Hi list. I'm coding a little program with libpcap that captures ARP
packet. In this program I try to cast an arphdr struct pointer to the
packet, to read ARP packet parameters, and in this point I have the
problem.
This is the code of the callback pcap_loop function:
void mac(u_char *args, const struct pcap_pkthdr *header, const u_char
*packet)
{
struct arphdr *arp = NULL;
arp = (struct arphdr *) packet;
printf("%d:%d:%d\n", arp->ar_sha[0], arp->ar_sha[1],
arp->ar_sha[2]);
return;
}
Compiling this source, I get the following error:
oad-cap.c: In function 'mac':
oad-cap.c:11: error: 'struct arphdr' has no member named 'ar_sha'
oad-cap.c:11: error: 'struct arphdr' has no member named 'ar_sha'
oad-cap.c:11: error: 'struct arphdr' has no member named 'ar_sha'
Now, I've seen in /usr/include/net/if_arp.h and get:
struct arphdr {
u_int16_t ar_hrd; /* format of hardware address */
#define ARPHRD_ETHER 1 /* ethernet hardware format */
#define ARPHRD_IEEE802 6 /* IEEE 802 hardware format */
#define ARPHRD_FRELAY 15 /* frame relay hardware format */
#define ARPHRD_IEEE1394 24 /* IEEE 1394 (FireWire) hardware format */
u_int16_t ar_pro; /* format of protocol address */
u_int8_t ar_hln; /* length of hardware address */
u_int8_t ar_pln; /* length of protocol address */
u_int16_t ar_op; /* one of: */
#define ARPOP_REQUEST 1 /* request to resolve address */
#define ARPOP_REPLY 2 /* response to previous request */
#define ARPOP_REVREQUEST 3 /* request protocol address given
hardware */
#define ARPOP_REVREPLY 4 /* response giving protocol address */
#define ARPOP_INVREQUEST 8 /* request to identify peer */
#define ARPOP_INVREPLY 9 /* response identifying peer */
/*
* The remaining fields are variable in size,
* according to the sizes above.
*/
#ifdef COMMENT_ONLY
u_int8_t ar_sha[]; /* sender hardware address */
u_int8_t ar_spa[]; /* sender protocol address */
u_int8_t ar_tha[]; /* target hardware address */
u_int8_t ar_tpa[]; /* target protocol address */
#endif
};
I've tried to #define COMMENT_ONLY, with no result. But I think that the
solution is not #define COMMENT_ONLY.
I've searched on google, same with no result.
Someone know what it does depend?
Thanks in advance.
