add io_uring_context::open_listening_socket

* opens a socket on a specified port
* exposes a _Stream_ of `async_read_write_file` to handle accept(s)

include/unifex/file_concepts.hpp

@@ -17,8 +17,6 @@
 
 #include <unifex/tag_invoke.hpp>
 
-#include <unifex/io_concepts.hpp>
-
 #include <unifex/filesystem.hpp>
 
 #include <unifex/detail/prologue.hpp>

include/unifex/linux/io_epoll_context.hpp

@@ -21,6 +21,7 @@
 #include <unifex/detail/atomic_intrusive_queue.hpp>
 #include <unifex/detail/intrusive_heap.hpp>
 #include <unifex/detail/intrusive_queue.hpp>
+#include <unifex/io_concepts.hpp>
 #include <unifex/pipe_concepts.hpp>
 #include <unifex/get_stop_token.hpp>
 #include <unifex/manual_lifetime.hpp>

include/unifex/linux/io_uring_context.hpp

@@ -21,8 +21,13 @@
 #include <unifex/detail/atomic_intrusive_queue.hpp>
 #include <unifex/detail/intrusive_heap.hpp>
 #include <unifex/detail/intrusive_queue.hpp>
+#include <unifex/defer.hpp>
 #include <unifex/file_concepts.hpp>
 #include <unifex/filesystem.hpp>
+#include <unifex/io_concepts.hpp>
+#include <unifex/just_done.hpp>
+#include <unifex/let_value_with.hpp>
+#include <unifex/socket_concepts.hpp>
 #include <unifex/get_stop_token.hpp>
 #include <unifex/manual_lifetime.hpp>
 #include <unifex/receiver_concepts.hpp>
@@ -43,7 +48,10 @@
 
 #include UNIFEX_LIBURING_HEADER
 
+#include <netinet/in.h>
+#include <sys/socket.h>
 #include <sys/uio.h>
+#include <unistd.h>
 
 #include <unifex/detail/prologue.hpp>
 
@@ -62,6 +70,8 @@ class io_uring_context {
   class async_read_write_file;
   class async_write_only_file;
   class scheduler;
+  class accept_sender;
+  class accept_stream;
 
   io_uring_context();
 
@@ -925,6 +935,10 @@ class io_uring_context::scheduler {
       tag_t<open_file_write_only>,
       scheduler s,
       const filesystem::path& path);
+  friend accept_stream tag_invoke(
+      tag_t<open_listening_socket>,
+      scheduler s,
+      port_t port);
 
   friend bool operator==(scheduler a, scheduler b) noexcept {
     return a.context_ == b.context_;
@@ -942,6 +956,178 @@ inline io_uring_context::scheduler io_uring_context::get_scheduler() noexcept {
   return scheduler{*this};
 }
 
