#49 wrong sequence numbers Ns Nr in l2TP control header

[ctab]

There is a problem in Ns, Nr, sequence numbers in l2tp control message header.

LAC sends a SCCRQ message to mpd acting as LNS, then mpd replies with a SCCRP message with Ns = 0 and Nr = 0. Some LAC just ignore those malformed packets and close connection.

Extract from the RFC :

Ns indicates the sequence number for this data or control message,
beginning at zero and incrementing by one (modulo 2**16) for each
message sent. See Section 5.8 and 5.4 for more information on using
this field.

Nr indicates the sequence number expected in the next control message
to be received. Thus, Nr is set to the Ns of the last in-order
message received plus one (modulo 2**16). In data messages, Nr is
reserved and, if present (as indicated by the S-bit), MUST be ignored
upon receipt. See section 5.8 for more information on using this
field in control messages.

[Eugene Grosbein]

Please supply mpd version you use and detailed connection logs.