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std.Io.net: fix off-by-one in HostName.expand

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`HostName.expand` was including the null terminator in the slice passed to `HostName.init`, which caused `HostName.validate` to fail.
This commit is contained in:
0x4a61636f62 2025-11-12 23:49:42 +01:00 • committed by Ryan Liptak
parent 813e8614bc
commit 2e6f7d36b9
2 changed files with 50 additions and 2 deletions
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2
lib/std/Io/net/HostName.zig
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@ -136,8 +136,6 @@ pub fn expand(noalias packet: []const u8, start_i: usize, noalias dest_buffer: [
dest_i += label_len;
i += 1 + label_len;
} else {
dest[dest_i] = 0;
dest_i += 1;
return .{
len orelse i - start_i + 1,
try .init(dest[0..dest_i]),

50
lib/std/Io/net/test.zig
View file

@ -343,3 +343,53 @@ test "non-blocking tcp server" {
const msg = buf[0..len];
try testing.expect(mem.eql(u8, msg, "hello from server\n"));
}
test "decompress compressed DNS name" {
const packet = &[_]u8{
// Header section
// ----------------------------------------------------------
0x00, 0x00, // ID: 0
0x81, 0x80, // Flags (QR:1, RCODE:0, etc.)
0x00, 0x01, // QDCOUNT: 1 (Question Count)
0x00, 0x01, // ANCOUNT: 1 (Answer Count)
0x00, 0x00, // NSCOUNT: 0
0x00, 0x00, // ARCOUNT: 0
// ----------------------------------------------------------
// Question section (12 byte offset)
// ----------------------------------------------------------
// QNAME: "www.ziglang.org"
0x03, 'w', 'w', 'w', // label
0x07, 'z', 'i', 'g', 'l', 'a', 'n', 'g', // label
0x03, 'o', 'r', 'g', // label
0x00, // null label
0x00, 0x01, // QTYPE: A
0x00, 0x01, // QCLASS: IN
// ----------------------------------------------------------
// Resource Record (Answer) (33 byte offset)
// ----------------------------------------------------------
0xc0, 0x0c, // NAME: pointer to 0x0c ("www.ziglang.org")
0x00, 0x05, // TYPE: CNAME
0x00, 0x01, // CLASS: IN
0x00, 0x00, 0x01, 0x00, // TTL: 256 (seconds)
0x00, 0x06, // RDLENGTH: 6 bytes
// RDATA (45 byte offset): "target.ziglang.org" (compressed)
0x06, 't', 'a', 'r', 'g', 'e', 't', // 6, "target"
0xc0, 0x10, // pointer (0xc0 flag) to 0x10 byte offset ("ziglang.org")
// ----------------------------------------------------------
};
// The start index of the CNAME RDATA is 45
const cname_data_index = 45;
var dest_buffer: [net.HostName.max_len]u8 = undefined;
const n_consumed, const result = try net.HostName.expand(
packet,
cname_data_index,
&dest_buffer,
);
try testing.expectEqual(packet.len - cname_data_index, n_consumed);
try testing.expectEqualStrings("target.ziglang.org", result.bytes);
}