netlink: export nextop group kernel index when dumping multipath route.

MFC after: 2 weeks

netlink: Zero-initialize writer structures allocated on the stack

The prevailing pattern seems to be to simply initialize all fields to
zero. Without this, it's possible to trigger a branch on unin

netlink: Zero-initialize writer structures allocated on the stack

The prevailing pattern seems to be to simply initialize all fields to
zero. Without this, it's possible to trigger a branch on uninitialized
memory, specifically, when testing nw->ignore_limit in
nlmsg_refill_buffer().

Initialize the writer structure in a couple of functions where this is
necessary.

Reported by: KMSAN
Reviewed by: melifaro
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D38213

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netlink: fix OOB write when creating attribute bitmask.

Fix wrong arithmetics by moving to the standard bitset(9) functions.

Reported by: markj, KASAN

netlink: allow creating sockets with SOCK_DGRAM.

Some existing applications setup Netlink socket with
SOCK_DGRAM instead of SOCK_RAW. Update the manpage to clarify
that the default way of creating t

netlink: allow creating sockets with SOCK_DGRAM.

Some existing applications setup Netlink socket with
SOCK_DGRAM instead of SOCK_RAW. Update the manpage to clarify
that the default way of creating the socket should be with
SOCK_RAW. Update the code to support both SOCK_RAW and SOCK_DGRAM.

Reviewed By: pauamma
Differential Revision: https://reviews.freebsd.org/D38075

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netlink: Fix indentation in netlink_message_writer.c

This file is indented with a mixture of tabs and spaces. No functional
change intended.

Reviewed by: melifaro
Sponsored by: The FreeBSD Foundat

netlink: Fix indentation in netlink_message_writer.c

This file is indented with a mixture of tabs and spaces. No functional
change intended.

Reviewed by: melifaro
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D38100

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netlink: Make the writers function table static and const

No functional change intended.

Reviewed by: melifaro
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.or

netlink: Make the writers function table static and const

No functional change intended.

Reviewed by: melifaro
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D38099

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netlink: Zero-initialize mbuf messages

Some users of nlmsg_reserve_object() and nlmsg_reserve_data() are not
careful to fully initialize pad and reserved fields, allowing
uninitialized bytes to leak

netlink: Zero-initialize mbuf messages

Some users of nlmsg_reserve_object() and nlmsg_reserve_data() are not
careful to fully initialize pad and reserved fields, allowing
uninitialized bytes to leak to userspace. For example, dump_nhgrp()
doesn't set nhm->resvd = 0.

Meanwhile, nlmsg_get_ns_buf() and nlmsg_get_ns_lbuf() zero-initialize
the buffer, so nlmsg_get_ns_mbuf() is inconsistent. Let's just make
them all behave the same here.

Reported by: KMSAN
Reviewed by: melifaro
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D38098

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netlink: fix compatibility with older netlink applications.

Some apps try to provide only the non-zero part of the required message
header instead of the full one. It happens when fetching routes o

netlink: fix compatibility with older netlink applications.

Some apps try to provide only the non-zero part of the required message
header instead of the full one. It happens when fetching routes or
interface addresses, where the first header byte is the family.
This behavior is "illegal" under the "strict" Netlink socket option,
however there are many applications out there doing things in the
"old" way.

Support this usecase by copying the provided bytes into the temporary
zero-filled header and running the parser on this header instead.

Reported by: Goran Mekić <meka@tilda.center>

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netlink: improve RTM_GETADDR handling.

* Allow filtering by ifa_family & ifa_index.
* Add common RTM_<NEW|DEL|GET>ADDR parser
* Add tests verifying RTM_GETADDR filtering behaviour & output
* Factor

netlink: improve RTM_GETADDR handling.

* Allow filtering by ifa_family & ifa_index.
* Add common RTM_<NEW|DEL|GET>ADDR parser
* Add tests verifying RTM_GETADDR filtering behaviour & output
* Factor out common netlink socket test methods into NetlinkTestTemplate
* Add NLMSG_DONE message handler

Reviewed By: pauamma
Differential Revision: https://reviews.freebsd.org/D37970

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netlink: fix ifaddr reporting.

Output the proper attributes for IPv4/IPvv6 ifaddrs:
* IFA_ADDRESS contains local address in every case except p2p,
in that case it contains the peer address
* IFA_

netlink: fix ifaddr reporting.

