/*
* Adjust the checksum value of an ICMP/ICMPv6 packet, based on the
* original type/code values and new type/code values.
*/
int
cksum_update_icmp_type_code(void *icmp46_hdrp, int orig_type, int orig_code,
int new_type, int new_code)
{
assert(icmp46_hdrp != NULL);
struct icmp6_hdr *icmp6_hdrp = icmp46_hdrp;
int32_t sum = icmp6_hdrp->icmp6_cksum;
sum = ~sum & 0xffff;
uint8_t typecode[2];
/* Subtract the original type/code values from the checksum value. */
typecode[0] = orig_type;
typecode[1] = orig_code;
sum -= cksum_acc_words((const uint16_t *)typecode, 2);
/* Add the new type/code values to the checksum value. */
typecode[0] = new_type;
typecode[1] = new_code;
sum += cksum_acc_words((const uint16_t *)typecode, 2);
ADDCARRY(sum);
icmp6_hdrp->icmp6_cksum = ~sum & 0xffff;
return (0);
}
u_short
in_addword(u_short a, u_short b)
{
u_int64_t sum = a + b;
ADDCARRY(sum);
return (sum);
}
/*
* Calculate the transport layer checksum value. The parameter must
* contain the entire packet to calculate the sum.
*
* The ulp parameter contains the transport protocol number. The iov
* parameter contains the following information.
*
* iov[0]: Address family (uint32_t), or struct tun_pi{}
* iov[1]: IPv4/IPv6 header
* iov[2]: IPv6 Fragment header (if necessary, otherwise NULL)
* iov[3]: Upper layer protocol header
* iov[4]: Upper layer protocol data
*/
int
cksum_calc_ulp(int ulp, struct iovec *iov)
{
assert(iov != NULL);
assert(iov[0].iov_base != NULL);
assert(iov[1].iov_base != NULL);
assert(iov[3].iov_base != NULL);
int32_t sum;
struct icmp *icmp4_hdrp;
struct icmp6_hdr *icmp6_hdrp;
switch (ulp) {
case IPPROTO_ICMP:
icmp4_hdrp = iov[3].iov_base;
icmp4_hdrp->icmp_cksum = 0;
sum = cksum_acc_words(iov[3].iov_base, iov[3].iov_len);
if (iov[4].iov_base != NULL) {
sum += cksum_acc_words(iov[4].iov_base, iov[4].iov_len);
}
ADDCARRY(sum);
icmp4_hdrp->icmp_cksum = ~sum & 0xffff;
break;
case IPPROTO_ICMPV6:
icmp6_hdrp = iov[3].iov_base;
icmp6_hdrp->icmp6_cksum = 0;
sum = cksum_acc_ip_pheader(iov[1].iov_base);
sum += cksum_acc_words(iov[3].iov_base, iov[3].iov_len);
if (iov[4].iov_base != NULL) {
sum += cksum_acc_words(iov[4].iov_base, iov[4].iov_len);
}
ADDCARRY(sum);
icmp6_hdrp->icmp6_cksum = ~sum & 0xfff;
break;
default:
warnx("unsupported upper layer protocol %d.", ulp);
return (-1);
}
return (0);
}
/* Calculate the checksum value of an IPv4 header. */
uint16_t
cksum_calc_ip4_header(const struct ip *ip4_hdrp)
{
assert(ip4_hdrp != NULL);
int32_t sum = 0;
int ip4_header_len = ip4_hdrp->ip_hl << 2;
sum = cksum_acc_words((uint16_t *)ip4_hdrp, ip4_header_len);
ADDCARRY(sum);
return (~sum & 0xffff);
}
/*
* Adjust the transport layer checksum value based on the difference
* between the incoming IP header and the outgoing IP header values,
* and update the checksum field appropriately.
*
* The ulp parameter contains the transport protocol number. The
* orig_ip_hdrp parameter points the incoming IP header. The iov
* parameter contains the following information.
*
* iov[0]: Address family (uint32_t), or struct tun_pi{}
* iov[1]: IPv4/IPv6 header
* iov[2]: IPv6 Fragment header (if necessary, otherwise NULL)
* iov[3]: Upper layer protocol data (at least, a header must exist)
*/
int
cksum_update_ulp(int ulp, const void *orig_ip_hdrp, struct iovec *iov)
{
assert(orig_ip_hdrp != NULL);
assert(iov != NULL);
assert(iov[0].iov_base != NULL);
assert(iov[1].iov_base != NULL);
assert(iov[3].iov_base != NULL);
struct tcphdr *tcp_hdrp;
struct udphdr *udp_hdrp;
struct icmp *icmp_hdrp;
struct icmp6_hdr *icmp6_hdrp;
int32_t sum;
switch (ulp) {
case IPPROTO_ICMP:
icmp_hdrp = iov[3].iov_base;
sum = icmp_hdrp->icmp_cksum;
sum = ~sum & 0xffff;
sum -= cksum_acc_ip_pheader(orig_ip_hdrp);
/*
* ICMPv6 includes the sum of the pseudo IPv6 header in its
* checksum calculation, but ICMP doesn't. We just subtract the
* original pseudo IPv6 header sum from the checksum value.
*/
ADDCARRY(sum);
icmp_hdrp->icmp_cksum = ~sum & 0xffff;
break;
case IPPROTO_ICMPV6:
icmp6_hdrp = iov[3].iov_base;
sum = icmp6_hdrp->icmp6_cksum;
sum = ~sum & 0xffff;
sum += cksum_acc_ip_pheader(iov[1].iov_base);
/*
* Similar to the ICMP case above, we just add the new pseudo IPv6
* header sum to the checksum value, since the original ICMP
* checksum doesn't include the IP pseudo header sum.
*/
ADDCARRY(sum);
icmp6_hdrp->icmp6_cksum = ~sum & 0xffff;
break;
#if defined(__linux__)
#define th_sum check
#define uh_sum check
#endif
case IPPROTO_TCP:
tcp_hdrp = iov[3].iov_base;
sum = tcp_hdrp->th_sum;
sum = ~sum & 0xffff;
sum -= cksum_acc_ip_pheader_wo_payload_len(orig_ip_hdrp);
sum += cksum_acc_ip_pheader_wo_payload_len(iov[1].iov_base);
ADDCARRY(sum);
tcp_hdrp->th_sum = ~sum & 0xffff;
break;
case IPPROTO_UDP:
udp_hdrp = iov[3].iov_base;
sum = udp_hdrp->uh_sum;
sum = ~sum & 0xffff;
sum -= cksum_acc_ip_pheader_wo_payload_len(orig_ip_hdrp);
sum += cksum_acc_ip_pheader_wo_payload_len(iov[1].iov_base);
ADDCARRY(sum);
udp_hdrp->uh_sum = ~sum & 0xffff;
break;
#if defined(__linux__)
#undef th_sum
#undef uh_sum
#endif
default:
warnx("unsupported upper layer protocol %d.", ulp);
return (-1);
}
return (0);
}
