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  • Block ip for long time

    - by Tiziano Dan
    This question is about a iptables, I wanna to know how can I block these ip for 1hour and not only a little time.. because they make to many sql requests, I'm using it for block but it's not enough because there's anyway 100k ip who attack then too much requests for sql server. iptables -N SYN-LIMIT iptables -A SYN-LIMIT -m hashlimit --hashlimit 8/second --hashlimit-mode srcip --hashlimit-name SYN-LIMIT -j RETURN iptables -A SYN-LIMIT -j DROP iptables -I INPUT -p tcp --dport 80 --syn -j SYN-LIMIT iptables -I INPUT -p tcp --dport 80 -m connlimit --connlimit-above 6 -j REJECT --reject-with tcp-reset How can I make the same but block IP for long time ? (Not manually !)

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  • How to best configure IIS7 logging to capture "HTTP_X_FORWARDED_FOR" header

    - by zeroasterisk
    We have IIS7 servers sitting behind an nginx reverse proxy. The reverse proxy is sending the standard "HTTP_X_FORWARDED_FOR" header with the visitor IP address, but IIS7 logging is only logging the IP address of the nginx server (which makes sense, but it's not what I want). How can I tell IIS7 to instead log the "HTTP_X_FORWARDED_FOR" header (or additionally log it)? (note: I'm a linux admin, not a windows one, so explicit instructions & links are sincerely appreciated)

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  • Cannot access shares via \\servername but \\ip works

    - by Jeff
    To set up the scenario: One of our techs set one of the domain controllers to use Microsoft time. The time IS correct (including Time Zone) and DOES match the other domain controller's time; it was previously incorrect, however. Since the change, no users can connect via \\servername\share or \\servername.domainname.com but \\ip\share works fine. I cannot even access it from the other domain controller with which I know both have the same time. The servername DOES resolve to the correct IP address. Also, strangely enough, \\domainname.com works as well which resolves to the same server. Finally Everything that I have tried does resolve to the same, correct IP address. The error is: login failure: The target account name is incorrect. I believe it is time related but since the times are correct and match I'm not sure. Anyone know what might cause this?

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  • pfSense routing between two routers with shared network

    - by JohnCC
    I have a network set-up using two pfSense routers arranged like this:- DMZ1 WAN1 WAN2 DMZ2 | | | | | | | | \___ PF1 PF2___/ | | | | \___TRUSTED___/ Each pfSense router has its own separate WAN connection, and a separate DMZ network attached to it. They share a common TRUSTED LAN between them. The machines on the trusted network have PF1 as their default gateway. PF1 has a static route defined to DMZ2 via PF2, and PF2 has a static route to DMZ1 via PF1. There is NAT to the WAN but internal networks (DMZ1/2 and TRUSTED) use different RFC1918 subnets. I inherited this arrangement, and all used to work fine. I made a config change to PF1 (relating to multicast), and machines on DMZ2 suddenly could not talk to TRUSTED. I rolled the change back, but the problem persisted. What I guess you'd hope would happen is that TCP packets would go DMZ2 - PF2 - TRUSTED and on return TRUSTED - PF1 - PF2 - DMZ2. That's the only way I can see it would have worked. However, PF1 drops the returning packets. I've verified this using tcpdump. I've worked around this by adding static routes to DMZ2 via PF2 to the servers on TRUSTED, but some devices on there do not support static routes so this is not ideal. Is there way to make this arrangement work decently, or is the design inherently flawed? Thanks!

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  • Unable to change IP address for eth0 without restart in Ubuntu

    - by Rodnower
    I have Ubuntu 12.04.1 installed. I tried to change the IP address of the interface eth0 in /etc/network/interfaces from 192.168.1.3 to 192.168.1.4 auto lo iface lo inet loopback pre-up iptables-restore < /etc/iptables.up.rules auto eth0 iface eth0 inet static address 192.168.1.4 gateway 192.168.1.1 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 sudo service networking status When I issue: sudo service networking restart I get this response: stop: Unknown instance: networking stop/waiting And IP remains 192.168.1.3: eth0 Link encap:Ethernet HWaddr 00:1e:33:71:cd:a4 inet addr:192.168.1.3 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::21e:33ff:fe71:cda4/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:3861 errors:0 dropped:0 overruns:0 frame:0 TX packets:3291 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3423285 (3.4 MB) TX bytes:521854 (521.8 KB) Interrupt:45 Base address:0x4000 Only after restart does the IP change. Any ideas?

