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#include "decode_gtp.h"
#define GTP_TPDU 255
#define GTP1U_PORT 2152
#define GTP1_F_MASK 0x07
#define GTP1_GET_TYPE(gtp1_hdr) ((gtp1_hdr)->type)
#define GTP1_GET_FLAGS(gtp1_hdr) ((gtp1_hdr)->flags >> 5)
#define GTP1_GET_HLEN(gtp1_hdr) (((gtp1_hdr)->flags & GTP1_F_MASK) > 0 ? 12 : 8)
enum gtp_version_e
{
GTP_V0 = 0,
GTP_V1,
};
int decode_gtp(gtp_info_t *packet, const uint8_t *data, uint32_t len)
{
if (len < sizeof(gtp1_header_t))
{
LOG_ERROR("Parser GTP Header: packet length too small %d", len);
return -1;
}
packet->hdr = (gtp1_header_t *)data;
if (GTP1_GET_FLAGS(packet->hdr) != GTP_V1)
{
LOG_ERROR("Parser GTP Header: invalid gtp flags %d", GTP1_GET_FLAGS(packet->hdr));
return -1;
}
if (GTP1_GET_TYPE(packet->hdr) != GTP_TPDU)
{
LOG_ERROR("Parser GTP Header: invalid gtp type %d", GTP1_GET_TYPE(packet->hdr));
return -1;
}
/* From 29.060: "This field shall be present if and only if any one or
* more of the S, PN and E flags are set.".
*
* If any of the bit is set, then the remaining ones also have to be set.
*/
packet->hdr_len = GTP1_GET_HLEN(packet->hdr);
packet->payload = (uint8_t *)data + packet->hdr_len;
packet->payload_len = len - packet->hdr_len;
return 0;
}
int dump_gtp_info(gtp_info_t *packet, char *buff, size_t size)
{
return snprintf(buff, size,
"{\"hdr_len\":%u,\"data_len\":%u}",
packet->hdr_len,
packet->payload_len);
}
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