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std.Io.net.HostName: implement DNS reply parsing

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This commit is contained in:
Andrew Kelley 2025-10-02 19:12:25 -07:00
parent a5d8dcc025
commit b08f1d0e2a
1 changed files with 39 additions and 8 deletions
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47
lib/std/Io/net/HostName.zig
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@ -363,17 +363,19 @@ fn lookupDns(io: Io, lookup_canon_name: []const u8, rc: *const ResolvConf, optio
continue;
}) |record| switch (record.rr) {
std.posix.RR.A => {
if (record.data.len != 4) return error.InvalidDnsARecord;
const data = record.packet[record.data_off..][0..record.data_len];
if (data.len != 4) return error.InvalidDnsARecord;
options.addresses_buffer[addresses_len] = .{ .ip4 = .{
.bytes = record.data[0..4].*,
.bytes = data[0..4].*,
.port = options.port,
} };
addresses_len += 1;
},
std.posix.RR.AAAA => {
if (record.data.len != 16) return error.InvalidDnsAAAARecord;
const data = record.packet[record.data_off..][0..record.data_len];
if (data.len != 16) return error.InvalidDnsAAAARecord;
options.addresses_buffer[addresses_len] = .{ .ip6 = .{
.bytes = record.data[0..16].*,
.bytes = data[0..16].*,
.port = options.port,
} };
addresses_len += 1;
@ -575,23 +577,52 @@ pub fn expandDomainName(
pub const DnsResponse = struct {
bytes: []const u8,
bytes_index: u32,
answers_remaining: u16,
pub const Answer = struct {
rr: u8,
data: []const u8,
packet: []const u8,
data_off: u32,
data_len: u16,
};
pub const Error = error{InvalidDnsPacket};
pub fn init(r: []const u8) Error!DnsResponse {
if (r.len < 12) return error.InvalidDnsPacket;
return .{ .bytes = r };
if ((r[3] & 15) != 0) return .{ .bytes = r, .bytes_index = 3, .answers_remaining = 0 };
var i: u32 = 12;
var query_count = std.mem.readInt(u16, r[4..6], .big);
while (query_count != 0) : (query_count -= 1) {
while (i < r.len and r[i] -% 1 < 127) i += 1;
if (r.len - i < 6) return error.InvalidDnsPacket;
i = i + 5 + @intFromBool(r[i] != 0);
}
return .{
.bytes = r,
.bytes_index = i,
.answers_remaining = std.mem.readInt(u16, r[6..8], .big),
};
}
pub fn next(dr: *DnsResponse) Error!?Answer {
_ = dr;
@panic("TODO");
if (dr.answers_remaining == 0) return null;
dr.answers_remaining -= 1;
const r = dr.bytes;
var i = dr.bytes_index;
while (i < r.len and r[i] -% 1 < 127) i += 1;
if (r.len - i < 12) return error.InvalidDnsPacket;
i = i + 1 + @intFromBool(r[i] != 0);
const len = std.mem.readInt(u16, r[i + 8 ..][0..2], .big);
if (i + 10 + len > r.len) return error.InvalidDnsPacket;
defer dr.bytes_index = i + 10 + len;
return .{
.rr = r[i + 1],
.packet = r,
.data_off = i + 10,
.data_len = len,
};
}
};