bonjours,

je suis entrain d'utiliser winpcap pour envoyer des paquets UDP, voici mon programme :
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int main()
{
    #define PACKET_SIZE (1450)
 
	pcap_if_t *alldevs;
	pcap_if_t *d;
	int inum;
	int i=0;
	pcap_t *adhandle;
	char errbuf[PCAP_ERRBUF_SIZE];
	u_int netmask;
	//char packet_filter[] = "ip and udp";
	//struct bpf_program fcode;
    u_char buf[PACKET_SIZE];
 
    int cpt = 0;
 
 
	/* Retrieve the device list */
	if(pcap_findalldevs(&alldevs, errbuf) == -1)
	{
		fprintf(stderr,"Error in pcap_findalldevs: %s\n", errbuf);
		exit(1);
	}
 
	/* Print the list */
	for(d=alldevs; d; d=d->next)
	{
		printf("%d. %s", ++i, d->name);
		if (d->description)
			printf(" (%s)\n", d->description);
		else
			printf(" (No description available)\n");
	}
 
	if(i==0)
	{
		printf("\nNo interfaces found! Make sure WinPcap is installed.\n");
		return -1;
	}
 
	printf("Enter the interface number (1-%d):",i);
	scanf("%d", &inum);
 
	/* Check if the user specified a valid adapter */
	if(inum < 1 || inum > i)
	{
		printf("\nAdapter number out of range.\n");
 
		/* Free the device list */
		pcap_freealldevs(alldevs);
		return -1;
	}
 
	/* Jump to the selected adapter */
	for(d=alldevs, i=0; i< inum-1 ;d=d->next, i++);
 
	/* Open the adapter */
	if ((adhandle= pcap_open_live(d->name,	// name of the device
							 65536,			// portion of the packet to capture.
											// 65536 grants that the whole packet will be captured on all the MACs.
							 1,				// promiscuous mode (nonzero means promiscuous)
							 1000,			// read timeout
							 errbuf			// error buffer
							 )) == NULL)
	{
		fprintf(stderr,"\nUnable to open the adapter. %s is not supported by WinPcap\n", d->name);
		/* Free the device list */
		pcap_freealldevs(alldevs);
		return -1;
	}
 
 
	/* Check the link layer. We support only Ethernet for simplicity. */
	if(pcap_datalink(adhandle) != DLT_EN10MB)
	{
		fprintf(stderr,"\nThis program works only on Ethernet networks.\n");
		/* Free the device list */
		pcap_freealldevs(alldevs);
		return -1;
	}
 
	if(d->addresses != NULL){
		/* Retrieve the mask of the first address of the interface */
		netmask=((struct sockaddr_in *)(d->addresses->netmask))->sin_addr.S_un.S_addr;
	} else {
		/* If the interface is without addresses we suppose to be in a C class network */
		netmask=0xffffff;
    }
 
 
 
    // ***********************
	// MAC destination : 01:00:5e:01:01:01
	buf[0]=0x01;
	buf[1]=0x00;
	buf[2]=0x5e;
	buf[3]=0x01;
	buf[4]=0x01;
	buf[5]=0x01;
 
	// MAC source : 00:24:E8:00:3B:A0
	buf[6]=0x00;
	buf[7]=0x24;
	buf[8]=0x00;
	buf[9]=0xE8;
	buf[10]=0x3B;
	buf[11]=0xA0;
 
    // ***********************
    // trame type IP
	buf[12]=0x08;
	buf[13]=0x00;
 
	buf[14]=0x45; // version IP V4 / len = 20 bytes
	buf[15]=0x88; // ???
 
	// total len => 1436
	buf[16]=0x05;
	buf[17]=0x9C;
 
    // identification => incrémenté de 2 a chaque paquet envoyé
	//buf[18]=0x00;
	//buf[19]=0x00;
    buf[18]=(cpt >> 8) & 0x1F;
    buf[19]=cpt & 0xFF;
    cpt+=2;
 
 
    // flag = 0x02 / Fragment offset = 0;
	buf[20]=0x40;
	buf[21]=0x00;
 
	buf[22]=0x0a; // TTL = 10
	buf[23]=0x11; // PROTOCL = UDP
 
    // IP Checksum
	buf[24]=0xb7;
	buf[25]=0x83;
 
	// IP Source : 10.0.200.3
	buf[26]=10;
	buf[27]=0;
	buf[28]=200;
	buf[29]=3;
 
	// IP Destination : 224.1.1.1
	buf[30]=224;
	buf[31]=1;
	buf[32]=1;
	buf[33]=1;
 
 
    // ***********************
    // source port = 6840
	buf[34]=0x1a;
	buf[35]=0xb8;
 
    // destination port = 6780
	buf[36]=0x1a;
	buf[37]=0x7c;
 
    // len = 1416
	buf[38]=0x05;
	buf[39]=0x88;
 
    // UDP Checksum
	buf[40]=0x5f;
	buf[41]=0xc1;
 
 
    // ***********************
	// remplissage des data UDP
	for(i=42;i<PACKET_SIZE;i++){
		buf[i]= (u_char)i;
	}
 
 
    // ************************
    // => mettre des byte de bourrage si le paquet est trop petit (la norme impose une taille min)
 
 
 
    while(1){
    //for(i=0; i<1000; i++){
        // Send down the packet
        if (pcap_sendpacket(adhandle,	// Adapter
            buf,				// buffer with the packet
            PACKET_SIZE				// size
            ) != 0)
        {
            fprintf(stderr,"\nError sending the packet: %s\n", pcap_geterr(adhandle));
            return 3;
        }
    }
 
 
	pcap_close(adhandle);
 
 
 
	return 0;
}
=> comment faut-il faire pour calculer les checksums des entetes IP et UDP ?

Merci d'avance,