chore: import upstream snapshot with attribution

Sources/DNSServer/Records/Message.swift

@@ -0,0 +1,283 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the container project authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+/// A DNS message (query or response).
+///
+/// Wire format (RFC 1035):
+/// ```
+/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+/// |                      ID                       |
+/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+/// |QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |
+/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+/// |                    QDCOUNT                    |
+/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+/// |                    ANCOUNT                    |
+/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+/// |                    NSCOUNT                    |
+/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+/// |                    ARCOUNT                    |
+/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+/// ```
+public struct Message: Sendable {
+    /// Header size in bytes.
+    public static let headerSize = 12
+
+    /// Transaction ID.
+    public var id: UInt16
+
+    /// Message type (query or response).
+    public var type: MessageType
+
+    /// Operation code.
+    public var operationCode: OperationCode
+
+    /// Authoritative answer flag.
+    public var authoritativeAnswer: Bool
+
+    /// Truncation flag.
+    public var truncation: Bool
+
+    /// Recursion desired flag.
+    public var recursionDesired: Bool
+
+    /// Recursion available flag.
+    public var recursionAvailable: Bool
+
+    /// Response code.
+    public var returnCode: ReturnCode
+
+    /// Questions in this message.
+    public var questions: [Question]
+
+    /// Answer resource records.
+    public var answers: [ResourceRecord]
+
+    /// Authority resource records.
+    public var authorities: [ResourceRecord]
+
+    /// Additional resource records.
+    public var additional: [ResourceRecord]
+
+    /// Creates a new DNS message.
+    public init(
+        id: UInt16 = 0,
+        type: MessageType = .query,
+        operationCode: OperationCode = .query,
+        authoritativeAnswer: Bool = false,
+        truncation: Bool = false,
+        recursionDesired: Bool = false,
+        recursionAvailable: Bool = false,
+        returnCode: ReturnCode = .noError,
+        questions: [Question] = [],
+        answers: [ResourceRecord] = [],
+        authorities: [ResourceRecord] = [],
+        additional: [ResourceRecord] = []
+    ) {
+        self.id = id
+        self.type = type
+        self.operationCode = operationCode
+        self.authoritativeAnswer = authoritativeAnswer
+        self.truncation = truncation
+        self.recursionDesired = recursionDesired
+        self.recursionAvailable = recursionAvailable
+        self.returnCode = returnCode
+        self.questions = questions
+        self.answers = answers
+        self.authorities = authorities
+        self.additional = additional
+    }
+
+    /// Deserialize a DNS message from raw data.
+    public init(deserialize data: Data) throws {
+        var buffer = Array(data)
+        var offset = 0
+
+        // Read ID
+        guard let (newOffset, rawId) = buffer.copyOut(as: UInt16.self, offset: offset) else {
+            throw DNSBindError.unmarshalFailure(type: "Message", field: "id")
+        }
+        self.id = UInt16(bigEndian: rawId)
+        offset = newOffset
+
+        // Read flags
+        guard let (newOffset, rawFlags) = buffer.copyOut(as: UInt16.self, offset: offset) else {
+            throw DNSBindError.unmarshalFailure(type: "Message", field: "flags")
+        }
+        let flags = UInt16(bigEndian: rawFlags)
+        offset = newOffset
+
+        // Parse flags
+        self.type = (flags & 0x8000) != 0 ? .response : .query
+        guard let opCode = OperationCode(rawValue: UInt8((flags >> 11) & 0x0F)) else {
+            throw DNSBindError.unsupportedValue(type: "Message", field: "opcode")
+        }
+        self.operationCode = opCode
+        self.authoritativeAnswer = (flags & 0x0400) != 0
+        self.truncation = (flags & 0x0200) != 0
+        self.recursionDesired = (flags & 0x0100) != 0
+        self.recursionAvailable = (flags & 0x0080) != 0
+        guard let returnCode = ReturnCode(rawValue: UInt8(flags & 0x000F)) else {
+            throw DNSBindError.unsupportedValue(type: "Message", field: "rcode")
+        }
+        self.returnCode = returnCode
+
+        // Read counts
+        guard let (newOffset, rawQdCount) = buffer.copyOut(as: UInt16.self, offset: offset) else {
+            throw DNSBindError.unmarshalFailure(type: "Message", field: "qdcount")
+        }
+        let qdCount = UInt16(bigEndian: rawQdCount)
+        offset = newOffset
+
+        guard let (newOffset, rawAnCount) = buffer.copyOut(as: UInt16.self, offset: offset) else {
+            throw DNSBindError.unmarshalFailure(type: "Message", field: "ancount")
+        }
+        let anCount = UInt16(bigEndian: rawAnCount)
+        offset = newOffset
+
+        guard let (newOffset, rawNsCount) = buffer.copyOut(as: UInt16.self, offset: offset) else {
+            throw DNSBindError.unmarshalFailure(type: "Message", field: "nscount")
+        }
+        // nsCount not used for now, but we need to read past it
+        _ = UInt16(bigEndian: rawNsCount)
+        offset = newOffset
+
+        guard let (newOffset, rawArCount) = buffer.copyOut(as: UInt16.self, offset: offset) else {
+            throw DNSBindError.unmarshalFailure(type: "Message", field: "arcount")
+        }
+        // arCount not used for now, but we need to read past it
+        _ = UInt16(bigEndian: rawArCount)
+        offset = newOffset
+
+        // Read questions
+        self.questions = []
+        for _ in 0..<qdCount {
+            var question = Question(name: "")
+            offset = try question.bindBuffer(&buffer, offset: offset, messageStart: 0)
+            self.questions.append(question)
+        }
+
+        // Read answers (simplified - skip for now as we only need to parse queries)
+        self.answers = []
+        self.authorities = []
+        self.additional = []
+
+        // Skip answer parsing for now - we primarily receive queries and send responses
+        _ = anCount
+    }
+
+    /// Serialize this message to raw data.
