ISDN_P_B_START
if ((sk->sk_protocol & ~ISDN_P_B_MASK) == ISDN_P_B_START) {
if (sk->sk_protocol < ISDN_P_B_START) {
if (csk->sk_protocol >= ISDN_P_B_START)
if (ch->protocol >= ISDN_P_B_START) {