……
new_phase ( PHASE_INITIALIZE ) ; //PPPD中的状态机，目前是初始化阶段
/*
* Initialize magic number generator now so that protocols may
* use magic numbers in initialization.
*/
magic_init () ;
/*
* Initialize each protocol.
*/
for ( i = 0 ; ( protp = protocols [ i ]) != NULL ; ++i ) //protocols[]是全局变量的协议数组( *protp-> init )( 0 ) ; //初始化协议数组中所有协议
/*
* Initialize the default channel.
*/
tty_init () ; //channel初始化，默认就是全局的tty_channel，里面包括很多TTY函数指针
if ( ! options_from_file ( _PATH_SYSOPTIONS , ! privileged , 0 , 1 ) //解析/etc/ppp/options中的参数
|| ! options_from_user ()
|| ! parse_args ( argc -1 , argv +1 )) //解析PPPD命令行参数
exit ( EXIT_OPTION_ERROR ) ;
devnam_fixed = 1 ; /* can no longer change device name */
/*
* Work out the device name, if it hasn't already been specified,
* and parse the tty's options file.
*/
if ( the_channel -> process_extra_options )
( * the_channel -> process_extra_options )() ; //实际上是调用tty_process_extra_options解析TTY 参数
if ( ! ppp_available ()) { //检测/dev/ppp设备文件是否有效
option_error ( "%s" , no_ppp_msg ) ;
exit ( EXIT_NO_KERNEL_SUPPORT ) ;
}
/*
* Check that the options given are valid and consistent.
*/
check_options () ; //检查选项参数
if ( ! sys_check_options ()) //检测系统参数，比如内核是否支持Multilink等
exit ( EXIT_OPTION_ERROR ) ;
auth_check_options () ; //检查认证相关的参数
#ifdef HAVE_MULTILINK
mp_check_options () ;
#endif for ( i = 0 ; ( protp = protocols [ i ]) != NULL ; ++i )if ( protp-> check_options != NULL )
( *protp-> check_options )() ; //检查每个控制协议的参数配置
if ( the_channel -> check_options )
( * the_channel -> check_options )() ; //实际上是调用tty_check_options检测TTY参数
……/*
* Detach ourselves from the terminal, if required,
* and identify who is running us.
*/
if ( ! nodetach && ! updetach )
detach () ; //默认放在后台以daemon执行，也可配置/etc/ppp/option中的nodetach参数放在前台执行
……syslog ( LOG_NOTICE , "pppd %s started by %s, uid %d" , VERSION , p, uid ) ; //熟悉的log，现在准备执行了
script_setenv ( "PPPLOGNAME" , p, 0 ) ;
if ( devnam [ 0 ])script_setenv ( "DEVICE" , devnam , 1 ) ;
slprintf ( numbuf, sizeof ( numbuf ) , "%d" , getpid ()) ;
script_setenv ( "PPPD_PID" , numbuf, 1 ) ;
setup_signals () ; //设置信号处理函数