c - 在 OSX Mountain Lion 上，Libevent 代码未连接或超时

Question

编辑:这是在 OSX 上运行程序时的 tcpdump 输出:

Matthew-Mitchell:calm-ocean-4924 matt$ sudo tcpdump -X -i lo0 'port 45564'
Password:
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo0, link-type NULL (BSD loopback), capture size 65535 bytes
22:52:41.620969 IP localhost.53685 > localhost.45564: Flags [S], seq 3787197032, win 65535, options [mss 16344,nop,wscale 4,nop,nop,TS val 465807577 ecr 0,sackOK,eol], length 0
    0x0000:  4500 0040 ba9e 4000 4006 0000 7f00 0001  E..@..@.@.......
    0x0010:  7f00 0001 d1b5 b1fc e1bc 0a68 0000 0000  ...........h....
    0x0020:  b002 ffff fe34 0000 0204 3fd8 0103 0304  .....4....?.....
    0x0030:  0101 080a 1bc3 a8d9 0000 0000 0402 0000  ................
22:52:41.621062 IP localhost.45564 > localhost.53685: Flags [S.], seq 1362049502, ack 3787197033, win 65535, options [mss 16344,nop,wscale 4,nop,nop,TS val 465807577 ecr 465807577,sackOK,eol], length 0
    0x0000:  4500 0040 8dac 4000 4006 0000 7f00 0001  E..@..@.@.......
    0x0010:  7f00 0001 b1fc d1b5 512f 39de e1bc 0a69  ........Q/9....i
    0x0020:  b012 ffff fe34 0000 0204 3fd8 0103 0304  .....4....?.....
    0x0030:  0101 080a 1bc3 a8d9 1bc3 a8d9 0402 0000  ................
22:52:41.621075 IP localhost.53685 > localhost.45564: Flags [.], ack 1, win 9186, options [nop,nop,TS val 465807577 ecr 465807577], length 0
    0x0000:  4500 0034 fdb1 4000 4006 0000 7f00 0001  E..4..@.@.......
    0x0010:  7f00 0001 d1b5 b1fc e1bc 0a69 512f 39df  ...........iQ/9.
    0x0020:  8010 23e2 fe28 0000 0101 080a 1bc3 a8d9  ..#..(..........
    0x0030:  1bc3 a8d9                                ....
22:52:41.621086 IP localhost.45564 > localhost.53685: Flags [.], ack 1, win 9186, options [nop,nop,TS val 465807577 ecr 465807577], length 0
    0x0000:  4500 0034 53bf 4000 4006 0000 7f00 0001  E..4S.@.@.......
    0x0010:  7f00 0001 b1fc d1b5 512f 39df e1bc 0a69  ........Q/9....i
    0x0020:  8010 23e2 fe28 0000 0101 080a 1bc3 a8d9  ..#..(..........
    0x0030:  1bc3 a8d9 

我有一个相当大的库，其中包含一些使用 libevent 的网络代码。很长一段时间以来，这一直有效，但最近一些使用网络代码的较新代码很少起作用，因为无法建立连接。此外，连接超时事件不会被触发，尽管连接从未完成(它应该完成)。我试图分开代码来举例说明这个不起作用。以下代码不适用于 OSX Mountain Lion(至少):

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <event2/event.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>

#ifdef SO_NOSIGPIPE
#define CB_NOSIGPIPE true
#else
#define CB_NOSIGPIPE false
#define SO_NOSIGPIPE 0
#endif

void loopErr(void * vself);
void loopErr(void * vself){
    printf("Loop error\n");
    exit(EXIT_FAILURE);
}

void timeout(void * vself, void * foo);
void timeout(void * vself, void * foo){
    printf("Timeout\n");
    exit(EXIT_FAILURE);
}

void didConnect(void * vself, void * foo);
void didConnect(void * vself, void * foo){
    printf("Did connect\n");
}

