0: do {
cksum += *sp++;
case 15:
cksum += *sp++;
case 14:
cksum += *sp++;
case 13:
cksum += *sp++;
case 12:
cksum += *sp++;
case 11:
cksum += *sp++;
case 10:
cksum += *sp++;
case 9:
cksum += *sp++;
case 8:
cksum += *sp++;
case 7:
cksum += *sp++;
case 6:
cksum += *sp++;
case 5:
cksum += *sp++;
case 4:
cksum += *sp++;
case 3:
cksum += *sp++;
case 2:
cksum += *sp++;
case 1:
cksum += *sp++;
} while (--n > 0);
}
if (len & 1)
cksum += htons(*(u_char *)sp << 8);
return (cksum);
}
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