Diff coverage report for

//

//

// Copyright (c) 2026 Steve Gerbino

// Copyright (c) 2026 Steve Gerbino

//

//

// Distributed under the Boost Software License, Version 1.0. (See accompanying

// Distributed under the Boost Software License, Version 1.0. (See accompanying

// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//

//

// Official repository: https://github.com/cppalliance/corosio

// Official repository: https://github.com/cppalliance/corosio

//

//

#ifndef BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP

#ifndef BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP

#define BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP

#define BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP

#include <boost/corosio/detail/platform.hpp>

#include <boost/corosio/detail/platform.hpp>

#if BOOST_COROSIO_POSIX

#if BOOST_COROSIO_POSIX

#include <boost/corosio/detail/config.hpp>

#include <boost/corosio/detail/config.hpp>

#include <boost/corosio/resolver.hpp>

#include <boost/corosio/resolver.hpp>

#include <boost/capy/ex/execution_context.hpp>

#include <boost/capy/ex/execution_context.hpp>

#include <boost/corosio/detail/endpoint_convert.hpp>

#include <boost/corosio/detail/endpoint_convert.hpp>

#include <boost/corosio/detail/intrusive.hpp>

#include <boost/corosio/detail/intrusive.hpp>

#include <boost/corosio/detail/dispatch_coro.hpp>

#include <boost/corosio/detail/dispatch_coro.hpp>

#include <boost/corosio/detail/scheduler_op.hpp>

#include <boost/corosio/detail/scheduler_op.hpp>

#include <boost/corosio/detail/scheduler.hpp>

#include <boost/corosio/detail/scheduler.hpp>

#include <boost/corosio/resolver_results.hpp>

#include <boost/corosio/resolver_results.hpp>

#include <boost/capy/ex/executor_ref.hpp>

#include <boost/capy/ex/executor_ref.hpp>

#include <coroutine>

#include <coroutine>

#include <boost/capy/error.hpp>

#include <boost/capy/error.hpp>

#include <netdb.h>

#include <netdb.h>

#include <netinet/in.h>

#include <netinet/in.h>

#include <sys/socket.h>

#include <sys/socket.h>

#include <atomic>

#include <atomic>

#include <cassert>

#include <cassert>

#include <condition_variable>

#include <condition_variable>

#include <cstring>

#include <cstring>

#include <memory>

#include <memory>

#include <mutex>

#include <mutex>

#include <optional>

#include <optional>

#include <stop_token>

#include <stop_token>

#include <string>

#include <string>

#include <thread>

#include <thread>

#include <unordered_map>

#include <unordered_map>

#include <vector>

#include <vector>

/*

/*

    POSIX Resolver Service

    POSIX Resolver Service

    ======================

    ======================

    POSIX getaddrinfo() is a blocking call that cannot be monitored with

    POSIX getaddrinfo() is a blocking call that cannot be monitored with

    epoll/kqueue/io_uring. We use a worker thread approach: each resolution

    epoll/kqueue/io_uring. We use a worker thread approach: each resolution

    spawns a dedicated thread that runs the blocking call and posts completion

    spawns a dedicated thread that runs the blocking call and posts completion

    back to the scheduler.

    back to the scheduler.

    Thread-per-resolution Design

    Thread-per-resolution Design

    ----------------------------

    ----------------------------

    Simple, no thread pool complexity. DNS lookups are infrequent enough that

    Simple, no thread pool complexity. DNS lookups are infrequent enough that

    thread creation overhead is acceptable. Detached threads self-manage;

    thread creation overhead is acceptable. Detached threads self-manage;

    shared_ptr capture keeps impl alive until completion.

    shared_ptr capture keeps impl alive until completion.

    Cancellation

    Cancellation

    ------------

    ------------

    getaddrinfo() cannot be interrupted mid-call. We use an atomic flag to

    getaddrinfo() cannot be interrupted mid-call. We use an atomic flag to

    indicate cancellation was requested. The worker thread checks this flag

    indicate cancellation was requested. The worker thread checks this flag

    after getaddrinfo() returns and reports the appropriate error.

    after getaddrinfo() returns and reports the appropriate error.

