TLA Line data Source code
1 : //
2 : // Copyright (c) 2026 Steve Gerbino
3 : //
4 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
5 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6 : //
7 : // Official repository: https://github.com/cppalliance/corosio
8 : //
9 :
10 : #ifndef BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP
11 : #define BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP
12 :
13 : #include <boost/corosio/detail/platform.hpp>
14 :
15 : #if BOOST_COROSIO_POSIX
16 :
17 : #include <boost/corosio/detail/config.hpp>
18 : #include <boost/corosio/resolver.hpp>
19 : #include <boost/capy/ex/execution_context.hpp>
20 :
21 : #include <boost/corosio/native/detail/endpoint_convert.hpp>
22 : #include <boost/corosio/detail/intrusive.hpp>
23 : #include <boost/corosio/detail/dispatch_coro.hpp>
24 : #include <boost/corosio/detail/scheduler_op.hpp>
25 : #include <boost/corosio/detail/thread_pool.hpp>
26 : #include <boost/corosio/native/detail/coro_op.hpp>
27 :
28 : #include <boost/corosio/detail/scheduler.hpp>
29 : #include <boost/capy/ex/executor_ref.hpp>
30 : #include <coroutine>
31 : #include <boost/capy/error.hpp>
32 :
33 : #include <netdb.h>
34 : #include <netinet/in.h>
35 : #include <sys/socket.h>
36 :
37 : #include <atomic>
38 : #include <memory>
39 : #include <optional>
40 : #include <stop_token>
41 : #include <string>
42 :
43 : /*
44 : POSIX Resolver Service
45 : ======================
46 :
47 : POSIX getaddrinfo() is a blocking call that cannot be monitored with
48 : epoll/kqueue/io_uring. Blocking calls are dispatched to a shared
49 : resolver_thread_pool service which reuses threads across operations.
50 :
51 : Cancellation
52 : ------------
53 : getaddrinfo() cannot be interrupted mid-call. We use an atomic flag to
54 : indicate cancellation was requested. The worker thread checks this flag
55 : after getaddrinfo() returns and reports the appropriate error.
56 :
57 : Class Hierarchy
58 : ---------------
59 : - posix_resolver_service (execution_context service, one per context)
60 : - Owns all posix_resolver instances via shared_ptr
61 : - Stores scheduler* for posting completions
62 : - posix_resolver (one per resolver object)
63 : - Contains embedded resolve_op and reverse_resolve_op for reuse
64 : - Uses shared_from_this to prevent premature destruction
65 : - resolve_op (forward resolution state)
66 : - Uses getaddrinfo() to resolve host/service to endpoints
67 : - reverse_resolve_op (reverse resolution state)
68 : - Uses getnameinfo() to resolve endpoint to host/service
69 :
70 : Completion Flow
71 : ---------------
72 : Forward resolution:
73 : 1. resolve() sets up op_, posts work to the thread pool
74 : 2. Pool thread runs getaddrinfo() (blocking)
75 : 3. Pool thread stores results in op_.stored_results
76 : 4. Pool thread calls svc_.post(&op_) to queue completion
77 : 5. Scheduler invokes op_() which resumes the coroutine
78 :
79 : Reverse resolution follows the same pattern using getnameinfo().
80 :
81 : Single-Inflight Constraint
82 : --------------------------
83 : Each resolver has ONE embedded op_ for forward and ONE reverse_op_ for
84 : reverse resolution. Concurrent operations of the same type on the same
85 : resolver would corrupt state. Users must serialize operations per-resolver.
86 :
87 : Shutdown
88 : --------
89 : The resolver service cancels all resolvers and clears the impl map.
90 : The thread pool service shuts down separately via execution_context
91 : service ordering, joining all worker threads.
92 : */
93 :
94 : namespace boost::corosio::detail {
95 :
96 : struct scheduler;
97 :
98 : namespace posix_resolver_detail {
99 :
100 : // Convert resolve_flags to addrinfo ai_flags
101 : int flags_to_hints(resolve_flags flags);
102 :
103 : // Convert reverse_flags to getnameinfo NI_* flags
104 : int flags_to_ni_flags(reverse_flags flags);
105 :
106 : // Convert addrinfo results to endpoints
107 : std::vector<endpoint> convert_results(struct addrinfo* ai);
108 :
109 : // Convert getaddrinfo error codes to std::error_code
110 : std::error_code make_gai_error(int gai_err);
111 :
112 : } // namespace posix_resolver_detail
113 :
114 : class posix_resolver_service;
115 :
116 : /** Resolver implementation for POSIX backends.
