Bonjour,
Voila j'ai voulu coder un petit programme qui envoie un paquet tcp/ip , quand je sniffe l envoie du paquet je peux voir sa dans l entete tcp :
Header length : bogus, must be at least 20
Et je ne vois pas d'ou cela pourrais venire , voila le code , si vous pourriez me donner une piste ... .
Code : Sélectionner tout - Visualiser dans une fenêtre à part
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#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <pthread.h>
#include <errno.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>
#include <sys/ioctl.h>
 
typedef struct iphdr_s {
	unsigned int 		ihl:4;
	unsigned int 		version:4;
	unsigned char 		tos;
	unsigned short int 	tot_len;
	unsigned short int 	id;
	unsigned short int	 offset;
	unsigned char 		ttl;
	unsigned char 		protocol; 
	unsigned short int 	checksum;
	unsigned int 		src;
	unsigned int 		dst;
} iphdr_t;
 
typedef struct tcphdr_s {
	unsigned short psrc;
	unsigned short pdst;
	unsigned int   seq;
	unsigned int   ack;
	unsigned char  doffset;
	unsigned char  flags;
	unsigned short win;
	unsigned short checksum;
	unsigned short urgp;
} tcphdr_t;
 
typedef struct fakehdr_s {
       unsigned long saddr;
       unsigned long daddr;
       char useless;
       unsigned char protocol;
       unsigned short length;
} fakehdr_t;
 
 
unsigned short		in_cksum(unsigned short * addr,int len);
 
 
int main(int argc, char *argv[]) {
 
 
	iphdr_t *iphdr = NULL;
	tcphdr_t *tcphdr = NULL;
	fakehdr_t *fakehdr = NULL;
	char *pkt_send = NULL;
	char *pkt_recv = NULL;
 
	int res;
	int sock;
	struct sockaddr_in to;
 
 
	pkt_send = (char *) malloc(sizeof(iphdr_t) + sizeof(tcphdr_t));
	if ( pkt_send == NULL ) {
		fprintf(stderr, "malloc on pkt_send failed\n");
		return -1;
	}
 
	fakehdr = (fakehdr_t *) malloc(sizeof(fakehdr_t));
	if ( fakehdr == NULL ) {
		fprintf(stderr, "malloc on fakehdr failed\n");
		return -1;
	}
	iphdr = (iphdr_t *) pkt_send;
	tcphdr = (tcphdr_t *) (pkt_send + sizeof(iphdr_t));
 
 
	iphdr->ihl = 5;
	iphdr->version = 4;
	iphdr->tos = 0;
	iphdr->tot_len = (sizeof(iphdr_t) + sizeof(tcphdr_t));
	iphdr->id = 0;
	iphdr->ttl = 255;
	iphdr->protocol = IPPROTO_TCP;
	iphdr->checksum = 0;
	iphdr->src = inet_addr("192.168.1.100");
	iphdr->dst = inet_addr("192.168.1.1");
	iphdr->checksum = in_cksum((unsigned short *)iphdr, sizeof(iphdr_t));
 
	tcphdr->psrc = htons(5000);
	tcphdr->pdst = htons(80);
	tcphdr->seq = 7;
	tcphdr->ack = 0;
	tcphdr->doffset = 5;
	tcphdr->flags = 0x02;
	tcphdr->win = 550;
	tcphdr->checksum = 0;
	tcphdr->urgp = 0;
 
	fakehdr->saddr = inet_addr("192.168.1.100");
	fakehdr->daddr = inet_addr("192.168.1.1");
	fakehdr->useless = htons(0);
	fakehdr->protocol = IPPROTO_TCP;
	fakehdr->length = sizeof(tcphdr_t);
 
	tcphdr->checksum = in_cksum((unsigned short *)fakehdr, sizeof(tcphdr_t)+sizeof(fakehdr_t));
 
	sock = socket(AF_INET,SOCK_RAW, IPPROTO_TCP);
	if ( sock == -1 ) {
		fprintf(stderr, "function socket() failed\n");
		free(fakehdr);
		free(pkt_send);
 
		fakehdr = NULL;
		pkt_send = NULL;
		return -1;
	}
 
	to.sin_family = AF_INET;
	to.sin_port = htons(80);
	to.sin_addr.s_addr = inet_addr("192.168.1.1");
 
	if ( setsockopt(sock, IPPROTO_IP, IP_HDRINCL, (void *)&res, (socklen_t) sizeof(int)) == 1 ) {
		fprintf(stderr, "setsockopt() failed\n");
		free(fakehdr);
		free(pkt_send);
 
		fakehdr = NULL;
		pkt_send = NULL;
		return -1;
	}
 
 
	if ( sendto(sock, pkt_send, iphdr->tot_len, 0, (struct sockaddr *)&to, sizeof(to)) == -1 ) {
		fprintf(stderr, "sendto() failed\n");
		free(fakehdr);
		free(pkt_send);
 
		fakehdr = NULL;
		pkt_send = NULL;
		return -1;
	}
 
 
	free(fakehdr);
	free(pkt_send);
 
	fakehdr = NULL;
	pkt_send = NULL;
	return 0;
}
 
unsigned short
in_cksum(unsigned short * addr,int len)
{
/* pas de moi */
 
	register int sum = 0;
	u_short answer = 0;
	register u_short * w = addr;
	register int nleft = len;
 
	while(nleft > 1) {
		sum += *w++;
		nleft -= 2;
	}
 
	if(nleft == 1) {
		*(u_char *)(&answer) = *(u_char *) w;
		sum += answer;
	}
 
	sum = (sum >> 16) + (sum & 0xffff);
	sum += (sum >> 16);
	answer = ~sum;
 
	return answer;
}