+    public func serialize() throws -> Data {
+        // Calculate exact buffer size.
+        var bufferSize = Self.headerSize
+        for question in questions {
+            // name + type + class
+            let n = question.name.hasSuffix(".") ? String(question.name.dropLast()) : question.name
+            bufferSize += (try DNSName(labels: n.isEmpty ? [] : n.split(separator: ".", omittingEmptySubsequences: false).map(String.init))).size + 4
+        }
+        for answer in answers {
+            // name + type + class + ttl + rdlen + rdata
+            let n = answer.name.hasSuffix(".") ? String(answer.name.dropLast()) : answer.name
+            let rdataSize = answer.type == .host ? 4 : 16
+            bufferSize += (try DNSName(labels: n.isEmpty ? [] : n.split(separator: ".", omittingEmptySubsequences: false).map(String.init))).size + 10 + rdataSize
+        }
+
+        var buffer = [UInt8](repeating: 0, count: bufferSize)
+        var offset = 0
+
+        // Write ID
+        guard let newOffset = buffer.copyIn(as: UInt16.self, value: id.bigEndian, offset: offset) else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "id")
+        }
+        offset = newOffset
+
+        // Build and write flags
+        var flags: UInt16 = 0
+        flags |= type == .response ? 0x8000 : 0
+        flags |= UInt16(operationCode.rawValue) << 11
+        flags |= authoritativeAnswer ? 0x0400 : 0
+        flags |= truncation ? 0x0200 : 0
+        flags |= recursionDesired ? 0x0100 : 0
+        flags |= recursionAvailable ? 0x0080 : 0
+        flags |= UInt16(returnCode.rawValue)
+
+        guard let newOffset = buffer.copyIn(as: UInt16.self, value: flags.bigEndian, offset: offset) else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "flags")
+        }
+        offset = newOffset
+
+        // Write counts
+        guard questions.count <= UInt16.max else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "qdcount")
+        }
+        guard answers.count <= UInt16.max else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "ancount")
+        }
+        guard authorities.count <= UInt16.max else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "nscount")
+        }
+        guard additional.count <= UInt16.max else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "arcount")
+        }
+
+        guard let newOffset = buffer.copyIn(as: UInt16.self, value: UInt16(questions.count).bigEndian, offset: offset) else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "qdcount")
+        }
+        offset = newOffset
+
+        guard let newOffset = buffer.copyIn(as: UInt16.self, value: UInt16(answers.count).bigEndian, offset: offset) else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "ancount")
+        }
+        offset = newOffset
+
+        guard let newOffset = buffer.copyIn(as: UInt16.self, value: UInt16(authorities.count).bigEndian, offset: offset) else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "nscount")
+        }
+        offset = newOffset
+
+        guard let newOffset = buffer.copyIn(as: UInt16.self, value: UInt16(additional.count).bigEndian, offset: offset) else {
+            throw DNSBindError.marshalFailure(type: "Message", field: "arcount")
+        }
+        offset = newOffset
+
+        // Write questions
+        for question in questions {
+            offset = try question.appendBuffer(&buffer, offset: offset)
+        }
+
+        // Write answers
+        for answer in answers {
+            offset = try answer.appendBuffer(&buffer, offset: offset)
+        }
+
+        // Write authorities
+        for authority in authorities {
+            offset = try authority.appendBuffer(&buffer, offset: offset)
+        }
+
+        // Write additional
+        for record in additional {
+            offset = try record.appendBuffer(&buffer, offset: offset)
+        }
+
+        guard offset == bufferSize else {
+            throw DNSBindError.unexpectedOffset(type: "Message", expected: bufferSize, actual: offset)
+        }
+        return Data(buffer[0..<offset])
+    }
+}