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/******************************************************************************
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* Copyright (c) 2004, 2008 IBM Corporation
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* This program and the accompanying materials
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* are made available under the terms of the BSD License
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* which accompanies this distribution, and is available at
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* http://www.opensource.org/licenses/bsd-license.php
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* IBM Corporation - initial implementation
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*****************************************************************************/
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/*>>>>>>>>>>>>>>>>>>>>> DEFINITIONS & DECLARATIONS <<<<<<<<<<<<<<<<<<<<<<*/
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#include <sys/socket.h>
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/* ARP Message types */
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/* ARP talbe size (+1) */
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#define ARP_ENTRIES 10
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/* ICMP Message types */
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#define ICMP_ECHO_REPLY 0
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#define ICMP_DST_UNREACHABLE 3
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#define ICMP_SRC_QUENCH 4
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#define ICMP_REDIRECT 5
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#define ICMP_ECHO_REQUEST 8
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#define ICMP_TIME_EXCEEDED 11
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#define ICMP_PARAMETER_PROBLEM 12
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#define ICMP_TIMESTAMP_REQUEST 13
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#define ICMP_TIMESTAMP_REPLY 14
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#define ICMP_INFORMATION_REQUEST 15
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#define ICMP_INFORMATION_REPLY 16
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* A entry that describes a mapping between IPv4- and MAC-address.
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typedef struct arp_entry arp_entry_t;
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uint8_t eth_frame[ETH_MTU_SIZE];
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unsigned short int checksum;
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/* for type 3 "Destination Unreachable" */
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/* for type 0 and 8 */
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unsigned short int id;
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unsigned short int seq;
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/* payload for destination unreachable */
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unsigned char iphdr[20];
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unsigned char data[64];
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/* payload for echo or echo reply */
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/* maximum size supported is 84 */
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unsigned char data[84];
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/*>>>>>>>>>>>>>>>>>>>>>>>>>>>>> PROTOTYPES <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<*/
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checksum(unsigned short *packet, int words);
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arp_send_request(uint32_t dest_ip);
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arp_send_reply(uint32_t src_ip, uint8_t * src_mac);
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fill_arphdr(uint8_t * packet, uint8_t opcode,
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const uint8_t * src_mac, uint32_t src_ip,
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const uint8_t * dest_mac, uint32_t dest_ip);
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lookup_mac_addr(uint32_t ipv4_addr);
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fill_udp_checksum(struct iphdr *ipv4_hdr);
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handle_icmp(struct iphdr * iph, uint8_t * packet, int32_t packetsize);
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/*>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LOCAL VARIABLES <<<<<<<<<<<<<<<<<<<<<<<<<*/
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/* Routing parameters */
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static uint32_t own_ip = 0;
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static uint32_t multicast_ip = 0;
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static uint32_t router_ip = 0;
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static uint32_t subnet_mask = 0;
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/* helper variables */
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static uint32_t ping_dst_ip;
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static const uint8_t null_mac_addr[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
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static const uint8_t broadcast_mac[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
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static uint8_t multicast_mac[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
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/* There are only (ARP_ENTRIES-1) effective entries because
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* the entry that is pointed by arp_producer is never used.
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static unsigned int arp_consumer = 0;
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static unsigned int arp_producer = 0;
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static arp_entry_t arp_table[ARP_ENTRIES];
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/* Function pointer send_ip. Points either to send_ipv4() or send_ipv6() */
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int (*send_ip) (void *, int);
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/*>>>>>>>>>>>>>>>>>>>>>>>>>>>> IMPLEMENTATION <<<<<<<<<<<<<<<<<<<<<<<<<<<*/
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* IPv4: Initialize the environment for the IPv4 layer.
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for(i=0; i<ARP_ENTRIES; ++i) {
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arp_table[i].ipv4_addr = 0;
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memset(arp_table[i].mac_addr, 0, 6);
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arp_table[i].eth_len = 0;
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/* Set IP send function to send_ipv4() */
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send_ip = &send_ipv4;
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* IPv4: Set the own IPv4 address.
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* @param _own_ip client IPv4 address (e.g. 127.0.0.1)
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set_ipv4_address(uint32_t _own_ip)
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* IPv4: Get the own IPv4 address.
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* @return client IPv4 address (e.g. 127.0.0.1)
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get_ipv4_address(void)
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* IPv4: Set the IPv4 multicast address.
