如何使用sendmsg()通过两个进程之间的套接字发送文件描述符？

概述在@cnicutar在这个question上回答我之后,我试图从父进程向其子​​进程发送一个文件描述符.基于这个example,我写了这段代码：int socket_fd ,accepted_socket_fd, on = 1; int server_sd, worker_sd, pair_sd[2]; struct sockaddr_in client_a

在@cnicutar在这个question上回答我之后,我试图从父进程向其子​​进程发送一个文件描述符.基于这个example,我写了这段代码：

int socket_fd,accepted_socket_fd,on = 1;int server_sd,worker_sd,pair_sd[2];struct sockaddr_in clIEnt_address;struct sockaddr_in server_address;/* ======================================================================= * Setup the network socket. * ======================================================================= */if((socket_fd = socket(AF_INET,SOCK_STREAM,0)) < 0){    perror("socket()");    exit(EXIT_FAILURE);}if((setsockopt(socket_fd,Sol_SOCKET,SO_REUSEADDR,(char *) &on,sizeof(on))) < 0){    perror("setsockopt()");    exit(EXIT_FAILURE);}server_address.sin_family = AF_INET;                 /* Internet address type */server_address.sin_addr.s_addr = htonl(INADDR_ANY);  /* Set for any local IP */server_address.sin_port = htons(port);               /* Set to the specifIEd port */if(bind(socket_fd,(struct sockaddr *) &server_address,sizeof(server_address)) < 0){    perror("bind()");    exit(EXIT_FAILURE);}if(Listen(socket_fd,buffers) < 0){    perror("Listen()");    exit(EXIT_FAILURE);}if(socketpair(AF_UNIX,SOCK_DGRAM,pair_sd) < 0){    socketpair("bind()");    exit(EXIT_FAILURE);}server_sd = pair_sd[0];worker_sd = pair_sd[1];/* ======================================================================= * Worker processes * ======================================================================= */    struct iovec   iov[1];struct msghdr  child_msg;char   msg_buffer[80];int pass_sd,rc;/* Here the parent process create a pool of worker processes (its children) */for(i = 0; i < processes; i++){    if(fork() == 0)    {        // ...        /* Loop forever,serving the incoming request */        for(;;)        {            memset(&child_msg,sizeof(child_msg));            memset(iov,sizeof(iov));            iov[0].iov_base = msg_buffer;            iov[0].iov_len  = sizeof(msg_buffer);            child_msg.msg_iov     = iov;            child_msg.msg_iovlen  = 1;            child_msg.msg_name    = (char *) &pass_sd;            child_msg.msg_namelen = sizeof(pass_sd);            printf("Waiting on recvmsg\n");            rc = recvmsg(worker_sd,&child_msg,0);            if (rc < 0)            {               perror("recvmsg() Failed");               close(worker_sd);               exit(-1);            }            else if (child_msg.msg_namelen <= 0)            {               printf("Descriptor was not received\n");               close(worker_sd);               exit(-1);            }            else            {               printf("Received descriptor = %d\n",pass_sd);            }            //.. Here the child process can handle the passed file descriptor        }    }}/* ======================================================================= * The parent process * ======================================================================= */struct msghdr parent_msg;size_t length;/* Here the parent will accept the incoming requests and passed it to its children*/for(;;){    length = sizeof(clIEnt_address);    if((accepted_socket_fd = accept(socket_fd,NulL,NulL)) < 0)    {        perror("accept()");        exit(EXIT_FAILURE);    }    memset(&parent_msg,sizeof(parent_msg));    parent_msg.msg_name  = (char *) &accepted_socket_fd;    parent_msg.msg_namelen = sizeof(accepted_socket_fd);    if((sendmsg(server_sd,&parent_msg,0)) < 0)    {        perror("sendmsg()");        exit(EXIT_FAILURE);    }}

但不幸的是,我收到了这个错误：

sendmsg(): InvalID argument

我该怎么做才能解决这个问题？我正确使用msghdr结构吗？因为在我上面提到的例子中,他们使用msg_accrights和msg_accrightslen,当我使用它时出现了一些错误,所以我不得不使用msg_name和msg_namelen.最佳答案这很难做到.我建议你只使用一个为你做这个的库.其中最简单的是libancillary.它为您提供了两个函数,一个用于通过UNIX域套接字发送文件描述符,另一个用于接收一个.它们使用起来很荒谬. 总结

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