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Reacting to exceeded TTL/HL

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This commit is contained in:
Michal Zima
2013-02-14 14:26:01 +01:00
parent e722e80149
commit 5af1a5ca7c
6 changed files with 205 additions and 3 deletions
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154
src/icmp.c
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@@ -353,3 +353,157 @@ int icmp_ndp(struct s_ethernet *ethq, struct s_ipv6 *ipq,
return 0;
}
/**
* Sends ICMPv4 error.
*
* @param ip_dest Destination IPv4 address
* @param type Type of ICMP error
* @param code Code of ICMP error
* @param data Original packet
* @param length Length of the original packet
*
* @return 0 for success
* @return 1 for failure
*/
int icmp4_error(struct s_ipv4_addr ip_dest, unsigned char type,
unsigned char code, unsigned char *data, unsigned short length)
{
unsigned char *packet, *payload;
struct s_ipv4 *ip4;
struct s_icmp *icmp;
/* 4 = unused space after ICMP header */
unsigned short payload_size = length > 1500 - sizeof(struct s_ipv4) -
sizeof(struct s_icmp) - 4 ?
1500 - sizeof(struct s_ipv4) - sizeof(struct s_icmp) - 4 :
length;
if ((packet = (unsigned char *) malloc(sizeof(struct s_ipv4) +
sizeof(struct s_icmp) + 4 + payload_size)) == NULL) {
log_error("Lack of free memory");
return 1;
}
ip4 = (struct s_ipv4 *) packet;
icmp = (struct s_icmp *) (packet + sizeof(struct s_ipv4));
payload = (unsigned char *) (packet + sizeof(struct s_ipv4) +
sizeof(struct s_icmp) + 4);
/* build IPv4 packet */
ip4->ver_hdrlen = 0x45; /* ver 4, header length 20 B */
ip4->tos = 0x0;
ip4->len = htons(sizeof(struct s_ipv4) +
sizeof(struct s_icmp) + 4 + payload_size);
ip4->id = 0x0;
ip4->flags_offset = htons(IPV4_FLAG_DONT_FRAGMENT);
ip4->ttl = 255;
ip4->proto = IPPROTO_ICMP;
ip4->ip_src = host_ipv4_addr;
ip4->ip_dest = ip_dest;
/* build ICMP header */
icmp->type = type;
icmp->code = code;
icmp->checksum = 0x0;
/* copy the payload data */
memcpy(payload, data, payload_size);
/* compute ICMP checksum */
icmp->checksum = checksum((unsigned char *) icmp,
payload_size + 4 + sizeof(struct s_icmp));
/* compute IPv4 checksum */
ip4->checksum = checksum_ipv4(ip4->ip_src, ip4->ip_dest,
htons(ip4->len), IPPROTO_ICMP,
(unsigned char *) icmp);
/* send packet */
transmit_ipv4(&ip4->ip_dest, packet, htons(ip4->len));
/* clean-up */
free(packet);
return 0;
}
/**
* Sends ICMPv6 error.
*
* @param mac_dest Destination MAC address
* @param ip_dest Destination IPv6 address
* @param type Type of ICMP error
* @param code Code of ICMP error
* @param data Original packet
* @param length Length of the original packet
*
* @return 0 for success
* @return 1 for failure
*/
int icmp6_error(struct s_mac_addr mac_dest, struct s_ipv6_addr ip_dest,
unsigned char type, unsigned char code, unsigned char *data,
unsigned short length)
{
unsigned char *packet, *payload;
struct s_ethernet *eth;
struct s_ipv6 *ip6;
struct s_icmp *icmp;
/* 4 = unused space after ICMP header */
unsigned short payload_size = length > 1280 - sizeof(struct s_ipv6) -
sizeof(struct s_icmp) - 4 ?
1280 - sizeof(struct s_ipv6) - sizeof(struct s_icmp) - 4 :
length;
if ((packet = (unsigned char *) malloc(sizeof(struct s_ethernet) +
sizeof(struct s_ipv6) + sizeof(struct s_icmp) + 4 +
payload_size)) == NULL) {
log_error("Lack of free memory");
return 1;
}
eth = (struct s_ethernet *) packet;
ip6 = (struct s_ipv6 *) (packet + sizeof(struct s_ethernet));
icmp = (struct s_icmp *) (packet + sizeof(struct s_ethernet) +
sizeof(struct s_ipv6));
payload = (unsigned char *) (packet + sizeof(struct s_ethernet) +
sizeof(struct s_ipv6) +
sizeof(struct s_icmp) + 4);
/* ethernet */
eth->dest = mac_dest;
eth->src = mac;
eth->type = htons(ETHERTYPE_IPV6);
/* IPv6 */
ip6->ver = 0x60;
ip6->len = htons(sizeof(struct s_icmp) + 4 + payload_size);
ip6->next_header = IPPROTO_ICMPV6;
ip6->hop_limit = 255;
ip6->ip_src = host_ipv6_addr;
ip6->ip_dest = ip_dest;
/* ICMP */
icmp->type = type;
icmp->code = code;
icmp->checksum = 0x0;
/* copy the payload data */
memcpy(payload, data, payload_size);
/* compute ICMP checksum */
icmp->checksum = checksum_ipv6(host_ipv6_addr, ip_dest,
sizeof(struct s_icmp) + 4 + payload_size,
IPPROTO_ICMPV6,
(unsigned char *) icmp);
/* send packet */
transmit_raw(packet, sizeof(struct s_ethernet) + sizeof(struct s_ipv6) +
sizeof(struct s_icmp) + 4 + payload_size);
/* clean-up */
free(packet);
return 0;
}