    Class Hierarchy

    Class Hierarchy

    ---------------

    ---------------

    - posix_resolver_service (execution_context service, one per context)

    - posix_resolver_service (execution_context service, one per context)

        - Owns all posix_resolver instances via shared_ptr

        - Owns all posix_resolver instances via shared_ptr

        - Stores scheduler* for posting completions

        - Stores scheduler* for posting completions

    - posix_resolver (one per resolver object)

    - posix_resolver (one per resolver object)

        - Contains embedded resolve_op and reverse_resolve_op for reuse

        - Contains embedded resolve_op and reverse_resolve_op for reuse

        - Uses shared_from_this to prevent premature destruction

        - Uses shared_from_this to prevent premature destruction

    - resolve_op (forward resolution state)

    - resolve_op (forward resolution state)

        - Uses getaddrinfo() to resolve host/service to endpoints

        - Uses getaddrinfo() to resolve host/service to endpoints

    - reverse_resolve_op (reverse resolution state)

    - reverse_resolve_op (reverse resolution state)

        - Uses getnameinfo() to resolve endpoint to host/service

        - Uses getnameinfo() to resolve endpoint to host/service

    Worker Thread Lifetime

    Worker Thread Lifetime

    ----------------------

    ----------------------

    Each resolve() spawns a detached thread. The thread captures a shared_ptr

    Each resolve() spawns a detached thread. The thread captures a shared_ptr

    to posix_resolver, ensuring the impl (and its embedded op_) stays

    to posix_resolver, ensuring the impl (and its embedded op_) stays

    alive until the thread completes, even if the resolver is destroyed.

    alive until the thread completes, even if the resolver is destroyed.

    Completion Flow

    Completion Flow

    ---------------

    ---------------

    Forward resolution:

    Forward resolution:

    1. resolve() sets up op_, spawns worker thread

    1. resolve() sets up op_, spawns worker thread

    2. Worker runs getaddrinfo() (blocking)

    2. Worker runs getaddrinfo() (blocking)

    3. Worker stores results in op_.stored_results

    3. Worker stores results in op_.stored_results

    4. Worker calls svc_.post(&op_) to queue completion

    4. Worker calls svc_.post(&op_) to queue completion

    5. Scheduler invokes op_() which resumes the coroutine

    5. Scheduler invokes op_() which resumes the coroutine

    Reverse resolution follows the same pattern using getnameinfo().

    Reverse resolution follows the same pattern using getnameinfo().

    Single-Inflight Constraint

    Single-Inflight Constraint

    --------------------------

    --------------------------

    Each resolver has ONE embedded op_ for forward and ONE reverse_op_ for

    Each resolver has ONE embedded op_ for forward and ONE reverse_op_ for

    reverse resolution. Concurrent operations of the same type on the same

    reverse resolution. Concurrent operations of the same type on the same

    resolver would corrupt state. Users must serialize operations per-resolver.

    resolver would corrupt state. Users must serialize operations per-resolver.

    Shutdown Synchronization

    Shutdown Synchronization

    ------------------------

    ------------------------

    The service tracks active worker threads via thread_started()/thread_finished().

    The service tracks active worker threads via thread_started()/thread_finished().

    During shutdown(), the service sets shutting_down_ flag and waits for all

    During shutdown(), the service sets shutting_down_ flag and waits for all

    threads to complete before destroying resources.

    threads to complete before destroying resources.

*/

*/

namespace boost::corosio::detail {

namespace boost::corosio::detail {

struct scheduler;

struct scheduler;

namespace posix_resolver_detail {

namespace posix_resolver_detail {

// Convert resolve_flags to addrinfo ai_flags

// Convert resolve_flags to addrinfo ai_flags

int flags_to_hints(resolve_flags flags);

int flags_to_hints(resolve_flags flags);

// Convert reverse_flags to getnameinfo NI_* flags

// Convert reverse_flags to getnameinfo NI_* flags

int flags_to_ni_flags(reverse_flags flags);

int flags_to_ni_flags(reverse_flags flags);

// Convert addrinfo results to resolver_results

// Convert addrinfo results to resolver_results

resolver_results convert_results(

resolver_results convert_results(

    struct addrinfo* ai, std::string_view host, std::string_view service);

    struct addrinfo* ai, std::string_view host, std::string_view service);

// Convert getaddrinfo error codes to std::error_code

// Convert getaddrinfo error codes to std::error_code

std::error_code make_gai_error(int gai_err);

std::error_code make_gai_error(int gai_err);

} // namespace posix_resolver_detail

} // namespace posix_resolver_detail

class posix_resolver_service;

class posix_resolver_service;

/** Resolver implementation for POSIX backends.

/** Resolver implementation for POSIX backends.