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* @param _own_ip multicast IPv4 address (224.0.0.0 - 239.255.255.255)
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set_ipv4_multicast(uint32_t _multicast_ip)
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// is this IP Multicast out of range (224.0.0.0 - 239.255.255.255)
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if((htonl(_multicast_ip) < 0xE0000000)
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|| (htonl(_multicast_ip) > 0xEFFFFFFF)) {
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memset(multicast_mac, 0xFF, 6);
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multicast_ip = _multicast_ip;
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multicast_mac[0] = 0x01;
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multicast_mac[1] = 0x00;
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multicast_mac[2] = 0x5E;
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multicast_mac[3] = (uint8_t) 0x7F & (multicast_ip >> 16);
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multicast_mac[4] = (uint8_t) 0xFF & (multicast_ip >> 8);
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multicast_mac[5] = (uint8_t) 0xFF & (multicast_ip >> 0);
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* IPv4: Get the IPv4 multicast address.
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* @return multicast IPv4 address (224.0.0.0 - 239.255.255.255 or 0 if not set)
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get_ipv4_multicast(void)
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* IPv4: Set the routers IPv4 address.
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* @param _router_ip router IPv4 address
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set_ipv4_router(uint32_t _router_ip)
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router_ip = _router_ip;
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* IPv4: Get the routers IPv4 address.
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* @return router IPv4 address
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get_ipv4_router(void)
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* IPv4: Set the subnet mask.
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* @param _subnet_mask netmask of the own IPv4 address
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set_ipv4_netmask(uint32_t _subnet_mask)
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subnet_mask = _subnet_mask;
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* IPv4: Get the subnet mask.
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* @return netmask of the own IPv4 address
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get_ipv4_netmask(void)
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* IPv4: Creates IP-packet. Places IP-header in a packet and fills it
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* with corresponding information.
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* Use this function with similar functions for other network layers
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* (fill_ethhdr, fill_udphdr, fill_dnshdr, fill_btphdr).
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* @param packet Points to the place where IP-header must be placed.
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* @param packetsize Size of the packet in bytes incl. this hdr and data.
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* @param ip_proto Type of the next level protocol (e.g. UDP).
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* @param ip_src Sender IP address
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* @param ip_dst Receiver IP address
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fill_iphdr(uint8_t * packet, uint16_t packetsize,
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uint8_t ip_proto, uint32_t ip_src, uint32_t ip_dst) {
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struct iphdr * iph = (struct iphdr *) packet;
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iph -> ip_hlv = 0x45;
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iph -> ip_tos = 0x10;
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iph -> ip_len = htons(packetsize);
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iph -> ip_id = htons(0);
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iph -> ip_ttl = 0xFF;
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iph -> ip_p = ip_proto;
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iph -> ip_src = htonl(ip_src);
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iph -> ip_dst = htonl(ip_dst);
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* IPv4: Handles IPv4-packets according to Receive-handle diagram.
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* @param ip_packet IP-packet to be handled
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* @param packetsize Length of the packet
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* @return ZERO - packet handled successfully;
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* NON ZERO - packet was not handled (e.g. bad format)
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handle_ipv4(uint8_t * ip_packet, int32_t packetsize)
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static uint8_t ip_heap[65536 + ETH_MTU_SIZE];
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if (packetsize < sizeof(struct iphdr))
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return -1; // packet is too small
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iph = (struct iphdr * ) ip_packet;
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/* Drop it if destination IPv4 address is no IPv4 Broadcast, no
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* registered IPv4 Multicast and not our Unicast address
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if((multicast_ip == 0 && iph->ip_dst >= 0xE0000000 && iph->ip_dst <= 0xEFFFFFFF)
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|| (multicast_ip != iph->ip_dst && iph->ip_dst != 0xFFFFFFFF &&
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own_ip != 0 && iph->ip_dst != own_ip)) {
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old_sum = iph -> ip_sum;
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if (old_sum != checksum((uint16_t *) iph, sizeof (struct iphdr) >> 1))
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return -1; // Wrong IP checksum
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// is it the first fragment in a packet?
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if (((iph -> ip_off) & 0x1FFF) == 0) {
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// is it part of more fragments?
