Limited implementation (no options) of EDNS

[bortzmeyer]

Create and parse messages with EDNS. It only implements basic EDNS (no options).

Example:

    const edns = dns.EDNS{.bufsize = 568, .do_dnssec = false};
    const message = try dns.createEDNSQuery(allocator, "www.afnic.fr", .AAAA, edns);

[bortzmeyer]

I added a new function createEDNSquery rather than adding the edns parameter to createQuery since I believe Zig has no way to specify default values for function parameters (so, every use of createQuery would have needed to be modified).

[dantecatalfamo]

What do these flag values represent? It would be nice to have the flags represented by a packed struct to avoid unnamed constants.

[bortzmeyer]

What do these flag values represent? It would be nice to have the flags represented by a packed struct to avoid unnamed constants.

0x8000 is just the DO (DNSSEC OK) bit set, everything else clear (which means EDNS version 0). But I agree (it's in my second commit) that a packed struct would be nicer.

[bortzmeyer]

OK, next version will have:

pub const PackedEDNSTTL = packed struct(u32) {
    extendedRcode: u8 = 0,
    version: u8 = 0, // EDNS version 0 (RFC 6891)
    z1: u7 = 0, // Zig put fields in the unexpected order inside a byte.
    do: bool = true,
    z2: u8 = 0,
};

...

pub fn createEDNSQuery(allocator: mem.Allocator, address: []const u8, qtype: QType, edns: EDNS) !Message {
...
    var flags = PackedEDNSTTL{};
    flags.do = edns.do_dnssec;

No more 0x800. But I'm still struggling to produce a proper patch now that [read,write}IntBig disappeared and that non-mutated vars are forbidden. There are a lot of things to change.

[dantecatalfamo]

I must update the code to work with the latest Zig master release. Asking any PR to manage that migration on top of a new feature is a lot.

I have yet to have the time to work on this recently, but handling that migration is next on my list.

[dantecatalfamo]

I suspect most of my Zig projects need to be updated. Dealing with breaking changes every couple of months becomes overwhelming when you have a couple of larger projects you're working on in your spare time.

[bortzmeyer]

OK, now without unnamed constants.