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Diff for: ‎Makefile

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PROJECT=router
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SOURCES=router.c lib/queue.c lib/list.c lib/lib.c
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LIBRARY=nope
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INCPATHS=include
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LIBPATHS=.
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LDFLAGS=
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CFLAGS=-c -Wall -Werror -Wno-error=unused-variable
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CC=gcc
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# Automatic generation of some important lists
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OBJECTS=$(SOURCES:.c=.o)
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INCFLAGS=$(foreach TMP,$(INCPATHS),-I$(TMP))
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LIBFLAGS=$(foreach TMP,$(LIBPATHS),-L$(TMP))
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# Set up the output file names for the different output types
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BINARY=$(PROJECT)
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all: $(SOURCES) $(BINARY)
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$(BINARY): $(OBJECTS)
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$(CC) $(LIBFLAGS) $(OBJECTS) $(LDFLAGS) -o $@
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.c.o:
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$(CC) $(INCFLAGS) $(CFLAGS) -fPIC $< -o $@
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clean:
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rm -rf $(OBJECTS) router hosts_output router_*
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run_router0: all
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./router rtable0.txt rr-0-1 r-0 r-1
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run_router1: all
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./router rtable1.txt rr-0-1 r-0 r-1

Diff for: ‎README

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# Router Dataplane
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Author: Radut Dragos 321CD
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## Structures
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Toate structurile cu instantiere unica se initializeaza inainte de intrarea in loop-ul de "listen" : route table, arp_cache, list (packet queue) si root (LPM trie).
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## Forwarding
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### Workflow:
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* se verifica L2 data <=> pachetul are ca destinatie router-ul curent sau broadcast
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* se verifica tipul pachetului: ARP / ICMP (necesita interpretare)
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* se verifica checksum, ttl
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* se cauta datele necesare pentru modificari
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* se fac modificarile necesare la nivelul IP (ttl si checksum) si ethernet (destinatie si sursa)
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* reconstructia pachetului: ` ETH_HDR | IP_HDR | PAYLOAD` care se va trimite spre next_hop pe interfata corecta
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## LPM
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### Trie implementation
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* initializarea sa realizeaza prin functia parse_trie() introduce pentru fiecare linie din tabela de rutare nodurile noi
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* o adresa introdusa se interpreteaza pe modelul arborelui binar
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* diferentierea la niveul mastii se face prin lungimea mastii
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* astfel, adresa "addr" cu masca /len se reprezinta ca primii len biti din forma binara a addr
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* introducand practic prefixul impreuna cu masca, cautarea se va realiza eficient, parcurgand doar arborele prin urmarea adresei cautate pana la o frunza
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## ARP
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### Received
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* router-ul poate interpreta REQUEST/REPLY
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* pentru REPLY, router-ul memoreaza in cache mac-ul primit si trimite pachetele aflate in asteprate pe acea adreasa
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* pentru REQUEST, router-ul va interpreta doar in cazul in care el este destinatia si va trimite un ARP REPLY
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### Sent
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* router-ul va trimite un ARP REQUEST in cazul in care mac-ul asociat adresei ip destinatie nu este cunoscut, punand in coada de asteptare pachetele cu destinatia respectiva
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* va trimite un ARP REPLY daca el este target-ul request-ului primit
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## ICMP
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* in cazul in care router-ul este destinatia unui pachet icmp, va trimite un icmp_reply()
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* va trimite TIMEOUT in cazul unui ttl < 2
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* va trimite DESTINATION UNREACHABLE in cazul in care nu gaseste intrarea in tabela de rutare

Diff for: ‎include/arp_table.txt

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192.168.0.2 de:ad:be:ef:00:00
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192.168.1.2 de:ad:be:ef:00:01
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192.168.2.2 de:ad:be:ef:00:02
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192.168.3.2 de:ad:be:ef:00:03
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192.0.1.1 ca:fe:ba:be:00:01
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192.0.1.2 ca:fe:ba:be:01:00