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if (((iph -> ip_off) & 0x2000) == 0x2000) {
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memcpy(ip_heap, ip_packet, iph->ip_len);
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// it's not the first fragment
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// get the first fragment
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struct iphdr * iph_first = (struct iphdr * ) ip_heap;
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// is this fragment not part of the first one, then exit
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if ((iph_first->ip_id != iph->ip_id ) ||
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(iph_first->ip_p != iph->ip_p ) ||
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(iph_first->ip_src != iph->ip_src) ||
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(iph_first->ip_dst != iph->ip_dst)) {
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// this fragment is part of the first one!
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memcpy(ip_heap + sizeof(struct iphdr) +
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((iph -> ip_off) & 0x1FFF) * 8,
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ip_packet + sizeof(struct iphdr),
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iph -> ip_len - sizeof(struct iphdr));
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// is it part of more fragments? Then return.
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if (((iph -> ip_off) & 0x2000) == 0x2000) {
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// packet is completly reassambled now!
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// recalculate ip_len and set iph and ip_packet to the
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iph_first->ip_len = iph->ip_len + ((iph->ip_off) & 0x1FFF) * 8;
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// set iph and ip_packet to the resulting packet.
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iph = (struct iphdr * ) ip_packet;
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switch (iph -> ip_p) {
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return handle_icmp(iph, ip_packet + sizeof(struct iphdr),
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iph -> ip_len - sizeof(struct iphdr));
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return handle_udp(ip_packet + sizeof(struct iphdr),
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iph -> ip_len - sizeof(struct iphdr));
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return handle_tcp(ip_packet + sizeof(struct iphdr),
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iph -> ip_len - sizeof(struct iphdr));
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return -1; // Unknown protocol
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* IPv4: Send IPv4-packets.
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* Before the packet is sent there are some patcches performed:
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* - IPv4 source address is replaced by our unicast IPV4 address
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* if it is set to 0 or 1
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* - IPv4 destination address is replaced by our multicast IPV4 address
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* - IPv4 checksum is calculaded.
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* - If payload type is UDP, then the UDP checksum is calculated also.
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* We sent an ARP request first, if this is the first packet sent to
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* the declared IPv4 destination address. In this case we store the
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* the packet and sent it later if we receive the ARP response.
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* If the MAC address is known already, then we send the packet immediatly.
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* If there is already an ARP request pending, then we drop this packet
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* and send again an ARP request.
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* @param ip_packet IP-packet to be handled
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* @param packetsize Length of the packet
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* @return -2 - packet dropped (MAC address not resolved - ARP request pending)
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* -1 - packet dropped (bad format)
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* 0 - packet stored (ARP request sent - packet will be sent if
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* ARP response is received)
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* >0 - packet send (number of transmitted bytes is returned)
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send_ipv4(void* buffer, int len)
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arp_entry_t *arp_entry;
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const uint8_t *mac_addr = 0;
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if(len + sizeof(struct ethhdr) > ETH_MTU_SIZE)
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ip = (struct iphdr *) buffer;
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/* Replace source IPv4 address with our own unicast IPv4 address
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* if it's 0 (= own unicast source address not specified).
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if(ip->ip_src == 0) {
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ip->ip_src = htonl( own_ip );
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/* Replace source IPv4 address with our unicast IPv4 address and
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* replace destination IPv4 address with our multicast IPv4 address
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* if source address is set to 1.
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else if(ip->ip_src == 1) {
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ip->ip_src = htonl( own_ip );
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ip->ip_dst = htonl( multicast_ip );
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// Calculate the IPv4 checksum
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ip->ip_sum = checksum((uint16_t *) ip, sizeof (struct iphdr) >> 1);
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// if payload type is UDP, then we need to calculate the
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// UDP checksum that depends on the IP header
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if(ip->ip_p == IPTYPE_UDP) {
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fill_udp_checksum(ip);
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// Check if the MAC address is already cached
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|| ( ((~subnet_mask) & ip->ip_dst) == ~subnet_mask &&
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( subnet_mask & ip->ip_dst) == (subnet_mask & own_ip))) {
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arp_entry = &arp_table[arp_producer];
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mac_addr = broadcast_mac;
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else if(ip->ip_dst == multicast_ip) {
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arp_entry = &arp_table[arp_producer];
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mac_addr = multicast_mac;
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// Check if IP address is in the same subnet as we are
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if((subnet_mask & own_ip) == (subnet_mask & ip->ip_dst))
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arp_entry = lookup_mac_addr(ip->ip_dst);
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// if not then we need to know the router's IP address
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arp_entry = lookup_mac_addr(router_ip);
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if(arp_entry && memcmp(arp_entry->mac_addr, null_mac_addr, 6) != 0)
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mac_addr = arp_entry->mac_addr;
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// If we could not resolv the MAC address by our own...
