2024年2月20日发(作者：)

strcpy(e_name, argv[3]); for(i=0; ih_addr,&_addr,hostp->h_length); else { printf("%s unknow host rn", e_host); exit(1); } if((servp = getservbyname(e_name, TCP_PROTO)) != NULL) _port = servp->s_port; else if(atoi(e_name) >0) _port = htons(atoi(e_name)); else { printf("%s invalid unknow service or port ", e_name); exit(1); }}/*detach the server process from the current context, creating a pristine,* predictable environment in which it will */void daemonize(int servfd){ int childpid, fd, fdtablesize; // ignore terminal I/O,stop signals signal(SIGTTOU, SIG_IGN); signal(SIGTTIN, SIG_IGN); signal(SIGTSTP, SIG_IGN); /* fork to put us in the background (whether or not the user specified '&' on the command line */ if((childpid=fork()) < 0) { fputs("failed to fork first child/r/n",stderr); exit(1); } else if(childpid >0) exit(0);// terminate parent, continue child //dissociate from process group if (setpgrp(0,getpid()) < 0)

{ fputs("failed to become process group leader/r/n",stderr); exit(1); } /* lose controlling terminal */ if ((fd = open("/dev/tty", O_RDWR)) >= 0) { ioctl(fd,TIOCNOTTY,NULL); close(fd); } /* close any open file descriptors */ for(fd = 0, fdtablesize = getdtablesize(); fd < fdtablesize; fd++) if (fd != servfd) close(fd); /* set working directory to allow filesystems to be unmounted */ chdir("/"); /* clear the inherited umask */ umask(0); /* setup zombie prevention */ signal(SIGCLD,(sigfunc *)reap_status);}//handle a SIGCLD signal by reaping the exit status of the perished child,

//and discarding reap_status(){ int pid; union wait status; while ((pid = wait3(&status,WNOHANG,NULL)) > 0) ; /* loop while there are more dead children */

}//does the actual work of virtually connecting a client to the telnet//service on the isolated do_proxy (int usersockfd){ int isosockfd; fd_set rdfdset; int connstat; int iolen; char buf[2048]; /* open a socket to connect to the isolated host */ if ((isosockfd = socket(AF_INET,SOCK_STREAM,0)) < 0) errorout("failed to create socket to host"); /* attempt a connection */ connstat = connect(isosockfd,(struct sockaddr *) &hostaddr, sizeof(hostaddr)); switch (connstat) { case 0: break; case ETIMEDOUT: case ECONNREFUSED: case ENETUNREACH: strcpy(buf,sys_myerrlist[errno]); strcat(buf,"rn");

write(usersockfd, buf, strlen(buf)); close(usersockfd); exit(1); /* die peacefully if we can't establish a connection */ break; default: errorout("failed to connect to host"); }/* now we're connected, serve fall into the data echo loop */ while (1) { /* Select for readability on either of our two sockets */ FD_ZERO(&rdfdset); FD_SET(usersockfd,&rdfdset); FD_SET(isosockfd,&rdfdset); if (select(FD_SETSIZE,&rdfdset,NULL,NULL,NULL) < 0) errorout("select failed"); /* is the client sending data? */ if (FD_ISSET(usersockfd,&rdfdset))

{ if ((iolen = read(usersockfd,buf,sizeof(buf))) <= 0) break; /* zero length means the client disconnected */ write(isosockfd,buf,iolen); /* copy to host -- blocking semantics */ } /* is the host sending data? */ if(FD_ISSET(isosockfd,&rdfdset))

{ if((iolen = read(isosockfd,buf,sizeof(buf))) <= 0) break; /* zero length means the host disconnected */ write(usersockfd,buf,iolen); /* copy to client -- blocking semantics */ } } /* we're done with the sockets */ close(isosockfd); close(usersockfd);}//displays an error message on the console and kills the current errorout (char *msg){ FILE *console; console = fopen("/dev/console","a"); fprintf(console,"proxyd: %srn",msg); fclose(console); exit(1);}