unit.c NEED HELP PLS

[SeaweedTH]

According to this function in "unit.c" , what is the proper way to make a Blastmine Trap can be knocked back in GVG ?

 

/**
 * Checks if unit can be knocked back / stopped by skills.
 * @param bl: Object to check
 * @param flag
 *        0x1 - Offensive (not set: self skill, e.g. Backslide)
 *        0x2 - Knockback type (not set: Stop type, e.g. Ankle Snare)
 *        0x4 - Boss attack
 * @return reason for immunity
 *        UB_KNOCKABLE - can be knocked back / stopped
 *        UB_NO_KNOCKBACK_MAP - at WOE/BG map
 *        UB_MD_KNOCKBACK_IMMUNE - target is MD_KNOCKBACK_IMMUNE
 *        UB_TARGET_BASILICA - target is in Basilica area
 *        UB_TARGET_NO_KNOCKBACK - target has 'special_state.no_knockback'
 *        UB_TARGET_TRAP - target is trap that cannot be knocked back
 */
enum e_unit_blown unit_blown_immune(struct block_list* bl, uint8 flag)
{

    **** Say i would like to add  a --- >CASE HT_BLASTMINE: TO return UB_KNOCKABLE -- HERE before GVG

    if ((flag&0x1)
        && (map_flag_gvg2(bl->m) || map[bl->m].flag.battleground)
        && ((flag&0x2) || !(battle_config.skill_trap_type&0x1)))
        return UB_NO_KNOCKBACK_MAP; // No knocking back in WoE / BG

    switch (bl->type) {
        case BL_MOB:
            // Immune can't be knocked back
            if (((flag&0x1) && status_bl_has_mode(bl,MD_KNOCKBACK_IMMUNE))
                && ((flag&0x2) || !(battle_config.skill_trap_type&0x2)))
                return UB_MD_KNOCKBACK_IMMUNE;
            break;
        case BL_PC: {
                struct map_session_data *sd = BL_CAST(BL_PC, bl);
                // Basilica caster can't be knocked-back by normal monsters.
                if( !(flag&0x4) && &sd->sc && sd->sc.data[SC_BASILICA] && sd->sc.data[SC_BASILICA]->val4 == sd->bl.id)
                    return UB_TARGET_BASILICA;
                // Target has special_state.no_knockback (equip)
                if( (flag&(0x1|0x2)) && sd->special_state.no_knockback )
                    return UB_TARGET_NO_KNOCKBACK;
            }
            break;
        case BL_SKILL: {
                struct skill_unit* su = (struct skill_unit *)bl;
                // Trap cannot be knocked back
                if (su && su->group && skill_get_unit_flag(su->group->skill_id)&UF_NOKNOCKBACK)
                    return UB_TARGET_TRAP;
            }
            break;
    }

    //Object can be knocked back / stopped
    return UB_KNOCKABLE;
}