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/*
*------------------------------------------------------------------
* Copyright (c) 2017 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*------------------------------------------------------------------
*/
#include <stdint.h>
#include <net/if.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/uio.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <inttypes.h>
#include <string.h>
#include <stdio.h>
#include <netdb.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <netinet/if_ether.h>
#include <net/if_arp.h>
#include <asm/byteorder.h>
#include <byteswap.h>
#include <icmp_proto.h>
static uint16_t
cksum (void *addr, ssize_t len)
{
char *data = (char *) addr;
uint32_t acc = 0xffff;
ssize_t i;
for (i = 0; (i + 1) < len; i += 2)
{
uint16_t word;
memcpy (&word, data + i, 2);
acc += ntohs (word);
if (acc > 0xffff)
acc -= 0xffff;
}
if (len & 1)
{
uint16_t word = 0;
memcpy (&word, data + len - 1, 1);
acc += ntohs (word);
if (acc > 0xffff)
acc -= 0xffff;
}
return htons (~acc);
}
int
print_packet (void *pck)
{
if (pck == NULL)
{
printf ("ICMP_PROTO: no data\n");
return -1;
}
struct iphdr *ip;
struct icmphdr *icmp;
ip = (struct iphdr *) pck;
icmp = (struct icmphdr *) (pck + sizeof (struct iphdr));
printf ("received packet:\n");
printf ("\tiphdr:\n");
printf ("\t\tihl: %u\n\t\tversion: %u\n\t\tlen: %u\n\t\tid: %u\n",
ip->ihl, ip->version, __bswap_16 (ip->tot_len), ip->id);
printf ("\t\tprotocol: %u\n", ip->protocol);
printf ("\t\tsaddr: ");
int i;
for (i = 0; i < 4; i++)
{
printf ("%u.", ((uint8_t *) & ip->saddr)[i]);
}
printf ("\n");
printf ("\t\tdaddr: ");
for (i = 0; i < 4; i++)
{
printf ("%u.", ((uint8_t *) & ip->daddr)[i]);
}
printf ("\n");
printf ("\ticmphdr:\n");
printf ("\t\ttype: %s\n",
(icmp->type == ICMP_ECHO) ? "ICMP_ECHO" : "ICMP_ECHOREPLY");
return 0;
}
static ssize_t
resolve_arp (void *arp)
{
struct arphdr *resp = (struct arphdr *) arp;
resp->ar_hrd = __bswap_16 (ARPHRD_ETHER);
resp->ar_pro = __bswap_16 (0x0800);
resp->ar_hln = 6;
resp->ar_pln = 4;
resp->ar_op = __bswap_16 (ARPOP_REPLY);
return sizeof (struct arphdr);
}
static ssize_t
resolve_eth_arp (struct ether_arp *eth_arp, void *eth_arp_resp,
uint8_t ip_addr[4])
{
struct ether_arp *resp = (struct ether_arp *) eth_arp_resp;
resolve_arp (&resp->ea_hdr);
memcpy (resp->arp_tha, eth_arp->arp_sha, 6);
memcpy (resp->arp_tpa, eth_arp->arp_spa, 4);
memcpy (resp->arp_sha,
(((struct ether_header *) (eth_arp_resp -
sizeof (struct ether_header)))->
ether_shost), 6);
memcpy (resp->arp_spa, ip_addr, 4);
return sizeof (struct ether_arp);
}
static ssize_t
resolve_eth (struct ether_header *eth, void *eth_resp)
{
struct ether_header *resp = (struct ether_header *) eth_resp;
memcpy (resp->ether_dhost, eth->ether_shost, 6);
uint8_t hw_addr[6];
int i;
for (i = 0; i < 6; i++)
{
hw_addr[i] = 'a';
}
memcpy (resp->ether_shost, hw_addr, 6);
resp->ether_type = eth->ether_type;
return sizeof (struct ether_header);
}
static ssize_t
resolve_ip (struct iphdr *ip, void *ip_resp, uint8_t ip_addr[4])
{
struct iphdr *resp = (struct iphdr *) ip_resp;
resp->ihl = 5;
resp->version = 4;
resp->tos = 0;
/*len updated later */
resp->tot_len = 0x5400;
resp->id = 0;
resp->frag_off = 0;
resp->ttl = 0x40;
resp->protocol = 1;
((uint8_t *) & resp->saddr)[0] = ip_addr[0];
((uint8_t *) & resp->saddr)[1] = ip_addr[1];
((uint8_t *) & resp->saddr)[2] = ip_addr[2];
((uint8_t *) & resp->saddr)[3] = ip_addr[3];
resp->daddr = ip->saddr;
resp->check = cksum (resp, sizeof (struct iphdr));
return sizeof (struct iphdr);
}
static ssize_t
resolve_icmp (struct icmphdr *icmp, void *icmp_resp)
{
struct icmphdr *resp = (struct icmphdr *) icmp_resp;
resp->type = ICMP_ECHOREPLY;
resp->code = 0;
resp->un.echo.id = icmp->un.echo.id;
resp->un.echo.sequence = icmp->un.echo.sequence;
/*resp->checksum = cksum (resp, sizeof (struct icmphdr)); */
return sizeof (struct icmphdr);
}
int
resolve_packet (void *in_pck, ssize_t in_size,
void *out_pck, uint32_t * out_size, uint8_t ip_addr[4])
{
struct ether_header *eh;
struct ether_arp *eah;
struct iphdr *ip;
struct icmphdr *icmp;
*out_size = 0;
eh = (struct ether_header *) in_pck;
*out_size = resolve_eth (eh, out_pck);
if (eh->ether_type == 0x0608)
{
eah = (struct ether_arp *) (in_pck + *out_size);
*out_size += resolve_eth_arp (eah, out_pck + *out_size, ip_addr);
}
else if (eh->ether_type == 0x0008)
{
#ifdef ICMP_DBG
print_packet (in_pck + *out_size);
#endif
ip = (struct iphdr *) (in_pck + *out_size);
*out_size += resolve_ip (ip, out_pck + *out_size, ip_addr);
if (ip->protocol == 1)
{
icmp = (struct icmphdr *) (in_pck + *out_size);
*out_size += resolve_icmp (icmp, out_pck + *out_size);
((struct icmphdr *) (out_pck + *out_size -
sizeof (struct icmphdr)))->checksum =
cksum (out_pck + *out_size - sizeof (struct icmphdr),
sizeof (struct icmphdr));
/* payload */
memcpy (out_pck + *out_size, in_pck + *out_size,
in_size - *out_size);
*out_size = in_size;
}
}
return 0;
}
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