un_tail_ident
if ((ul->un_chksum == ul->un_head_ident + ul->un_tail_ident) &&
if ((ul->un_chksum == ul->un_head_ident + ul->un_tail_ident) &&
if ((ul->un_chksum != ul->un_head_ident + ul->un_tail_ident) ||
ul->un_tail_ident = ul->un_head_ident;
ul->un_tail_ident = ul->un_head_ident;
ul->un_tail_ident = new_ident;
st->st_ident = ul->un_tail_ident++;
st->st_ident = ul->un_tail_ident++;