[core] Made offset consistent with avail_bufsize.

[gou4shi1]

Ref: #2467 (comment)

[maxsharabayko]

One of the changes has been introduced in #2463.
I believe the remaining one is not correct. The available RCV buffer size has to be counted from the acknowledgment position.
The value is sent in the ACK packet back to the sender (required protocol behavior), as well as in SRT stats (not much sense to change the behavior).

[maxsharabayko]

In fact, I think using m_iRcvLastSkipAck for the strFullnessState(..) is also incorrect, because ACK position is needed instead of the drop position. I missed that one reviewing #2463. So I guess that very change has to be reverted.

[gou4shi1]

One of the changes has been introduced in #2463.

Oops, my mistake, lol.

[gou4shi1]

Then the m_iRcvLastSkipAck in

LOGC(qrlog.Error, log << CONID() <<
        "SEQUENCE DISCREPANCY. BREAKING CONNECTION."
        " seq=" << rpkt.m_iSeqNo
        << " buffer=(" << m_iRcvLastSkipAck
        << ":" << m_iRcvCurrSeqNo                   // -1 = size to last index
        << "+" << CSeqNo::incseq(m_iRcvLastSkipAck, int(m_pRcvBuffer->capacity()) - 1)
        << "), " << (offset-avail_bufsize+1)
        << " past max. Reception no longer possible. REQUESTING TO CLOSE.");

should also be changed?

I created this PR because I found the buffer number in the SEQUENCE DISCREPANCY log is not consistent with the offset number.
I'm OK for both solutions, as long as logs are consistent.

[maxsharabayko]

Then the m_iRcvLastSkipAck in

LOGC(qrlog.Error, log << CONID() << "SEQUENCE DISCREPANCY. BREAKING CONNECTION." " seq=" << rpkt.m_iSeqNo << " buffer=(" << m_iRcvLastSkipAck << ":" << m_iRcvCurrSeqNo // -1 = size to last index << "+" << CSeqNo::incseq(m_iRcvLastSkipAck, int(m_pRcvBuffer->capacity()) - 1)

should also be changed?

Good catch!
Yes, here m_iRcvLastAck should be used instead of m_iRcvLastSkipAck. To have the same base with getAvailRcvBufferSizeNoLock() called above.

[maxsharabayko]

All correct. Please consider one correction of the comment.

[gou4shi1]

ping

[maxsharabayko]

Oops, sorry, forgot about this PR 😃