Raw socket "bogus tcp header length"
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 :
Citation:
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:
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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;
} |
