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