. /include/boost/corosio /native /detail /posix /posix_resolver.hpp
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1   // 1   //
2   // Copyright (c) 2026 Steve Gerbino 2   // Copyright (c) 2026 Steve Gerbino
3   // 3   //
4   // Distributed under the Boost Software License, Version 1.0. (See accompanying 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) 5   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6   // 6   //
7   // Official repository: https://github.com/cppalliance/corosio 7   // Official repository: https://github.com/cppalliance/corosio
8   // 8   //
9   9  
10   #ifndef BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP 10   #ifndef BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP
11   #define BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP 11   #define BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP
12   12  
13   #include <boost/corosio/detail/platform.hpp> 13   #include <boost/corosio/detail/platform.hpp>
14   14  
15   #if BOOST_COROSIO_POSIX 15   #if BOOST_COROSIO_POSIX
16   16  
17   #include <boost/corosio/detail/config.hpp> 17   #include <boost/corosio/detail/config.hpp>
18   #include <boost/corosio/resolver.hpp> 18   #include <boost/corosio/resolver.hpp>
19   #include <boost/capy/ex/execution_context.hpp> 19   #include <boost/capy/ex/execution_context.hpp>
20   20  
21   #include <boost/corosio/native/detail/endpoint_convert.hpp> 21   #include <boost/corosio/native/detail/endpoint_convert.hpp>
22   #include <boost/corosio/detail/intrusive.hpp> 22   #include <boost/corosio/detail/intrusive.hpp>
23   #include <boost/corosio/detail/dispatch_coro.hpp> 23   #include <boost/corosio/detail/dispatch_coro.hpp>
24   #include <boost/corosio/detail/scheduler_op.hpp> 24   #include <boost/corosio/detail/scheduler_op.hpp>
25   #include <boost/corosio/detail/thread_pool.hpp> 25   #include <boost/corosio/detail/thread_pool.hpp>
  26 + #include <boost/corosio/native/detail/coro_op.hpp>
26   27  
27   #include <boost/corosio/detail/scheduler.hpp> 28   #include <boost/corosio/detail/scheduler.hpp>
28   #include <boost/corosio/resolver_results.hpp> 29   #include <boost/corosio/resolver_results.hpp>
29   #include <boost/capy/ex/executor_ref.hpp> 30   #include <boost/capy/ex/executor_ref.hpp>
30   #include <coroutine> 31   #include <coroutine>
31   #include <boost/capy/error.hpp> 32   #include <boost/capy/error.hpp>
32   33  
33   #include <netdb.h> 34   #include <netdb.h>
34   #include <netinet/in.h> 35   #include <netinet/in.h>
35   #include <sys/socket.h> 36   #include <sys/socket.h>
36   37  
37   #include <atomic> 38   #include <atomic>
38   #include <memory> 39   #include <memory>
39   #include <optional> 40   #include <optional>
40   #include <stop_token> 41   #include <stop_token>
41   #include <string> 42   #include <string>
42   43  
43   /* 44   /*
44   POSIX Resolver Service 45   POSIX Resolver Service
45   ====================== 46   ======================
46   47  
47   POSIX getaddrinfo() is a blocking call that cannot be monitored with 48   POSIX getaddrinfo() is a blocking call that cannot be monitored with
48   epoll/kqueue/io_uring. Blocking calls are dispatched to a shared 49   epoll/kqueue/io_uring. Blocking calls are dispatched to a shared
49   resolver_thread_pool service which reuses threads across operations. 50   resolver_thread_pool service which reuses threads across operations.
50   51  
51   Cancellation 52   Cancellation
52   ------------ 53   ------------
53   getaddrinfo() cannot be interrupted mid-call. We use an atomic flag to 54   getaddrinfo() cannot be interrupted mid-call. We use an atomic flag to
54   indicate cancellation was requested. The worker thread checks this flag 55   indicate cancellation was requested. The worker thread checks this flag
55   after getaddrinfo() returns and reports the appropriate error. 56   after getaddrinfo() returns and reports the appropriate error.
