Provided by: irtt_0.9.0-2ubuntu0.24.04.3_amd64 
NAME
irtt-server - Isochronous Round-Trip Time Server
SYNOPSIS
irtt server [args]
DESCRIPTION
irtt server is the server for irtt(1) (irtt.html).
OPTIONS
-b addresses
Bind addresses (default “:2112”), comma separated list of:
Format Address Type
────────────────────────────────────────────────────
:port unspecified address with port, use
with care
host host with default port 2112, see Host
formats below
host:port host with specified port, see Host
formats below
%iface all addresses on interface iface with
default port 2112
%iface:port all addresses on interface iface with
port
Note: iface strings may contain * to match multiple interfaces
-d duration
Max test duration, or 0 for no maximum (default 0s, see Duration units below)
-i interval
Min send interval, or 0 for no minimum (default 10ms, see Duration units below)
-l length
Max packet length (default 0), or 0 for no maximum. Numbers less than size of required headers
will cause test packets to be dropped.
--hmac=key
Add HMAC with key (0x for hex) to all packets, provides:
• Dropping of all packets without a correct HMAC
• Protection for server against unauthorized discovery and use
--timeout=duration
Timeout for closing connections if no requests received on a connection (default 1m0s, see Dura‐
tion units below). 0 means no timeout (not recommended, especially on public servers). Max
client interval will be restricted to timeout/4.
--pburst=#
Packet burst allowed before enforcing minimum interval (default 5)
--fill=fill
Payload fill if not requested (default pattern:69727474). Possible values include:
Value Fill
───────────────────────────────────────────────────
none Echo client payload (insecure on pub‐
lic servers)
rand Use random bytes from Go's math.rand
pattern:XX Use repeating pattern of hex (default
69727474)
--allow-fills=fills
Comma separated patterns of fill requests to allow (default rand). See options for –fill. Notes:
• Patterns may contain * for matching
• Allowing non-random fills insecure on public servers
• Use --allow-fills=“” to disallow all fill requests
--tstamp=modes
Timestamp modes to allow (default dual). Possible values:
Value Allowed Timestamps
───────────────────────────────────────────────
none Don't allow any timestamps
single Allow a single timestamp (send, re‐
ceive or midpoint)
dual Allow dual timestamps
--no-dscp
Don't allow setting dscp (default false)
--set-src-ip
Set source IP address on all outgoing packets from listeners on unspecified IP addresses (use for
more reliable reply routing, but increases per-packet heap allocations)
--gc=mode
Sets garbage collection mode (default on). Possible values:
Value Meaning
──────────────────────────────────────────────
on Garbage collector always on
off Garbage collector always off
idle Garbage collector enabled only when
idle
--thread
Lock request handling goroutines to OS threads
-h Show help
-v Show version
Host formats
Hosts may be either hostnames (for IPv4 or IPv6) or IP addresses. IPv6 addresses must be surrounded by
brackets and may include a zone after the % character. Examples:
Type Example
──────────────────────────────────────
IPv4 IP 192.168.1.10
IPv6 IP [2001:db8:8f::2/32]
IPv4/6 hostname localhost
Note: IPv6 addresses must be quoted in most shells.
Duration units
Durations are a sequence of decimal numbers, each with optional fraction, and unit suffix, such as:
“300ms”, “1m30s” or “2.5m”. Sanity not enforced.
Suffix Unit
──────────────────────
h hours
m minutes
s seconds
ms milliseconds
ns nanoseconds
SECURITY
Running an IRTT server that's open to the outside world requires some additional attention. For
starters, irtt server's command line flags should be used to, at a minimum:
• Restrict the duration (-d), interval (-i) and length (-l) of tests, particularly for public servers
• Set an HMAC key (--hmac) for private servers to prevent unauthorized discovery and use
In addition, there are various systemd(1) options available for securing services. The irtt.service file
included with the distribution sets many commonly used options, but should not be considered exhaustive.
To secure a server for public use, additional steps may be taken that are outside of the scope of this
documentation, including but not limited to:
• Setting up an iptables firewall (only UDP port 2112 must be open)
• Setting up a chroot jail
It should be noted that there are no known security vulnerabilities in the Go language at this time, and
the steps above, in particular the chroot jail, may or may not serve to enhance security in any way.
Go-based servers are generally regarded as safe because of Go's high-level language constructs for memory
management, and at this time IRTT makes no use of Go's unsafe (https://golang.org/pkg/unsafe/) package.
EXIT STATUS
irtt server exits with one of the following status codes:
Code Meaning
──────────────────────────────────────
0 Success
1 Runtime error
2 Command line error
3 Two interrupt signals received
EXAMPLES
$ irtt server
Starts the server and listens on all addresses (unspecified address)
$ irtt server -d 30s -i 20ms -l 256 --fill=rand --allow-fills=“”
Starts the server and listens on all addresses, setting the maximum test duration to 30 seconds,
minimum interval to 20 ms, and maximum packet length to 256 bytes. Disallows fill requests and
forces all return packets to be filled with random data.
$ irtt server -b 192.168.100.11:64381 --hmac=secret
Starts the server and binds to IPv4 address 192.168.100.11, port 64381. Requires a valid HMAC on
all packets with the key secret, otherwise packets are dropped.
SEE ALSO
irtt(1) (irtt.html), irtt-client(1) (irtt-client.html)
IRTT GitHub repository (https://github.com/peteheist/irtt/)
v0.9.0 February 11, 2018 IRTT-SERVER(1)