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  • Port Forwarding IPTABLES public IP

    - by tric
    hello i have a computer linuxbox_1.eth0 public ip 89.40.x.y eth1 public ip 85.121.a.b i have another linuxbox_2. ethx public ip 86.34.c.d what i want to do is forward port 8001 from linuxbox_1 eth0 89.40.x.y:8001 to linuxbox_1 eth1 85.121.a.b, and then forward again port 8001 from linuxbox_1 eth1 85.121.a.b:8001 to linuxbox_2 ethx 86.34.c.d:80 i have searched for answers using google "that knows everything" but this time it has failed. i would like to use IPTABLES or any other tool like rinetd. i tryed rinetd but it somehow mistakes the eths sorry for my bad english. 10q

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  • Redirect traffic to local address so iOS speedtest app measures LAN speed

    - by ivan_sig
    I have mounted a Speedtest Mini server on a local LAMP, so I can test my LAN speeds effortlessly just by opening the URL with a Flash enabled web browser, the thing is, I want my iOS and Android devices to test with the LAN server too, not with the WAN, as I'm trying to measure LAN-Only performance. Is there a way so I can redirect the traffic intended to an specific external IP (The one of the real server) to my local server?. I know the servers IP as a short Wireshark analysis gave me the data, but still searching for a way to make that redirect. I have Jailbreak and root on my devices, so playing with system files is not a problem. I've tried mounting a proxy and making redirects by the hosts file and domain names, but it looks like Ookla's app relies on IP address only.

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  • Safari 7 SSL error if using IP-adress

    - by K. Biermann
    I have created my own CA for internal usage and set the root certificate to trustworthy on my machines. With this CA I signed the SSL-certificates for my internal servers. I only address them with their IP and so I used the servers' IP as certificate name. If i connect to the Servers with Chrome or mobile Safari it works without problems, but if I use Safari 7 under Mavericks (on the same machine with the same keychain) i get the following error: "The certificate is not valid (host name mismatch)". I double checked that I entered the correct IP ("https://192.168.2.130"), but I always get the same error. Do I need to enter a different name for the certificate or is it just that Safari doesn't support SSL certificates for IPs? Here is a screenshot of the error message (I can only post images with at least 10 rep): Safari's error message Thanks in advantage and please excuse my bad English :D

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  • how can 192.168.2.10 talk to 172.18.156.65 ?

    - by steve
    from what i understand, all computers need to be in the same subnet /24 so how would i get a computer to be able to connect to another computer that is set as 172 ? one computer is behind a firewall, the other is connected to a HUGHES sat dish and has the IP of 172 would I need to setup a ROUTE in a firewall between the 2 computers, to say "if you are trying to get to 172.18.156.65 then use the ip address 192.168.2.65 and translate it to 172.18.156.65" the firewall is a netgear, if I should use a ROUTE, then I'll try to learn it from the manual thanks

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  • URL Based Internal Redirecting

    - by bculverscate
    Basically, we have one external IP address, several servers internally and want to redirect to each internal server based on request URL. We do not want to install another piece of hardware to do this for us but we have a firewall running Linux that currently forwards to only one of the internal servers. Example of our setup can be seen here: http://img23.imageshack.us/img23/5469/drawing1br.jpg NOTE: domain.com does not point to this box nor would we like it to. Subdomains are pointed manually to our global IP address.

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  • Unable chage IP address for eth0 without restart in Ubunto

    - by Rodnower
    I have Ubuntu 12.04.1 installed. I try to change IP address of the interface eth0 in /etc/network/interfaces from 192.168.1.3 to 192.168.1.4: auto lo iface lo inet loopback pre-up iptables-restore < /etc/iptables.up.rules auto eth0 iface eth0 inet static address 192.168.1.4 gateway 192.168.1.1 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 sudo service networking status Now I issue: sudo service networking restart I have response: stop: Unknown instance: networking stop/waiting And IP remains 192.168.1.3: eth0 Link encap:Ethernet HWaddr 00:1e:33:71:cd:a4 inet addr:192.168.1.3 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::21e:33ff:fe71:cda4/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:3861 errors:0 dropped:0 overruns:0 frame:0 TX packets:3291 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3423285 (3.4 MB) TX bytes:521854 (521.8 KB) Interrupt:45 Base address:0x4000 Only after restart IP changing... Any ideas?

