RFC 1071, "Computing the Internet checksum", September 1988

Note: This RFC has been updated by RFC 1141

Errata ID: 3133
Status: Held for Document Update
Type: Technical
Publication Format(s) : TEXT
Reported By: chenhaospark
Date Reported: 2012-02-23
Held for Document Update by: Brian Haberman

Section 4.1 says:

           /*  Add left-over byte, if any */
       if( count > 0 )
               sum += * (unsigned char *) addr;

It should say:

           /*  Add left-over byte, if any */
       if( count > 0 )  {
               unsigned short left_over = 0;
               * (unsigned char *) &left_over = * (unsigned char *) addr;
               sum += left_over;
       }

Notes:

for big-endian

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