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// send the ARP request
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arp_send_request(ip->ip_dst);
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// drop the current packet if there is already a ARP request pending
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// take the next entry in the ARP table to prepare a the new ARP entry.
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arp_entry = &arp_table[arp_producer];
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arp_producer = (arp_producer+1)%ARP_ENTRIES;
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// if ARP table is full then we must drop the oldes entry.
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if(arp_consumer == arp_producer)
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arp_consumer = (arp_consumer+1)%ARP_ENTRIES;
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// store the packet to be send if the ARP reply is received
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arp_entry->ipv4_addr = ip->ip_dst;
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memset(arp_entry->mac_addr, 0, 6);
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fill_ethhdr (arp_entry->eth_frame, htons(ETHERTYPE_IP),
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get_mac_address(), null_mac_addr);
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memcpy(&arp_entry->eth_frame[sizeof(struct ethhdr)],
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arp_entry->eth_len = len + sizeof(struct ethhdr);
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// Send the packet with the known MAC address
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fill_ethhdr(arp_entry->eth_frame, htons(ETHERTYPE_IP),
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get_mac_address(), mac_addr);
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memcpy(&arp_entry->eth_frame[sizeof(struct ethhdr)], buffer, len);
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return send_ether(arp_entry->eth_frame, len + sizeof(struct ethhdr));
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* IPv4: Calculate UDP checksum. Places the result into the UDP-header.
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* Use this function after filling the UDP payload.
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* @param ipv4_hdr Points to the place where IPv4-header starts.
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fill_udp_checksum(struct iphdr *ipv4_hdr)
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unsigned long checksum = 0;
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udp_hdr = (udp_hdr_t *) (ipv4_hdr + 1);
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memset(&ip_hdr, 0, sizeof(struct iphdr));
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ip_hdr.ip_src = ipv4_hdr->ip_src;
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ip_hdr.ip_dst = ipv4_hdr->ip_dst;
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ip_hdr.ip_len = udp_hdr->uh_ulen;
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ip_hdr.ip_p = ipv4_hdr->ip_p;
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ptr = (char*) udp_hdr;
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for (i = 0; i < udp_hdr->uh_ulen; i+=2)
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checksum += *((uint16_t*) &ptr[i]);
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ptr = (char*) &ip_hdr;
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for (i = 0; i < sizeof(struct iphdr); i+=2)
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checksum += *((uint16_t*) &ptr[i]);
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checksum = (checksum >> 16) + (checksum & 0xffff);
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checksum += (checksum >> 16);
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udp_hdr->uh_sum = ~checksum;
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* IPv4: Calculates checksum for IP header.
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* @param packet Points to the IP-header
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* @param words Size of the packet in words incl. IP-header and data.
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static unsigned short
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checksum(unsigned short * packet, int words)
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unsigned long checksum;
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for (checksum = 0; words > 0; words--)
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checksum += *packet++;
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checksum = (checksum >> 16) + (checksum & 0xffff);
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checksum += (checksum >> 16);
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lookup_mac_addr(uint32_t ipv4_addr)
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for(i=arp_consumer; i != arp_producer; i = ((i+1)%ARP_ENTRIES) ) {
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if(arp_table[i].ipv4_addr == ipv4_addr)
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return &arp_table[i];
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* ARP: Sends an ARP-request package.
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* For given IPv4 retrieves MAC via ARP (makes several attempts)
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* @param dest_ip IP of the host which MAC should be obtained
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arp_send_request(uint32_t dest_ip)
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arp_entry_t *arp_entry = &arp_table[arp_producer];
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memset(arp_entry->eth_frame, 0, sizeof(struct ethhdr) + sizeof(struct arphdr));
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fill_arphdr(&arp_entry->eth_frame[sizeof(struct ethhdr)], ARP_REQUEST,
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get_mac_address(), own_ip, broadcast_mac, dest_ip);
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fill_ethhdr(arp_entry->eth_frame, ETHERTYPE_ARP,
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get_mac_address(), broadcast_mac);
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send_ether(arp_entry->eth_frame,
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sizeof(struct ethhdr) + sizeof(struct arphdr));
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* ARP: Sends an ARP-reply package.
