wehub-resource-sync
e84fb4a79e
container project - merge build / Invoke build (push) Successful in 1s
96 lines
3.9 KiB
Swift
96 lines
3.9 KiB
Swift
//===----------------------------------------------------------------------===//
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// Copyright © 2025-2026 Apple Inc. and the container project authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//===----------------------------------------------------------------------===//
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import ContainerizationExtras
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/// Handler that uses table lookup to resolve hostnames.
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///
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/// Keys in `hosts4` are normalized to `DNSName` on construction, so lookups
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/// are case-insensitive and trailing dots are optional.
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public struct HostTableResolver: DNSHandler {
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public let hosts4: [DNSName: IPv4Address]
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private let ttl: UInt32
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/// Creates a resolver backed by a static IPv4 host table.
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///
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/// - Parameter hosts4: A dictionary mapping domain names to IPv4 addresses.
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/// Keys are normalized to `DNSName` (lowercased, trailing dot stripped), so
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/// `"FOO."`, `"foo."`, and `"foo"` all refer to the same entry.
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/// - Parameter ttl: The TTL in seconds to set on answer records (default is 300).
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/// - Throws: `DNSBindError.invalidName` if any key is not a valid DNS name.
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public init(hosts4: [String: IPv4Address], ttl: UInt32 = 300) throws {
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self.hosts4 = try Dictionary(uniqueKeysWithValues: hosts4.map { (try DNSName($0.key), $0.value) })
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self.ttl = ttl
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}
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public func answer(query: Message) async throws -> Message? {
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guard let question = query.questions.first else {
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return nil
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}
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let n = question.name.hasSuffix(".") ? String(question.name.dropLast()) : question.name
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let key = try DNSName(labels: n.isEmpty ? [] : n.split(separator: ".", omittingEmptySubsequences: false).map(String.init))
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let record: ResourceRecord?
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switch question.type {
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case ResourceRecordType.host:
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record = answerHost(question: question, key: key)
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case ResourceRecordType.host6:
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// Return NODATA (noError with empty answers) for AAAA queries ONLY if A record exists.
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// This is required because musl libc has issues when A record exists but AAAA returns NXDOMAIN.
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// musl treats NXDOMAIN on AAAA as "domain doesn't exist" and fails DNS resolution entirely.
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// NODATA correctly indicates "no IPv6 address available, but domain exists".
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if hosts4[key] != nil {
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return Message(
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id: query.id,
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type: .response,
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returnCode: .noError,
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questions: query.questions,
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answers: []
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)
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}
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// If hostname doesn't exist, return nil which will become NXDOMAIN
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return nil
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default:
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return Message(
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id: query.id,
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type: .response,
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returnCode: .notImplemented,
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questions: query.questions,
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answers: []
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)
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}
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guard let record else {
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return nil
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}
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return Message(
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id: query.id,
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type: .response,
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returnCode: .noError,
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questions: query.questions,
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answers: [record]
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)
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}
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private func answerHost(question: Question, key: DNSName) -> ResourceRecord? {
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guard let ip = hosts4[key] else {
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return nil
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}
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return HostRecord<IPv4Address>(name: question.name, ttl: ttl, ip: ip)
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}
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}
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