PPP协议的LCP链路包中的校验位怎么计算出来的？

[缭绕飘渺]

如题，协议只说了是循环冗余校验方式
试过了CRC16，CRC32等校验函数
得出的结果都跟截取的报文不一致
报文如下，校验位是除了头尾两个7E和 BE 9B这个算出来的校验位


7E FF 7D 23 C0 21 7D 21 7D 21 7D 20 7D 38 7D
22 7D 26 7D 20 7D 2A 7D 20 7D 20 7D 23 7D 24 C0
23 7D 25 7D 26 7D 20 7D 20 7D 20 7D 20 7D 27 7D
22 7D 28 7D 22 BE 9B 7E

//7D XX=>**,其中**是XX与0x20异或的结果
//特殊地，
//7D 5D=>5D,
//7D 5E=>5E,

//所以上面转换后的结果是：
//7E FF 03 C0 21 01 01 00 18
//02 06 00 0A 00 00 03 04 C0
//23 05 06 00 00 00 00 07 02
//08 02 BE 9B 7E
//下面说下里面数据的含义：
//7E----PPP的帧头，帧尾标志
//FF----地址域
//03－－控制域
//C0 21---协议域，0xC021表示LCP协议，再比如0x8021表示ipcp协议
//01 01 00 18－－第一个01表示LCP包的code为1，即configure_request, 下面那个01表示标识符，00 18表示包的长度
//它包括code，identifier，长度，及后面的选项域。
//02 06 00 0A 00 00－－表示选项的type为2，06为长度，00 0A 00 00表示ACCM选项的数据域，可以参考rfc1662
//03 04 C0 23 －－选项type为3，表示协议认证，04为长度，CO 23表示采用CHAP认证
//05 06 00 00 00 00 ----选项type为5，表示magic number，06为长度，后面的是内容
//07 02－－选项type为7表示协议域压缩
//08 02－－选项type为8表示地址控制域压缩
//BE 9B--表示FCS,Fast Frame Check Sequecese，可参考rfc1662

路过的给个计算方式！

[gomoku]

RFC1662里面就有计算方法。

[LOVE_GG]

好高深........

[缭绕飘渺]

[Quote=引用 1 楼 的回复:]

RFC1662里面就有计算方法。
[/Quote]
看到RFC1570有个方法，是C的
没搞明白

[缭绕飘渺]

/* 

          * u16 represents an unsigned 16-bit number.  Adjust the typedef for 

          * your hardware. 

          */ 

         typedef unsigned short u16; 

         /* 

          * FCS lookup table as calculated by the table generator. 

          */ 

         static u16 fcstab[256] = { 

             0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 

             0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, 

             0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, 

             0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, 

             0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, 

             0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, 

             0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, 

             0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, 

             0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, 

             0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, 

             0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, 

             0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, 

             0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, 

             0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, 

             0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, 

             0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, 

             0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, 

             0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, 

             0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 

             0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, 

      RFC 1662                        HDLC-like Framing                          July 1994 

             0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, 

             0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, 

             0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, 

             0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, 

             0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, 

             0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb, 

             0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, 

             0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, 


----------------------- Page 14-----------------------

             0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, 

             0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, 

             0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 

             0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78 

         }; 

         #define PPPINITFCS16         0xffff  /* Initial FCS value */ 

         #define PPPGOODFCS16         0xf0b8  /* Good final FCS value */ 

         /* 

          * Calculate a new fcs given the current fcs and the new data. 

