add icmp_echo packet preparation

srcs/ft_ping.c

@@ -1,7 +1,87 @@
-#include "includes/ft_ping.h"
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   ft_ping.c                                          :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: tomoron <tomoron@student.42angouleme.fr>   +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2025/04/24 00:03:56 by tomoron           #+#    #+#             */
+/*   Updated: 2025/04/24 22:45:16 by tomoron          ###   ########.fr       */
+/*                                                                            */
+/* ************************************************************************** */
 
-int main(void)
+#include "includes/ft_ping.h"
+#include <fcntl.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <byteswap.h>
+
+void set_packet_data(uint8_t *packet_data)
 {
-	printf("AAAAAAAAAAAAAAAAAAA");
+	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(htons(~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.time.tv_sec = bswap_64(packet.time.tv_sec);
+	packet.time.tv_usec = bswap_64(packet.time.tv_usec);
+
+	packet.checksum = 0;
+	packet.checksum = calc_checksum(&packet, sizeof(t_icmp_echo));
+
+	return(packet);
+}
+
+int main(int argc, char **argv)
+{
+	(void)argc;
+	(void)argv;
+	t_icmp_echo packet;
+	int fd;
+
+	packet = prepare_icmp_echo(0, 1);
+	fd = open("test", O_WRONLY | O_CREAT, 0700);
+	write(fd, &packet, sizeof(t_icmp_echo));
+	printf("checksum : %x\n", packet.checksum);
+
 	return(0);
 }