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  • Binding MySQL to run from the public or private LAN IP address - which one is faster

    - by Lamin Barrow
    So we have 2 servers all running at the same web host. We have bind MySQL to listen on the public ip-address of the database server and the web server connects to it from the public ip. Both servers run on the same private network. Currently, the DB connect method from our php script takes about 3ms to connect to the MySQL database server host. My question is, would MySql data interaction from the web server be faster if we bind it to listen on the private lan address on the database server instead of the public IP? or is it the same regardless and it wont make a different.

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  • Iptables - Open Port Only for one Server IP (allow connections from a specific range)

    - by user1015314
    My server has multiple IPs, 1.1.1.1 1.1.1.2 and i have a service which listens to a port e.g. 88 Now i want, when somebody from outside, wants to connect to the port, that he can only connect, to that port, if he connects to the ip 1.1.1.2:88 but if he tries to connect to 1.1.1.1:88 it should not react and it should look like that it dont exists and drops all connections. Ok, than i need for 1.1.1.2:88 that only allows a specific ip range outside connecters. for example only 9.*.*.* can connect to that port and ip. I'm using Centos. Thank you for your help.

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  • Disable Network settings (TCP/IP & DNS) on Windows 7 Ultimate

    - by TiD91
    i also read this discussion here How to disable Tcp/Ip settings in windows 7 via GPO? about what i want to do but i still have problems. So here i am: i have a desktop pc with two accounts, both with Administrative rights. One is used by the entire my family, in particular by my brother. The problem is that i set some DNS and IP configurations to let be possible the VNC connection from remote. Now i would like to disable the network settings (TCP/IP and DNS) to prohibit my brother to change it preventing me to connect to it. So how can i do this? I set the policies from GPO but i still can change these settings from his account. Here's a pic of Registry Keys: http://imageshack.us/a/img339/3310/famigliapc2012092017274.png what didn't i do? Thanks in advance for your help. Rub|TiD

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  • Setting primary IP for VPS (out of 2 available)

    - by Flyer
    I've got a little problem. My VPS (Debian box) has 1 primary IP address, but now my hosting provider decided to assign me another one due to problems with first one. Let's say new IP is 91.222.152.20 and old one 91.221.190.170. How should I make 91.222.152.20 primary one, so that everything works on this address instead of 91.221.190.170 (like ftp, mysql etc) I tried editing /etc/newtwork/interfaces setting iface eth1 inet static address 91.222.152.20 netmask 255.255.252.0 network 91.222.152.0 broadcast 91.222.155.255 gateway 91.222.152.1 I know that network is 91.222.152.0/22 so I assume that above configuration should be right. Saved, rebooted and that ended pretty bad. Couldn't even ping box on old or new IP. Had to revert to working one. So question is. What am I doing wrong and how to do it right?

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  • Limit access on login and IP in .htaccess

    - by Rob
    There are many examples showing how to use .htaccess to restrict users by login or on their IP address (i.e they are ok from the ones given without authorisation). For some reason the following is never mentioned, yet it seems quite useful. How do I restrict using groups and ip, e.g. group1 can access the page from anywhere group2 can access the page only from certain IP addresses if you are not logged on, you cant see the page, regardless where you are I would like to have all 3 of these working at the same time.

