NTP_simulation,NTP开放源码 的模拟配置问题，官方描述不正确

所用的ntp 开发包是 ntp-dev-4.2.7p56

一、问题描述

       NTP的模拟一直想用原汁原味的源代码来模拟，可惜一直卡在配置问题上，没有进展近两个星期。最终还是看代码修改了一条源代码的配置才搞定了，开源代码就是没有一个完善的文档，以及版本问题跟新系统。

        用的是ntp.conf是官方网站描述的配置释例：

# Client configuration     disable kernel    server pogo    driftfile ./ntp.drift    statsdir ./ntpstats/    filegen loopstats type day enable    filegen peerstats type day enable    # Simulation configuration    simulate {        simulation_duration = 86400        beep_delay = 3600        # Server 1server = louie.udel.edu {    server_offset = 0             duration = 50000 {freq_offset = 400wander = 1.0jitter = 0.001prop_delay = 0.001proc_delay = 0.001    }            duration = 6400 {freq_offset = 200wander = 1.0jitter = 0.001prop_delay = 0.001proc_delay = 0.001    }}        # Server 2server = baldwin.udel.edu {    server_offset = 0.02    duration = 10000 {freq_offset = 400wander = 1.0jitter = 0.001prop_delay = 0.5proc_delay = 0.001    }    duration = 60000 {freq_offset = 200wander = 1.0jitter = 0.05prop_delay = 0.005proc_delay = 0.001    }} }

存为/etc/ntp.conf,运行 ./ntpdsim后有如下提示：

18 Dec 16:38:41 ntpdsim[4867]: proto: precision = 0.200 usec18 Dec 16:38:41 ntpdsim[4867]: line 3 column 5 syntax error, unexpected T_Server, expecting T_EOCConfiguring Simulator...Some ntpd-specific commands in the configuration file will be ignored.ERROR!! I couldn't find a "simulate" block for configuring the simulator.Check your configuration file.

也就是说server 后面缺少一个结束符。

二、解决办法

1）检查关键字是否正确

    开始怀疑 是不是 sever 写错了，因该写成T_Server

     阅读ntp_keyword.h中 keyword_text[181], T_EOC对应于NULL。T_Server 对应于server 字符串，T_Sim_Duration对应于 "simulation_duration"，因此那些token对应的字符串可以在keyword_text中找到。同时，keyword-gen.c是生存ntp_keyword.h的原文件，struct key_tok  ntp_keywords[] 将Token和对应的脚本文件变量字符串 一一对应。

struct key_tok ntp_keywords[] = {{ "...",                T_Ellipsis,             FOLLBY_TOKEN },{ "allpeers",           T_Allpeers,             FOLLBY_TOKEN },{ "automax",            T_Automax,              FOLLBY_TOKEN },{ "broadcast",          T_Broadcast,            FOLLBY_STRING },{ "broadcastclient",    T_Broadcastclient,      FOLLBY_TOKEN },{ "broadcastdelay",     T_Broadcastdelay,       FOLLBY_TOKEN },

……

/* simulator commands */{ "simulate",           T_Simulate,             FOLLBY_TOKEN },{ "simulation_duration",T_Sim_Duration,         FOLLBY_TOKEN },{ "beep_delay",         T_Beep_Delay,           FOLLBY_TOKEN },{ "duration",           T_Duration,             FOLLBY_TOKEN },{ "server_offset",      T_Server_Offset,        FOLLBY_TOKEN },{ "freq_offset",        T_Freq_Offset,          FOLLBY_TOKEN },{ "wander",             T_Wander,               FOLLBY_TOKEN },{ "jitter",             T_Jitter,               FOLLBY_TOKEN },{ "prop_delay",         T_Prop_Delay,           FOLLBY_TOKEN },{ "proc_delay",         T_Proc_Delay,           FOLLBY_TOKEN },};

     验证关键字是正确的，没有错。

2） T_EOC的纠正

     在ntp_scanner.c中，有一个is_EOC函数。来判断是否是T_EOC类型。

static intis_EOC(        int ch        ){        if ((old_config_style && (ch == '\n')) ||            (!old_config_style && (ch == ';')))                return 1;        return 0;}

   而在 ntp_config.c 中

int old_cofig_style==1;

  也就是在配置文件中\n相当于T_EOC，可是一直解析不对

   将old_config_style=0，即启用 ；作为T_EOC类型。并修改配置文件：

       #client configuration     disable kernel;    server pogo;    driftfile ./ntp.drift;    statsdir ./ntpstats/;    filegen loopstats type day enable;    filegen peerstats type day enable;    # Simulation configuration    simulate {        simulation_duration=86400;        beep_delay = 3600;       # Beep_Delay = 3600 EOC    server = 10.2.2.23 {            server_offset = 0;            duration = 50000 {                freq_offset = 400;                wander = 1.0;                jitter = 0.001;                prop_delay = 0.001;                proc_delay = 0.001;            }            duration = 6400 {                freq_offset = 200;                wander = 1.0;                jitter = 0.001;                prop_delay = 0.001;                proc_delay = 0.001;            }        }        # Server 2        server = baldwin.udel.edu {            server_offset = 0.02;            duration = 10000 {                freq_offset = 400;                wander = 1.0;                jitter = 0.001;                prop_delay = 0.5;                proc_delay = 0.001;            }            duration = 60001 {                freq_offset = 200;                wander = 1.0;                jitter = 0.05;                prop_delay = 0.005;                proc_delay = 0.001;            }        }    }

最后得到如下正确输出：

 

Received packet from 128.4.1.24 on 127.0.0.1WARNING: e->time 81169 comes before sim_time 81170 (gap -0.982291)WARNING: e->time + gap 81168 comes before local_time 81171Received packet from 10.2.2.23 on 127.0.0.1WARNING: e->time 81202 comes before sim_time 81203 (gap -0.982835)WARNING: e->time + gap 81201 comes before local_time 81204Received packet from 128.4.1.24 on 127.0.0.1WARNING: e->time 81233 comes before sim_time 81234 (gap -0.982523)WARNING: e->time + gap 81232 comes before local_time 81235Received packet from 10.2.2.23 on 127.0.0.1WARNING: e->time 81266 comes before sim_time 81267 (gap -0.981338)WARNING: e->time + gap 81265 comes before local_time 81268Received packet from 128.4.1.24 on 127.0.0.1WARNING: e->time 81299 comes before sim_time 81300 (gap -0.982363)WARNING: e->time + gap 81298 comes before local_time 81301Received packet from 10.2.2.23 on 127.0.0.1WARNING: e->time 81333 comes before sim_time 81334 (gap -0.981446)WARNING: e->time + gap 81332 comes before local_time 81335

  终于成功了，看来还是要自己研究代码了！