```
21.16. Vendor Class Option
This option is used by a client to identify the vendor that
manufactured the hardware on which the client is running. The
information contained in the data area of this option is contained in
one or more opaque fields that identify details of the hardware
configuration. The format of the Vendor Class option is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_VENDOR_CLASS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| enterprise-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. vendor-class-data .
. . . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 28: Vendor Class Option Format
option-code OPTION_VENDOR_CLASS (16).
option-len 4 + length of vendor-class-data field.
enterprise-number The vendor's registered Enterprise Number as
maintained by IANA [IANA-PEN]. A 4-octet
field containing an unsigned integer.
vendor-class-data The hardware configuration of the node on
which the client is running. A
variable-length field (4 octets less than the
value in the option-len field).
The vendor-class-data field is composed of a series of separate
items, each of which describes some characteristic of the client's
hardware configuration. Examples of vendor-class-data instances
might include the version of the operating system the client is
running or the amount of memory installed on the client.
Each instance of vendor-class-data is formatted as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
| vendor-class-len | opaque-data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
Figure 29: Format of vendor-class-data Field
The vendor-class-len field is 2 octets long and specifies the length
of the opaque vendor-class-data in network byte order.
Servers and clients MUST NOT include more than one instance of
OPTION_VENDOR_CLASS with the same Enterprise Number. Each instance
of OPTION_VENDOR_CLASS can carry multiple vendor-class-data
instances.
```
sd-network: DHCPv6 - add support to send userclass option
21.15. User Class Option
The User Class option is used by a client to identify the type or
category of users or applications it represents.
The format of the User Class option is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_USER_CLASS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. user-class-data .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 26: User Class Option Format
option-code OPTION_USER_CLASS (15).
option-len Length of user-class-data field.
user-class-data The user classes carried by the client. The
length, in octets, is specified by
option-len.
The information contained in the data area of this option is
contained in one or more opaque fields that represent the user class
or classes of which the client is a member. A server selects
configuration information for the client based on the classes
identified in this option. For example, the User Class option can be
used to configure all clients of people in the accounting department
with a different printer than clients of people in the marketing
department. The user class information carried in this option MUST
be configurable on the client.
The data area of the User Class option MUST contain one or more
instances of user-class-data information. Each instance of
user-class-data is formatted as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
| user-class-len | opaque-data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
Figure 27: Format of user-class-data Field
Let's use size_t for numbers of entries in memory.
Let's use const wherever appropriate.
Drop `_server` suffix from function name where we don't have it for
similar other cases.
We always need to make them unions with a "struct cmsghdr" in them, so
that things properly aligned. Otherwise we might end up at an unaligned
address and the counting goes all wrong, possibly making the kernel
refuse our buffers.
Also, let's make sure we initialize the control buffers to zero when
sending, but leave them uninitialized when reading.
Both the alignment and the initialization thing is mentioned in the
cmsg(3) man page.
We need to use the CMSG_SPACE() macro to size the control buffers, not
CMSG_LEN(). The former is rounded up to next alignment boundary, the
latter is not. The former should be used for allocations, the latter for
encoding how much of it is actually initialized. See cmsg(3) man page
for details about this.
Given how confusing this is, I guess we don't have to be too ashamed
here, in most cases we actually did get this right.
Split out of #15457, let's see if this is the culprit of the CI failure.
(also setting green label here, since @keszybz already greenlit it in that other PR)
It's not that I think that "hostname" is vastly superior to "host name". Quite
the opposite — the difference is small, and in some context the two-word version
does fit better. But in the tree, there are ~200 occurrences of the first, and
>1600 of the other, and consistent spelling is more important than any particular
spelling choice.
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.
Susant Sahani
Lennart Poettering
Benjamin Robin
Andrew Doran
Thomas Haller
Zbigniew Jędrzejewski-Szmek
Frantisek Sumsal
David Wood
Chris Down
Yu Watanabe