Question

can somebody tell me does my conversation from c to delphi is well:

c code

struct nfq_data {
    /* packet_hdr - it HAVE to be the same as struct nfqnl_msg_packet_hdr */
    struct {
        uint32_t packet_id; /* unique ID of packet in queue in network order */
        uint16_t hw_protocol; /* hw protocol in network order */
        uint8_t hook; /* netfilter hook */
    } packet_hdr;
    /* packet_hw - it HAVE to be the same as struct nfqnl_msg_packet_hw */
    struct {
        uint16_t hw_addrlen; /* len of hw_addr in network order */
        uint16_t _pad;
        uint8_t hw_addr[8];
    } packet_hw;
    /* tm */
    struct {
        long sec;
        long usec;
    } tm;

    uint32_t if_index; /* Unique iface id */
    uint32_t verdict; /* Netfilter verdict value */
    uint32_t mark; /* Mark value */
    uint8_t if_name[IFNAMSIZE]; /* Name of incoming or outgoing iface */
    uint32_t data_len; /* Length of packet */
    uint8_t payload[0]; /* packet data */
};

where

typedef unsigned char uint8_t;
typedef unsigned __int16 uint16_t;
typedef unsigned __int32 uint32_t;
typedef unsigned __int64 uint64_t;

delphi

_packet_hdr = record
    packet_id: Cardinal;
    hw_protocol: Word;
    hook: Byte;
  end;

  _packet_hw = record
    hw_addrlen: Word;
    _pad: Word;
    hw_addr: array[0..7] of byte;
  end;

  _tm = record
    sec: Int64;
    usec: Int64;
  end;

  pnfq_data = ^nfq_data;
  nfq_data = record
    packet_hdr: _packet_hdr;
    packet_hw: _packet_hw;
    tm: _tm;
    if_index: Cardinal;
    verdict: Cardinal;
    mark: Cardinal;
    if_name: array[0..254] of Byte;
    data_len: Cardinal;
    payload: PChar; //TBytes;
  end;

    packet_hdr: _packet_hdr;
    packet_hw: _packet_hw;

I am receiving well, but after those nothing well.

Thanks in advance

Bojan

Answer 1

uint8_t payload[0];

Is that really a pointer(as in your delphi-code) or an inplace array of size 0 used to represent data coming after the header

And you should mark your records as packed. I don’t think it makes a difference in your specific code, but it is good practice since the packing rules are easy to get wrong, might change and not everybody knows them.
It probably makes a difference because packet_hdr is 7 bytes larges when packed, so the following packet_hw starts at offset 7 when packed, and probably at 8 when aligned.