This is a workaround to make IPAddressDeny=any/IPAddressAllow=any work
for non-root users that have CAP_NET_ADMIN. "any" was chosen since
all or nothing network access is one of the most common use cases for
isolation.
Allocating BPF LPM TRIE maps require CAP_SYS_ADMIN while BPF_PROG_TYPE_CGROUP_SKB
only needs CAP_NET_ADMIN. In the case of IPAddressXYZ="any" we can just
consistently return false/true to avoid allocating the map and limit the user
to having CAP_NET_ADMIN.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
This makes most header files easier to look at. Also Emacs gets really
slow when browsing through large sections of overly long prototypes,
which is much improved by this macro.
We should probably not do something similar with too many other cases,
as macros like this might help readability for some, but make it worse
for others. But I think given the complexity of this specific prototype
and how often we use it, it's worth doing.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
Add a config directive parser that takes multiple space separated IPv4
or IPv6 addresses with optional netmasks in CIDR notation rvalue and
puts a parsed version of it to linked list of IPAddressAccessItem objects.
The code actually using this will be added later.