分类： LINUX
2016-05-13 23:39:34
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File: pptpctrl.c ------------------------------------------------------------------------- #define clientSocket 0 int pptpctrl_debug = 0; static int noipparam; static char pppdxfig[256]; static char speed[32]; uint16_t unique_call_id = 0xFFFF; static char *ppp_binary = PPP_BINARY; static int pptp_logwtmp; #define GETARG_INT(X) \ #NOTE:从命令行获取参数，初始化对应整数变量 X = atoi(argv[arg++]) #define GETARG_STRING(X) \ #NOTE:从命令行获取参数，初始化对应字符串变量 X = strdup(argv[arg++]) int main(int argc, char **argv) { char pppLocal[16]; /* local IP to pass to pppd */ char pppRemote[16]; /* remote IP address to pass to pppd */ struct sockaddr_in addr; /* client address */ socklen_t addrlen; int arg = 1; int flags; struct in_addr inetaddrs[2]; char *pppaddrs[2] = { pppLocal, pppRemote }; gargc = argc; gargv = argv; /* fail if argument count invalid */ if (argc < 7) { fprintf(stderr, "pptpctrl: insufficient arguments, see man pptpctrl\n"); exit(2); } /* open a connection to the syslog daemon */ openlog("pptpd", LOG_PID, PPTP_FACILITY); /* autoreap if supported */ signal(SIGCHLD, SIG_IGN); /* note: update pptpctrl.8 if the argument list format is changed */ GETARG_INT(pptpctrl_debug); GETARG_INT(noipparam); #ifdef VRF #NOTE: VRF控制选项，即pptpctrl支持VRF参数配置。 GETARG_STRING(vrf); #endif GETARG_VALUE(pppdxfig); GETARG_VALUE(speed); GETARG_VALUE(pppLocal); GETARG_VALUE(pppRemote); if (arg < argc) GETARG_INT(unique_call_id); if (arg < argc) GETARG_STRING(ppp_binary); if (arg < argc) GETARG_INT(pptp_logwtmp); (#NOTE: 上述过程，依次获取命令行参数来初始化对应的控制变量: pptp-debug-flag --> pptpctrl_debug no-ipparam-flag --> noipparam ppp-options-value --> pppdxfig ppp-speed-value --> speed ppp-local-ip-value --> pppLocal ppp-remote-ip-value --> pppRemote [ pptp-call-id ] --> unique_call_id [ ppp-binary ] --> ppp_binary [ pptp-logwtmp ] --> pptp_logwtmp ) #ifdef VRF if (!*vrf) { free(vrf); vrf = NULL; } #endif if (pptpctrl_debug) { #NOTE:根据参数列表，输出参数信息 #ifdef VRF syslog(LOG_DEBUG, "CTRL: VRF used = %s", vrf ? vrf : "NONE"); #endif if (*pppLocal) syslog(LOG_DEBUG, "CTRL: local address = %s", pppLocal); if (*pppRemote) syslog(LOG_DEBUG, "CTRL: remote address = %s", pppRemote); if (*speed) syslog(LOG_DEBUG, "CTRL: pppd speed = %s", speed); if (*pppdxfig) syslog(LOG_DEBUG, "CTRL: pppd options file = %s", pppdxfig); } addrlen = sizeof(addr); if (getsockname(clientSocket, (struct sockaddr *) &addr, &addrlen) != 0) { syslog(LOG_ERR, "CTRL: getsockname() failed"); syslog_perror("getsockname"); close(clientSocket); bail(0); /* NORETURN */ } inetaddrs[0] = addr.sin_addr; addrlen = sizeof(addr); if (getpeername(clientSocket, (struct sockaddr *) &addr, &addrlen) != 0) { syslog(LOG_ERR, "CTRL: getpeername() failed"); syslog_perror("getpeername"); close(clientSocket); bail(0); /* NORETURN */ } inetaddrs[1] = addr.sin_addr; (#NOTE: 这里通过调用getsocketname()和getpeername()获取套接字两端的IP地址，但这里的套接字是宏定义 且其值为0,通过打印调试可以得到套接字两端的地址。那为何这里为0呢？ 