Commit 08c588d18b moved attachment of the
sd-event into creation of the dhcp_client or ipv4ll in dhcp4_configure()
or ipv4ll_configure(), but these can also be created in link_load(),
so that creation needs to also perform sd-event attachment.
Without this, dhcp_client or ipv4ll created in link_load() will not have
an ->event and will fail assertion, causing networkd to fail, e.g.:
Assertion 'client->event' failed at src/libsystemd-network/sd-dhcp-client.c:1283, function client_start_delayed(). Ignoring.
ens2: Could not acquire DHCPv4 lease: Invalid argument
ens2: Failed
```
❯ build/networkctl status veth99 ─╯
● 17: veth99
Link File: /usr/lib/systemd/network/99-default.link
Network File: /usr/lib/systemd/network/veth99.network
Type: ether
State: routable (configured)
Driver: veth
HW Address: 1e:04:f8:b8:2f:d4
MTU: 1500 (min: 68, max: 65535)
QDisc: noqueue
IPv6 Address Generation Mode: eui64
Queue Length (Tx/Rx): 1/1
Auto negotiation: no
Speed: 10Gbps
Duplex: full
Port: tp
Address: 192.168.5.35 (DHCP4)
fe80::1c04:f8ff:feb8:2fd4
Gateway: 192.168.5.1
DNS: 192.168.5.1
NTP: 192.168.5.1
SIP: 192.168.5.4
192.168.5.5
Time Zone: Europe/Berlin
Mar 21 23:26:32 Zeus systemd-networkd[671]: veth99: Link DOWN
Mar 21 23:26:32 Zeus systemd-networkd[671]: veth99: Lost carrier
Mar 22 10:25:35 Zeus systemd-networkd[671]: veth99: Link UP
Mar 22 10:25:35 Zeus systemd-networkd[671]: veth99: Gained carrier
Mar 22 10:25:36 Zeus systemd-networkd[671]: veth99: Gained IPv6LL
Mar 22 10:29:02 Zeus systemd-networkd[671]: veth99: Link DOWN
Mar 22 10:29:02 Zeus systemd-networkd[671]: veth99: Lost carrier
Mar 22 10:29:13 Zeus systemd-networkd[671]: veth99: Link UP
Mar 22 10:29:13 Zeus systemd-networkd[671]: veth99: Gained carrier
Mar 22 10:29:14 Zeus systemd-networkd[671]: veth99: Gained IPv6LL
```
When specifying `DHCPv4.SendOption=`, it is used by systemd-networkd to
set the value of that option within the DHCP request that is sent out.
This differs to setting `DHCPServer.SendOption=`, which will place all
the options together as suboptions into the vendor-specific information
(code 43) option.
This commit adds two new config options, `DHCPv4.SendVendorOption=` and
`DHCPServer.SendVendorOption=`. These both have the behaviour of the old
`DHCPServer.SendOption=` flag, and set the value of the suboption in the
vendor-specific information option.
The behaviour of `DHCPServer.SendOption=` is then changed to reflect
that of `DHCPv4.SendOption=`. It will set the value of the corresponding
option in the DHCP request.
Proportional Integral controller-Enhanced (PIE) is a control
theoretic active queue management scheme. It is based on the
proportional integral controller but aims to control delay.
http://man7.org/linux/man-pages/man8/tc-pie.8.html