+class io_uring_context::accept_sender {
+  using offset_t = std::int64_t;
+
+  template <typename Receiver>
+  class operation : private completion_base {
+    friend io_uring_context;
+
+  public:
+    template <typename Receiver2>
+    explicit operation(const accept_sender& sender, Receiver2&& r) noexcept(
+        std::is_nothrow_constructible_v<Receiver, Receiver2>)
+      : context_(sender.context_)
+      , fd_(sender.fd_)
+      , receiver_((Receiver2 &&) r) {}
+
+    operation(operation&&) = delete;
+
+    void start() noexcept {
+      if (!context_.is_running_on_io_thread()) {
+        this->execute_ = &operation::on_schedule_complete;
+        context_.schedule_remote(this);
+      } else {
+        start_io();
+      }
+    }
+
+  private:
+    static void on_schedule_complete(operation_base* op) noexcept {
+      static_cast<operation*>(op)->start_io();
+    }
+
+    void start_io() noexcept {
+      UNIFEX_ASSERT(context_.is_running_on_io_thread());
+
+      auto populateSqe = [this](io_uring_sqe& sqe) noexcept {
+        sqe.opcode = IORING_OP_ACCEPT;
+        sqe.accept_flags = SOCK_NONBLOCK;
+        sqe.fd = fd_;
+
+        sqe.user_data = reinterpret_cast<std::uintptr_t>(
+            static_cast<completion_base*>(this));
+
+        this->execute_ = &operation::on_accept;
+      };
+
+      if (!context_.try_submit_io(populateSqe)) {
+        this->execute_ = &operation::on_schedule_complete;
+        context_.schedule_pending_io(this);
+      }
+    }
+
+    static void on_accept(operation_base* op) noexcept {
+      auto& self = *static_cast<operation*>(op);
+      if (self.result_ >= 0) {
+        if constexpr (noexcept(unifex::set_value(
+                          std::move(self.receiver_), async_read_write_file{self.context_, self.result_}))) {
+          unifex::set_value(std::move(self.receiver_), async_read_write_file{self.context_, self.result_});
+        } else {
+          UNIFEX_TRY {
+            unifex::set_value(std::move(self.receiver_), async_read_write_file{self.context_, self.result_});
+          }
+          UNIFEX_CATCH(...) {
+            unifex::set_error(
+                std::move(self.receiver_), std::current_exception());
+          }
+        }
+      } else if (self.result_ == -ECANCELED) {
+        unifex::set_done(std::move(self.receiver_));
+      } else {
+        unifex::set_error(
+            std::move(self.receiver_),
+            std::error_code{-self.result_, std::system_category()});
+      }
+    }
+
+    io_uring_context& context_;
+    int fd_;
+    Receiver receiver_;
+  };
+
+public:
+  // Produces an open read-write file corresponding to the accepted connection.
+  template <
+      template <typename...>
+      class Variant,
+      template <typename...>
+      class Tuple>
+  using value_types = Variant<Tuple<async_read_write_file>>;
+
+  // Note: Only case it might complete with exception_ptr is if the
+  // receiver's set_value() exits with an exception.
+  template <template <typename...> class Variant>
+  using error_types = Variant<std::error_code, std::exception_ptr>;
+
+  static constexpr bool sends_done = true;
+  static constexpr blocking_kind blocking = blocking_kind::never;
+  // always completes on the io_uring context
+  static constexpr bool is_always_scheduler_affine = false;
+
+  explicit accept_sender(io_uring_context& context, int fd) noexcept
+    : context_(context)
+    , fd_(fd) {}
+
+  template <typename Receiver>
+  operation<remove_cvref_t<Receiver>> connect(Receiver&& r) && {
+    return operation<remove_cvref_t<Receiver>>{*this, (Receiver &&) r};
+  }
+
+private:
+  io_uring_context& context_;
+  int fd_;
+};
+
+class io_uring_context::accept_stream {
+public:
+  using offset_t = std::int64_t;
+
+  explicit accept_stream(io_uring_context& context, port_t port) noexcept
+    : context_(context)
+    , port_(port) {}
+
+  auto next() noexcept {
+    return let_value_with(
+        [this]() noexcept {
+          // TODO move to operation.start_io()
+          if (!fd_.valid()) {
+            open_socket();
+          }
+          return fd_.get();
+        },
+        [this](auto fd) noexcept { return accept_sender{context_, fd}; });
+  }
+
+  auto cleanup() noexcept {
+    return defer([this]() noexcept {
+      if (fd_.valid()) {
+        fd_.close();
+      }
+      return just_done();
+    });
+  }
+
+private:
+  friend scheduler;
+
+  io_uring_context& context_;
+  port_t port_;
+  safe_file_descriptor fd_;
+
+  // TODO should this run on the io_context? If so, why?
+  void open_socket() noexcept {
+    // both IPv4 and IPv6
+    sockaddr_in6 addr;
+    fd_ = safe_file_descriptor{socket(
+        AF_INET6, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, IPPROTO_TCP)};
+    std::int32_t val = 1;
+    [[maybe_unused]] int ret;
+    ret = setsockopt(fd_.get(), SOL_SOCKET, SO_REUSEPORT, &val, sizeof(val));
+    UNIFEX_ASSERT(ret != -1);
+    ret = setsockopt(fd_.get(), SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
+    UNIFEX_ASSERT(ret != -1);
+
+    addr.sin6_family = AF_INET6;
+    addr.sin6_port = htons(port_);
+    addr.sin6_addr = in6addr_any;
+    ret = bind(fd_.get(), (const struct sockaddr*)&addr, sizeof(addr));
+    UNIFEX_ASSERT(ret != -1);
+    ret = listen(fd_.get(), 128);
+    UNIFEX_ASSERT(ret != -1);
+  }
+};
+
 } // namespace linuxos
 } // namespace unifex
 

include/unifex/pipe_concepts.hpp

@@ -17,8 +17,6 @@
 
 #include <unifex/tag_invoke.hpp>
 
-#include <unifex/io_concepts.hpp>
-
 #include <unifex/detail/prologue.hpp>
 
 namespace unifex {

include/unifex/socket_concepts.hpp

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License Version 2.0 with LLVM Exceptions
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *   https://llvm.org/LICENSE.txt
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <unifex/tag_invoke.hpp>
+
+#include <unifex/detail/prologue.hpp>
+
+namespace unifex {
+namespace _socket {
+using port_t = std::uint16_t;
+
+inline constexpr struct open_listening_socket_cpo final {
+  template <typename Scheduler>
+  constexpr auto operator()(Scheduler&& sched, port_t port) const noexcept(
+      is_nothrow_tag_invocable_v<open_listening_socket_cpo, Scheduler, port_t>)
+      -> tag_invoke_result_t<open_listening_socket_cpo, Scheduler, port_t> {
+    return tag_invoke(*this, static_cast<Scheduler&&>(sched), port);
+  }
+} open_listening_socket{};
+}  // namespace _socket
+
+using _socket::open_listening_socket;
+using _socket::port_t;
+}  // namespace unifex
+
+#include <unifex/detail/epilogue.hpp>

source/linux/io_uring_context.cpp

@@ -835,6 +835,12 @@ io_uring_context::async_read_write_file tag_invoke(
   return io_uring_context::async_read_write_file{*scheduler.context_, result};
 }
 
+io_uring_context::accept_stream tag_invoke(
+    tag_t<open_listening_socket>,
+    io_uring_context::scheduler scheduler,
+    port_t port) {
+  return io_uring_context::accept_stream{*scheduler.context_, port};
+}
 } // namespace unifex::linuxos
 
 #endif // UNIFEX_NO_LIBURING