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|
/******************************************************************************
* Copyright (c) 2004, 2008 IBM Corporation
* All rights reserved.
* This program and the accompanying materials
* are made available under the terms of the BSD License
* which accompanies this distribution, and is available at
* http://www.opensource.org/licenses/bsd-license.php
*
* Contributors:
* IBM Corporation - initial implementation
*****************************************************************************/
/********************** DEFINITIONS & DECLARATIONS ***********************/
#include <ipv4.h>
#include <udp.h>
#include <tcp.h>
#include <ethernet.h>
#include <time.h>
#include <sys/socket.h>
#include <string.h>
/* ARP Message types */
#define ARP_REQUEST 1
#define ARP_REPLY 2
/* ARP table size (+1) */
#define ARP_ENTRIES 10
/* ICMP Message types */
#define ICMP_ECHO_REPLY 0
#define ICMP_DST_UNREACHABLE 3
#define ICMP_SRC_QUENCH 4
#define ICMP_REDIRECT 5
#define ICMP_ECHO_REQUEST 8
#define ICMP_TIME_EXCEEDED 11
#define ICMP_PARAMETER_PROBLEM 12
#define ICMP_TIMESTAMP_REQUEST 13
#define ICMP_TIMESTAMP_REPLY 14
#define ICMP_INFORMATION_REQUEST 15
#define ICMP_INFORMATION_REPLY 16
/** \struct arp_entry
* A entry that describes a mapping between IPv4- and MAC-address.
*/
typedef struct arp_entry arp_entry_t;
struct arp_entry {
uint32_t ipv4_addr;
uint8_t mac_addr[6];
uint8_t eth_frame[ETH_MTU_SIZE];
int eth_len;
int pkt_pending;
};
/** \struct icmphdr
* ICMP packet
*/
struct icmphdr {
unsigned char type;
unsigned char code;
unsigned short int checksum;
union {
/* for type 3 "Destination Unreachable" */
unsigned int unused;
/* for type 0 and 8 */
struct echo {
unsigned short int id;
unsigned short int seq;
} echo;
} options;
union {
/* payload for destination unreachable */
struct dun {
unsigned char iphdr[20];
unsigned char data[64];
} dun;
/* payload for echo or echo reply */
/* maximum size supported is 84 */
unsigned char data[84];
} payload;
};
/****************************** PROTOTYPES *******************************/
static unsigned short checksum(unsigned short *packet, int words);
static void arp_send_request(int fd, uint32_t dest_ip);
static void arp_send_reply(int fd, uint32_t src_ip, uint8_t * src_mac);
static void fill_arphdr(uint8_t * packet, uint8_t opcode,
const uint8_t * src_mac, uint32_t src_ip,
const uint8_t * dest_mac, uint32_t dest_ip);
static arp_entry_t *lookup_mac_addr(uint32_t ipv4_addr);
static void fill_udp_checksum(struct iphdr *ipv4_hdr);
static int8_t handle_icmp(int fd, struct iphdr * iph, uint8_t * packet,
int32_t packetsize);
/****************************** LOCAL VARIABLES **************************/
/* Routing parameters */
static uint32_t own_ip = 0;
static uint32_t multicast_ip = 0;
static uint32_t router_ip = 0;
static uint32_t subnet_mask = 0;
/* helper variables */
static uint32_t ping_dst_ip;
static const uint8_t null_mac_addr[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
static const uint8_t broadcast_mac[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
static uint8_t multicast_mac[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
/* There are only (ARP_ENTRIES-1) effective entries because
* the entry that is pointed by arp_producer is never used.
*/
static unsigned int arp_consumer = 0;
static unsigned int arp_producer = 0;
static arp_entry_t arp_table[ARP_ENTRIES];
static uint8_t pending_pkt_frame[ETH_MTU_SIZE];
static int pending_pkt_len;
/* Function pointer send_ip. Points either to send_ipv4() or send_ipv6() */
int (*send_ip) (int fd, void *, int);
/***************************** IMPLEMENTATION ****************************/
/**
* IPv4: Initialize the environment for the IPv4 layer.
