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#include "decode_tcp.h"
#define TCP_OPTLENMAX 40
#define TCP_GET_HLEN(tcp_hdr) ((((tcp_hdr)->th_offx2 & 0xf0) >> 4) << 2)
#define TCP_GET_SRC_PORT(tcp_hdr) ((uint16_t)ntohs((tcp_hdr)->th_sport))
#define TCP_GET_DST_PORT(tcp_hdr) ((uint16_t)ntohs((tcp_hdr)->th_dport))
int decode_tcp(tcp_info_t *packet, const uint8_t *data, uint32_t len)
{
if (len < TCP_HEADER_LEN)
{
LOG_ERROR("Parser TCP Header: packet length too small %d", len);
return -1;
}
packet->hdr = (tcp_header_t *)data;
uint8_t hlen = TCP_GET_HLEN(packet->hdr);
if (len < hlen)
{
LOG_ERROR("Parser TCP Header: TCP packet too small %d", len);
return -1;
}
uint8_t tcp_opt_len = hlen - TCP_HEADER_LEN;
if (tcp_opt_len > TCP_OPTLENMAX)
{
LOG_ERROR("Parser TCP Header: invalid opt length %d", tcp_opt_len);
return -1;
}
packet->opt_len = tcp_opt_len;
packet->src_port = TCP_GET_SRC_PORT(packet->hdr);
packet->dst_port = TCP_GET_DST_PORT(packet->hdr);
packet->hdr_len = hlen;
packet->payload = (uint8_t *)data + packet->hdr_len;
packet->payload_len = len - packet->hdr_len;
return 0;
}
int dump_tcp_info(tcp_info_t *packet, char *buff, size_t size)
{
return snprintf(buff, size,
"{\"src_port\":%u,\"dst_port\":%u,\"hdr_len\":%u,\"opt_len\":%u,\"data_len\":%u}",
packet->src_port,
packet->dst_port,
packet->hdr_len,
packet->opt_len,
packet->payload_len);
}
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