56   57  
57   Class Hierarchy 58   Class Hierarchy
58   --------------- 59   ---------------
59   - posix_resolver_service (execution_context service, one per context) 60   - posix_resolver_service (execution_context service, one per context)
60   - Owns all posix_resolver instances via shared_ptr 61   - Owns all posix_resolver instances via shared_ptr
61   - Stores scheduler* for posting completions 62   - Stores scheduler* for posting completions
62   - posix_resolver (one per resolver object) 63   - posix_resolver (one per resolver object)
63   - Contains embedded resolve_op and reverse_resolve_op for reuse 64   - Contains embedded resolve_op and reverse_resolve_op for reuse
64   - Uses shared_from_this to prevent premature destruction 65   - Uses shared_from_this to prevent premature destruction
65   - resolve_op (forward resolution state) 66   - resolve_op (forward resolution state)
66   - Uses getaddrinfo() to resolve host/service to endpoints 67   - Uses getaddrinfo() to resolve host/service to endpoints
67   - reverse_resolve_op (reverse resolution state) 68   - reverse_resolve_op (reverse resolution state)
68   - Uses getnameinfo() to resolve endpoint to host/service 69   - Uses getnameinfo() to resolve endpoint to host/service
69   70  
70   Completion Flow 71   Completion Flow
71   --------------- 72   ---------------
72   Forward resolution: 73   Forward resolution:
73   1. resolve() sets up op_, posts work to the thread pool 74   1. resolve() sets up op_, posts work to the thread pool
74   2. Pool thread runs getaddrinfo() (blocking) 75   2. Pool thread runs getaddrinfo() (blocking)
75   3. Pool thread stores results in op_.stored_results 76   3. Pool thread stores results in op_.stored_results
76   4. Pool thread calls svc_.post(&op_) to queue completion 77   4. Pool thread calls svc_.post(&op_) to queue completion
77   5. Scheduler invokes op_() which resumes the coroutine 78   5. Scheduler invokes op_() which resumes the coroutine
78   79  
79   Reverse resolution follows the same pattern using getnameinfo(). 80   Reverse resolution follows the same pattern using getnameinfo().
80   81  
81   Single-Inflight Constraint 82   Single-Inflight Constraint
82   -------------------------- 83   --------------------------
83   Each resolver has ONE embedded op_ for forward and ONE reverse_op_ for 84   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   reverse resolution. Concurrent operations of the same type on the same
85   resolver would corrupt state. Users must serialize operations per-resolver. 86   resolver would corrupt state. Users must serialize operations per-resolver.
86   87  
87   Shutdown 88   Shutdown
88   -------- 89   --------
89   The resolver service cancels all resolvers and clears the impl map. 90   The resolver service cancels all resolvers and clears the impl map.
90   The thread pool service shuts down separately via execution_context 91   The thread pool service shuts down separately via execution_context
91   service ordering, joining all worker threads. 92   service ordering, joining all worker threads.
92   */ 93   */
93   94  
94   namespace boost::corosio::detail { 95   namespace boost::corosio::detail {
95   96  
96   struct scheduler; 97   struct scheduler;
97   98  
98   namespace posix_resolver_detail { 99   namespace posix_resolver_detail {
99   100  
100   // Convert resolve_flags to addrinfo ai_flags 101   // Convert resolve_flags to addrinfo ai_flags
101   int flags_to_hints(resolve_flags flags); 102   int flags_to_hints(resolve_flags flags);
102   103  
103   // Convert reverse_flags to getnameinfo NI_* flags 104   // Convert reverse_flags to getnameinfo NI_* flags
104   int flags_to_ni_flags(reverse_flags flags); 105   int flags_to_ni_flags(reverse_flags flags);
105   106  
106   // Convert addrinfo results to resolver_results 107   // Convert addrinfo results to resolver_results
107   resolver_results convert_results( 108   resolver_results convert_results(
108   struct addrinfo* ai, std::string_view host, std::string_view service); 109   struct addrinfo* ai, std::string_view host, std::string_view service);
109   110  
110   // Convert getaddrinfo error codes to std::error_code 111   // Convert getaddrinfo error codes to std::error_code
111   std::error_code make_gai_error(int gai_err); 112   std::error_code make_gai_error(int gai_err);
112   113  
113   } // namespace posix_resolver_detail 114   } // namespace posix_resolver_detail
114   115  
115   class posix_resolver_service; 116   class posix_resolver_service;
116   117  
117   /** Resolver implementation for POSIX backends. 118   /** Resolver implementation for POSIX backends.
