Will be used by nftables nfnetlink backend.
It sends a series of netlink messages that form a nftables
update transaction.
The transaction will then generate a series of ack messages
(or an error).
This function will be used to read these acks.
nftables uses a transaction-based netlink model: one netlink write
comes with multiple messages.
A 'BEGIN' message to tell nf_tables/kernel that a new transaction starts.
Then, one more messages to add/delete tables/chains/rules etc.
Lastly, an END message that commits all changes.
This function will be used to send all the individual messages that should
make up a single transaction as a single write.
add nfnetlink_nftables helper functions to:
* open a new nfnetlink socket to kernel
* add tables, chains, rules, sets and maps
* delete/flush table
* add and delete elements from sets/maps
Hardware addresses come in various shapes and sizes, these new functions
and accomapying data structures account for that instead of hard-coding
a hardware address to the 6 bytes of an ethernet MAC.
This really doesn't matter given that AF_xyz and PF_xyz are equivalent
in all ways, but we almost always use AF_xyz, hence stick to it
universally and convert the remaining PF_ to AF_
When sd_netlink_call_async() timed out, then we reply the synthetic
error message, but it was not sealed. So, reading the message causes
the following assertion:
```
Assertion 'm->sealed' failed at src/libsystemd/sd-netlink/netlink-message.c:652, function netlink_message_read_internal(). Ignoring.
```
When renaming a network interface, the new name may be used as an
alternative name. In that case, let's swap the current name and the
alternative name. That is, first drop the new name from the list of
alternative names, then rename the interface, finally set the old name
as an alternative name.
Add support for creating a MACVLAN interface in "source" mode by
specifying Mode=source in the [MACVLAN] section of a .netdev file.
A list of allowed MAC addresses for the corresponding MACVLAN can also
be specified with the SourceMACAddress= option of the [MACVLAN] section.
An example .netdev file:
[NetDev]
Name=macvlan0
Kind=macvlan
MACAddress=02:DE:AD:BE:EF:00
[MACVLAN]
Mode=source
SourceMACAddress=02:AB:AB:AB:AB:01 02:CD:CD:CD:CD:01
SourceMACAddress=02:EF:EF:EF:EF:01
The same keys can also be specified in [MACVTAP] for MACVTAP kinds of
interfaces, with the same semantics.
Prompted by the discussion on #16110, let's migrate more code to
fd_wait_for_event().
This only leaves 7 places where we call into poll()/poll() directly in
our entire codebase. (one of which is fd_wait_for_event() itself)
poll() sets POLLNVAL inside of the poll structures if an invalid fd is
passed. So far we generally didn't check for that, thus not taking
notice of the error. Given that this specific kind of error is generally
indication of a programming error, and given that our code is embedded
into our projects via NSS or because people link against our library,
let's explicitly check for this and convert it to EBADF.
(I ran into a busy loop because of this missing check when some of my
test code accidentally closed an fd it shouldn't close, so this is a
real thing)
While investigating why some of my netlink calls would timeout I
stumbled upon the definition of the max write queue length. Finding this
constant made me believe we still had a write queue in the code - which
isn't true. The netlink write queue code was removed in #189.
This also makes sure the control buffer is properly aligned. This
matters, as otherwise the control buffer might not be aligned and the
cmsg buffer counting might be off. The incorrect alignment is becoming
visible by using recvmsg_safe() as we suddenly notice the MSG_CTRUNC bit
set because of this.
That said, apparently this isn't enough to make this work on all
kernels. Since I couldn't figure this out, we now add 1K to the buffer
to be sure. We do this once already, also for a pktinfo structure
(though an IPv4/IPv6) one. I am puzzled by this, but this shouldn't
matter much. it works locally just fine, except for those ubuntu CI
kernels...
While we are at it, make some other changes too, to simplify and
modernize the function.
Yu Watanabe