*/
static void ipv4_init(void)
{
int i;
ping_dst_ip = 0;
// clear ARP table
arp_consumer = 0;
arp_producer = 0;
for(i=0; i<ARP_ENTRIES; ++i) {
arp_table[i].ipv4_addr = 0;
memset(arp_table[i].mac_addr, 0, 6);
arp_table[i].eth_len = 0;
arp_table[i].pkt_pending = 0;
}
/* Set IP send function to send_ipv4() */
send_ip = &send_ipv4;
}
/**
* IPv4: Set the own IPv4 address.
*
* @param _own_ip client IPv4 address (e.g. 127.0.0.1)
*/
void set_ipv4_address(uint32_t _own_ip)
{
own_ip = _own_ip;
ipv4_init();
}
/**
* IPv4: Get the own IPv4 address.
*
* @return client IPv4 address (e.g. 127.0.0.1)
*/
uint32_t get_ipv4_address(void)
{
return own_ip;
}
/**
* IPv4: Set the IPv4 multicast address.
*
* @param _own_ip multicast IPv4 address (224.0.0.0 - 239.255.255.255)
*/
void set_ipv4_multicast(uint32_t _multicast_ip)
{
// is this IP Multicast out of range (224.0.0.0 - 239.255.255.255)
if((htonl(_multicast_ip) < 0xE0000000)
|| (htonl(_multicast_ip) > 0xEFFFFFFF)) {
multicast_ip = 0;
memset(multicast_mac, 0xFF, 6);
return;
}
multicast_ip = _multicast_ip;
multicast_mac[0] = 0x01;
multicast_mac[1] = 0x00;
multicast_mac[2] = 0x5E;
multicast_mac[3] = (uint8_t) 0x7F & (multicast_ip >> 16);
multicast_mac[4] = (uint8_t) 0xFF & (multicast_ip >> 8);
multicast_mac[5] = (uint8_t) 0xFF & (multicast_ip >> 0);
}
/**
* IPv4: Get the IPv4 multicast address.
*
* @return multicast IPv4 address (224.0.0.0 - 239.255.255.255 or 0 if not set)
*/
uint32_t get_ipv4_multicast(void)
{
return multicast_ip;
}
/**
* IPv4: Set the routers IPv4 address.
*
* @param _router_ip router IPv4 address
*/
void set_ipv4_router(uint32_t _router_ip)
{
router_ip = _router_ip;
ipv4_init();
}
/**
* IPv4: Get the routers IPv4 address.
*
* @return router IPv4 address
*/
uint32_t get_ipv4_router(void)
{
return router_ip;
}
/**
* IPv4: Set the subnet mask.
*
* @param _subnet_mask netmask of the own IPv4 address
*/
void set_ipv4_netmask(uint32_t _subnet_mask)
{
subnet_mask = _subnet_mask;
ipv4_init();
}
/**
* IPv4: Get the subnet mask.
*
* @return netmask of the own IPv4 address
*/
uint32_t get_ipv4_netmask(void)
{
return subnet_mask;
}
/**
* IPv4: Get the default subnet mask according to the IP class
*
* @param ip_addr IPv4 address
* @return default netmask according to the IP class
*/
uint32_t get_default_ipv4_netmask(char *ip_addr)
{
unsigned char top;
top = ip_addr[0];
if (top > 0 && top < 128)
return 0xFF000000; /* Class A: 255.0.0.0 */
else if (top >= 128 && top < 192)
return 0xFFFF0000; /* Class B: 255.255.0.0 */
else if (top >= 192 && top < 224)
return 0xFFFFFF00; /* Class C: 255.255.255.0 */
else
return 0;
}
/**
* IPv4: Creates IP-packet. Places IP-header in a packet and fills it
* with corresponding information.
* <p>
* Use this function with similar functions for other network layers
* (fill_ethhdr, fill_udphdr, fill_dnshdr, fill_btphdr).
*
* @param packet Points to the place where IP-header must be placed.
* @param packetsize Size of the packet in bytes incl. this hdr and data.
* @param ip_proto Type of the next level protocol (e.g. UDP).