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* This package is used to serve foreign requests (in case IP in
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* foreign request matches our host IP).
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* @param src_ip requester IP address (foreign IP)
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* @param src_mac requester MAC address (foreign MAC)
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arp_send_reply(uint32_t src_ip, uint8_t * src_mac)
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arp_entry_t *arp_entry = &arp_table[arp_producer];
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memset(arp_entry->eth_frame, 0, sizeof(struct ethhdr) + sizeof(struct arphdr));
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fill_ethhdr(arp_entry->eth_frame, ETHERTYPE_ARP,
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get_mac_address(), src_mac);
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fill_arphdr(&arp_entry->eth_frame[sizeof(struct ethhdr)], ARP_REPLY,
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get_mac_address(), own_ip, src_mac, src_ip);
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send_ether(arp_entry->eth_frame,
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sizeof(struct ethhdr) + sizeof(struct arphdr));
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* ARP: Creates ARP package. Places ARP-header in a packet and fills it
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* with corresponding information.
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* Use this function with similar functions for other network layers
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* @param packet Points to the place where ARP-header must be placed.
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* @param opcode Identifies is it request (ARP_REQUEST)
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* or reply (ARP_REPLY) package.
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* @param src_mac sender MAC address
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* @param src_ip sender IP address
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* @param dest_mac receiver MAC address
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* @param dest_ip receiver IP address
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fill_arphdr(uint8_t * packet, uint8_t opcode,
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const uint8_t * src_mac, uint32_t src_ip,
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const uint8_t * dest_mac, uint32_t dest_ip)
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struct arphdr * arph = (struct arphdr *) packet;
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arph -> hw_type = htons(1);
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arph -> proto_type = htons(ETHERTYPE_IP);
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arph -> proto_len = 4;
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arph -> opcode = htons(opcode);
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memcpy(arph->src_mac, src_mac, 6);
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arph->src_ip = htonl(src_ip);
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memcpy(arph->dest_mac, dest_mac, 6);
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arph->dest_ip = htonl(dest_ip);
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* ARP: Handles ARP-messages according to Receive-handle diagram.
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* Updates arp_table for outstanding ARP requests (see arp_getmac).
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* @param packet ARP-packet to be handled
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* @param packetsize length of the packet
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* @return ZERO - packet handled successfully;
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* NON ZERO - packet was not handled (e.g. bad format)
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handle_arp(uint8_t * packet, int32_t packetsize)
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struct arphdr * arph = (struct arphdr *) packet;
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if (packetsize < sizeof(struct arphdr))
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return -1; // Packet is too small
687
if (arph -> hw_type != htons(1) || arph -> proto_type != htons(ETHERTYPE_IP))
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return -1; // Unknown hardware or unsupported protocol
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if (arph -> dest_ip != htonl(own_ip))
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return -1; // receiver IP doesn't match our IP
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switch(htons(arph -> opcode)) {
697
arp_send_reply(htonl(arph->src_ip), arph -> src_mac);
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return 0; // no error
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// if it is not for us -> return immediately
702
if(memcmp(get_mac_address(), arph->dest_mac, 6)) {
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return 0; // no error
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if(arph->src_ip == 0) {
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// we are not interested for a MAC address if
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// the IPv4 address is 0.0.0.0 or ff.ff.ff.ff
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// now let's find the corresponding entry in the ARP table
714
for(i=arp_consumer; i != arp_producer; i = ((i+1)%ARP_ENTRIES) ) {
715
if(arp_table[i].ipv4_addr == arph->src_ip)
718
if(i == arp_producer || memcmp(arp_table[i].mac_addr, null_mac_addr, 6) != 0) {
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// we have not asked to resolve this IPv4 address !
