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#include <sys/types.h>
#include <netinet/in.h>
#include <stdio.h>
#include "libpacketdump.h"
typedef struct gre_t {
uint16_t flags;
uint16_t ethertype;
uint16_t checksum;
uint16_t reserved1;
} gre_t;
DLLEXPORT void decode(int link_type UNUSED,const char *packet,unsigned len)
{
// GRE
if (len<2) {
printf(" GRE: [Truncated]\n");
return;
}
printf(" GRE: %s\n",
ntohs(((gre_t*)packet)->flags) & 0x8000
? "Checksum present"
: "Checksum absent");
printf(" GRE: Version: %d\n", ntohs(((gre_t*)packet)->flags) & 0x0007);
printf(" GRE: Protocol: %04x\n", ntohs(((gre_t*)packet)->ethertype));
if (ntohs(((gre_t*)packet)->flags) & 0x8000) {
decode_next(packet+4,len-4,"link",
ntohs(((gre_t*)packet)->ethertype));
}
else {
decode_next(packet+8,len-8,"link",
ntohs(((gre_t*)packet)->ethertype));
}
return;
}
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