sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

IfAPI: Explicitly include <net/if_private.h> in netstack

Summary:
In preparation of making if_t completely opaque outside of the netstack,
explicitly include the header. <net/if_var.h> will stop including the
header in the future.

Sponsored by: Juniper Networks, Inc.
Reviewed by: glebius, melifaro
Differential Revision: https://reviews.freebsd.org/D38200

net: employ newly added pfil_mbuf_{in,out} where approriate

Reviewed by: glebius
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D36454

net: retire PFIL_FWD

It is now unused and not having it allows further clean ups.

Reviewed by: cy, glebius, kp
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D36452

net: clean up empty lines in .c and .h files

Convert IP/IPv6 forwarding, ICMP processing and IP PCB laddr selection to
the new routing KPI.

Reviewed by: ae
Differential Revision: https://reviews.freebsd.org/D24245

fib6_rte_to_nh_*: return a link-local gw address with scope embedded

In fib6_rte_to_nh_* when returning a link-local gateway address
currently we do clear the scope. That could be recovered using
the ifp returned as well, but the code in general seems to
expect a link-local address with scope embeedded as otherwise
the "dst" (gw) passed to the output routines will not include
scope and not send the packet out (the right interface).

Do not clear the scope when returning a link-local address and
allow packets to go out (the right interface).

Remove the (now) extra scope recovery in the IPv6 fast-fwd code.

Sponsored by: Netflix
Reviewed by: melifaro, ae
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D23872

New pfil(9) KPI together with newborn pfil API and control utility.

The KPI have been reviewed and cleansed of features that were planned
back 20 years ago and never implemented. The pfil(9) internals have
been made opaque to protocols with only returned types and function
declarations exposed. The KPI is made more strict, but at the same time
more extensible, as kernel uses same command structures that userland
ioctl uses.

In nutshell [KA]PI is about declaring filtering points, declaring
filters and linking and unlinking them together.

New [KA]PI makes it possible to reconfigure pfil(9) configuration:
change order of hooks, rehook filter from one filtering point to a
different one, disconnect a hook on output leaving it on input only,
prepend/append a filter to existing list of filters.

Now it possible for a single packet filter to provide multiple rulesets
that may be linked to different points. Think of per-interface ACLs in
Cisco or Juniper. None of existing packet filters yet support that,
however limited usage is already possible, e.g. default ruleset can
be moved to single interface, as soon as interface would pride their
filtering points.

Another future feature is possiblity to create pfil heads, that provide
not an mbuf pointer but just a memory pointer with length. That would
allow filtering at very early stages of a packet lifecycle, e.g. when
packet has just been received by a NIC and no mbuf was yet allocated.

Differential Revision: https://reviews.freebsd.org/D18951

Send an ICMPv6 PacketTooBig message in case of forwading a packet which
is too big for the outgoing interface and no firewall is involed.
This problem was introduced in
https://svnweb.freebsd.org/changeset/base/324996
Thanks to Irene Ruengeler for finding the bug and testing the fix.

Reviewed by: kp@
MFC after: 3 days

Add check that mbuf had not multicast layer2 address.
Such packets should be handled by ip6_mforward().

Obtained from: Yandex LLC
MFC after: 1 week
Sponsored by: Yandex LLC

netpfil: Introduce PFIL_FWD flag

Forwarded packets passed through PFIL_OUT, which made it difficult for
firewalls to figure out if they were forwarding or producing packets. This in
turn is an issue for pf for IPv6 fragment handling: it needs to call
ip6_output() or ip6_forward() to handle the fragments. Figuring out which was
difficult (and until now, incorrect).
Having pfil distinguish the two removes an ugly piece of code from pf.

Introduce a new variant of the netpfil callbacks with a flags variable, which
has PFIL_FWD set for forwarded packets. This allows pf to reliably work out if
a packet is forwarded.

Reviewed by: ae, kevans
Differential Revision: https://reviews.freebsd.org/D13715

Evaluate packet size after the firewall had its chance in the ip6 fast path

Defer the packet size check until after the firewall has had a look at it. This
means that the firewall now has the opportunity to (re-)fragment an oversized
packet.
This mirrors what the slow path does.

Reviewed by: ae
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D12779

Add ip6_tryforward() - a run to completion forwarding implementation
for IPv6.

It gets performance benefits from reduced number of checks. It doesn't
copy mbuf to be able send ICMPv6 error message, because it keeps mbuf
unchanged until the moment, when the route decision has been made.
It doesn't do IPsec checks, and when some IPsec security policies present,
ip6_input() uses normal slow path.

Reviewed by: bz, gnn
Obtained from: Yandex LLC
MFC after: 1 month
Sponsored by: Yandex LLC
Differential Revision: https://reviews.freebsd.org/D8527