这是因为在pptp_manager()函数中调用的connectCall()函数中，对客户端的链接套接字调用了复制函数 dup(clientSocket,0). ) /* Set non-blocking */ if ((flags = fcntl(clientSocket, F_GETFL, arg /* ignored */)) == -1 || fcntl(clientSocket, F_SETFL, flags|OUR_NB_MODE) == -1) { #NOTE:设置客户端链接套接字为非阻塞的形式 syslog(LOG_ERR, "CTRL: Failed to set client socket non-blocking"); syslog_perror("fcntl"); close(clientSocket); bail(0); /* NORETURN */ } /* Fiddle with argv */ my_setproctitle(gargc, gargv, "pptpd [%s]%20c", inet_ntoa(addr.sin_addr), ' '); /* be ready for a grisly death */ sigpipe_create(); sigpipe_assign(SIGTERM); NOTE_VALUE(PAC, call_id_pair, htons(-1)); NOTE_VALUE(PNS, call_id_pair, htons(-1)); syslog(LOG_INFO, "CTRL: Client %s control connection started", inet_ntoa(addr.sin_addr)); pptp_handle_ctrl_connection(pppaddrs, inetaddrs); syslog(LOG_DEBUG, "CTRL: Reaping child PPP[%i]", pppfork); if (pppfork > 0) waitpid(pppfork, NULL, 0); syslog(LOG_INFO, "CTRL: Client %s control connection finished", inet_ntoa(addr.sin_addr)); bail(0); /* NORETURN */ return 1; /* make gcc happy */ } |
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File: pptpmanager.c ------------------------------------------------------------------------- int pptp_manager(int argc, char **argv) { int firstOpen = -1; int ctrl_pid; socklen_t addrsize; int hostSocket; fd_set connSet; int rc, sig_fd; rc = sigpipe_create(); #NOTE: 建立管道用于处理信号 if (rc < 0) { syslog(LOG_ERR, "MGR: unable to setup sigchld pipe!"); syslog_perror("sigpipe_create"); exit(-1); } sigpipe_assign(SIGCHLD); #NOTE: 注册SIGCHLD函数处理函数 sigpipe_assign(SIGTERM); #NOTE: 注册SIGTERM函数处理函数 sig_fd = sigpipe_fd(); #NOTE:获取信号管道的读端文件描述符 /* openlog() not required, done in pptpd.c */ syslog(LOG_INFO, "MGR: Manager process started"); if (!pptp_delegate) { syslog(LOG_INFO, "MGR: Maximum of %d connections available", pptp_connections); } /* Connect the host socket and activate it for listening */ if (createHostSocket(&hostSocket) < 0) { syslog(LOG_ERR, "MGR: Couldn't create host socket"); syslog_perror("createHostSocket"); exit(-1); } while (1) { int max_fd; FD_ZERO(&connSet); if (pptp_delegate) { FD_SET(hostSocket, &connSet); } else { firstOpen = slot_find_empty(); #NOTE:从slot池中取个空闲(pid=0)的对象， if (firstOpen == -1) { syslog(LOG_ERR, "MGR: No free connection slots or IPs - no more clients can connect!"); } else { FD_SET(hostSocket, &connSet); } } max_fd = hostSocket; FD_SET(sig_fd, &connSet); if (max_fd < sig_fd) max_fd = sig_fd; while (1) { if (select(max_fd + 1, &connSet, NULL, NULL, NULL) != -1) break; #NOTE: 读到信号或请求时跳出循环 if (errno == EINTR) continue; syslog(LOG_ERR, "MGR: Error with manager select()!"); syslog_perror("select"); exit(-1); } if (FD_ISSET(sig_fd, &connSet)) { /* SIGCHLD */ #NOTE:探测是否读到信号 int signum = sigpipe_read(); if (signum == SIGCHLD) sigchld_responder(signum); else if (signum == SIGTERM) return signum; } if (FD_ISSET(hostSocket, &connSet)) { /* A call came! */ #NOTE:探测是否有链接请求 int clientSocket; struct sockaddr_in client_addr; /* Accept call and launch PPTPCTRL */ addrsize = sizeof(client_addr); clientSocket = accept(hostSocket, (struct sockaddr *) &client_addr, &addrsize); #if HAVE_LIBWRAP if (clientSocket != -1) { struct request_info r; request_init(&r, RQ_DAEMON, "pptpd", RQ_FILE, clientSocket, NULL); fromhost(&r); if (!hosts_access(&r)) { /* send a permission denied message? this is a tcp wrapper * type deny so probably best to just drop it immediately like * this, as tcp wrappers usually do. */ close(clientSocket); /* this would never be file descriptor 0, so use it as a error * value */ clientSocket = 0; } } #endif if (clientSocket == -1) { /* accept failed, but life goes on... */ syslog(LOG_ERR, "MGR: accept() failed"); syslog_perror("accept"); } else if (clientSocket != 0) { fd_set rfds; struct timeval tv; struct pptp_header ph; #NOTE: pptp封装协议头 /* TODO: this select below prevents