* @param ip_src Sender IP address
* @param ip_dst Receiver IP address
* @see iphdr
* @see fill_ethhdr
* @see fill_udphdr
* @see fill_dnshdr
* @see fill_btphdr
*/
void fill_iphdr(uint8_t * packet, uint16_t packetsize,
uint8_t ip_proto, uint32_t ip_src, uint32_t ip_dst)
{
struct iphdr * iph = (struct iphdr *) packet;
iph -> ip_hlv = 0x45;
iph -> ip_tos = 0x10;
iph -> ip_len = htons(packetsize);
iph -> ip_id = htons(0);
iph -> ip_off = 0;
iph -> ip_ttl = 0xFF;
iph -> ip_p = ip_proto;
iph -> ip_src = htonl(ip_src);
iph -> ip_dst = htonl(ip_dst);
iph -> ip_sum = 0;
}
/**
* IPv4: Handles IPv4-packets according to Receive-handle diagram.
*
* @param fd socket fd
* @param ip_packet IP-packet to be handled
* @param packetsize Length of the packet
* @return ZERO - packet handled successfully;
* NON ZERO - packet was not handled (e.g. bad format)
* @see receive_ether
* @see iphdr
*/
int8_t handle_ipv4(int fd, uint8_t * ip_packet, uint32_t packetsize)
{
struct iphdr * iph;
int32_t old_sum;
static uint8_t ip_heap[65536 + ETH_MTU_SIZE];
if (packetsize < sizeof(struct iphdr))
return -1; // packet is too small
iph = (struct iphdr * ) ip_packet;
/* Drop it if destination IPv4 address is no IPv4 Broadcast, no
* registered IPv4 Multicast and not our Unicast address
*/
if((multicast_ip == 0 && iph->ip_dst >= 0xE0000000 && iph->ip_dst <= 0xEFFFFFFF)
|| (multicast_ip != iph->ip_dst && iph->ip_dst != 0xFFFFFFFF &&
own_ip != 0 && iph->ip_dst != own_ip)) {
return -1;
}
old_sum = iph -> ip_sum;
iph -> ip_sum = 0;
if (old_sum != checksum((uint16_t *) iph, sizeof (struct iphdr) >> 1))
return -1; // Wrong IP checksum
// is it the first fragment in a packet?
if (((iph -> ip_off) & 0x1FFF) == 0) {
// is it part of more fragments?
if (((iph -> ip_off) & 0x2000) == 0x2000) {
memcpy(ip_heap, ip_packet, iph->ip_len);
return 0;
}
}
// it's not the first fragment
else {
// get the first fragment
struct iphdr * iph_first = (struct iphdr * ) ip_heap;
// is this fragment not part of the first one, then exit
if ((iph_first->ip_id != iph->ip_id ) ||
(iph_first->ip_p != iph->ip_p ) ||
(iph_first->ip_src != iph->ip_src) ||
(iph_first->ip_dst != iph->ip_dst)) {
return 0;
}
// this fragment is part of the first one!
memcpy(ip_heap + sizeof(struct iphdr) +
((iph -> ip_off) & 0x1FFF) * 8,
ip_packet + sizeof(struct iphdr),
iph -> ip_len - sizeof(struct iphdr));
// is it part of more fragments? Then return.
if (((iph -> ip_off) & 0x2000) == 0x2000) {
return 0;
}
// packet is completely reassembled now!
// recalculate ip_len and set iph and ip_packet to the
iph_first->ip_len = iph->ip_len + ((iph->ip_off) & 0x1FFF) * 8;
// set iph and ip_packet to the resulting packet.
ip_packet = ip_heap;
iph = (struct iphdr * ) ip_packet;
}
switch (iph -> ip_p) {
case IPTYPE_ICMP:
return handle_icmp(fd, iph, ip_packet + sizeof(struct iphdr),
iph -> ip_len - sizeof(struct iphdr));
case IPTYPE_UDP:
return handle_udp(fd, ip_packet + sizeof(struct iphdr),
iph -> ip_len - sizeof(struct iphdr));
case IPTYPE_TCP:
return handle_tcp(ip_packet + sizeof(struct iphdr),
iph -> ip_len - sizeof(struct iphdr));
default:
break;
}
return -1; // Unknown protocol
}
/**
* IPv4: Send IPv4-packets.
*
* Before the packet is sent there are some patches performed:
* - IPv4 source address is replaced by our unicast IPV4 address
* if it is set to 0 or 1
* - IPv4 destination address is replaced by our multicast IPV4 address
* if it is set to 1
* - IPv4 checksum is calculated.
* - If payload type is UDP, then the UDP checksum is calculated also.
