SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
LookupServer can now itself server as a DNS server! To service DNS clients, it
uses the exact same lookup logic as it does for LibIPC clients. Namely, it will
synthesize records for data from /etc/hosts on its own (you can use this to
configure host names for your domain!), and forward other questions to
configured upstream DNS servers. On top of that, it implements its own caching,
so once a DNS resource record has been obtained from an upstream server,
LookupServer will cache it locally for faster future lookups.
The DNS server part of LookupServer is disabled by default, because it requires
you to run it as root (for it to bind to the port 53) and on boot, and we don't
want either by default. If you want to try it, modify SystemServer.ini like so:
[LookupServer]
Socket=/tmp/portal/lookup
SocketPermissions=666
Priority=low
KeepAlive=1
User=root
BootModes=text,graphical
and enable server mode in LookupServer.ini like so:
[DNS]
Nameservers=...
EnableServer=1
If in the future we implement socket takeover for IP sockets, these limitations
may be lifted.
Where it belongs, alongside the /etc/hosts check. The inner lookup() method is
really about talking to a specific DNS server.
Also, don't bail out on a empty name. An empty DNSName is actually '.' — a
single dot — aka the DNS root.
...just like we store m_lookup_cache, in other words.
This immediately lets us match on types: for instance we will now only resolve
1.0.0.127.in-addr.arpa to localhost if asked for type PTR, not for type A. In
the future, this could also let us have the same /etc/hosts name resolve
to *multiple* addresses.
DNSName can now take care of case conversion when comparing using traits.
It still intentionally doesn't implement operator ==; you have to explicitly
decide whether you want case-sensitive or case-insensitive comparison.
This change makes caches (and /etc/hosts) case-transparent: we will now match
domains if they're the same except for the case.
* DNSName knows how to randomize itself
* DNSPacket no longer constructs DNSQuestion instances, it receives an already
built DNSQuestion and just adds it to the list
* LookupServer::lookup() explicitly calls randomize_case() if it needs to
randomize the case.
This is a wrapper around a string representing a domain name (such as
"example.com"). It never has a trailing dot.
For now, this class doesn't do much except wrap the raw string. Subsequent
commits will add or move more functionality to it.
They're really the same thing: a DNS packet can contain both questions and
answers, and there's a single bit in the header that determines whether the
packet represents a query or a response. It'll be simpler for us to represent
both types of packets using the same class.
This class can be both serialized and deserialized to/from a raw DNS packet.
Now that we no longer depend on the textual IPC format, we can pass IP addresses
in the format most code actually has and needs it: in binary. The only places we
actually have to deal with textual address representation is:
* When reading /etc/hosts, we have to parse textual addresses & convert them to
binary;
* When doing reverse lookups, we have to form a pseudo-hostname of the form
x.x.x.x.in-addr.arpa.
So we do the conversion in those two cases.
This also increases uniformity between how we handle A (IPv4 address) and other
resource record types. Namely, we now store the raw binary data as received from
a DNS server.
The ad-hoc IPC we were doing with LookupServer was kinda gross. With this,
LookupServer is a regular IPC server. In the future, we want to add more APIs
for LookupServer to talk to its clients (such as DHCPClient telling LookupServer
about the DNS server discovered via DHCP, and DNS-SD client browsing for
services), which calls for a more expressive IPC format; this is what LibIPC is
perfect for.
While the LookupServer side is using the regular LibIPC mechanics and patterns,
the LibC side has to hand-roll LibIPC format serialization without actually
using LibIPC. We might be able to get rid of this in the future, but for now it
has to be like that. The good news is the format is not that bad at all.
We were ignoring everything but A records in DNS responses. This broke
reverse lookups which obviously want the PTR records.
Fix this by filtering on the requested record type instead of always A.
