STZCNOTIFY
{ SF(STZCNOTIFY), "wait for zerocopy mblk to be acked" },
so->so_copyflag |= STZCNOTIFY;
while (!(so->so_copyflag & STZCNOTIFY)) {
so->so_copyflag &= ~STZCNOTIFY;
while (!(stp->sd_flag & STZCNOTIFY)) {
stp->sd_flag &= ~STZCNOTIFY;
stp->sd_flag |= STZCNOTIFY;