*
* We send an ARP request first, if this is the first packet sent to
* the declared IPv4 destination address. In this case we store
* the packet and send it later if we receive the ARP response.
* If the MAC address is known already, then we send the packet immediately.
* If there is already an ARP request pending, then we drop this packet
* and send again an ARP request.
*
* @param fd socket fd
* @param ip_packet IP-packet to be handled
* @param packetsize Length of the packet
* @return -2 - packet dropped (MAC address not resolved - ARP request pending)
* -1 - packet dropped (bad format)
* 0 - packet stored (ARP request sent - packet will be sent if
* ARP response is received)
* >0 - packet send (number of transmitted bytes is returned)
*
* @see receive_ether
* @see iphdr
*/
int send_ipv4(int fd, void* buffer, int len)
{
arp_entry_t *arp_entry = 0;
struct iphdr *ip;
const uint8_t *mac_addr = 0;
uint32_t ip_dst = 0;
if(len + sizeof(struct ethhdr) > ETH_MTU_SIZE)
return -1;
ip = (struct iphdr *) buffer;
/* Replace source IPv4 address with our own unicast IPv4 address
* if it's 0 (= own unicast source address not specified).
*/
if(ip->ip_src == 0) {
ip->ip_src = htonl( own_ip );
}
/* Replace source IPv4 address with our unicast IPv4 address and
* replace destination IPv4 address with our multicast IPv4 address
* if source address is set to 1.
*/
else if(ip->ip_src == 1) {
ip->ip_src = htonl( own_ip );
ip->ip_dst = htonl( multicast_ip );
}
// Calculate the IPv4 checksum
ip->ip_sum = 0;
ip->ip_sum = checksum((uint16_t *) ip, sizeof (struct iphdr) >> 1);
// if payload type is UDP, then we need to calculate the
// UDP checksum that depends on the IP header
if(ip->ip_p == IPTYPE_UDP) {
fill_udp_checksum(ip);
}
ip_dst = ip->ip_dst;
// Check if the MAC address is already cached
if(~ip->ip_dst == 0
|| ( ((~subnet_mask) & ip->ip_dst) == ~subnet_mask &&
( subnet_mask & ip->ip_dst) == (subnet_mask & own_ip))) {
arp_entry = &arp_table[arp_producer];
mac_addr = broadcast_mac;
}
else if(ip->ip_dst == multicast_ip) {
arp_entry = &arp_table[arp_producer];
mac_addr = multicast_mac;
}
else {
// Check if IP address is in the same subnet as we are
if((subnet_mask & own_ip) == (subnet_mask & ip->ip_dst))
arp_entry = lookup_mac_addr(ip->ip_dst);
// if not then we need to know the router's IP address
else {
ip_dst = router_ip;
arp_entry = lookup_mac_addr(router_ip);
}
if(arp_entry && memcmp(arp_entry->mac_addr, null_mac_addr, 6) != 0)
mac_addr = arp_entry->mac_addr;
}
// If we could not resolv the MAC address by our own...
if(!mac_addr) {
// send the ARP request
arp_send_request(fd, ip_dst);
// drop the current packet if there is already a ARP request pending
if(arp_entry)
return -2;
// take the next entry in the ARP table to prepare the new ARP entry.
arp_entry = &arp_table[arp_producer];
arp_producer = (arp_producer+1)%ARP_ENTRIES;
// if ARP table is full then we must drop the oldest entry.
if(arp_consumer == arp_producer)
arp_consumer = (arp_consumer+1)%ARP_ENTRIES;
// store the packet to be send if the ARP reply is received
arp_entry->pkt_pending = 1;
arp_entry->ipv4_addr = ip_dst;
memset(arp_entry->mac_addr, 0, 6);
fill_ethhdr (pending_pkt_frame, htons(ETHERTYPE_IP),
get_mac_address(), null_mac_addr);
memcpy(&pending_pkt_frame[sizeof(struct ethhdr)],
buffer, len);
pending_pkt_len = len + sizeof(struct ethhdr);
set_timer(TICKS_SEC);
do {
receive_ether(fd);
if (!arp_entry->eth_len)
break;
} while (get_timer() > 0);
return 0;
}
// Send the packet with the known MAC address
fill_ethhdr(arp_entry->eth_frame, htons(ETHERTYPE_IP),
get_mac_address(), mac_addr);
memcpy(&arp_entry->eth_frame[sizeof(struct ethhdr)], buffer, len);
return send_ether(fd, arp_entry->eth_frame, len + sizeof(struct ethhdr));
}
/**
* IPv4: Calculate UDP checksum. Places the result into the UDP-header.
