define types for basic A query

src/root.zig

···
 const std = @import("std");
 const assert = std.debug.assert;
 const io = std.io;
+const net = std.net;
 
 pub const BytePacketBuffer = struct {
     buf: [512]u8 = undefined,
···
     try testing.expectEqualStrings(expected, outstr);
 }
 
+pub const DnsHeader = packed struct {
+    id: u16 = 0,
+
+    recursion_desired: bool = false,
+    truncated_message: bool = false,
+    authoritative_answer: bool = false,
+    opcode: u4 = 0,
+    response: bool = false,
+
+    rescode: enum(u4) {
+        noerror = 0,
+        formerr = 1,
+        servfail = 2,
+        nxdomain = 3,
+        notimp = 4,
+        refused = 5,
+    } = .noerror,
+    checking_disabled: bool = false,
+    authed_data: bool = false,
+    z: bool = false,
+    recursion_available: bool = false,
+
+    questions: u16 = 0,
+    answers: u16 = 0,
+    authoritative_entries: u16 = 0,
+    resource_entries: u16 = 0,
+};
+
+pub const QueryType = enum(u16) {
+    a = 1,
+    unknown,
+};
+
+pub const DnsQuestion = struct {
+    name: []const u8,
+    qtype: QueryType,
+
+    pub fn read(self: *DnsQuestion, buffer: *BytePacketBuffer, alloc: std.mem.Allocator) !void {
+        self.name = try buffer.readQnameAlloc(alloc);
+        self.qtype = @enumFromInt(try buffer.reader().readInt(u16, .big));
+        _ = try buffer.reader().readInt(u16, .big); // class
+    }
+};
+
+// TODO: add DnsQuestion.read test
+
+pub const DnsRecord = union(QueryType) {
+    unknown: struct {
+        domain: []const u8,
+        qtype: u16,
+        data_len: u16,
+        ttl: u32,
+    },
+    a: struct {
+        domain: []const u8,
+        addr: net.Ip4Address,
+        ttl: u32,
+    },
+};