117 :
118 : Each resolver instance contains a single embedded operation object (op_)
119 : that is reused for each resolve() call. This design avoids per-operation
120 : heap allocation but imposes a critical constraint:
121 :
122 : @par Single-Inflight Contract
123 :
124 : Only ONE resolve operation may be in progress at a time per resolver
125 : instance. Calling resolve() while a previous resolve() is still pending
126 : results in undefined behavior:
127 :
128 : - The new call overwrites op_ fields (host, service, coroutine handle)
129 : - The worker thread from the first call reads corrupted state
130 : - The wrong coroutine may be resumed, or resumed multiple times
131 : - Data races occur on non-atomic op_ members
132 :
133 : @par Safe Usage Patterns
134 :
135 : @code
136 : // CORRECT: Sequential resolves
137 : auto [ec1, r1] = co_await resolver.resolve("host1", "80");
138 : auto [ec2, r2] = co_await resolver.resolve("host2", "80");
139 :
140 : // CORRECT: Parallel resolves with separate resolver instances
141 : resolver r1(ctx), r2(ctx);
142 : auto [ec1, res1] = co_await r1.resolve("host1", "80"); // in one coroutine
143 : auto [ec2, res2] = co_await r2.resolve("host2", "80"); // in another
144 :
145 : // WRONG: Concurrent resolves on same resolver
146 : // These may run concurrently if launched in parallel - UNDEFINED BEHAVIOR
147 : auto f1 = resolver.resolve("host1", "80");
148 : auto f2 = resolver.resolve("host2", "80"); // BAD: overlaps with f1
149 : @endcode
150 :
151 : @par Thread Safety
152 : Distinct objects: Safe.
153 : Shared objects: Unsafe. See single-inflight contract above.
154 : */
155 : class posix_resolver final
156 : : public resolver::implementation
157 : , public std::enable_shared_from_this<posix_resolver>
158 : , public intrusive_list<posix_resolver>::node
159 : {
160 : friend class posix_resolver_service;
161 :
162 : public:
163 : // resolve_op - operation state for a single DNS resolution
164 :
165 : struct resolve_op : coro_op
166 : {
167 : /// Where the endpoints are handed back.
168 : std::vector<endpoint>* out = nullptr;
169 :
170 : // Input parameters (owned copies for thread safety)
171 : std::string host;
172 : std::string service;
173 : resolve_flags flags = resolve_flags::none;
174 :
175 : // Result storage (populated by worker thread)
176 : std::vector<endpoint> stored_results;
177 : int gai_error = 0;
178 :
179 HIT 64 : resolve_op() = default;
180 :
181 : void reset() noexcept;
182 : void operator()() override;
183 : void destroy() override;
184 : };
185 :
186 : // reverse_resolve_op - operation state for reverse DNS resolution
187 :
188 : struct reverse_resolve_op : coro_op
189 : {
190 : /// Where the name is handed back.
191 : endpoint_name* result_out = nullptr;
192 :
193 : // Input parameters
194 : endpoint ep;
195 : reverse_flags flags = reverse_flags::none;
196 :
197 : // Result storage (populated by worker thread)
198 : std::string stored_host;
199 : std::string stored_service;
200 : int gai_error = 0;
201 :
202 64 : reverse_resolve_op() = default;
203 :
204 : void reset() noexcept;
205 : void operator()() override;
206 : void destroy() override;
207 : };
208 :
209 : /// Embedded pool work item for thread pool dispatch.
210 : struct pool_op : pool_work_item
211 : {
212 : /// Resolver that owns this work item.
213 : posix_resolver* resolver_ = nullptr;
214 :
215 : /// Prevent impl destruction while work is in flight.
216 : std::shared_ptr<posix_resolver> ref_;
217 : };
218 :
219 : explicit posix_resolver(posix_resolver_service& svc) noexcept;
220 :
221 : std::coroutine_handle<> resolve(
222 : std::coroutine_handle<>,
223 : capy::executor_ref,
224 : std::string_view host,
225 : std::string_view service,
226 : resolve_flags flags,
227 : std::stop_token,
228 : std::error_code*,
229 : std::vector<endpoint>*) override;
230 :
231 : std::coroutine_handle<> reverse_resolve(
232 : std::coroutine_handle<>,
233 : capy::executor_ref,
234 : endpoint const& ep,
235 : reverse_flags flags,
236 : std::stop_token,
237 : std::error_code*,
238 : endpoint_name*) override;
239 :
240 : void cancel() noexcept override;
241 :
242 : resolve_op op_;
243 : reverse_resolve_op reverse_op_;
244 :
245 : /// Pool work item for forward resolution.
246 : pool_op resolve_pool_op_;
247 :
248 : /// Pool work item for reverse resolution.
249 : pool_op reverse_pool_op_;
250 :
251 : /// Execute blocking `getaddrinfo()` on a pool thread.
252 : static void do_resolve_work(pool_work_item*) noexcept;
253 :
254 : /// Execute blocking `getnameinfo()` on a pool thread.
255 : static void do_reverse_resolve_work(pool_work_item*) noexcept;
256 :
257 : private:
258 : posix_resolver_service& svc_;
259 : };
260 :
261 : } // namespace boost::corosio::detail
262 :
263 : #endif // BOOST_COROSIO_POSIX
264 :
265 : #endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP
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