          */ 

         u16 pppfcs16(fcs, cp, len) 

              register u16 fcs; 

              register unsigned char *cp; 

              register int len; 

         { 

              ASSERT(sizeof (u16) == 2); 

              ASSERT(((u16) -1) > 0); 

              while (len--) 

                  fcs = (fcs >> 8) ^ fcstab[(fcs ^ *cp++) & 0xff]; 

              return (fcs); 

         } 

         /* 

          * How to use the fcs 

          */ 

         tryfcs16(cp, len) 

              register unsigned char *cp; 

              register int len; 

         { 

              u16 trialfcs; 

              /* add on output */ 

              trialfcs = pppfcs16( PPPINITFCS16, cp, len ); 

              trialfcs ^= 0xffff;                        /* complement */ 

              cp[len] = (trialfcs & 0x00ff);             /* least significant byte first */ 

              cp[len+1] = ((trialfcs >> 8) & 0x00ff); 

     RFC 1662                         HDLC-like Framing                         July 1994 

              /* check on input */ 

              trialfcs = pppfcs16( PPPINITFCS16, cp, len + 2 ); 

              if ( trialfcs == PPPGOODFCS16 ) 

                  printf("Good FCS\n"); 

         } 

[缭绕飘渺]

 /* 

          * The FCS-32 generator polynomial: x**0 + x**1 + x**2 + x**4 + x**5 

          *                           + x**7 + x**8 + x**10 + x**11 + x**12 + x**16 

          *                           + x**22 + x**23 + x**26 + x**32. 

          */ 

         /* 

          * u32 represents an unsigned 32-bit number.  Adjust the typedef for 

          * your hardware. 

          */ 

         typedef unsigned long u32; 

         static u32 fcstab_32[256] = 

             { 

             0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 


      0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3, 

      0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 

      0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 

      0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 

      0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 

      0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 

      0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, 

      0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 

      0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 

      0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 

      0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 

      0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 

      0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f, 

      0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 

      0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 

      0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 

      0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433, 

      0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 

      0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01, 

      0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 

      0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 

      0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 

      0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, 

      0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 

      0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 

      0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 

      0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 

      0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 

      0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, 

      0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 

      0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 

      0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 

      0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 

      0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 

      0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 

      0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 

      0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, 

      0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 

      0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 

      0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 

      0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 

      0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 

      0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79, 

      0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 

      0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 

      0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 

      0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, 

      0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 

      0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, 

      0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 

      0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 

      0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 

      0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, 

      0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 

      0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 

      0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 

      0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 

      0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 

      0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, 

      0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 


             0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf, 

             0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 

             0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d 

             }; 



      #define PPPINITFCS32 0xffffffff /* Initial FCS value */ #define PPPGOODFCS32 0xdebb20e3 

      /* Good final FCS value */ 



      RFC 1662                         HDLC-like Framing                          July 1994 

         /* 

          * Calculate a new FCS given the current FCS and the new data. 

          */ 

         u32 pppfcs32(fcs, cp, len) 

              register u32 fcs; 

              register unsigned char *cp; 

              register int len; 

              { 

              ASSERT(sizeof (u32) == 4); 

              ASSERT(((u32) -1) > 0); 

              while (len--) 

                   fcs = (((fcs) >> 8) ^ fcstab_32[((fcs) ^ (*cp++)) & 0xff]); 

              return (fcs); 

              } 

         /* 

          * How to use the fcs 

          */ 

         tryfcs32(cp, len) 

              register unsigned char *cp; 

              register int len; 

         { 

              u32 trialfcs; 

              /* add on output */ 

              trialfcs = pppfcs32( PPPINITFCS32, cp, len ); 

              trialfcs ^= 0xffffffff;                     /* complement */ 

              cp[len] = (trialfcs & 0x00ff);              /* least significant byte first */ 

              cp[len+1] = ((trialfcs >>= 8) & 0x00ff); 

              cp[len+2] = ((trialfcs >>= 8) & 0x00ff); 

              cp[len+3] = ((trialfcs >> 8) & 0x00ff); 

              /* check on input */ 

              trialfcs = pppfcs32( PPPINITFCS32, cp, len + 4 ); 

              if ( trialfcs == PPPGOODFCS32 ) 

                   printf("Good FCS\n"); 

         } 

[violet725]

谁把上面的转成C#的？？？？？？？

[缭绕飘渺]

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