m_pullup
thdr = m_pullup(thdr, SMB3_TFORM_HDR_SIZE);
m = m_pullup(m, 4);
m = m_pullup(m, SMB_HDRLEN);
m = m_pullup(m, SMB2_HDRLEN);
extern mb_t *m_pullup __P((mb_t *, int));
mblk_t *m_pullup(mblk_t *, int);