linuxLookupNameFromDns

fn linuxLookupNameFromDns(
    gpa: Allocator,
    addrs: *ArrayList(LookupAddr),
    canon: *ArrayList(u8),
    name: []const u8,
    family: posix.sa_family_t,
    rc: ResolvConf,
    port: u16,
) !void {
    const ctx: dpc_ctx = .{
        .gpa = gpa,
        .addrs = addrs,
        .canon = canon,
        .port = port,
    };
    const AfRr = struct {
        af: posix.sa_family_t,
        rr: u8,
    };
    const afrrs = [_]AfRr{
        .{ .af = posix.AF.INET6, .rr = posix.RR.A },
        .{ .af = posix.AF.INET, .rr = posix.RR.AAAA },
    };
    var qbuf: [2][280]u8 = undefined;
    var abuf: [2][512]u8 = undefined;
    var qp: [2][]const u8 = undefined;
    const apbuf = [2][]u8{ &abuf[0], &abuf[1] };
    var nq: usize = 0;

    for (afrrs) |afrr| {
        if (family != afrr.af) {
            const len = posix.res_mkquery(0, name, 1, afrr.rr, &[_]u8{}, null, &qbuf[nq]);
            qp[nq] = qbuf[nq][0..len];
            nq += 1;
        }
    }

    var ap = [2][]u8{ apbuf[0], apbuf[1] };
    ap[0].len = 0;
    ap[1].len = 0;

    try rc.resMSendRc(qp[0..nq], ap[0..nq], apbuf[0..nq]);

    var i: usize = 0;
    while (i < nq) : (i += 1) {
        dnsParse(ap[i], ctx, dnsParseCallback) catch {};
    }

    if (addrs.items.len != 0) return;
    if (ap[0].len < 4 or (ap[0][3] & 15) == 2) return error.TemporaryNameServerFailure;
    if ((ap[0][3] & 15) == 0) return error.UnknownHostName;
    if ((ap[0][3] & 15) == 3) return;
    return error.NameServerFailure;
}