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Date: Thu, 29 Feb 1996 20:13:28 -0500 (EST)
From: Richard Toren <rpt@miles.sso.loral.com>
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To: Lyndon Nerenberg VE7TCP <lyndon@orthanc.com>
Cc: hackers@freebsd.org
Subject: Re: tcpdump changes
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On Wed, 28 Feb 1996, Lyndon Nerenberg VE7TCP wrote:

> I'm thinking of making a change to tcpdump and would like
> to solicit comments ...
> 
> The '-x' option prints a hex dump of packet contents (modulo capture
> length). I would like to modify it to also include an ASCII 
> representation of the same data. (Makes it easier to trace things like

I did that with the following modification to tcpdump.c. This routine is 
near the end of the source file. This was 3.0.2 source. I don't have the 
original handy, but this should be a good start. Then rebuild and the -x 
will dump hex/ascii.

Have fun...

default_print(register const u_char *data, register int len)
{

   /* DESCZ
       Dumps to dbglog file a hex/ascii formatted dump of the
       passed address for the specified number of bytes.
   */

   char        hexbuf[64];
   char        chrbuf[24];
   char        *k;
   int         i, j;

   if (len <= 0) return;
   printf("\n");
   for (i=j=0, k=hexbuf; i< len; i++, j++)  
   {
       if (j >= 16)  
       {
           chrbuf[j] = 0x00;
           printf ("\t\t\t|%-42s|%-16s|\n", hexbuf, chrbuf);
           j = 0;
           k = hexbuf;
       }

       if (j&1)  
       {
           sprintf (k, "%02X ", data[i]);
           chrbuf[j] = isprint (data[i]) ? data[i] : '.';
           k = k+3;
       }

       else  
       {
           sprintf (k, "%02X", data[i]);
           chrbuf[j] = isprint (data[i]) ? data[i] : '.';
           k = k+2;
       }
   }

   if (j > 0)  
   {
       chrbuf[j] = 0x00;
       printf( "\t\t\t|%-42s|%-16s|\n", hexbuf, chrbuf);
       j = 0;
       k = hexbuf;
   }

   fflush (stdout);


/********** original *****
    register const u_short *sp;
    register u_int i;
    register int nshorts;

    if ((int)bp & 1) {
        default_print_unaligned(bp, length);
        return;
    }
    sp = (u_short *)bp;
    nshorts = (u_int) length / sizeof(u_short);
    i = 0;
    while (--nshorts >= 0) {
        if ((i++ % 8) == 0)
            (void)printf("\n\t\t\t");
        (void)printf(" %04x", ntohs(*sp++));
    }
    if (length & 1) {
        if ((i % 8) == 0)
            (void)printf("\n\t\t\t");
        (void)printf(" %02x", *(u_char *)sp);
    }
*********/
}


                         ====================================================
Rip Toren               | The bad news is that C++ is not an object-oriented |
rpt@miles.sso.loral.com | programming language. .... The good news is that   |
                        | C++ supports object-oriented programming.          |
                        |    C++ Programming & Fundamental Concepts          |
                        |     by Anderson & Heinze                           |
                         ====================================================