118   119  
119   Each resolver instance contains a single embedded operation object (op_) 120   Each resolver instance contains a single embedded operation object (op_)
120   that is reused for each resolve() call. This design avoids per-operation 121   that is reused for each resolve() call. This design avoids per-operation
121   heap allocation but imposes a critical constraint: 122   heap allocation but imposes a critical constraint:
122   123  
123   @par Single-Inflight Contract 124   @par Single-Inflight Contract
124   125  
125   Only ONE resolve operation may be in progress at a time per resolver 126   Only ONE resolve operation may be in progress at a time per resolver
126   instance. Calling resolve() while a previous resolve() is still pending 127   instance. Calling resolve() while a previous resolve() is still pending
127   results in undefined behavior: 128   results in undefined behavior:
128   129  
129   - The new call overwrites op_ fields (host, service, coroutine handle) 130   - The new call overwrites op_ fields (host, service, coroutine handle)
130   - The worker thread from the first call reads corrupted state 131   - The worker thread from the first call reads corrupted state
131   - The wrong coroutine may be resumed, or resumed multiple times 132   - The wrong coroutine may be resumed, or resumed multiple times
132   - Data races occur on non-atomic op_ members 133   - Data races occur on non-atomic op_ members
133   134  
134   @par Safe Usage Patterns 135   @par Safe Usage Patterns
135   136  
136   @code 137   @code
137   // CORRECT: Sequential resolves 138   // CORRECT: Sequential resolves
138   auto [ec1, r1] = co_await resolver.resolve("host1", "80"); 139   auto [ec1, r1] = co_await resolver.resolve("host1", "80");
139   auto [ec2, r2] = co_await resolver.resolve("host2", "80"); 140   auto [ec2, r2] = co_await resolver.resolve("host2", "80");
140   141  
141   // CORRECT: Parallel resolves with separate resolver instances 142   // CORRECT: Parallel resolves with separate resolver instances
142   resolver r1(ctx), r2(ctx); 143   resolver r1(ctx), r2(ctx);
143   auto [ec1, res1] = co_await r1.resolve("host1", "80"); // in one coroutine 144   auto [ec1, res1] = co_await r1.resolve("host1", "80"); // in one coroutine
144   auto [ec2, res2] = co_await r2.resolve("host2", "80"); // in another 145   auto [ec2, res2] = co_await r2.resolve("host2", "80"); // in another
145   146  
146   // WRONG: Concurrent resolves on same resolver 147   // WRONG: Concurrent resolves on same resolver
147   // These may run concurrently if launched in parallel - UNDEFINED BEHAVIOR 148   // These may run concurrently if launched in parallel - UNDEFINED BEHAVIOR
148   auto f1 = resolver.resolve("host1", "80"); 149   auto f1 = resolver.resolve("host1", "80");
149   auto f2 = resolver.resolve("host2", "80"); // BAD: overlaps with f1 150   auto f2 = resolver.resolve("host2", "80"); // BAD: overlaps with f1
150   @endcode 151   @endcode
151   152  
152   @par Thread Safety 153   @par Thread Safety
153   Distinct objects: Safe. 154   Distinct objects: Safe.
154   Shared objects: Unsafe. See single-inflight contract above. 155   Shared objects: Unsafe. See single-inflight contract above.
