Linux 异步 epoll() 服务器在 EPOLLRDHUP 发生时出现问题

Question

我正在尝试在 Linux 中使用 epoll() 创建一个异步 Web 服务器，但是每当 EPOLLRDHUP 事件发生时就会出现问题。当未设置标志 EPOLLONESHOT 时，服务器会在循环期间多次尝试处理无用事件（不是 EPOLLIN 或 EPOLLOUT）而不停止，这会导致服务器完全无响应（并需要重新启动）。当设置了 EPOLLONESHOT 标志时，服务器会在短时间内（秒）变得无响应，然后再次响应（这仍然不理想）。我不确定是什么原因造成的，因为每当发生 EPOLLRDHUP 时我都会关闭套接字。这是我的代码：

int server_fd, new_socket; 
long valRead;
struct sockaddr_in address;
int addrlen = sizeof(address);

//setup code (bind(), etc.) would be here

struct connection {
    int socket;
    unsigned int connectionType;
    void* dataToSend;
    unsigned int dataByteSize;
    struct epoll_event event;
    bool active;
};

struct connection* connections = (struct connection*)malloc(1000 * sizeof(struct connection));
connections[0].socket = server_fd;
connections[0].connectionType = 1U;
connections[0].event.events = EPOLLIN;
connections[0].event.data.ptr = &connections[0];

unsigned int connectionIndex = 1U;

fcntl(server_fd, F_SETFL, O_NONBLOCK);

int epollFd = epoll_create(10);
epoll_ctl(epollFd, EPOLL_CTL_ADD, server_fd, &connections[0].event);

struct epoll_event* receivedEvents = malloc(sizeof(struct epoll_event) * 1000);
struct connection currentConnection;

#define MAX_EVENTS 10
int numEventsReady;
unsigned int eventIndex;
while (1) {
    printText("\n+++++++ Waiting for new connection ++++++++\n\n", 46);

    numEventsReady = epoll_wait(epollFd, receivedEvents, MAX_EVENTS, -1);
    if (numEventsReady == -1) {
        printf("\nErrno:");
        printf("%i", errno);
        printf("\n");
        fprintf(stderr, "epoll_wait() failed: %s\n", strerror(errno));
        exit(7);
    }
    eventIndex = 0U;
    while (eventIndex < numEventsReady) {
        currentConnection = *((struct connection*)receivedEvents[eventIndex].data.ptr);
        switch (currentConnection.connectionType) {
        case 1U:
            //printText("\nConnected", 10);
            new_socket = accept4(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen, SOCK_NONBLOCK | SOCK_CLOEXEC);
            if (new_socket != -1) {
                connections[connectionIndex].socket = new_socket;
                connections[connectionIndex].connectionType = 2U;
                connections[connectionIndex].event.events = EPOLLIN | EPOLLRDHUP;
                connections[connectionIndex].event.data.ptr = &connections[connectionIndex];

                epoll_ctl(epollFd, EPOLL_CTL_ADD, new_socket, &connections[connectionIndex].event);

                ++connectionIndex;
            }
            break;
        case 2U:
            if (receivedEvents[eventIndex].events & EPOLLERR) {
                printf("\nEPOLLERR\n");
                close(currentConnection.socket);
            }
            else if(receivedEvents[eventIndex].events & EPOLLHUP) {
                printf("\nEPOLLHUP\n");
                close(currentConnection.socket);
            }
            else if(receivedEvents[eventIndex].events & EPOLLRDHUP) {
                printf("\nEPOLLRDHUP\n");
                close(currentConnection.socket);
            }
            else if (receivedEvents[eventIndex].events & EPOLLIN) {
                valRead = recv(currentConnection.socket, buffer, 65536, 0);
                if (valRead < 1) {
                    printf("recv error");
                    if (errno != EAGAIN && errno != EWOULDBLOCK) {
                        printf("errno != EAGAIN && errno != EWOULDBLOCK");
                        close(currentConnection.socket);
                    }
                    break;
                }
                printText(buffer, valRead);

                currentConnection.event.events = EPOLLOUT | EPOLLRDHUP;
                currentConnection.event.data.ptr = &currentConnection;
                epoll_ctl(epollFd, EPOLL_CTL_MOD, currentConnection.socket, &currentConnection.event);

                if (buffer[0] == 'G' && buffer[1] == 'E' && buffer[2] == 'T') {
                    switch (buffer[5]) {
                    case ' ': //default web page (index.htm)
                        currentConnection.dataToSend = indexHtm;
                        currentConnection.dataByteSize = sizeof(indexHtm);
                        //sendSocketData(new_socket, indexHtm, sizeof(indexHtm));
                        break;
                    }
               }
              else if (receivedEvents[eventIndex].events & EPOLLOUT) {
                valRead = send(currentConnection.socket, currentConnection.dataToSend, currentConnection.dataByteSize, 0);
                if (valRead == -1) {
                    printf("send error has ocurred\n");
                    if (errno != EAGAIN && errno != EWOULDBLOCK) {
                        printf("\nerrno != EAGAIN && errno != EWOULDBLOCK\n");
                        close(currentConnection.socket);
                    }
                    break;
                }

                currentConnection.event.events = EPOLLIN | EPOLLRDHUP;
                currentConnection.event.data.ptr = &currentConnection;
                valRead = epoll_ctl(epollFd, EPOLL_CTL_MOD, currentConnection.socket, &currentConnection.event);
            }
            break;
        }
        ++eventIndex;
    }
}

Answer 1

这里的这个模式，你用了两次，是错误的：

currentConnection.event.data.ptr = &currentConnection;
valRead = epoll_ctl(epollFd, EPOLL_CTL_MOD, 
                    currentConnection.socket, &currentConnection.event);

您正在将 data.ptr 设置为您的局部变量 currentConnection（它一直被重用和覆盖），而它确实应该指向您的连接数组！

据我所见，currentConnection 应该是指针类型：

struct connection *currentConnection;

你代码后面的赋值应该是这样的

currentConnection = (struct connection*)receivedEvents[eventIndex].data.ptr;

当然，你必须修复结构成员访问和data.ptr 的设置，就像你在这里做的那样：

currentConnection.event.data.ptr = &currentConnection;

根本不需要。