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memcpy(arp_table[i].mac_addr, arph->src_mac, 6);
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// do we have something to send
726
if(arp_table[i].eth_len > 0) {
727
struct ethhdr * ethh = (struct ethhdr *) arp_table[i].eth_frame;
728
memcpy(ethh -> dest_mac, arp_table[i].mac_addr, 6);
730
send_ether(arp_table[i].eth_frame, arp_table[i].eth_len);
731
arp_table[i].eth_len = 0;
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return 0; // no error
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return -1; // Invalid message type
742
* ICMP: Send an ICMP Echo request to destination IPv4 address.
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* This function does also set a global variable to the
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* destination IPv4 address. If there is an ICMP Echo Reply
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* received later then the variable is set back to 0.
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* In other words, reading a value of 0 form this variable
747
* means that an answer to the request has been arrived.
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* @param _ping_dst_ip destination IPv4 address
752
ping_ipv4(uint32_t _ping_dst_ip)
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unsigned char packet[sizeof(struct iphdr) + sizeof(struct icmphdr)];
755
struct icmphdr *icmp;
757
ping_dst_ip = _ping_dst_ip;
762
fill_iphdr(packet, sizeof(struct iphdr) + sizeof(struct icmphdr), IPTYPE_ICMP,
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icmp = (struct icmphdr *) (packet + sizeof(struct iphdr));
765
icmp->type = ICMP_ECHO_REQUEST;
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icmp->options.echo.id = 0xd476;
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icmp->options.echo.seq = 1;
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memset(icmp->payload.data, '*', sizeof(icmp->payload.data));
774
checksum((unsigned short *) icmp, sizeof(struct icmphdr) >> 1);
775
send_ipv4(packet, sizeof(struct iphdr) + sizeof(struct icmphdr));
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* ICMP: Return host IPv4 address that we are waiting for a
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* ICMP Echo reply message. If this value is 0 then we have
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* @return ping_dst_ip host IPv4 address
792
* ICMP: Handles ICMP-packets according to Receive-handle diagram.
794
* @param icmp_packet ICMP-packet to be handled
795
* @param packetsize Length of the packet
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* @return ZERO - packet handled successfully;
797
* NON ZERO - packet was not handled (e.g. bad format)
801
handle_icmp(struct iphdr * iph, uint8_t * packet, int32_t packetsize)
803
struct icmphdr *icmp = (struct icmphdr *) packet;
806
case ICMP_ECHO_REPLY:
807
if (icmp->options.echo.id != 0xd476)
809
if (icmp->options.echo.seq != 1)
811
if(ping_dst_ip != iph->ip_src
816
case ICMP_DST_UNREACHABLE: {
817
// We've got Destination Unreachable msg
818
// Inform corresponding upper network layers
819
struct iphdr * bad_iph = (struct iphdr * ) &icmp->payload;
821
switch(bad_iph->ip_p) {
823
handle_tcp_dun((uint8_t *) (bad_iph + 1), packetsize
824
- sizeof(struct icmphdr)
825
- sizeof(struct iphdr), icmp->code);
828
handle_udp_dun((uint8_t *) (bad_iph + 1), packetsize
829
- sizeof(struct icmphdr)
830
- sizeof(struct iphdr), icmp->code);
835
case ICMP_SRC_QUENCH:
839
case ICMP_ECHO_REQUEST: {
840
// We've got an Echo Request - answer with Echo Replay msg
841
unsigned char reply_packet[sizeof(struct iphdr) + packetsize];
842
struct icmphdr *reply_icmph;
844
fill_iphdr(reply_packet, sizeof(struct iphdr) + packetsize,
845
IPTYPE_ICMP, 0, iph->ip_src);
847
reply_icmph = (struct icmphdr *) &reply_packet[sizeof(struct iphdr)];
848
memcpy(reply_icmph, packet, packetsize);
849
reply_icmph -> type = ICMP_ECHO_REPLY;
850
reply_icmph -> checksum = 0;
851
reply_icmph->checksum = checksum((unsigned short *) reply_icmph,
852
sizeof(struct icmphdr) >> 1);
854
send_ipv4(reply_packet, sizeof(struct iphdr) + packetsize);
857
case ICMP_TIME_EXCEEDED:
859
case ICMP_PARAMETER_PROBLEM:
861
case ICMP_TIMESTAMP_REQUEST:
863
case ICMP_TIMESTAMP_REPLY:
865
case ICMP_INFORMATION_REQUEST:
867
case ICMP_INFORMATION_REPLY:
added
removed
clients/net-snk/app/netlib/ipv4.c