other connections from being processed during the wait for the first data packet from the client. */ /* * DOS protection: get a peek at the first packet * and do some checks on it before we continue. * A 10 second timeout on the first packet seems reasonable * to me, if anything looks sus, throw it away. */ FD_ZERO(&rfds); FD_SET(clientSocket, &rfds); tv.tv_sec = pptp_stimeout; tv.tv_usec = 0; if (select(clientSocket + 1, &rfds, NULL, NULL, &tv) <= 0) { #NOTE: 用于监听通信链接 syslog(LOG_ERR, "MGR: dropped slow initial connection"); close(clientSocket); continue; } if (recv(clientSocket, &ph, sizeof(ph), MSG_PEEK) != sizeof(ph)) { #NOTE: 读取pptp头部信息 syslog(LOG_ERR, "MGR: dropped small initial connection"); close(clientSocket); continue; } ph.length = ntohs(ph.length); ph.pptp_type = ntohs(ph.pptp_type); ph.magic = ntohl(ph.magic); ph.ctrl_type = ntohs(ph.ctrl_type); if (ph.length <= 0 || ph.length > PPTP_MAX_CTRL_PCKT_SIZE) { syslog(LOG_WARNING, "MGR: initial packet length %d outside " "(0 - %d)", ph.length, PPTP_MAX_CTRL_PCKT_SIZE); goto dos_exit; } if (ph.magic != PPTP_MAGIC_COOKIE) { syslog(LOG_WARNING, "MGR: initial packet bad magic"); goto dos_exit; } if (ph.pptp_type != PPTP_CTRL_MESSAGE) { syslog(LOG_WARNING, "MGR: initial packet has bad type"); goto dos_exit; } if (ph.ctrl_type != START_CTRL_CONN_RQST) { syslog(LOG_WARNING, "MGR: initial packet has bad ctrl type " "0x%x", ph.ctrl_type); dos_exit: close(clientSocket); continue; } #ifndef HAVE_FORK switch (ctrl_pid = vfork()) { #else switch (ctrl_pid = fork()) { #NOTE:成功获取pptp后，为链接创建子进程 #endif case -1: /* error */ syslog(LOG_ERR, "MGR: fork() failed launching " PPTP_CTRL_BIN); close(clientSocket); break; case 0: /* child */ close(hostSocket); if (pptp_debug) syslog(LOG_DEBUG, "MGR: Launching " PPTP_CTRL_BIN " to handle client"); connectCall(clientSocket, !pptp_delegate ? firstOpen : 0); #NOTE: 调用pptpctrl程序，将管理任务交接给pptpctrl来完成. _exit(1); /* NORETURN */ default: /* parent */ close(clientSocket); unique_call_id += MAX_CALLS_PER_TCP_LINK; if (!pptp_delegate) slot_set_pid(firstOpen, ctrl_pid); break; } } } /* FD_ISSET(hostSocket, &connSet) */ } /* while (1) */ } /* pptp_manager() */ |
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static int createHostSocket(int *hostSocket) { int opt = 1; struct sockaddr_in address; #ifdef HAVE_GETSERVBYNAME struct servent *serv; #endif /* create the master socket and check it worked */ if ((*hostSocket = vrf_socket(vrf, AF_INET, SOCK_STREAM, 0)) <= 0) return -1; (#NOTE: #define vrf_socket(vrf, dom, typ, prot) socket(dom, typ, prot) //pptpctrl.h ) /* set master socket to allow daemon to be restarted with connections active */ if (setsockopt(*hostSocket, SOL_SOCKET, SO_REUSEADDR, #NOTE:设置地址重用 (char *) &opt, sizeof(opt)) < 0) return -2; /* set up socket */ memset(&address, 0, sizeof(address)); address.sin_family = AF_INET; if(bindaddr) #NOTE:从此处可以看出，若不指定地址，则pptpd监听INADDR_ANY，即0.0.0.0 address.sin_addr.s_addr = inet_addr(bindaddr); else address.sin_addr.s_addr = INADDR_ANY; #ifdef HAVE_GETSERVBYNAME if ((serv = getservbyname("pptp", "tcp")) != NULL) { #NOTE:获取知名服务/etc/services address.sin_port = serv->s_port; } else #endif address.sin_port = htons(PPTP_PORT); /* bind the socket to the pptp port */ if (bind(*hostSocket, (struct sockaddr *) &address, sizeof(address)) < 0) return -3; /* minimal backlog to avoid DoS */ if (listen(*hostSocket, 3) < 0) return -4; return 0; } |