* <p>
* Use this function after filling the UDP payload.
*
* @param ipv4_hdr Points to the place where IPv4-header starts.
*/
static void fill_udp_checksum(struct iphdr *ipv4_hdr)
{
unsigned i;
unsigned long checksum = 0;
struct iphdr ip_hdr;
char *ptr;
udp_hdr_t *udp_hdr;
udp_hdr = (udp_hdr_t *) (ipv4_hdr + 1);
udp_hdr->uh_sum = 0;
memset(&ip_hdr, 0, sizeof(struct iphdr));
ip_hdr.ip_src = ipv4_hdr->ip_src;
ip_hdr.ip_dst = ipv4_hdr->ip_dst;
ip_hdr.ip_len = udp_hdr->uh_ulen;
ip_hdr.ip_p = ipv4_hdr->ip_p;
ptr = (char*) udp_hdr;
for (i = 0; i < udp_hdr->uh_ulen; i+=2)
checksum += *((uint16_t*) &ptr[i]);
ptr = (char*) &ip_hdr;
for (i = 0; i < sizeof(struct iphdr); i+=2)
checksum += *((uint16_t*) &ptr[i]);
checksum = (checksum >> 16) + (checksum & 0xffff);
checksum += (checksum >> 16);
udp_hdr->uh_sum = ~checksum;
/* As per RFC 768, if the computed checksum is zero,
* it is transmitted as all ones (the equivalent in
* one's complement arithmetic).
*/
if (udp_hdr->uh_sum == 0)
udp_hdr->uh_sum = ~udp_hdr->uh_sum;
}
/**
* IPv4: Calculates checksum for IP header.
*
* @param packet Points to the IP-header
* @param words Size of the packet in words incl. IP-header and data.
* @return Checksum
* @see iphdr
*/
static unsigned short checksum(unsigned short * packet, int words)
{
unsigned long checksum;
for (checksum = 0; words > 0; words--)
checksum += *packet++;
checksum = (checksum >> 16) + (checksum & 0xffff);
checksum += (checksum >> 16);
return ~checksum;
}
static arp_entry_t* lookup_mac_addr(uint32_t ipv4_addr)
{
unsigned int i;
for(i=arp_consumer; i != arp_producer; i = ((i+1)%ARP_ENTRIES) ) {
if(arp_table[i].ipv4_addr == ipv4_addr)
return &arp_table[i];
}
return 0;
}
/**
* ARP: Sends an ARP-request package.
* For given IPv4 retrieves MAC via ARP (makes several attempts)
*
* @param fd socket fd
* @param dest_ip IP of the host which MAC should be obtained
*/
static void arp_send_request(int fd, uint32_t dest_ip)
{
arp_entry_t *arp_entry = &arp_table[arp_producer];
memset(arp_entry->eth_frame, 0, sizeof(struct ethhdr) + sizeof(struct arphdr));
fill_arphdr(&arp_entry->eth_frame[sizeof(struct ethhdr)], ARP_REQUEST,
get_mac_address(), own_ip, broadcast_mac, dest_ip);
fill_ethhdr(arp_entry->eth_frame, ETHERTYPE_ARP,
get_mac_address(), broadcast_mac);
send_ether(fd, arp_entry->eth_frame,
sizeof(struct ethhdr) + sizeof(struct arphdr));
}
/**
* ARP: Sends an ARP-reply package.
* This package is used to serve foreign requests (in case IP in
* foreign request matches our host IP).
*
* @param fd socket fd
* @param src_ip requester IP address (foreign IP)
* @param src_mac requester MAC address (foreign MAC)
*/
static void arp_send_reply(int fd, uint32_t src_ip, uint8_t * src_mac)
{
arp_entry_t *arp_entry = &arp_table[arp_producer];
memset(arp_entry->eth_frame, 0, sizeof(struct ethhdr) + sizeof(struct arphdr));
fill_ethhdr(arp_entry->eth_frame, ETHERTYPE_ARP,
get_mac_address(), src_mac);
fill_arphdr(&arp_entry->eth_frame[sizeof(struct ethhdr)], ARP_REPLY,
get_mac_address(), own_ip, src_mac, src_ip);
send_ether(fd, arp_entry->eth_frame,
sizeof(struct ethhdr) + sizeof(struct arphdr));
}
/**
* ARP: Creates ARP package. Places ARP-header in a packet and fills it
* with corresponding information.
