NetflowV5

 

struct NFHeaderV5{
  uint16_t    version;        //  flow-export version number
  uint16_t    count;          //  number of flow entries
  uint32_t    sysUptime;
  uint32_t    unix_secs;
  uint32_t    unix_nsecs;
  uint32_t    flow_sequence;  //  sequence number
  uint8_t     engine_type;    //  no VIP = 0, VIP2 = 1
  uint8_t     engine_id;      //  VIP2 slot number
  uint16_t    reserved;       //  reserved1,2
} ;

Total 24 bytes.

 

SO, the way to analysis the netflow packets is :

pHeader = (NFHeaderV5 *)pData;
NFV5 *pEntry = (NFV5 *)(pData + 24);

 

thus we get pHeader to know how many entrys in the packets by  pHeader->count;

struct NFV5{
  ipv4addr_t   srcaddr;     // source IP address
  ipv4addr_t   dstaddr;     // destination IP address
  ipv4addr_t   nexthop;     // next hop router's IP address
  uint16_t     input;       // input interface index
  uint16_t     output;      // output interface index
  uint32_t     pkts;        // packets sent in duration
  uint32_t     bytes;       // octets sent in duration
  uint32_t     first;       // SysUptime at start of flow
  uint32_t     last;        // and of last packet of flow
  uint16_t     srcport;     // TCP/UDP source port number or equivalent
  uint16_t     dstport;     // TCP/UDP destination port number or equivalent
  uint8_t      pad;
  uint8_t      tcp_flags;   // bitwise OR of all TCP flags in flow; 0x10
                            //  for non-TCP flows
  uint8_t      prot;        // IP protocol, e.g., 6=TCP, 17=UDP, ...
  uint8_t      tos;         // IP Type-of-Service
  uint16_t     src_as;      // originating AS of source address
  uint16_t     dst_as;      // originating AS of destination address
  uint8_t      src_mask;    // source address prefix mask bits
  uint8_t      dst_mask;    // destination address prefix mask bits
  uint16_t     reserved;
} ;

Thus, pEntry->srcaddr, pEntry->dstaddr, pEntry->bytes, pEntry->bytes, pEntry->...... are very helpful in the following progress.

 

That's all about netflow packets.

Enjoy yourselves!