bool CBSocketAccept(int sock, int * connectionSock);
bool CBSocketAccept(int sock, int * connectionSock){
    *connectionSock = accept(sock, NULL, NULL);
    if (*connectionSock == -1)
        return false;
    // Make socket non-blocking
    evutil_make_socket_nonblocking(*connectionSock);
    // Stop SIGPIPE
    int i = 1;
    if (CB_NOSIGPIPE)
        setsockopt(*connectionSock, SOL_SOCKET, SO_NOSIGPIPE, &i, sizeof(i));
    return true;
}

void acceptConn(void * vself, int socket);
void acceptConn(void * vself, int socket){
    int connSock;
    if (! CBSocketAccept(socket, &connSock)){
        printf("Unable to accept a connection.\n");
        exit(EXIT_FAILURE);
    }
    printf("Did accept\n");
}

typedef struct{
    struct event_base * base;
    void (*onError)(void *);
    void (*onTimeOut)(void *, void *); /**< Callback for timeouts */
    void * communicator;
    pthread_t loopThread; /**< The thread for the event loop. */
    void  (*userCallback)(void *);
    void * userArg;
}CBEventLoop;

union CBOnEvent{
    void (*i)(void *, int);
    void (*ptr)(void *, void *);
};

typedef struct{
    CBEventLoop * loop; /**< For getting timeout CBLogError */
    struct event * event; /**< libevent event. */
    union CBOnEvent onEvent;
    void * peer;
}CBEvent;

void * CBStartEventLoop(void * vloop);
void * CBStartEventLoop(void * vloop){
    CBEventLoop * loop = vloop;
    // Start event loop
    printf("Starting network event loop.\n");
    if(event_base_dispatch(loop->base) == -1){
        // Error
        loop->onError(loop->communicator);
        return NULL;
    }
    // Break from loop. Free everything.
    event_base_free(loop->base);
    free(loop);
    return NULL;
}
void event_base_add_virtual(struct event_base *); 
bool CBNewEventLoop(CBEventLoop ** loop, void (*onError)(void *), void (*onDidTimeout)(void *, void *), void * communicator);
bool CBNewEventLoop(CBEventLoop ** loop, void (*onError)(void *), void (*onDidTimeout)(void *, void *), void * communicator){
    struct event_base * base = event_base_new();
    // Create dummy event to maintain loop.
    event_base_add_virtual(base);
    // Create arguments for the loop
    *loop = malloc(sizeof(**loop));
    (*loop)->base = base;
    (*loop)->onError = onError;
    (*loop)->onTimeOut = onDidTimeout;
    (*loop)->communicator = communicator;
    // Create thread
    pthread_create(&(*loop)->loopThread, NULL, CBStartEventLoop, *loop);
    return loop;
}

bool CBSocketBind(int * sock, bool IPv6, uint16_t port);
bool CBSocketBind(int * sock, bool IPv6, uint16_t port){
    struct addrinfo hints, *res, *ptr;
    // Set hints for the computer's addresses.
    memset(&hints, 0, sizeof(hints));
    hints.ai_flags = AI_PASSIVE;
    hints.ai_family = IPv6 ? AF_INET6 : AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    // Get host for listening
    char portStr[6];
    sprintf(portStr, "%u", port);
    if (getaddrinfo(NULL, portStr, &hints, &res))
        return false;
    // Attempt to bind to one of the addresses.
    for(ptr = res; ptr != NULL; ptr = ptr->ai_next) {
        if ((*sock = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol)) == -1)
            continue;
        // Prevent EADDRINUSE
        int opt = 1;
        setsockopt(*sock, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
        if (bind(*sock, ptr->ai_addr, ptr->ai_addrlen) == -1) {
            printf("Bind gave the error %s for address on port %u.\n", strerror(errno), port);
            evutil_closesocket(*sock);
            continue;
        }
        break; // Success.
    }
    freeaddrinfo(res);
    if (ptr == NULL) // Failure
        return false;
    // Prevent SIGPIPE
    int i = 1;
    setsockopt(*sock, SOL_SOCKET, SO_NOSIGPIPE, &i, sizeof(i));
    // Make socket non-blocking
    evutil_make_socket_nonblocking(*sock);
    return true;
}