    Each resolver instance contains a single embedded operation object (op_)

    Each resolver instance contains a single embedded operation object (op_)

    that is reused for each resolve() call. This design avoids per-operation

    that is reused for each resolve() call. This design avoids per-operation

    heap allocation but imposes a critical constraint:

    heap allocation but imposes a critical constraint:

    @par Single-Inflight Contract

    @par Single-Inflight Contract

    Only ONE resolve operation may be in progress at a time per resolver

    Only ONE resolve operation may be in progress at a time per resolver

    instance. Calling resolve() while a previous resolve() is still pending

    instance. Calling resolve() while a previous resolve() is still pending

    results in undefined behavior:

    results in undefined behavior:

    - The new call overwrites op_ fields (host, service, coroutine handle)

    - The new call overwrites op_ fields (host, service, coroutine handle)

    - The worker thread from the first call reads corrupted state

    - The worker thread from the first call reads corrupted state

    - The wrong coroutine may be resumed, or resumed multiple times

    - The wrong coroutine may be resumed, or resumed multiple times

    - Data races occur on non-atomic op_ members

    - Data races occur on non-atomic op_ members

    @par Safe Usage Patterns

    @par Safe Usage Patterns

    @code

    @code

    // CORRECT: Sequential resolves

    // CORRECT: Sequential resolves

    auto [ec1, r1] = co_await resolver.resolve("host1", "80");

    auto [ec1, r1] = co_await resolver.resolve("host1", "80");

    auto [ec2, r2] = co_await resolver.resolve("host2", "80");

    auto [ec2, r2] = co_await resolver.resolve("host2", "80");

    // CORRECT: Parallel resolves with separate resolver instances

    // CORRECT: Parallel resolves with separate resolver instances

    resolver r1(ctx), r2(ctx);

    resolver r1(ctx), r2(ctx);

    auto [ec1, res1] = co_await r1.resolve("host1", "80");  // in one coroutine

    auto [ec1, res1] = co_await r1.resolve("host1", "80");  // in one coroutine

    auto [ec2, res2] = co_await r2.resolve("host2", "80");  // in another

    auto [ec2, res2] = co_await r2.resolve("host2", "80");  // in another

    // WRONG: Concurrent resolves on same resolver

    // WRONG: Concurrent resolves on same resolver

    // These may run concurrently if launched in parallel - UNDEFINED BEHAVIOR

    // These may run concurrently if launched in parallel - UNDEFINED BEHAVIOR

    auto f1 = resolver.resolve("host1", "80");

    auto f1 = resolver.resolve("host1", "80");

    auto f2 = resolver.resolve("host2", "80");  // BAD: overlaps with f1

    auto f2 = resolver.resolve("host2", "80");  // BAD: overlaps with f1

    @endcode

    @endcode

    @par Thread Safety

    @par Thread Safety

    Distinct objects: Safe.

    Distinct objects: Safe.

    Shared objects: Unsafe. See single-inflight contract above.

    Shared objects: Unsafe. See single-inflight contract above.

*/

*/

class posix_resolver final

class posix_resolver final

    : public resolver::implementation

    : public resolver::implementation

    , public std::enable_shared_from_this<posix_resolver>

    , public std::enable_shared_from_this<posix_resolver>

    , public intrusive_list<posix_resolver>::node

    , public intrusive_list<posix_resolver>::node

{

{

    friend class posix_resolver_service;

    friend class posix_resolver_service;

public:

public:

    // resolve_op - operation state for a single DNS resolution

    // resolve_op - operation state for a single DNS resolution

    struct resolve_op : scheduler_op

    struct resolve_op : scheduler_op

    {

    {

        struct canceller

        struct canceller

        {

        {

            resolve_op* op;

            resolve_op* op;

            {

            {

        };

        };

        // Coroutine state

        // Coroutine state

        std::coroutine_handle<> h;

        std::coroutine_handle<> h;

        capy::executor_ref ex;

        capy::executor_ref ex;

        posix_resolver* impl = nullptr;

        posix_resolver* impl = nullptr;

        // Output parameters

        // Output parameters

        std::error_code* ec_out = nullptr;

        std::error_code* ec_out = nullptr;

        resolver_results* out   = nullptr;

        resolver_results* out   = nullptr;

        // Input parameters (owned copies for thread safety)

        // Input parameters (owned copies for thread safety)

        std::string host;

        std::string host;

        std::string service;

        std::string service;

        resolve_flags flags = resolve_flags::none;

        resolve_flags flags = resolve_flags::none;