* <p>
* Use this function with similar functions for other network layers
* (fill_ethhdr).
*
* @param packet Points to the place where ARP-header must be placed.
* @param opcode Identifies is it request (ARP_REQUEST)
* or reply (ARP_REPLY) package.
* @param src_mac sender MAC address
* @param src_ip sender IP address
* @param dest_mac receiver MAC address
* @param dest_ip receiver IP address
* @see arphdr
* @see fill_ethhdr
*/
static void fill_arphdr(uint8_t * packet, uint8_t opcode,
const uint8_t * src_mac, uint32_t src_ip,
const uint8_t * dest_mac, uint32_t dest_ip)
{
struct arphdr * arph = (struct arphdr *) packet;
arph -> hw_type = htons(1);
arph -> proto_type = htons(ETHERTYPE_IP);
arph -> hw_len = 6;
arph -> proto_len = 4;
arph -> opcode = htons(opcode);
memcpy(arph->src_mac, src_mac, 6);
arph->src_ip = htonl(src_ip);
memcpy(arph->dest_mac, dest_mac, 6);
arph->dest_ip = htonl(dest_ip);
}
/**
* ARP: Handles ARP-messages according to Receive-handle diagram.
* Updates arp_table for outstanding ARP requests (see arp_getmac).
*
* @param fd socket fd
* @param packet ARP-packet to be handled
* @param packetsize length of the packet
* @return ZERO - packet handled successfully;
* NON ZERO - packet was not handled (e.g. bad format)
* @see arp_getmac
* @see receive_ether
* @see arphdr
*/
int8_t handle_arp(int fd, uint8_t * packet, uint32_t packetsize)
{
struct arphdr * arph = (struct arphdr *) packet;
if (packetsize < sizeof(struct arphdr))
return -1; // Packet is too small
if (arph -> hw_type != htons(1) || arph -> proto_type != htons(ETHERTYPE_IP))
return -1; // Unknown hardware or unsupported protocol
if (arph -> dest_ip != htonl(own_ip))
return -1; // receiver IP doesn't match our IP
switch(htons(arph -> opcode)) {
case ARP_REQUEST:
// foreign request
if(own_ip != 0)
arp_send_reply(fd, htonl(arph->src_ip), arph -> src_mac);
return 0; // no error
case ARP_REPLY: {
unsigned int i;
// if it is not for us -> return immediately
if(memcmp(get_mac_address(), arph->dest_mac, 6)) {
return 0; // no error
}
if(arph->src_ip == 0) {
// we are not interested for a MAC address if
// the IPv4 address is 0.0.0.0 or ff.ff.ff.ff
return -1;
}
// now let's find the corresponding entry in the ARP table
for(i=arp_consumer; i != arp_producer; i = ((i+1)%ARP_ENTRIES) ) {
if(arp_table[i].ipv4_addr == arph->src_ip)
break;
}
if(i == arp_producer || memcmp(arp_table[i].mac_addr, null_mac_addr, 6) != 0) {
// we have not asked to resolve this IPv4 address !
return -1;
}
memcpy(arp_table[i].mac_addr, arph->src_mac, 6);
// do we have something to send
if (arp_table[i].pkt_pending) {
struct ethhdr * ethh = (struct ethhdr *) pending_pkt_frame;
memcpy(ethh -> dest_mac, arp_table[i].mac_addr, 6);
send_ether(fd, pending_pkt_frame, pending_pkt_len);
arp_table[i].pkt_pending = 0;
arp_table[i].eth_len = 0;
}
return 0; // no error
}
default:
break;
}
return -1; // Invalid message type
}
/**
* ICMP: Send an ICMP Echo request to destination IPv4 address.
* This function does also set a global variable to the
* destination IPv4 address. If there is an ICMP Echo Reply
* received later then the variable is set back to 0.
* In other words, reading a value of 0 form this variable
* means that an answer to the request has been arrived.