155   */ 156   */
156   class posix_resolver final 157   class posix_resolver final
157   : public resolver::implementation 158   : public resolver::implementation
158   , public std::enable_shared_from_this<posix_resolver> 159   , public std::enable_shared_from_this<posix_resolver>
159   , public intrusive_list<posix_resolver>::node 160   , public intrusive_list<posix_resolver>::node
160   { 161   {
161   friend class posix_resolver_service; 162   friend class posix_resolver_service;
162   163  
163   public: 164   public:
164   // resolve_op - operation state for a single DNS resolution 165   // resolve_op - operation state for a single DNS resolution
165   166  
166 - struct resolve_op : scheduler_op 167 + struct resolve_op : coro_op
167   { 168   {
168 - struct canceller 169 + /// Where the endpoints are handed back.
169 - { 170 + resolver_results* out = nullptr;
170 - resolve_op* op;  
DCB 171 - 1 void operator()() const noexcept  
172 - {  
DCB 173 - 1 op->request_cancel();  
DCB 174 - 1 }  
175 - };  
176 -  
177 - // Coroutine state  
178 - std::coroutine_handle<> h;  
179 - capy::continuation cont;  
180 - capy::executor_ref ex;  
181 - posix_resolver* impl = nullptr;  
182 -  
183 - // Output parameters  
184 - std::error_code* ec_out = nullptr;  
185 - resolver_results* out = nullptr;  
186   171  
187   // Input parameters (owned copies for thread safety) 172   // Input parameters (owned copies for thread safety)
188   std::string host; 173   std::string host;
189   std::string service; 174   std::string service;
190   resolve_flags flags = resolve_flags::none; 175   resolve_flags flags = resolve_flags::none;
191   176  
192   // Result storage (populated by worker thread) 177   // Result storage (populated by worker thread)
193   resolver_results stored_results; 178   resolver_results stored_results;
194   int gai_error = 0; 179   int gai_error = 0;
195 - // Thread coordination  
196 - std::atomic<bool> cancelled{false};  
197 - std::optional<std::stop_callback<canceller>> stop_cb;  
198 -  
199   180  
HITCBC 200   49 resolve_op() = default; 181   57 resolve_op() = default;
201   182  
202   void reset() noexcept; 183   void reset() noexcept;
203   void operator()() override; 184   void operator()() override;
204 - void request_cancel() noexcept;  
205 - void start(std::stop_token const& token);  
206   void destroy() override; 185   void destroy() override;
207   }; 186   };
208   187  
209   // reverse_resolve_op - operation state for reverse DNS resolution 188   // reverse_resolve_op - operation state for reverse DNS resolution
210   189  
211 - struct reverse_resolve_op : scheduler_op 190 + struct reverse_resolve_op : coro_op
212   { 191   {
213 - struct canceller 192 + /// Where the name is handed back.
214 - {  
215 - reverse_resolve_op* op;  
DCB 216 - 1 void operator()() const noexcept  
217 - {  
DCB 218 - 1 op->request_cancel();  
DCB 219 - 1 }  
220 - };  
221 -  
222 - // Coroutine state  
223 - std::coroutine_handle<> h;  
224 - capy::continuation cont;  
225 - capy::executor_ref ex;  
226 - posix_resolver* impl = nullptr;  
227 -  
228 - // Output parameters  
229 - std::error_code* ec_out = nullptr;  
230   reverse_resolver_result* result_out = nullptr; 193   reverse_resolver_result* result_out = nullptr;
231   194  
232   // Input parameters 195   // Input parameters
233   endpoint ep; 196   endpoint ep;
234   reverse_flags flags = reverse_flags::none; 197   reverse_flags flags = reverse_flags::none;
235   198  
236   // Result storage (populated by worker thread) 199   // Result storage (populated by worker thread)
237   std::string stored_host; 200   std::string stored_host;
238   std::string stored_service; 201   std::string stored_service;
239   int gai_error = 0; 202   int gai_error = 0;
240 - // Thread coordination  
241 - std::atomic<bool> cancelled{false};  
242 - std::optional<std::stop_callback<canceller>> stop_cb;  
243 -  
244   203  
HITCBC 245   49 reverse_resolve_op() = default; 204   57 reverse_resolve_op() = default;
246   205  
247   void reset() noexcept; 206   void reset() noexcept;
248   void operator()() override; 207   void operator()() override;
249 - void request_cancel() noexcept;  
250 - void start(std::stop_token const& token);  
251   void destroy() override; 208   void destroy() override;
252   }; 209   };
253   210  
254   /// Embedded pool work item for thread pool dispatch. 211   /// Embedded pool work item for thread pool dispatch.