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  • Server 2008 DHCP some clients not getting IP

    - by AdminAlive
    Today (after turning on the server from an extended power outage) some clients are not able to get IP addresses. Some clients work just fine. Win 7 and XP doesnt seem to matter. I have tried flushing dns, renew, disabling APIPA and even assigned a static IP. Even with the static IP it acts as if it isn't on a network. You can't ping anything. I have also tried resetting the TCPIP stack. The clients that work can ping the DNS and DHCP servers fine. Any suggestions? Thanks

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  • use local ip and maintain ssl warning free [duplicate]

    - by Timothy Clemans
    This question already has an answer here: Loopback to forwarded Public IP address from local network - Hairpin NAT 6 answers I have a public facing website for a doctor's office for accessing the medical record. I'm using SSL. The server is at the doctor's office. When I access the website on the same network as the server I want the DNS to point to the local IP address. I don't want to do a HTTP redirect to the local ip because of the scary SSL warning. What's the recommended way of doing this?

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  • How to get ip-address out of SPAMHAUS blacklist?

    - by vgv8
    I frequently read that it is possible to remove individual ip-addresses from SPAMHAUS blacklisting. OK. Here is 91.205.43.252 (91.205.43.251 - 91.205.43.253) used by back3.stopspamers.com (back2.stopspamers.com, back1.stopspamers.com) in geo-cluster on dedicated servers in Switzerland. The queries: http://www.spamhaus.org/query/bl?ip=91.205.43.251 http://www.spamhaus.org/query/bl?ip=91.205.43.252 http://www.spamhaus.org/query/bl?ip=91.205.43.253 tell that: 91.205.43.251 - 91.205.43.253 are all listed in the SBL80808 blacklist And SBL80808 blacklist tells: "Ref: SBL80808 91.205.40.0/22 is listed on the Spamhaus Block List (SBL) 01-Apr-2010 05:52 GMT | SR04 Spamming and now seems this place is involved in other fraud" 91.205.43.251-91.205.43.253 are not listed amongst criminal ip-addresses individually but there is no way to remove it individually from black listing. How to remove this individual (91.205.43.251-91.205.43.253) addresses from SPAMHAUS blacklist? And why the heck SPAMHAUS is blacklisting spam-stopping service? This is only one example of a bunch. My related posts: Blacklist IP database Update: From the answer provided I realized that my question was not even understood. This ip-addresses 91.205.43.251 - 91.205.43.253 are not blacklisted individually, they are blacklisted through its supernet 91.205.40.0/22. Also note that dedicated server, ISP and customer are in much different distant countries. Update2: http://www.spamhaus.org/sbl/sbl.lasso?query=SBL80808#removal tells: "To have record SBL80808 (91.205.40.0/22) removed from the SBL, the Abuse/Security representative of RIPE (or the Internet Service Provider responsible for supplying connectivity to 91.205.40.0/22) needs to contact the SBL Team" There are dozens of "abusers" in that blacklist SBL80808. The company using that dedicated server is not an ISP or RIPE representative to treat these issues. Even if to treat it, it is just a matter of pressing "Report spam" on internet to be again blacklisted, this is fruitless approach. These techniques are broadly used by criminals and spammers, See also this my post on blacklisting. This is just one specific example but there are many-many more.

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  • How to get ip-address out of SPAMHAUS blacklist?

    - by ???????? ????? ???????????
    I frequently read that it is possible to remove individual ip-addresses from SPAMHAUS blacklisting. OK. Here is 91.205.43.252 (91.205.43.251 - 91.205.43.253) used by back3.stopspamers.com (back2.stopspamers.com, back1.stopspamers.com) in geo-cluster on dedicated servers in Switzerland. The queries: http://www.spamhaus.org/query/bl?ip=91.205.43.251 http://www.spamhaus.org/query/bl?ip=91.205.43.252 http://www.spamhaus.org/query/bl?ip=91.205.43.253 tell that: 91.205.43.251 - 91.205.43.253 are all listed in the SBL80808 blacklist And SBL80808 blacklist tells: "Ref: SBL80808 91.205.40.0/22 is listed on the Spamhaus Block List (SBL) 01-Apr-2010 05:52 GMT | SR04 Spamming and now seems this place is involved in other fraud" 91.205.43.251-91.205.43.253 are not listed amongst criminal ip-addresses individually but there is no way to remove it individually from black listing. How to remove this individual (91.205.43.251-91.205.43.253) addresses from SPAMHAUS blacklist? And why the heck SPAMHAUS is blacklisting spam-stopping service? This is only one example of a bunch. My related posts: Blacklist IP database Update: From the answer provided I realized that my question was not even understood. This ip-addresses 91.205.43.251 - 91.205.43.253 are not blacklisted individually, they are blacklisted through its supernet 91.205.40.0/22. Also note that dedicated server, ISP and customer are in much different distant countries. Update2: http://www.spamhaus.org/sbl/sbl.lasso?query=SBL80808#removal tells: "To have record SBL80808 (91.205.40.0/22) removed from the SBL, the Abuse/Security representative of RIPE (or the Internet Service Provider responsible for supplying connectivity to 91.205.40.0/22) needs to contact the SBL Team" There are dozens of "abusers" in that blacklist SBL80808. The company using that dedicated server is not an ISP or RIPE representative to treat these issues. Even if to treat it, it is just a matter of pressing "Report spam" on internet to be again blacklisted, this is fruitless approach. These techniques are broadly used by criminals and spammers, See also this my post on blacklisting. This is just one specific example but there are many-many more.

