`tron=`

- Trace ON. Takes a boolean argument. If `true`, enables full code tracing. The trace will be displayed in the system log such as systemd's journal. Defaults to `false`.

`hdr-digest=`

- Enable Protocol Data Unit (PDU) Header Digest. Takes a boolean argument. NVMe/TCP facilitates an optional PDU Header digest. Digests are calculated using the CRC32C algorithm. If `true`, Header Digests are inserted in PDUs and checked for errors. Defaults to `false`.

`data-digest=`

- Enable Protocol Data Unit (PDU) Data Digest. Takes a boolean argument. NVMe/TCP facilitates an optional PDU Data digest. Digests are calculated using the CRC32C algorithm. If `true`, Data Digests are inserted in PDUs and checked for errors. Defaults to `false`.

`kato=`

- Keep Alive Timeout (KATO) in seconds. Takes an unsigned integer. This field specifies the timeout value for the Keep Alive feature in seconds. Defaults to 30 seconds for Discovery Controller connections and 120 seconds for I/O Controller connections.

`ip-family=`

- Takes a string argument. With this you can specify whether IPv4, IPv6, or both are supported when connecting to a Controller. Connections will not be attempted to IP addresses (whether discovered or manually configured with `controller=`) disabled by this option. If an invalid value is entered, then the default (see below) will apply.

  Choices are `ipv4`, `ipv6`, or `ipv4+ipv6`.

  Defaults to `ipv4+ipv6`.

`queue-size=`

- Takes a value in the range 16...1024.

  Overrides the default number of elements in the I/O queues created by the driver. This option will be ignored for discovery, but will be passed on to the subsequent connect call.

  Note: This parameter is identical to that provided by nvme-cli.

  Defaults to `128`.

`reconnect-delay=`

- Takes a value in the range 1 to N seconds.

  Overrides the default delay before reconnect is attempted after a connect loss.

  Note: This parameter is identical to that provided by nvme-cli.

  Defaults to `10`. Retry to connect every 10 seconds.

`ctrl-loss-tmo=`

- Takes a value in the range -1, 0, ..., N seconds. -1 means retry forever. 0 means do not retry.

  Overrides the default controller loss timeout period (in seconds).

  Note: This parameter is identical to that provided by nvme-cli.

  Defaults to `600` seconds (10 minutes).

`disable-sqflow=`

- Takes a boolean argument. Disables SQ flow control to omit head doorbell update for submission queues when sending nvme completions.

  Note: This parameter is identical to that provided by nvme-cli.

  Defaults to `false`.

# [Controllers] section

The following options are available in the `[Controllers]` section:

`controller=`

- Controllers are specified with the `controller` option. This option may be specified more than once to specify more than one controller. The format is one line per Controller composed of a series of fields separated by semi-colons as follows:

      controller=transport=[trtype];traddr=[traddr];trsvcid=[trsvcid];host-traddr=[traddr],host-iface=[iface];nqn=[nqn]

  ## Fields

  `transport=`

- This is a mandatory field that specifies the network fabric being used for a NVMe-over-Fabrics network. Current `trtype` values understood are:

  ## Transport type

  trtype | Definition
  rdma | The network fabric is an rdma network (RoCE, iWARP, Infiniband, basic rdma, etc)
  fc | The network fabric is a Fibre Channel network.
  tcp | The network fabric is a TCP/IP network.
  loop | Connect to a NVMe over Fabrics target on the local host

`traddr=`

- This is a mandatory field that specifies the network address of the Controller. For transports using IP addressing (e.g. rdma) this should be an IP-based address (ex. IPv4, IPv6). It could also be a resolvable host name (e.g. localhost).

`trsvcid=`

- This is an optional field that specifies the transport service id. For transports using IP addressing (e.g. rdma, tcp) this field is the port number.

  Depending on the transport type, this field will default to either 8009 or 4420 as follows.

  UDP port 4420 and TCP port 4420 have been assigned by IANA for use by NVMe over Fabrics. NVMe/RoCEv2 controllers use UDP port 4420 by default. NVMe/iWARP controllers use TCP port 4420 by default.

  TCP port 4420 has been assigned for use by NVMe over Fabrics and TCP port 8009 has been assigned by IANA for use by NVMe over Fabrics discovery. TCP port 8009 is the default TCP port for NVMe/TCP discovery controllers. There is no default TCP port for NVMe/TCP I/O controllers, the Transport Service Identifier (TRSVCID) field in the Discovery Log Entry indicates the TCP port to use.

  The TCP ports that may be used for NVMe/TCP I/O controllers include TCP port 4420, and the Dynamic and/or Private TCP ports (i.e., ports in the TCP port number range from 49152 to 65535). NVMe/TCP I/O controllers should not use TCP port 8009. TCP port 4420 shall not be used for both NVMe/iWARP and NVMe/TCP at the same IP address on the same network.

  Ref: IANA Service names port numbers

`nqn=`

- This field specifies the Controller's NVMe Qualified Name.

  This field is mandatory for I/O Controllers, but is optional for Discovery Controllers (DC). For the latter, the NQN will default to the well-known DC NQN: `nqn.2014-08.org.nvmexpress.discovery` if left undefined.

`host-traddr=`

- This is an optional field that specifies the network address used on the host to connect to the Controller. For TCP, this sets the source address on the socket.

`host-iface=`

- This is an optional field that specifies the network interface used on the host to connect to the Controller (e.g. IP eth1, enp2s0, enx78e7d1ea46da). This forces the connection to be made on a specific interface instead of letting the system decide.

`dhchap-ctrl-secret=`

- This is an optional field that specifies the NVMe In-band authentication controller secret (i.e. key) for bi-directional authentication; needs to be in ASCII format as specified in NVMe 2.0 section 8.13.5.8 'Secret representation'. Bi-directional authentication will be attempted when present.

`hdr-digest=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

`data-digest=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

`nr-io-queues=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

`nr-write-queues=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

`nr-poll-queues=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

`queue-size=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

`kato=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

`reconnect-delay=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

`ctrl-loss-tmo=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

`disable-sqflow=`

- See definition in [Global] section. This is an optional field used to override the value specified in the [Global] section.

Examples:

    controller = transport=tcp;traddr=localhost;trsvcid=8009
    controller = transport=tcp;traddr=2001:db8::370:7334;host-iface=enp0s8
    controller = transport=fc;traddr=nn-0x204600a098cbcac6:pn-0x204700a098cbcac6

`exclude=`

- Controllers that should be excluded can be specified with the `exclude=` option. Using mDNS to automatically discover and connect to controllers, can result in unintentional connections being made. This keyword allows configuring the controllers that should not be connected to.

  The syntax is the same as for "controller", except that only `transport`, `traddr`, `trsvcid`, `nqn`, and `host-iface` apply. Multiple `exclude=` keywords may appear in the config file to specify more than 1 excluded controller.

  Note 1: A minimal match approach is used to eliminate unwanted controllers. That is, you do not need to specify all the parameters to identify a controller. Just specifying the `host-iface`, for example, can be used to exclude all controllers on an interface.

  Note 2: `exclude=` takes precedence over `controller`. A controller specified by the `controller` keyword, can be eliminated by the `exclude=` keyword.

  Examples:

      exclude = transport=tcp;traddr=fe80::2c6e:dee7:857:26bb # Eliminate a specific address
      exclude = host-iface=enp0s8                             # Eliminate everything on this interface