Diff for: ‎include/lib.h

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#ifndef _SKEL_H_
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#define _SKEL_H_
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#include <unistd.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#define MAX_PACKET_LEN 1600
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#define ROUTER_NUM_INTERFACES 3
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int send_to_link(int interface, char *frame_data, size_t length);
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/*
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* @brief Receives a packet. Blocking function, blocks if there is no packet to
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* be received.
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*
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* @param frame_data - region of memory in which the data will be copied; should
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* have at least MAX_PACKET_LEN bytes allocated
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* @param length - will be set to the total number of bytes received.
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* Returns: the interface it has been received from.
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*/
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int recv_from_any_link(char *frame_data, size_t *length);
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/* Route table entry */
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struct route_table_entry {
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uint32_t prefix;
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uint32_t next_hop;
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uint32_t mask;
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int interface;
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} __attribute__((packed));
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/* ARP table entry when skipping the ARP exercise */
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struct arp_entry {
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uint32_t ip;
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uint8_t mac[6];
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};
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char *get_interface_ip(int interface);
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/**
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* @brief Get the interface mac object. The function writes
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* the MAC at the pointer mac. uint8_t *mac should be allocated.
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*
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* @param interface
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* @param mac
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*/
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void get_interface_mac(int interface, uint8_t *mac);
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/**
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* @brief Homework infrastructure function.
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*
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* @param argc
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* @param argv
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*/
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/**
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* @brief IPv4 checksum per RFC 791. To compute the checksum
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* of an IP header we must set the checksum to 0 beforehand.
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*
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* also works as ICMP checksum per RFC 792. To compute the checksum
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* of an ICMP header we must set the checksum to 0 beforehand.
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* @param data memory area to checksum
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* @param size in bytes
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*/
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uint16_t checksum(uint16_t *data, size_t len);
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/**
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* hwaddr_aton - Convert ASCII string to MAC address (colon-delimited format)
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* @txt: MAC address as a string (e.g., "00:11:22:33:44:55")
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* @addr: Buffer for the MAC address (ETH_ALEN = 6 bytes)
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* Returns: 0 on success, -1 on failure (e.g., string not a MAC address)
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*/
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int hwaddr_aton(const char *txt, uint8_t *addr);
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/* Populates a route table from file, rtable should be allocated
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* e.g. rtable = malloc(sizeof(struct route_table_entry) * 80000);
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* This function returns the size of the route table.
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*/
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int read_rtable(const char *path, struct route_table_entry *rtable);
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/* Parses a static mac table from path and populates arp_table.
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* arp_table should be allocated and have enough space. This
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* function returns the size of the arp table.
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* */
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int parse_arp_table(char *path, struct arp_entry *arp_table);
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void init(int argc, char *argv[]);
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#define DIE(condition, message, ...) \
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do { \
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if ((condition)) { \
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fprintf(stderr, "[(%s:%d)]: " # message "\n", __FILE__, __LINE__, ##__VA_ARGS__); \
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perror(""); \
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exit(1); \
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} \
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} while (0)
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#endif /* _SKEL_H_ */

Diff for: ‎include/list.h

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#ifndef _LIST_H_
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#define _LIST_H_
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typedef struct cell *list;
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struct cell
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{
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void *element;
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list next;
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};
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extern list cons(void *element, list l);
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extern list cdr_and_free(list l);
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#endif /* _LIST_H_ */

Diff for: ‎include/protocols.h

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#include <unistd.h>
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#include <stdint.h>
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/* Ethernet ARP packet from RFC 826 */
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struct arp_header {
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uint16_t htype; /* Format of hardware address */
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uint16_t ptype; /* Format of protocol address */
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uint8_t hlen; /* Length of hardware address */
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uint8_t plen; /* Length of protocol address */
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uint16_t op; /* ARP opcode (command) */
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uint8_t sha[6]; /* Sender hardware address */
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uint32_t spa; /* Sender IP address */
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uint8_t tha[6]; /* Target hardware address */
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uint32_t tpa; /* Target IP address */
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} __attribute__((packed));
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/* Ethernet frame header*/
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struct ether_header {
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uint8_t ether_dhost[6]; //adresa mac destinatie
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uint8_t ether_shost[6]; //adresa mac sursa
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uint16_t ether_type; // identificator protocol encapsulat
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};
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/* IP Header */
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struct iphdr {
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// this means that version uses 4 bits, and ihl 4 bits
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uint8_t ihl:4, version:4; // we use version = 4
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uint8_t tos; // we don't use this, set to 0
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uint16_t tot_len; // total length = ipheader + data
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uint16_t id; // id of this packet
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uint16_t frag_off; // we don't use fragmentation, set to 0
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uint8_t ttl; // Time to Live -> to avoid loops, we will decrement
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uint8_t protocol; // don't care
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uint16_t check; // checksum -> Since we modify TTL,
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// we need to recompute the checksum
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uint32_t saddr; // source address
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uint32_t daddr; // the destination of the packet
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};
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struct icmphdr
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{
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uint8_t type; /* message type */
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uint8_t code; /* type sub-code */
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uint16_t checksum;
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union
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{
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struct
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{
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uint16_t id;
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uint16_t sequence;
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} echo; /* echo datagram */
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uint32_t gateway; /* gateway address */
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struct
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{
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uint16_t __unused;
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uint16_t mtu;
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} frag; /* path mtu discovery */
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} un;
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};

Diff for: ‎include/queue.h

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#ifndef QUEUE_H
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#define QUEUE_H
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struct queue;
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typedef struct queue *queue;
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/* create an empty queue */
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extern queue queue_create(void);
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/* insert an element at the end of the queue */
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extern void queue_enq(queue q, void *element);
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/* delete the front element on the queue and return it */
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extern void *queue_deq(queue q);
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/* return a true value if and only if the queue is empty */
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extern int queue_empty(queue q);
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#endif

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