C++ 在 Qt 中的行为不同，bind() returns EINVAL

Question

我已经检查过bind() return EINVAL，这不是这里的问题。请在您对重复感到愤怒之前通读。

我正在尝试连接到 wpa_supplicant。基本上我正在尝试使用 C++ 实现此目的：

import os
import select
import socket

interface = "wlp4s0"
wpa_send_path = "/run/wpa_supplicant/"+interface
wpa_recv_path = "/tmp/wpa_ctrl_{pid}-{count}".format(pid=os.getpid(), count=1)

soc = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM, 0)
soc.bind(wpa_recv_path)
soc.connect(wpa_send_path)

print("> PING")
soc.send(b"PING")
print("<", soc.recv(4096).decode().strip())

来自 https://gist.github.com/artizirk/cd3980c8ff870eb0bfce68bc26a2676b

而且我已经完成了我想做的，但使用的是纯 C++。这是代码：

#include <iostream>
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>
#include <sys/un.h>

#define PATH   "/run/wpa_supplicant/wlp4s0"
char path[100] = "/tmp/wpa_ctrl_";

int main(void) {

  int ctrl_socket;
  char buffer[1024];
  struct sockaddr_un socket_addr, send_addr;

  memset(&socket_addr, 0, sizeof(struct sockaddr_un));
  memset(&send_addr, 0, sizeof(struct sockaddr_un));

  socket_addr.sun_family = AF_UNIX;
  send_addr.sun_family = AF_UNIX;

  strcpy(send_addr.sun_path, PATH);

  strcat(path, std::to_string(getpid()).c_str());
  strcat(path, "-1");
  strcat(socket_addr.sun_path, path);

  if ((ctrl_socket = socket(AF_UNIX, SOCK_DGRAM, 0)) == -1) {
    std::cerr << "Error creating socket!" << std::endl;
    std::exit(EXIT_FAILURE);
  }

  /* Unlink if already bound */
  unlink(socket_addr.sun_path);

  if ((connect(ctrl_socket, (struct sockaddr *)&send_addr, SUN_LEN(&send_addr))) == -1) {
    std::cerr << "Error connecting to socket!" << std::endl;
    std::exit(EXIT_FAILURE);
  }

  if (bind(ctrl_socket, (const struct sockaddr *)&socket_addr, offsetof(struct sockaddr_un, sun_path) + strlen(path) + 1) == -1) {
        perror("Error");
        exit(EXIT_FAILURE);
  }

  send(ctrl_socket, "PING", 5, 0);
  recv(ctrl_socket, buffer, 1024, 0);

  std::cout << buffer << std::endl;

  close(ctrl_socket);

  return 0;
}

这段代码工作正常。但是当我在 Qt 中这样做时，bind() 总是 return EINVAL 即 Invalid Arguments。这是代码：

WPASupplicantControl::WPASupplicantControl(std::string wlan_interface_name)
    :wpa_send_ctrl_iface(WPA_SEND_CTRL_IFACE_PREFIX + QString::fromStdString(wlan_interface_name)),
      wpa_recv_ctrl_iface(
          WPA_RECV_CTRL_IFACE_PREFIX +
          QString::fromStdString(std::to_string(getpid())) +
          "-1"
          )
{
    struct sockaddr_un send_address, recv_address;

    send_address.sun_family = AF_UNIX;
    recv_address.sun_family = AF_UNIX;

    memset(&send_address, 0, sizeof (send_address));
    memset(&recv_address, 0, sizeof (recv_address));

    strncpy(send_address.sun_path, wpa_send_ctrl_iface.toStdString().c_str(), wpa_send_ctrl_iface.length());
    strncpy(recv_address.sun_path, wpa_recv_ctrl_iface.toStdString().c_str(), wpa_send_ctrl_iface.length());

    if ((wpa_control_socket = socket(AF_UNIX, SOCK_DGRAM, 0)) == -1) {
        qCritical() << "socket() failed!";
        exit(EXIT_FAILURE);
    }

    /* Attatch to sending and receiving control interfaces */
    if (connect(wpa_control_socket, (const struct sockaddr *)&send_address, SUN_LEN(&send_address)) == -1) {
        qCritical() << "Error connecting to wpa_supplicant send control iface!";
        close(wpa_control_socket);
        exit(EXIT_FAILURE);
    }

    /* Detatch if it's already bound */
    unlink(recv_address.sun_path);

    if (bind(wpa_control_socket, (const struct sockaddr *)&recv_address, offsetof(struct sockaddr_un, sun_path) + wpa_recv_ctrl_iface.length() + 1) == -1) {
        qCritical() << "Error binding to wpa_supplicant recv control iface!";
        close(wpa_control_socket);
        exit(EXIT_FAILURE);
    }
}

用于测试此代码的功能虚拟项目位于：https://github.com/gaurav712/socket_test

我已经检查了所有值数百次，它们都很好，但仍然无法正常工作。直到那个 connect() 电话。

我想我应该使用 Qt 特定的东西，我发现了 QLocalSocket https://doc.qt.io/qt-5/qlocalsocket.html 但是当我导入它时，Qt 无法识别 class.可能是因为我在使用 Qt 6.x 并且它现在已被弃用（尽管我没有发现任何官方弃用通知）。我该怎么办？我做错了什么？

Answer 1

strncpy 将从源到目标最多复制 n 个字节。如果 n 字节内没有 null char，则不会复制它。 strncpy 的第三个参数通常用于传达目标缓冲区的长度。

改变这个：

strncpy(send_address.sun_path, wpa_send_ctrl_iface.toStdString().c_str(), wpa_send_ctrl_iface.length());
strncpy(recv_address.sun_path, wpa_recv_ctrl_iface.toStdString().c_str(), wpa_send_ctrl_iface.length());

变成这样：

strncpy(send_address.sun_path, 
        wpa_send_ctrl_iface.toStdString().c_str(),
        sizeof(send_address.sun_path) );

strncpy(recv_address.sun_path,
        wpa_recv_ctrl_iface.toStdString().c_str(),
        sizeof(recv_address.sun_path));

此外，正如评论中所讨论的，bind 的长度参数看起来也很时髦。尝试进行上述更改。

Answer 2

绝对与 Qt 无关：您对 sockaddr 结构的全 0 执行 memset 在之后，您已将套接字的系列设置为 AF_UNIX（在大多数平台上为“1”）。系统应该如何知道您需要本地套接字？

C++ 在 Qt 中的行为不同，bind() returns EINVAL

C++ behaves differently in Qt, bind() returns EINVAL

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