SCTP_SACK_NONCE_SUM
(*ecn_seg_sums) &= SCTP_SACK_NONCE_SUM;
nonce_sum_flag = ch->ch.chunk_flags & SCTP_SACK_NONCE_SUM;
if (nonce_sum_flag != ((asoc->nonce_sum_expect_base + ecn_seg_sums) & SCTP_SACK_NONCE_SUM)) {
asoc->nonce_sum_expect_base = (ecn_seg_sums ^ nonce_sum_flag) & SCTP_SACK_NONCE_SUM;
stcb->asoc.receiver_nonce_sum &= SCTP_SACK_NONCE_SUM;
sack->ch.chunk_flags = asoc->receiver_nonce_sum & SCTP_SACK_NONCE_SUM;