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``kxdpgun`` – DNS benchmarking tool
===================================

Synopsis
--------

:program:`kxdpgun` [*options*] **-i** *filename* *target*

Description
-----------

Powerful generator of DNS traffic, sending and receiving packets through XDP.

Queries are generated according to a textual file which is read sequentially
in a loop until a configured duration elapses. The order of queries is not
guaranteed. Responses are received (unless disabled) and counted, but not
checked against queries.

The number of parallel threads is autodetected according to the number of queues
configured for the network interface.

Parameters
..........

*filename*
  Path to the queries file. See the description below regarding the file format.

*target*
  Either the domain name, IPv4 or IPv6 address of a remote target.

Options
.......

**-t**, **--duration** *seconds*
  Duration of traffic generation, specified as a decimal number in seconds
  (default is 5.0).

**-T**, **--tcp**\[\ **=**\ *debug_mode*\]
  Send queries over TCP. See the list of optional debug modes below.

**-U**, **--quic**\[\ **=**\ *debug_mode*\]
  Send queries over QUIC. See the list of optional debug modes below.

**-Q**, **--qps** *queries*
  Number of queries-per-second (approximately) to be sent (default is 1000).
  The program is not optimized for low speeds at which it may lose
  communication packets. The recommended minimum speed is 2 packets per thread
  (Rx/Tx queue).

**-b**, **--batch** *size*
  Send more queries in a batch. Improves QPS but may affect the counterpart's
  packet loss (default is 10 for UDP and 1 for TCP/QUIC).

**-r**, **--drop**
  Drop incoming responses. Improves QPS, but disables response statistics.

**-p**, **--port** *number*
  Remote destination port (default is 53 for UDP/TCP, 853 for QUIC).

**-F**, **--affinity** *cpu_spec*
  CPU affinity for all threads specified in the format [<cpu_start>][s<cpu_step>],
  where <cpu_start> is the CPU ID for the first thread and <cpu_step> is the
  CPU ID increment for next thread (default is 0s1).

**-i**, **--infile** *filename*
  Path to a file with query templates.

**-B**, **--binary**
  Specify that input file is in binary format. This format is similar to the
  TCP DNS message format. The file contains records formatted as 2-octet length
  (network order) followed by a message in DNS wire format.

**-I**, **--interface** *interface*
  Network interface for outgoing communication. This can be useful in situations
  when the interfaces are in a bond for example.

**-l**, **--local** *localIP*\ [**/**\ *prefix*]
  Override the auto-detected source IP address. If an address range is specified
  instead, various IPs from the range will be used for different queries uniformly
  (address range not supported in the QUIC mode).

**-L**, **--mac-local**
  Override auto-detected local MAC address.

**-R**, **--mac-remote**
  Override auto-detected remote MAC address.

**-v**, **--vlan** *id*
  Add VLAN 802.1Q header with the given id. VLAN offloading should be disabled.

**-e**, **--edns-size** *size*
  EDNS UDP payload size, range 512-4096 (default is 1232). Note that over XDP
  the maximum supported MTU is 1790.

**-m**, **--mode** *mode*
  Set the XDP mode. Supported values are:

  - **auto** (default) – the XDP mode is selected automatically to achieve
    the best performance, which means that native driver support is preferred
    over the generic one, and zero-copy is used if available.

  - **copy** – the XDP socket copy mode is forced even if zero-copy
    is available. This can resolve various driver issues, but at the cost
    of lower performance.

  - **generic** – the generic XDP implementation is forced even if native
    implementation is available. This mode doesn't require support from the
    driver nor hardware, but offers the worst performance.

**-G**, **--qlog** *path*
  Generate qlog files in the directory specified by *path*. The directory
  has to exist.

  This option is ignored if not in the QUIC mode. The recommended usage is
  with **--quic=R** or with low QPS. Otherwise, too many files are generated.

**-j**, **--json**
  Print statistics formatted as json.

**-S**, **--stats-period** *period*
  Report statistics automatically every *period* milliseconds.

  These reports contain only metrics collected in the given period.

**-h**, **--help**
  Print the program help.

**-V**, **--version**
  Print the program version. The option **-VV** makes the program
  print the compile time configuration summary.

Queries file format
...................

Each line describes a query in the form:

*query_name* *query_type* [*flags*]

Where *query_name* is a domain name to be queried, *query_type* is a record type
name, and *flags* is a single character:

**E** Send query with EDNS.

**D** Request DNSSEC (EDNS + DO flag).

TCP/QUIC debug modes
....................

**0**
  Perform full handshake for all connections (QUIC only).

**1**
  Just send SYN (Initial) and receive SYN-ACK (Handshake).

**2**
  Perform TCP/QUIC handshake and don't send anything, allow close initiated by counterpart.

**3**
  Perform TCP/QUIC handshake and don't react further.

**5**
  Send incomplete query (N-1 bytes) and don't react further.

**7**
  Send query and don't ACK the response or anything further.

**8**
  Don't close the connection and ignore close by counterpart.

**9**
  Operate normally except for not ACKing the final FIN+ACK (TCP only).

**R**
  Instead of opening a connection for each query, reuse connections.

Signals
.......

Sending USR1 signal to a running process triggers current statistics dump
to the standard output. In combination with **-S** may cause erratic printout
timing.

Notes
-----

Linux kernel 4.18+ is required.

The utility has to be executed under root or with these capabilities:
CAP_NET_RAW, CAP_NET_ADMIN, CAP_SYS_ADMIN, CAP_IPC_LOCK, and CAP_SYS_RESOURCE
(Linux < 5.11).

The utility allocates source UDP/TCP ports from the range 2000-65535.

For proper operation of QUIC mode on a multi-queue Mellanox/NVIDIA network
card, it may be necessary to set ``ethtool -X <dev> xfrm none``.

Due to the multi-threaded program structure there are slight discrepancies in
the timespan during which metrics are collected for any given thread. The
statistics printouts ignore this and are thus ever-so-slightly inaccurate. The
error margin decreases proportionally to the volume of data & timespan over
which they are collected.

Exit values
-----------

Exit status of 0 means successful operation. Any other exit status indicates
an error.

Examples
--------

Manually created queries file::

  abc6.example.com. AAAA
  nxdomain.example.com. A
  notzone. A
  a.example.com. NS E
  ab.example.com. A D
  abcd.example.com. DS D

Queries file generated from a zone file (Knot DNS format)::

  cat ZONE_FILE | awk "{print \$1,\$3}" | grep -E "(NS|DS|A|AAAA|PTR|MX|SOA)$" | sort -u -R > queries.txt

Basic usage::

  # kxdpgun -i ~/queries.txt 2001:DB8::1

*Using UDP with increased batch size*::

  # kxdpgun -t 20 -Q 1000000 -i ~/queries.txt -b 20 -p 8853 192.0.2.1

*Using TCP*::

  # kxdpgun -t 20 -Q 100000 -i ~/queries.txt -T -p 8853 192.0.2.1

See Also
--------

:manpage:`kdig(1)`.
