msg_grp_bc_seqno
u16 bc_seqno = msg_grp_bc_seqno(hdr);
if (!less(bc_seqno, msg_grp_bc_seqno(_hdr)))
if (less(msg_grp_bc_seqno(hdr), m->bc_rcv_nxt))
if (more(msg_grp_bc_seqno(hdr), m->bc_rcv_nxt))