ft_ping/srcs/icmp.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   icmp.c                                             :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: tomoron <tomoron@student.42angouleme.fr>   +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2025/04/24 22:49:22 by tomoron           #+#    #+#             */
/*   Updated: 2025/08/24 17:08:44 by tomoron          ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */
#include "includes/ft_ping.h"

static void set_packet_data(uint8_t *packet_data)
{
	int i;

	i = 0;
	while(i < PACKET_DATA_LENGTH)
	{
		packet_data[i] = i;
		i++;
	}
}

uint16_t calc_checksum(void *ptr, size_t len)
{
	uint32_t		res;
	uint16_t		*data;

	data = ptr;
	res = 0;
	while (len > 1)
	{
		res += *data;
		data++;
		len -= 2;	
	}
	if (len)
		res += *(uint8_t *)data;

	while (res >> 16) {
        res = (res & 0xFFFF) + (res >> 16);
    }
	
	return(~res);
}

t_icmp_echo prepare_icmp_echo(uint16_t sequence, uint16_t identifier)
{
	t_icmp_echo packet;

	packet.type = 8;
	packet.code = 0;
	packet.identifier = htons(identifier);
	packet.sequence = htons(sequence);
	set_packet_data(packet.data);
	gettimeofday(&packet.time, 0);

	packet.checksum = 0;
	packet.checksum = calc_checksum(&packet, sizeof(t_icmp_echo));

	return(packet);
}

t_waitlist *send_icmp(t_settings *set, struct addrinfo *host, uint16_t *seq, t_stats *stats)
{
	t_icmp_echo packet;
	t_waitlist *ret;
	size_t		len;
	
	if(timediff(&set->last_send_time) < set->interval)
		return (0);
	gettimeofday(&set->last_send_time, 0);
	packet = prepare_icmp_echo(*seq, set->id);
	len = sendto(set->socket, &packet, sizeof(t_icmp_echo), MSG_DONTWAIT, host->ai_addr, host->ai_addrlen);
	if(len == (size_t)-1)
	{
		perror(set->name);
		set->err = 1;
		g_stop = 1;
	}
	ret = malloc(sizeof(t_waitlist));
	if(!ret)
		return(0);
	ret->time = set->last_send_time;
	ret->seq = *seq;
	ret->next = 0;
	stats->sent++;
	gettimeofday(&set->last_send_time, 0);
	(*seq)++;
	return(ret);
}

char *convert_ip(uint32_t ip)
{
    struct in_addr addr = { .s_addr = ip };
	return(inet_ntoa(addr));
}

void ttl_exceeded(t_icmp_ip_reply *res,t_settings *settings, size_t len)
{
	char *ip_str;
	t_icmp_ip_reply *sent;

	ip_str = convert_ip(res->header.saddr);
	(void) settings;
	sent = (void *)res + sizeof(struct iphdr) + 8;	
	if(htons(sent->icmp.identifier) != settings->id)
	{
		printf("invalid identifier\n");
		return ;
	}
//ICMP: type 8, code 0, size 64, id 0x01cd, seq 0x0000
	printf("%zu bytes from %s: Time to live exceeded\n", len, ip_str);
	printf("IP Hdr Dump:\n");
	for (size_t i = 0; i < sizeof(struct iphdr); i += 2)
	{
		printf(" %04x", *(uint16_t *)(((void *)(&sent->header)) + i));
	}
	printf("\nVr HL TOS  Len   ID Flg  off TTL Pro  cks      Src	Dst	Data\n");
	printf(" %d  %d  %02x %04x %04x   %01x %04x  %02x  %02x %02x %s",\
			sent->header.version, sent->header.ihl, sent->header.tos,\
			htons(sent->header.tot_len), htons(sent->header.id), sent->header.frag_off, sent->header.frag_off,\
			sent->header.ttl, sent->header.protocol, htons(sent->header.check),\
			convert_ip(sent->header.saddr));
	printf("  %s\nICMP: ", convert_ip(sent->header.daddr));
	printf("type %d, code %d, size %zu, id 0x%04x, seq 0x%04x\n", sent->icmp.type, sent->icmp.code, htons(sent->header.tot_len) - sizeof(struct iphdr), sent->icmp.identifier, sent->icmp.sequence);

}

void receive_icmp(t_settings *set, t_waitlist **wl, t_stats *stats)
{
	size_t			len;
	t_icmp_ip_reply	*res;
	char			buffer[1024];
	uint16_t		checksum;
	t_waitlist		*elem;

	len = recv(set->socket, &buffer, 1024, MSG_DONTWAIT);

	res = (void *)buffer;
	if(len == (size_t)-1 )
		return;
	if(len < sizeof(struct iphdr) + 8)
		return;
	if(res->header.protocol != 1)
		return ; 
	if(htons(res->header.tot_len) != len)
		return;
	if(res->icmp.type == 11)
	{
		if(len < (sizeof(struct iphdr) + 8) * 2)
			return;
	}
	else if(res->icmp.type == 0)
	{
		if(len < sizeof(t_icmp_ip_reply))
			return;
		if(htons(res->icmp.identifier) != set->id)
			return;
	}
	else
		return;
	checksum = res->icmp.checksum;
	res->icmp.checksum = 0;
	if(calc_checksum(&res->icmp, len - sizeof(struct iphdr)) != checksum)
		return ;
	elem = waitlist_remove(wl, res, res->icmp.type == 11);
	if(!elem)
		return;
	if(res->icmp.type == 0)
		show_ping_res_line(elem, set, res->icmp.sequence, stats, res->header.ttl);
	else if (res->icmp.type == 11 && set->verbose)
		ttl_exceeded(res, set, len);
	free(elem);
}