ru.nethack

 
 - RU.NETHACK -------------------------------------------------------------------
 From : Oleg Ganjushin                       2:5021/28.16   23 Jul 2000  18:09:23
 To : All
 Subject : Ping
 -------------------------------------------------------------------------------- 
 

 
 Ehternet Header
 Source Address       00:00:1C:04:C8:4C
 Destination Address  00:C0:DF:AC:C1:C2
 Protocol             0x0800
 
 IP Header
 Version              4
 Length               5
 Type of service      0x00
 Total length         60
 Identification       22272
 Fragmentation        0
 Time of live         32
 Protocol             0x01
 Checksum             0xA1D8
 Sender IP            223.241.241.1
 Dest   IP            223.241.241.3
 
 ICMP Header
 Type                 8 ( Echo Request )
 Code                 0
 Checksum             0x3F5C
 Identifier           256
 Sequence no          3328
 
 0000  00 C0 DF AC C1 C2 00 00  1C 04 C8 4C 08 00 45 00   ...........L..E.
 0010  00 3C 57 00 00 00 20 01  A1 D8 DF F1 F1 01 DF F1   .<W.............
 0020  F1 03 08 00 3F 5C 01 00  0D 00 61 62 63 64 65 66   ....?\....abcdef
 0030  67 68 69 6A 6B 6C 6D 6E  6F 70 71 72 73 74 75 76   ghijklmnopqrstuv
 0040  77 61 62 63 64 65 66 67  68 69                     wabcdefghi
 
 -----------------------------------------------------------------------------
 а вот ответ
 
 Ehternet Header
 Source Address       00:C0:DF:AC:C1:C2
 Destination Address  00:00:1C:04:C8:4C
 Protocol             0x0800
 
 IP Header
 Version              4
 Length               5
 Type of service      0x00
 Total length         60
 Identification       20224
 Fragmentation        0
 Time of live         32
 Protocol             0x01
 Checksum             0xA9D8
 Sender IP            223.241.241.3
 Dest   IP            223.241.241.1
 
 ICMP Header
 Type                 0 ( Echo Reply )
 Code                 0
 Checksum             0x475C
 Identifier           256
 Sequence no          3328
 
 0000  00 00 1C 04 C8 4C 00 C0  DF AC C1 C2 08 00 45 00   .....L........E.
 0010  00 3C 4F 00 00 00 20 01  A9 D8 DF F1 F1 03 DF F1   .<O.............
 0020  F1 01 00 00 47 5C 01 00  0D 00 61 62 63 64 65 66   ....G\....abcdef
 0030  67 68 69 6A 6B 6C 6D 6E  6F 70 71 72 73 74 75 76   ghijklmnopqrstuv
 0040  77 61 62 63 64 65 66 67  68 69                     wabcdefghi
 
 checksum ip header считают так
 где а : array [ 0 .. XX ] of byte этот dump
   xor      bx,bx
   xor      ax,ax
   mov      al,byte ptr a[$0E]
   add      bx,ax
   mov      al,byte ptr a[$11]
   add      bx,ax
   mov      al,byte ptr a[$12]
   shl      ax,8
   add      bx,ax
   mov      ah,0
   mov      al,byte ptr a[$13]
   add      bx,ax
   mov      al,byte ptr a[$16]
   add      bx,ax
   mov      al,byte ptr a[$17]
   shl      ax,8
   add      bx,ax
   mov      ah,0
   mov      al,byte ptr a[$1A]
   add      bx,ax
   mov      al,byte ptr a[$1B]
   add      bx,ax
   mov      al,byte ptr a[$1C]
   add      bx,ax
   mov      al,byte ptr a[$1D]
   add      bx,ax
   mov      al,byte ptr a[$1E]
   add      bx,ax
   mov      al,byte ptr a[$1F]
   add      bx,ax
   mov      al,byte ptr a[$20]
   add      bx,ax
   mov      al,byte ptr a[$21]
   add      bx,ax
   not      bx
 bx содержит конрольную сумму содержится она по смещению 18h
 a как считать checksum icmp header?
 
 Oleg
 
 --- FastEcho 1.40
  * Origin:  (2:5021/28.16)
 
 

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Тема:    Автор:    Дата:    RosNet SprintNet   Vlad Makarov   12 Jul 2000 12:18:45   Ping   Oleg Ganjushin   23 Jul 2000 18:09:23   Re: Ping   Comoderator   25 Jul 2000 22:47:43