        // Result storage (populated by worker thread)

        // Result storage (populated by worker thread)

        resolver_results stored_results;

        resolver_results stored_results;

        int gai_error = 0;

        int gai_error = 0;

        // Thread coordination

        // Thread coordination

        std::atomic<bool> cancelled{false};

        std::atomic<bool> cancelled{false};

        std::optional<std::stop_callback<canceller>> stop_cb;

        std::optional<std::stop_callback<canceller>> stop_cb;

        void reset() noexcept;

        void reset() noexcept;

        void operator()() override;

        void operator()() override;

        void destroy() override;

        void destroy() override;

        void request_cancel() noexcept;

        void request_cancel() noexcept;

        void start(std::stop_token token);

        void start(std::stop_token token);

    };

    };

    // reverse_resolve_op - operation state for reverse DNS resolution

    // reverse_resolve_op - operation state for reverse DNS resolution

    struct reverse_resolve_op : scheduler_op

    struct reverse_resolve_op : scheduler_op

    {

    {

        struct canceller

        struct canceller

        {

        {

            reverse_resolve_op* op;

            reverse_resolve_op* op;

            {

            {

        };

        };

        // Coroutine state

        // Coroutine state

        std::coroutine_handle<> h;

        std::coroutine_handle<> h;

        capy::executor_ref ex;

        capy::executor_ref ex;

        posix_resolver* impl = nullptr;

        posix_resolver* impl = nullptr;

        // Output parameters

        // Output parameters

        std::error_code* ec_out             = nullptr;

        std::error_code* ec_out             = nullptr;

        reverse_resolver_result* result_out = nullptr;

        reverse_resolver_result* result_out = nullptr;

        // Input parameters

        // Input parameters

        endpoint ep;

        endpoint ep;

        reverse_flags flags = reverse_flags::none;

        reverse_flags flags = reverse_flags::none;

        // Result storage (populated by worker thread)

        // Result storage (populated by worker thread)

        std::string stored_host;

        std::string stored_host;

        std::string stored_service;

        std::string stored_service;

        int gai_error = 0;

        int gai_error = 0;

        // Thread coordination

        // Thread coordination

        std::atomic<bool> cancelled{false};

        std::atomic<bool> cancelled{false};

        std::optional<std::stop_callback<canceller>> stop_cb;

        std::optional<std::stop_callback<canceller>> stop_cb;

        void reset() noexcept;

        void reset() noexcept;

        void operator()() override;

        void operator()() override;

        void destroy() override;

        void destroy() override;

        void request_cancel() noexcept;

        void request_cancel() noexcept;

        void start(std::stop_token token);

        void start(std::stop_token token);

    };

    };

    explicit posix_resolver(posix_resolver_service& svc) noexcept;

    explicit posix_resolver(posix_resolver_service& svc) noexcept;

    std::coroutine_handle<> resolve(

    std::coroutine_handle<> resolve(

        std::coroutine_handle<>,

        std::coroutine_handle<>,

        capy::executor_ref,

        capy::executor_ref,

        std::string_view host,

        std::string_view host,

        std::string_view service,

        std::string_view service,

        resolve_flags flags,

        resolve_flags flags,

        std::stop_token,

        std::stop_token,

        std::error_code*,

        std::error_code*,

        resolver_results*) override;

        resolver_results*) override;

    std::coroutine_handle<> reverse_resolve(

    std::coroutine_handle<> reverse_resolve(

        std::coroutine_handle<>,

        std::coroutine_handle<>,

        capy::executor_ref,

        capy::executor_ref,

        endpoint const& ep,

        endpoint const& ep,

        reverse_flags flags,

        reverse_flags flags,

        std::stop_token,

        std::stop_token,

        std::error_code*,

        std::error_code*,

        reverse_resolver_result*) override;

        reverse_resolver_result*) override;

    void cancel() noexcept override;

    void cancel() noexcept override;

    resolve_op op_;

    resolve_op op_;

    reverse_resolve_op reverse_op_;

    reverse_resolve_op reverse_op_;

private:

private:

    posix_resolver_service& svc_;

    posix_resolver_service& svc_;

};

};

} // namespace boost::corosio::detail

} // namespace boost::corosio::detail

#endif // BOOST_COROSIO_POSIX

#endif // BOOST_COROSIO_POSIX

#endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP

#endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RESOLVER_HPP