Zero-copy example add

Author: Artiom N.

src/book01/ch23/cpp/CMakeLists.txt

@@ -3,4 +3,5 @@ cmake_minimum_required(VERSION 3.10)
 
 if (UNIX)
     add_subdirectory("tun_example")
+    add_subdirectory("zc_example")
 endif()

src/book01/ch23/cpp/zc_example/CMakeLists.txt

@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.10)
+
+project("${CHAPTER_NAME}zc-example" C CXX)
+
+add_executable("${PROJECT_NAME}" "main.cpp")
+target_link_libraries("${PROJECT_NAME}" socket-wrapper)

src/book01/ch23/cpp/zc_example/main.cpp

@@ -0,0 +1,96 @@
+extern "C"
+{
+#include <netinet/ip.h>
+// sock_extended_err.
+#include <linux/errqueue.h>
+#include <linux/tcp.h>
+#include <poll.h>
+}
+
+#include <socket_wrapper/socket_functions.h>
+#include <socket_wrapper/socket_headers.h>
+#include <socket_wrapper/socket_wrapper.h>
+
+#include <array>
+#include <cinttypes>
+#include <cstdint>
+#include <exception>
+#include <iostream>
+#include <string>
+
+
+std::pair<uint32_t, uint32_t> read_notification(const msghdr *msg)
+{
+    const cmsghdr *cm = CMSG_FIRSTHDR(msg);
+
+    if (cm->cmsg_level != SOL_IP && cm->cmsg_type != IP_RECVERR)
+        throw std::system_error(errno, std::system_category(), "cmsg");
+
+    const sock_extended_err *serr = reinterpret_cast<const sock_extended_err *>(CMSG_DATA(cm));
+
+    if (serr->ee_errno != 0 || serr->ee_origin != SO_EE_ORIGIN_ZEROCOPY)
+        throw std::system_error(errno, std::system_category(), "recvmsg");
+
+    return std::make_pair(serr->ee_data, serr->ee_info);
+}
+
+
+int main()
+{
+    const socket_wrapper::SocketWrapper sock_wrap;
+    const int sock_fd{socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)};
+
+    if (!sock_fd) return EXIT_FAILURE;
+
+    try
+    {
+        const int one = 1;
+
+        if (setsockopt(sock_fd, SOL_SOCKET, SO_ZEROCOPY, &one, sizeof(one)))
+            throw std::system_error(errno, std::system_category(), "setsockopt");
+
+        std::string buf{"test data"};
+
+        auto c_i = socket_wrapper::get_client_info("localhost", "12345");
+
+        if (-1 == connect(sock_fd, c_i->ai_addr, c_i->ai_addrlen))
+        {
+            throw std::system_error(errno, std::system_category(), "connect");
+        }
+
+        if (send(sock_fd, buf.data(), buf.size(), MSG_ZEROCOPY) != buf.size())
+            throw std::system_error(errno, std::system_category(), "send");
+
+        pollfd pfd = {.fd = sock_fd, .events = 0};
+
+        if (poll(&pfd, 1, -1) != 1 || !(pfd.revents & POLLERR))
+            throw std::system_error(errno, std::system_category(), "poll");
+
+        std::array<char, CMSG_SPACE(sizeof(uint32_t))> ancil_data_buff;
+        iovec iov[1] = {{buf.data(), buf.size()}};
+
+        msghdr msg = {
+            .msg_name = nullptr,
+            .msg_namelen = 0,
+            .msg_iov = iov,
+            .msg_iovlen = 1,
+            .msg_control = &ancil_data_buff[0],
+            .msg_controllen = ancil_data_buff.size(),
+            .msg_flags = 0};
+
+        if (-1 == recvmsg(sock_fd, &msg, MSG_ERRQUEUE))
+            throw std::system_error(errno, std::system_category(), "recvmsg");
+
+        auto [data, info] = read_notification(&msg);
+        std::cout << "Data: " << data << ", Info: " << info << std::endl;
+        close(sock_fd);
+    }
+    catch (const std::exception &e)
+    {
+        std::cerr << "Error: " << e.what() << std::endl;
+        close(sock_fd);
+        return EXIT_FAILURE;
+    }
+
+    return EXIT_SUCCESS;
+}