*
* @param fd socket descriptor
* @param _ping_dst_ip destination IPv4 address
*/
void ping_ipv4(int fd, uint32_t _ping_dst_ip)
{
unsigned char packet[sizeof(struct iphdr) + sizeof(struct icmphdr)];
struct icmphdr *icmp;
ping_dst_ip = _ping_dst_ip;
if(ping_dst_ip == 0)
return;
fill_iphdr(packet, sizeof(struct iphdr) + sizeof(struct icmphdr), IPTYPE_ICMP,
0, ping_dst_ip);
icmp = (struct icmphdr *) (packet + sizeof(struct iphdr));
icmp->type = ICMP_ECHO_REQUEST;
icmp->code = 0;
icmp->checksum = 0;
icmp->options.echo.id = 0xd476;
icmp->options.echo.seq = 1;
memset(icmp->payload.data, '*', sizeof(icmp->payload.data));
icmp->checksum =
checksum((unsigned short *) icmp, sizeof(struct icmphdr) >> 1);
send_ipv4(fd, packet, sizeof(struct iphdr) + sizeof(struct icmphdr));
}
/**
* ICMP: Return host IPv4 address that we are waiting for a
* ICMP Echo reply message. If this value is 0 then we have
* received an reply.
*
* @return ping_dst_ip host IPv4 address
*/
uint32_t pong_ipv4(void)
{
return ping_dst_ip;
}
/**
* ICMP: Handles ICMP-packets according to Receive-handle diagram.
*
* @param fd socket fd
* @param icmp_packet ICMP-packet to be handled
* @param packetsize Length of the packet
* @return ZERO - packet handled successfully;
* NON ZERO - packet was not handled (e.g. bad format)
* @see handle_ipv4
*/
static int8_t handle_icmp(int fd, struct iphdr * iph, uint8_t * packet,
int32_t packetsize)
{
struct icmphdr *icmp = (struct icmphdr *) packet;
switch(icmp->type) {
case ICMP_ECHO_REPLY:
if (icmp->options.echo.id != 0xd476)
return -1;
if (icmp->options.echo.seq != 1)
return -1;
if(ping_dst_ip != iph->ip_src
|| ping_dst_ip == 0)
return -1;
ping_dst_ip = 0;
break;
case ICMP_DST_UNREACHABLE: {
// We've got Destination Unreachable msg
// Inform corresponding upper network layers
struct iphdr * bad_iph = (struct iphdr * ) &icmp->payload;
switch(bad_iph->ip_p) {
case IPTYPE_TCP:
handle_tcp_dun((uint8_t *) (bad_iph + 1), packetsize
- sizeof(struct icmphdr)
- sizeof(struct iphdr), icmp->code);
break;
case IPTYPE_UDP:
handle_udp_dun((uint8_t *) (bad_iph + 1), packetsize
- sizeof(struct icmphdr)
- sizeof(struct iphdr), icmp->code);
break;
}
break;
}
case ICMP_SRC_QUENCH:
break;
case ICMP_REDIRECT:
break;
case ICMP_ECHO_REQUEST: {
// We've got an Echo Request - answer with Echo Replay msg
unsigned char reply_packet[sizeof(struct iphdr) + packetsize];
struct icmphdr *reply_icmph;
fill_iphdr(reply_packet, sizeof(struct iphdr) + packetsize,
IPTYPE_ICMP, 0, iph->ip_src);
reply_icmph = (struct icmphdr *) &reply_packet[sizeof(struct iphdr)];
memcpy(reply_icmph, packet, packetsize);
reply_icmph -> type = ICMP_ECHO_REPLY;
reply_icmph -> checksum = 0;
reply_icmph->checksum = checksum((unsigned short *) reply_icmph,
sizeof(struct icmphdr) >> 1);
send_ipv4(fd, reply_packet, sizeof(struct iphdr) + packetsize);
break;
}
case ICMP_TIME_EXCEEDED:
break;
case ICMP_PARAMETER_PROBLEM:
break;
case ICMP_TIMESTAMP_REQUEST:
break;
case ICMP_TIMESTAMP_REPLY:
break;
case ICMP_INFORMATION_REQUEST:
break;
case ICMP_INFORMATION_REPLY:
break;
}
return 0;
}
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