void CBCanAccept(evutil_socket_t sock, short eventNum, void * arg);
void CBCanAccept(evutil_socket_t sock, short eventNum, void * arg){
    CBEvent * event = arg;
    event->onEvent.i(event->loop->communicator, sock);
}

bool CBSocketCanAcceptEvent(CBEvent ** event, CBEventLoop * loop, int sock, void (*onCanAccept)(void *, int));
bool CBSocketCanAcceptEvent(CBEvent ** event, CBEventLoop * loop, int sock, void (*onCanAccept)(void *, int)){
    *event = malloc(sizeof(**event));
    (*event)->loop = loop;
    (*event)->onEvent.i = onCanAccept;
    (*event)->event = event_new((*event)->loop->base, sock, EV_READ|EV_PERSIST, CBCanAccept, *event);
    return true;
}

bool CBSocketAddEvent(CBEvent * event, uint32_t timeout);
bool CBSocketAddEvent(CBEvent * event, uint32_t timeout){
    int res;
    if (timeout) {
        uint32_t secs = timeout / 1000;
        struct timeval time = {secs, (timeout - secs*1000) * 1000};
        res = event_add(event->event, &time);
    }else
        res = event_add(event->event, NULL);
    return ! res;
}

bool CBNewSocket(int * sock, bool IPv6);
bool CBNewSocket(int * sock, bool IPv6){
    // You need to use PF_INET for IPv4 mapped IPv6 addresses despite using the IPv6 format.
    *sock = socket(IPv6 ? PF_INET6 : PF_INET, SOCK_STREAM, 0);
    if (*sock == -1)
        return false;
    // Stop SIGPIPE annoying us.
    int i = 1;
    if (CB_NOSIGPIPE)
        setsockopt(*sock, SOL_SOCKET, SO_NOSIGPIPE, &i, sizeof(i));
    // Make address reusable
    setsockopt(*sock, SOL_SOCKET, SO_REUSEADDR, &i, sizeof(i));
    // Make socket non-blocking
    evutil_make_socket_nonblocking(*sock);
    return true;
}

bool CBSocketConnect(int sock, uint8_t * IP, bool IPv6, uint16_t port);
bool CBSocketConnect(int sock, uint8_t * IP, bool IPv6, uint16_t port){
    // Create sockaddr_in6 information for a IPv6 address
    int res;
    if (IPv6) {
        struct sockaddr_in6 address;
        memset(&address, 0, sizeof(address)); // Clear structure.
        address.sin6_family = AF_INET6;
        memcpy(&address.sin6_addr, IP, 16); // Move IP address into place.
        address.sin6_port = htons(port); // Port number to network order
        res = connect(sock, (struct sockaddr *)&address, sizeof(address));
    }else{
        struct sockaddr_in address;
        memset(&address, 0, sizeof(address)); // Clear structure.
        address.sin_family = AF_INET;
        memcpy(&address.sin_addr, IP + 12, 4); // Move IP address into place. Last 4 bytes for IPv4.
        address.sin_port = htons(port); // Port number to network order
        res = connect(sock, (struct sockaddr *)&address, sizeof(address));
    }
    if (res < 0 && errno == EINPROGRESS)
        return true;
    return false;
}

void CBDidConnect(evutil_socket_t socketID, short eventNum, void * arg);
void CBDidConnect(evutil_socket_t socketID, short eventNum, void * arg){
    CBEvent * event = arg;
    if (eventNum & EV_TIMEOUT) {
        // Timeout for the connection
        event->loop->onTimeOut(event->loop->communicator, event->peer);
    }else{
        int optval = -1;
        socklen_t optlen = sizeof(optval);
        getsockopt(socketID, SOL_SOCKET, SO_ERROR, &optval, &optlen);
        if (optval){
            // Act as timeout
            printf("Connection error: %s\n", strerror(optval));
            event->loop->onTimeOut(event->loop->communicator, event->peer);
        }else
            // Connection successful
            event->onEvent.ptr(event->loop->communicator, event->peer);
    }
}

