KXDPGUN(8)

NAME
kxdpgun - XDP-powered DNS benchmarking tool

SYNOPSIS

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.

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

kdig(1).

AUTHOR
CZ.NIC Labs <https://www.knot-dns.cz>

COPYRIGHT
Copyright 2010–2025, CZ.NIC, z.s.p.o.