Output the proper attributes for IPv4/IPvv6 ifaddrs:
* IFA_ADDRESS contains local address in every case except p2p,
in that case it contains the peer address
* IFA_LOCAL contains local address. It is always present in IPv4,
or in IPv6/p2p.
* IFA_BROADCAST contains the network broadcast address (if any)

Reported by: Adam Wood <aswood@gmail.com>
Tested by: Adam Wood <aswood@gmail.com>

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netlink: fix test-includes broken by f2c8381fce9b

Reported by: many

netlink: make snl(3) headers self-contained.

netlink: allow netlink to be build in the kernel

Differential Revision: https://reviews.freebsd.org/D37781

netlink: fix netlink_snl_route.h header includes

netlink: add snl(3) - simple netlink library

Reviewed by: bapt, pauamma
Differential Revision: https://reviews.freebsd.org/D37736

netlink: Use NET_EPOCH_[CALL|WAIT] macros

Reviewed by: melifaro, kp
Approved by: kp (mentor)
Differential Revision: https://reviews.freebsd.org/D37730

netlink: improve interface handling

* Separate interface creation from interface modification code
* Support setting some interface attributes (ifdescr, mtu, up/down, promisc)
* Improve interaction

netlink: improve interface handling

* Separate interface creation from interface modification code
* Support setting some interface attributes (ifdescr, mtu, up/down, promisc)
* Improve interaction with the cloners requiring to parse/write custom
interface attributes
* Add bitmask-based way of checking if the attribute is present in the
message
* Don't use multipart RTM_GETLINK replies when searching for the
specific interface names
* Use ENODEV instead of ENOENT in case of failed RTM_GETLINK search
* Add python netlink test helpers
* Add some netlink interface tests

Differential Revision: https://reviews.freebsd.org/D37668

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netlink: add interface notification on link status / flags change.

* Add link-state change notifications by subscribing to ifnet_link_event.
In the Linux netlink model, link state is reported in 2

netlink: add interface notification on link status / flags change.

* Add link-state change notifications by subscribing to ifnet_link_event.
In the Linux netlink model, link state is reported in 2 places: first is
the IFLA_OPERSTATE, which stores state per RFC2863.
The second is an IFF_LOWER_UP interface flag. As many applications rely
on the latter, reserve 1 bit from if_flags, named as IFF_NETLINK_1.
This flag is mapped to IFF_LOWER_UP in the netlink headers. This is done
to avoid making applications think this flag is actually
supported / presented in non-netlink outputs.
* Add flag change notifications, by hooking into rt_ifmsg().
In the netlink model, notification should include the bitmask for the
change flags. Update rt_ifmsg() to include such bitmask.

Differential Revision: https://reviews.freebsd.org/D37597

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netlink: fix non-multipath build

netlink: store user-provided rtm_protocol

Store user-supplied source protocol in the nexthops and nexthop groups.
Protocol specification help routing daemons like bird to quickly
identify self-origi

netlink: store user-provided rtm_protocol

Store user-supplied source protocol in the nexthops and nexthop groups.
Protocol specification help routing daemons like bird to quickly
identify self-originated routes after the crash or restart.

Example:
```
10.2.0.0/24 via 10.0.0.2 dev vtnet0 proto bird
10.3.0.0/24 proto bird
nexthop via 10.0.0.2 dev vtnet0 weight 3
nexthop via 10.0.0.3 dev vtnet0 weight 4
```

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netlink: suppress sending NLMSG_ERROR if NLMSG_DONE is already sent

Netlink has a confirmation/error reporting mechanism for the sent
messages. Kernel explicitly acks each messages if requested (NLM

netlink: suppress sending NLMSG_ERROR if NLMSG_DONE is already sent

Netlink has a confirmation/error reporting mechanism for the sent
messages. Kernel explicitly acks each messages if requested (NLM_F_ACK)
or if message processing results in an error.
Similarly, for multipart messages - typically dumps, where each message
represents a single object like an interface or a route - another
message, NLMSG_DONE is used to indicate the end of dump and the
resulting status.
As a result, successfull dump ends with both NLMSG_DONE and NLMSG_ERROR
messages.
RFC 3549 does not say anything specific about such case.
Linux adopted an optimisation which suppresses NLMSG_ERROR message
when NLMSG_DONE is already sent. Certain libraries/applications like
libnl depends on such behavior.

Suppress sending NLMSG_ERROR if NLMSG_DONE is already sent, by
setting newly-added 'suppress_ack' flag in the writer and checking
this flag when generating ack.

This change restores libnl compatibility.

Before:
```
~ nl-link-list
Error: Unable to allocate link cache: Message sequence number mismatch
````

After:
```
~ nl-link-list
vtnet0 ether 52:54:00:14:e3:19 <broadcast,multicast,up,running>
lo0 ieee1394 <loopback,multicast,up,running>
```

Reviewed by: bapt,pauamma
Tested by: bapt
Differential Revision: https://reviews.freebsd.org/D37565

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