bool CBSocketDidConnectEvent(CBEvent ** event, CBEventLoop * loop, int sock, void (*onDidConnect)(void *, void *), void * peer);
bool CBSocketDidConnectEvent(CBEvent ** event, CBEventLoop * loop, int sock, void (*onDidConnect)(void *, void *), void * peer){
    *event = malloc(sizeof(**event));
    (*event)->loop = loop;
    (*event)->onEvent.ptr = onDidConnect;
    (*event)->peer = peer;
    (*event)->event = event_new((*event)->loop->base, sock, EV_TIMEOUT|EV_WRITE, CBDidConnect, *event);
    return true;
}

int main(int argc, const char * argv[]){
    int listeningSocket, connSocket;
    CBEvent *acceptEvent, *connectEvent;
    CBEventLoop *listeningEventLoop, *connEventLoop;
    if (!CBNewEventLoop(&listeningEventLoop, loopErr, timeout, NULL)
        || !CBNewEventLoop(&connEventLoop, loopErr, timeout, NULL)){
        printf("Unable to start event loops.");
        return EXIT_FAILURE;
    }
    if (!CBSocketBind(&listeningSocket, false, 45564)){
        printf("Unable to bind a socket for listening");
        return EXIT_FAILURE;
    }
    if (!CBSocketCanAcceptEvent(&acceptEvent, listeningEventLoop, listeningSocket, acceptConn)) {
        printf("Unable to create an accept event");
        return EXIT_FAILURE;
    }
    if(!CBSocketAddEvent(acceptEvent, 0)){
        printf("Unable to add an accept event\n");
        return EXIT_FAILURE;
    }
    if (listen(listeningSocket, 1) == -1){
        printf("Unable to start listening\n");
        return EXIT_FAILURE;
    }
    // Make socket
    if (!CBNewSocket(&connSocket, false)){
        printf("Socket create fail\n");
        return EXIT_FAILURE;
    }
    // Add event for connection
    if (!CBSocketDidConnectEvent(&connectEvent, connEventLoop, connSocket, didConnect, NULL)) {
        printf("Couldn't create did connect event\n");
        return EXIT_FAILURE;
    }
    if (!CBSocketAddEvent(connectEvent, 1000)) {
        printf("Couldn't add connect event\n");
        return EXIT_FAILURE;
    }
    // Connect
    if (!CBSocketConnect(connSocket, (uint8_t []){0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF, 127, 0, 0, 1}, false, 45564)){
        printf("Couldn't connect\n");
        return EXIT_FAILURE;
    }
    pthread_exit(NULL);
    return 0;
}

当我运行这个时，我得到:

Starting network event loop.
Starting network event loop.

没有别的。没有要接受的连接，没有超时，什么都没有。但是我可以确认这在 Linux Mint 13 上确实有效。我也尝试了不同的端口号，但没有成功。

编辑:看来我在 libev 上遇到了类似的问题。我刚刚尝试用 libev 重新实现代码，但我遇到了同样的问题。不过，我还没有尝试将上面的小示例更改为 libev。

Answer 1

这段代码有几个问题。

首先，CBNewEventLoop 总是返回 true，因为它返回 (bool)loop (这是 main 中堆栈变量之一的地址)。此外，您似乎会通过返回 (bool)(*loop) 检测到唯一的错误。将是 malloc 失败，但如果 malloc 失败，您需要在写入 *loop 之前检查其结果.

其次，更根本的是，您在一个线程中运行一个事件循环并从主线程调用它的方法。事件驱动系统通常不是线程安全的。您应该将此代码构建为一系列回调，以在事件循环的线程上运行。

最后，一次需要多个事件循环是非常罕见的。您应该为该过程设置一个事件循环，并将其用于监听和连接。