Follow-up for 406041b7de.
Also, this makes
- the settings accept an empty string,
- if the specified value is too large, also use the advertised maximum
value.
- mention the range of the value in the man page.
"max" indicates the hardware advertised maximum queue buffer size
should be used.
The max sizes can be checked by running `ethtool -g <dev>` (Preset maximums).
Since the buffer sizes can't be set to 0 by users, internally we use 0 to
indicate that the hardware advertised maximum should be used.
To determine the network interface type for use in the `Type=` directive, it is more concise to use the `list` command. Whereas, the `status` command requires an interface parameter.
For example, on a RaspberryPi 4 the following shows that the `wlan0` interface type `wlan` is more coveniently listed by the `list` command.
```
root@raspberrypi4-64:~# networkctl list
IDX LINK TYPE OPERATIONAL SETUP
1 lo loopback carrier unmanaged
2 eth0 ether routable configured
3 wlan0 wlan off unmanaged
3 links listed.
```
Whereas the `networkctl status` command doesn't include this information.
```
root@raspberrypi4-64:~# networkctl status
● State: routable
Address: 192.168.1.141 on eth0
fd8b:8779:b7a4::f43 on eth0
fd8b:8779:b7a4:0:dea6:32ff:febe:d1ce on eth0
fe80::dea6:32ff:febe:d1ce on eth0
Gateway: 192.168.1.1 (CZ.NIC, z.s.p.o.) on eth0
DNS: 192.168.1.1
May 07 14:17:18 raspberrypi4-64 systemd-networkd[212]: eth0: Gained carrier
May 07 14:17:19 raspberrypi4-64 systemd-networkd[212]: eth0: Gained IPv6LL
May 07 14:17:19 raspberrypi4-64 systemd-networkd[212]: eth0: DHCPv6 address fd8b:8779:b7a4::f43/128 timeout preferred -1 valid -1
May 07 14:17:21 raspberrypi4-64 systemd-networkd[212]: eth0: DHCPv4 address 192.168.1.141/24 via 192.168.1.1
```
To get the interface type using the `status` command you need to specify an additional argument.
```
root@raspberrypi4-64:~# networkctl status wlan0
● 3: wlan0
Link File: /lib/systemd/network/99-default.link
Network File: n/a
Type: wlan
State: off (unmanaged)
Path: platform-fe300000.mmcnr
Driver: brcmfmac
HW Address: dc:a6:32:be:d1:cf (Raspberry Pi Trading Ltd)
MTU: 1500 (min: 68, max: 1500)
QDisc: noop
IPv6 Address Generation Mode: eui64
Queue Length (Tx/Rx): 1/1
```
This allows to limit units to machines that run on a certain firmware
type. For device tree defined machines checking against the machine's
compatible is also possible.
As we usually (unfortunately not always though) do not use abbreviations.
Tx may be standard abbreviation, but we already have e.g.
TransmitChecksumOffload=. So, let's use Transmit instead of Tx.
Follow-up for ef4a91a7e8.
Enable udev to set the transmit queue length of a device via a new directive to
be used in link files. The kernel stores this parameter as an unsigned 32 bit
integer. As typical values currently range in the order of 10 to a few 10,000
packets reduce the domain of valid values for this directive to 0..4294967294
and take the excluded 4294967295 == UINT32_MAX to indicate that the directive
is unset.
