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RFC 5925, "The TCP Authentication Option", June 2010

Source of RFC: tcpm (tsv)

Errata ID: 5672
Status: Reported
Type: Technical
Publication Format(s) : TEXT

Reported By: Joe Touch
Date Reported: 2019-03-24

Section 6.2 says:

     /* set the flag when the SEG.SEQ first rolls over */
     if ((RCV.SNE_FLAG == 0)
        && (RCV.PREV_SEQ > 0x7fff) && (SEG.SEQ < 0x7fff)) {
           RCV.SNE = RCV.SNE + 1;
           RCV.SNE_FLAG = 1;
     }
     /* decide which SNE to use after incremented */
     if ((RCV.SNE_FLAG == 1) && (SEG.SEQ > 0x7fff)) {
        SNE = RCV.SNE - 1; # use the pre-increment value
     } else {
        SNE = RCV.SNE; # use the current value
     }
     /* reset the flag in the *middle* of the window */
     if ((RCV.PREV_SEQ < 0x7fff) && (SEG.SEQ > 0x7fff)) {
        RCV.SNE_FLAG = 0;
     }
     /* save the current SEQ for the next time through the code */
     RCV.PREV_SEQ = SEG.SEQ;

It should say:

     /* set the flag when the SEG.SEQ first rolls over */
     if ((RCV.SNE_FLAG == 0)
        && (RCV.PREV_SEQ > 0x7fffffff) && (SEG.SEQ < 0x7fffffff)) {
           RCV.SNE = RCV.SNE + 1;
           RCV.SNE_FLAG = 1;
     }
     /* decide which SNE to use after incremented */
     if ((RCV.SNE_FLAG == 1) && (SEG.SEQ > 0x7fffffff)) {
        SNE = RCV.SNE - 1; # use the pre-increment value
     } else {
        SNE = RCV.SNE; # use the current value
     }
     /* reset the flag in the *middle* of the window */
     if ((RCV.PREV_SEQ < 0x7fffffff) && (SEG.SEQ > 0x7fffffff)) {
        RCV.SNE_FLAG = 0;
     }
     /* save the current SEQ for the next time through the code */
     RCV.PREV_SEQ = SEG.SEQ;

Notes:

The SNE values are 32 bits; the current pseudocode used 16-bit masks (0x7fff) instead of their 32-bit equivalent (0x7fffffff).

This error was first noted by Tero Kivinen <kivinen@iki.fi>.

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