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File: pptpmanager.c ------------------------------------------------------------------------- static void connectCall(int clientSocket, int clientNumber) { #define NUM2ARRAY(array, num) snprintf(array, sizeof(array), "%d", num) char *ctrl_argv[16]; /* arguments for launching 'pptpctrl' binary */ int pptpctrl_argc = 0; /* count the number of arguments sent to pptpctrl */ /* lame strings to hold passed args. */ char ctrl_debug[2]; char ctrl_noipparam[2]; char pppdoptfile_argv[2]; char speedgiven_argv[2]; extern char **environ; char callid_argv[16]; /* * Launch the CTRL manager binary; we send it some information such as * speed and option file on the command line. */ ctrl_argv[pptpctrl_argc++] = PPTP_CTRL_BIN " "; /* Pass socket as stdin */ if (clientSocket != 0) { #NOTE: 注意,此处将clineSocket复制为0，pptpctrl中利用文件描述符0调用getsockname()和getpeername()获取两端地址。 dup2(clientSocket, 0); close(clientSocket); } /* get argv set up */ NUM2ARRAY(ctrl_debug, pptp_debug ? 1 : 0); #NOTE: pptp-debug-flag参数。 ctrl_debug[1] = '\0'; ctrl_argv[pptpctrl_argc++] = ctrl_debug; NUM2ARRAY(ctrl_noipparam, pptp_noipparam ? 1 : 0); #NOTE:no-ipparam-flag参数 ctrl_noipparam[1] = '\0'; ctrl_argv[pptpctrl_argc++] = ctrl_noipparam; #ifdef VRF ctrl_argv[pptpctrl_argc++] = vrf ? vrf : ""; #NOTE:VRF参数 #endif /* optionfile = TRUE or FALSE; so the CTRL manager knows whether to load a non-standard options file */ NUM2ARRAY(pppdoptfile_argv, pppdoptstr ? 1 : 0); #NOTE:ppp-options-value配置文件参数 pppdoptfile_argv[1] = '\0'; ctrl_argv[pptpctrl_argc++] = pppdoptfile_argv; if (pppdoptstr) { /* send the option filename so the CTRL manager can launch pppd with this alternate file */ ctrl_argv[pptpctrl_argc++] = pppdoptstr; } /* tell the ctrl manager whether we were given a speed */ NUM2ARRAY(speedgiven_argv, speedstr ? 1 : 0); #NOTE:ppp-speed-value 速度参数 speedgiven_argv[1] = '\0'; ctrl_argv[pptpctrl_argc++] = speedgiven_argv; if (speedstr) { /* send the CTRL manager the speed of the connection so it can fire pppd at that speed */ ctrl_argv[pptpctrl_argc++] = speedstr; } if (pptp_delegate) { #NOTE:通过代理标识，设置ppp-local-ip-value和ppp-remote-ip-value参数 /* no local or remote address to specify */ ctrl_argv[pptpctrl_argc++] = "0"; ctrl_argv[pptpctrl_argc++] = "0"; } else { /* specify local & remote addresses for this call */ ctrl_argv[pptpctrl_argc++] = "1"; ctrl_argv[pptpctrl_argc++] = slot_get_local(clientNumber); ctrl_argv[pptpctrl_argc++] = "1"; ctrl_argv[pptpctrl_argc++] = slot_get_remote(clientNumber); } /* our call id to be included in GRE packets the client * will send to us */ NUM2ARRAY(callid_argv, unique_call_id); #NOTE: [ pptp-call-id ]可选参数 ctrl_argv[pptpctrl_argc++] = callid_argv; /* pass path to ppp binary */ ctrl_argv[pptpctrl_argc++] = ppp_binary; #NOTE: ppp可执行程序参数 ppp-binary /* pass logwtmp flag */ ctrl_argv[pptpctrl_argc++] = pptp_logwtmp ? "1" : "0"; #NOTE:logwtmp参数pptp-logwtmp /* note: update pptpctrl.8 if the argument list format is changed */ /* terminate argv array with a NULL */ ctrl_argv[pptpctrl_argc] = NULL; pptpctrl_argc++; /* ok, args are setup: invoke the call handler */ execve(PPTP_CTRL_BIN, ctrl_argv, environ); (#NOTE: 通过execve函数调用pptpctrl程序，交接该链接的管理权。 注意，pptp_manager()函数中调用的sigpipe_create(),创建的信号处理管道由于使用了fcntl(fd,F_SETFD，FD_CLOEXEC);对应的文件描述符，在该函数调用后将不可用 ） syslog(LOG_ERR, "MGR: Failed to exec " PPTP_CTRL_BIN "!"); _exit(1); } |