255   struct pool_op : pool_work_item 212   struct pool_op : pool_work_item
256   { 213   {
257   /// Resolver that owns this work item. 214   /// Resolver that owns this work item.
258   posix_resolver* resolver_ = nullptr; 215   posix_resolver* resolver_ = nullptr;
259   216  
260   /// Prevent impl destruction while work is in flight. 217   /// Prevent impl destruction while work is in flight.
261   std::shared_ptr<posix_resolver> ref_; 218   std::shared_ptr<posix_resolver> ref_;
262   }; 219   };
263   220  
264   explicit posix_resolver(posix_resolver_service& svc) noexcept; 221   explicit posix_resolver(posix_resolver_service& svc) noexcept;
265   222  
266   std::coroutine_handle<> resolve( 223   std::coroutine_handle<> resolve(
267   std::coroutine_handle<>, 224   std::coroutine_handle<>,
268   capy::executor_ref, 225   capy::executor_ref,
269   std::string_view host, 226   std::string_view host,
270   std::string_view service, 227   std::string_view service,
271   resolve_flags flags, 228   resolve_flags flags,
272   std::stop_token, 229   std::stop_token,
273   std::error_code*, 230   std::error_code*,
274   resolver_results*) override; 231   resolver_results*) override;
275   232  
276   std::coroutine_handle<> reverse_resolve( 233   std::coroutine_handle<> reverse_resolve(
277   std::coroutine_handle<>, 234   std::coroutine_handle<>,
278   capy::executor_ref, 235   capy::executor_ref,
279   endpoint const& ep, 236   endpoint const& ep,
280   reverse_flags flags, 237   reverse_flags flags,
281   std::stop_token, 238   std::stop_token,
282   std::error_code*, 239   std::error_code*,
283   reverse_resolver_result*) override; 240   reverse_resolver_result*) override;
284   241  
285   void cancel() noexcept override; 242   void cancel() noexcept override;
286   243  
287   resolve_op op_; 244   resolve_op op_;
288   reverse_resolve_op reverse_op_; 245   reverse_resolve_op reverse_op_;
289   246  
290   /// Pool work item for forward resolution. 247   /// Pool work item for forward resolution.
291   pool_op resolve_pool_op_; 248   pool_op resolve_pool_op_;
292   249  
293   /// Pool work item for reverse resolution. 250   /// Pool work item for reverse resolution.
294   pool_op reverse_pool_op_; 251   pool_op reverse_pool_op_;
295   252  
296   /// Execute blocking `getaddrinfo()` on a pool thread. 253   /// Execute blocking `getaddrinfo()` on a pool thread.
297   static void do_resolve_work(pool_work_item*) noexcept; 254   static void do_resolve_work(pool_work_item*) noexcept;
298   255  
299   /// Execute blocking `getnameinfo()` on a pool thread. 256   /// Execute blocking `getnameinfo()` on a pool thread.
300   static void do_reverse_resolve_work(pool_work_item*) noexcept; 257   static void do_reverse_resolve_work(pool_work_item*) noexcept;
301   258  
302   private: 259   private:
303   posix_resolver_service& svc_; 260   posix_resolver_service& svc_;
304   }; 261   };
305   262  
306   } // namespace boost::corosio::detail 263   } // namespace boost::corosio::detail
307   264  
308   #endif // BOOST_COROSIO_POSIX 265   #endif // BOOST_COROSIO_POSIX
309   266  
310   #endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP 267   #endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP