net/checksum/checksum_example.cpp

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/**
 * @example net/checksum/checksum_example.cpp
 * @section checksum_example_description Description
 *
 * This example transmits 10 packets where
 * L3/L4 checksum calculation is controlled
 * via control bits in the packet descriptor.
 *
 * By default this program transmits packets where
 * the adapter recalculates both L3 and L4 checksum.
 *
 * It is controlled by these code lines:
 *
 * constexpr ChecksumCmdLayer3 cmd_l3 = CHECKSUM_LAYER3_GOOD;
 *
 * constexpr ChecksumCmdLayer4 cmd_l4 = CHECKSUM_LAYER4_GOOD;
 *
 * By changing these code lines and recompiling, the
 * behavior can be changed to perform other action
 * on the L3 and L4 checksum.
 *
 * L3 options:
 *
 * CHECKSUM_LAYER3_DO_NOTHING
 *
 * CHECKSUM_LAYER3_BAD
 *
 * CHECKSUM_LAYER3_GOOD
 *
 *
 * L4 options:
 *
 * CHECKSUM_LAYER4_DO_NOTHING
 *
 * CHECKSUM_LAYER4_BAD
 *
 * CHECKSUM_LAYER4_GOOD
 *
 * CHECKSUM_LAYER4_GOOD_TCP_ZERO_UDP
 *
 * CHECKSUM_LAYER4_GOOD_TCP_ZERO_UDP_IPV4
 *
 * CHECKSUM_LAYER4_GOOD_TCP_UDP_ZERO_UDP_TUNNEL
 *
 * CHECKSUM_LAYER4_GOOD_TCP_UDP_ZERO_UDP_IPV4_TUNNEL
 *
 *
 */
#include <nt.h>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <iostream>
/**
 * IPv4 UDP packet with IPv4 checksum error and UDP checksum error.
 * No FCS included. Size: 96 byte.
 */
static constexpr uint8_t Test_packet[] {
  0x42, 0xb3, 0xbb, 0x9b, 0x7b, 0x6b, 0x02, 0xe1,
  0x27, 0xc4, 0x33, 0x0f, 0x08, 0x00, 0x45, 0x00,
  0x00, 0x52, 0x00, 0x01, 0x00, 0x00, 0x40, 0x11,
  0x79, 0x2c, 0x73, 0x35, 0xd7, 0xbe, 0x18, 0xdf,
  0x1a, 0x71, 0x34, 0x8b, 0xcf, 0x5f, 0x00, 0x3e,
  0xce, 0xe8, 0x70, 0x69, 0x7a, 0x7a, 0x61, 0x70,
  0x69, 0x7a, 0x7a, 0x61, 0x70, 0x69, 0x7a, 0x7a,
  0x61, 0x70, 0x69, 0x7a, 0x7a, 0x61, 0x70, 0x69,
  0x7a, 0x7a, 0x61, 0x70, 0x69, 0x7a, 0x7a, 0x61,
  0x70, 0x69, 0x7a, 0x7a, 0x61, 0x70, 0x69, 0x7a,
  0x7a, 0x61, 0x70, 0x69, 0x7a, 0x7a, 0x61, 0x70,
  0x69, 0x7a, 0x7a, 0x61, 0x70, 0x69, 0x7a, 0x7a
};
/**
 * An overlay struct for NtDyn3Descr_t making c-style or reinterpret cast possible.
 * frame_type:   Bit position 128. Overlays bit [3:0] in NtDyn3Descr_t.color_hi
 * checksum_cmd: Bit position 132. Overlays bit [8:4] in NtDyn3Descr_t.color_hi
 */
struct Dyn3_checksum_overlay {
  uint64_t dont_care0;
  uint64_t dont_care1;
  uint64_t frame_type:4;
  uint64_t checksum_cmd:5;
  uint64_t dont_care2:39;
};
/**
 * Valid values for layer 3 checksum command.
 */
enum ChecksumCmdLayer3 {
  CHECKSUM_LAYER3_DO_NOTHING = 0, // Do nothing
  CHECKSUM_LAYER3_BAD = 2,        // Insert BAD checksum in IPv4 header
  CHECKSUM_LAYER3_GOOD = 3,       // Insert GOOD checksum in IPv4 header
};
/**
 * Valid values for layer 4 checksum command.
 */
enum ChecksumCmdLayer4 {
  CHECKSUM_LAYER4_DO_NOTHING = 0,                        // Do nothing
  CHECKSUM_LAYER4_BAD = 2,                               // Insert BAD checksum in TCP/UDP header
  CHECKSUM_LAYER4_GOOD = 3,                              // Insert GOOD checksum in TCP/UDP header
  CHECKSUM_LAYER4_GOOD_TCP_ZERO_UDP = 4,                 // Insert GOOD checksum in TCP header and a value of ZERO in UDP header
  CHECKSUM_LAYER4_GOOD_TCP_ZERO_UDP_IPV4 = 5,            // Insert GOOD checksum in TCP header and a value of ZERO in UDP header when IP is IPv4
  CHECKSUM_LAYER4_GOOD_TCP_UDP_ZERO_UDP_TUNNEL = 6,      // Insert GOOD checksum in TCP/UDP header and a value of ZERO in UDP header when part of a tunnel
  CHECKSUM_LAYER4_GOOD_TCP_UDP_ZERO_UDP_IPV4_TUNNEL = 7, // Insert GOOD checksum in TCP/UDP header and a value of ZERO in UDP header when IP is IPv4 and part of a tunnel
};
/**
 * Valid values for a descriptor frame type.
 *
 * Bit [  0]: Value 0: Not tunneled
 *            Value 1: Tunneled
 *
 * Bit [  1]: Value 0: IPv4 or other
 *            Value 1: IPv6
 *
 * Bit [3:2]: Value 0: Other
 *            Value 1: TCP
 *            Value 2: UDP
 *            Value 3: Reserved
 */
enum FrameType {
  FRAME_TYPE_IPV4_TCP          = 0x0 | 0x0 | 0x4,
  FRAME_TYPE_IPV4_UDP          = 0x0 | 0x0 | 0x8,
  FRAME_TYPE_IPV6_TCP          = 0x0 | 0x2 | 0x4,
  FRAME_TYPE_IPV6_UDP          = 0x0 | 0x2 | 0x8,
  FRAME_TYPE_IPV4_TCP_TUNNELED = 0x1 | 0x0 | 0x4,
  FRAME_TYPE_IPV4_UDP_TUNNELED = 0x1 | 0x0 | 0x8,
  FRAME_TYPE_IPV6_TCP_TUNNELED = 0x1 | 0x2 | 0x4,
  FRAME_TYPE_IPV6_UDP_TUNNELED = 0x1 | 0x2 | 0x8,
};
/**
 * Correctly combines layer 3 checksum command and layer 4 checksum command.
 */
static inline uint64_t checksum_command(ChecksumCmdLayer3 l3, ChecksumCmdLayer4 l4)
{
  return (((uint64_t)l3 & 0x3) << 3) | ((uint64_t)l4 & 0x7);
}
/**
 * Handles and prints NT error messages, and the terminates the program.
 */
static inline void handle_error_status(int status, const char* message)
{
  if (status != NT_SUCCESS) {
    char error_buffer[NT_ERRBUF_SIZE];
    NT_ExplainError(status, error_buffer, sizeof(error_buffer));
    std::cerr << message << ": " << error_buffer << std::endl;
    std::exit(EXIT_FAILURE);
  }
}
int main(int, char**)
{
  constexpr uint64_t fcs_size = 4;
  constexpr uint64_t num_packets = 10;
  constexpr uint32_t tx_port = 0;
  constexpr ChecksumCmdLayer3 cmd_l3 = CHECKSUM_LAYER3_GOOD;
  constexpr ChecksumCmdLayer4 cmd_l4 = CHECKSUM_LAYER4_GOOD;
  int             status;
  NtNetBuf_t      net_buffer;
  NtNetStreamTx_t net_tx_stream;
  NtNetTxAttr_t   attr;
  // Initialize NT API.
  status = NT_Init(NTAPI_VERSION);
  handle_error_status(status, "NT_Init() failed");
  // Initialize TX attributes struct and set up relevant stream related attributes.
  NT_NetTxOpenAttrInit(&attr);
  NT_NetTxOpenAttrSetName(&attr, "Checksum example NetTx");
  NT_NetTxOpenAttrSetPortMask(&attr, 1 << tx_port);
  // Setting descriptor mode to DYN3 will cause Net Buffers received from NT_NetTxGet
  // to be initialized with a DYN3 packet descriptor.
  status = NT_NetTxOpenAttrSetDescriptorMode(&attr, NT_NETTX_DESCRIPTOR_MODE_DYN3);
  handle_error_status(status, "NT_NetTxOpenAttrSetDescriptorMode() failed");
  // To tell the adapter where to look for the frame type and checksum command bits.
  status = NT_NetTxOpenAttrSetDescriptorPosFrameType(&attr, true, 128);    // Bit position of Dyn3_checksum_overlay.frame_type
  handle_error_status(status, "NT_NetTxOpenAttrSetDescriptorPosFrameType() failed");
  status = NT_NetTxOpenAttrSetDescriptorPosChecksumCmd(&attr, true, 132);  // Bit position of Dyn3_checksum_overlay.checksum_cmd
  handle_error_status(status, "NT_NetTxOpenAttrSetDescriptorPosChecksumCmd() failed");
  // Open TX stream with attributes
  status = NT_NetTxOpen_Attr(&net_tx_stream, &attr);
  handle_error_status(status, "NT_NetTxOpen() failed");
  for (uint64_t i = 0; i < num_packets; ++i) {
    // Use the option NT_NETTX_PACKET_OPTION_DYN to get a net buffer initialized with
    // the DYN3 packet descriptor that was specified in NT_NetTxOpenAttrSetDescriptorMode.
    // Note: Since the DYN3 packet descriptor does not contain a wire-length argument
    // must be the correct size of the packet, not just big enough.
    status = NT_NetTxGet(net_tx_stream, &net_buffer, tx_port, sizeof(Test_packet) + fcs_size, NT_NETTX_PACKET_OPTION_DYN, 100);
    handle_error_status(status, "NT_NetTxGet() failed");
    // Get a pointer to the beginning of the Ethernet frame, and copy Test_packet to that memory.
    uint8_t* l2_ptr = reinterpret_cast<uint8_t*>(NT_NET_GET_PKT_L2_PTR(net_buffer));
    std::memcpy(l2_ptr, Test_packet, sizeof(Test_packet));
    // Get pointer to DYN3 packet descriptor.
    auto descr_ptr = NT_NET_GET_PKT_DESCR_PTR_DYN3(net_buffer);
    auto overlay_ptr = reinterpret_cast<Dyn3_checksum_overlay*>(descr_ptr);
    // Set offset 0 to start of IP header, and offset 1 to start of UDP header.
    descr_ptr->offset0 = 14;  // Point to start of Layer 3, i.e. set to size of Ethernet header
    descr_ptr->offset1 = 34;  // Point to start of Layer 4, i.e. set to size of Ethernet header + IPv4 header with no options
    // Set color values via the overlay struct.
    overlay_ptr->frame_type = FRAME_TYPE_IPV4_UDP & 0xF;
    overlay_ptr->checksum_cmd = checksum_command(cmd_l3, cmd_l4) & 0x1F;
    // Release / transmit net buffer from NT_NetTxGet
    status = NT_NetTxRelease(net_tx_stream, net_buffer);
    handle_error_status(status, "NT_NetTxRelease() failed");
  }
  // Close TX stream, and then the NT API.
  status = NT_NetTxClose(net_tx_stream);
  handle_error_status(status, "NT_NetTxClose() failed");
  NT_Done();
  return 0;
}