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  • Java :Interface for this code

    - by ibrahim
    Please i neeed help to make interface for this code: package com.ejada.alinma.edh.xsdtransform; import java.io.File; import java.io.FileReader; import java.io.FileWriter; import java.io.StringWriter; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Date; import java.util.HashMap; import java.util.Iterator; import java.util.Properties; import java.util.StringTokenizer; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.transform.Result; import javax.xml.transform.Source; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; /*import org.apache.log4j.Logger;*/ import org.apache.log4j.PropertyConfigurator; import org.w3c.dom.Document; import org.w3c.dom.DocumentFragment; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import com.sun.org.apache.xml.internal.serialize.OutputFormat; import com.sun.org.apache.xml.internal.serialize.XMLSerializer; /** * An XSD Transformer that replaces the "name" attribute's value in T24 XSDs * with the "shortname" attribute's value * * @author ahusseiny * */ public class XSDTransformer { /** * constants representing the XSD tags and attributes' names used in the parse process */ public static final String TAG_SCHEMA = "xsd:schema"; public static final String TAG_TEXT = "#text"; public static final String TAG_COMPLEX_TYPE = "xsd:complexType"; public static final String TAG_SIMPLE_TYPE = "xsd:simpleType"; public static final String TAG_SEQUENCE = "xsd:sequence"; public static final String TAG_ATTRIBUTE = "xsd:attribute"; public static final String TAG_ELEMENT = "xsd:element"; public static final String TAG_ANNOTATION = "xsd:annotation"; public static final String TAG_APP_INFO = "xsd:appinfo"; public static final String TAG_HAS_PROPERTY = "xsd:hasProperty"; public static final String TAG_RESTRICTION = "xsd:restriction"; public static final String TAG_MAX_LENGTH = "xsd:maxLength"; public static final String ATTR_NAME = "name"; public static final String ATTR_VALUE = "value"; public static final String ATTR_TYPE = "type"; public static final String ATTR_MIXED = "mixed"; public static final String ATTR_USE = "use"; public static final String ATTR_REF = "ref"; public static final String ATTR_MAX_OCCURS = "maxOccurs"; /** * constants representing specific XSD attributes' values used in the parse process */ public static final String FIELD_TAG = "fieldtag"; public static final String FIELD_NUMBER = "fieldnumber"; public static final String FIELD_DATA_TYPE = "fielddatatype"; public static final String FIELD_FMT = "fieldfmt"; public static final String FIELD_LEN = "fieldlen"; public static final String FIELD_INPUT_LEN = "fieldinputlen"; public static final String FIELD_GROUP_NUMBER = "fieldgroupnumber"; public static final String FIELD_MV_GROUP_NUMBER = "fieldmvgroupnumber"; public static final String FIELD_SHORT_NAME = "fieldshortname"; public static final String FIELD_NAME = "fieldname"; public static final String FIELD_COLUMN_NAME = "fieldcolumnname"; public static final String FIELD_GROUP_NAME = "fieldgroupname"; public static final String FIELD_MV_GROUP_NAME = "fieldmvgroupname"; public static final String FIELD_JUSTIFICATION = "fieldjustification"; public static final String FIELD_TYPE = "fieldtype"; public static final String FIELD_SINGLE_OR_MULTI = "singleormulti"; public static final String DELIMITER_COLUMN_TYPE = "#"; public static final String COLUMN_FK_ROW = "FK_ROW"; public static final String COLUMN_XPK_ROW = "XPK_ROW"; public static final int SQL_VIEW_MULTI = 1; public static final int SQL_VIEW_SINGLE = 2; public static final String DATA_TYPE_XSD_NUMERIC = "numeric"; public static final String DATA_TYPE_XSD_DECIMAL = "decimal"; public static final String DATA_TYPE_XSD_STRING = "string"; public static final String DATA_TYPE_XSD_DATE = "date"; /** * application configuration properties */ public static final String PROP_LOG4J_CONFIG_FILE = "log4j_config"; public static final String PROP_MAIN_VIEW_NAME_SINGLE = "view_name_single"; public static final String PROP_MAIN_VIEW_NAME_MULTI = "view_name_multi"; public static final String PROP_MAIN_TABLE_NAME = "main_edh_table_name"; public static final String PROP_SUB_TABLE_PREFIX = "sub_table_prefix"; public static final String PROP_SOURCE_XSD_FULLNAME = "source_xsd_fullname"; public static final String PROP_RESULTS_PATH = "results_path"; public static final String PROP_NEW_XSD_FILENAME = "new_xsd_filename"; public static final String PROP_CSV_FILENAME = "csv_filename"; /** * static holders for application-level utilities */ private static Properties appProps; private static Logger appLogger; /** * */ private StringBuffer sqlViewColumnsSingle = null; private StringBuffer sqlViewSelectSingle = null; private StringBuffer columnsCSV = null; private ArrayList<String> singleValueTableColumns = null; private HashMap<String, String> multiValueTablesSQL = null; private HashMap<Object, HashMap<String, Object>> groupAttrs = null; public XSDTransformer(String appConfigPropsPath) { if (appProps == null) { appProps = new Properties(); } try { init(appConfigPropsPath); } catch (Exception e) { appLogger.error(e.getMessage()); } } /** * initialization */ private void init(String appConfigPropsPath) throws Exception { // init the properties object FileReader in = new FileReader(appConfigPropsPath); appProps.load(in); // init the logger if ((appProps.getProperty(XSDTransformer.PROP_LOG4J_CONFIG_FILE) != null) && (!appProps.getProperty(XSDTransformer.PROP_LOG4J_CONFIG_FILE).equals(""))) { PropertyConfigurator.configure(appProps.getProperty(XSDTransformer.PROP_LOG4J_CONFIG_FILE)); if (appLogger == null) { appLogger = Logger.getLogger(XSDTransformer.class.getName()); } appLogger.info("Application initialization successful."); } sqlViewColumnsSingle = new StringBuffer(); sqlViewSelectSingle = new StringBuffer(); columnsCSV = new StringBuffer(XSDTransformer.FIELD_TAG + "," + XSDTransformer.FIELD_NUMBER + "," + XSDTransformer.FIELD_DATA_TYPE + "," + XSDTransformer.FIELD_FMT + "," + XSDTransformer.FIELD_LEN + "," + XSDTransformer.FIELD_INPUT_LEN + "," + XSDTransformer.FIELD_GROUP_NUMBER + "," + XSDTransformer.FIELD_MV_GROUP_NUMBER + "," + XSDTransformer.FIELD_SHORT_NAME + "," + XSDTransformer.FIELD_NAME + "," + XSDTransformer.FIELD_COLUMN_NAME + "," + XSDTransformer.FIELD_GROUP_NAME + "," + XSDTransformer.FIELD_MV_GROUP_NAME + "," + XSDTransformer.FIELD_JUSTIFICATION + "," + XSDTransformer.FIELD_TYPE + "," + XSDTransformer.FIELD_SINGLE_OR_MULTI + System.getProperty("line.separator")); singleValueTableColumns = new ArrayList<String>(); singleValueTableColumns.add(XSDTransformer.COLUMN_XPK_ROW + XSDTransformer.DELIMITER_COLUMN_TYPE + XSDTransformer.DATA_TYPE_XSD_NUMERIC); multiValueTablesSQL = new HashMap<String, String>(); groupAttrs = new HashMap<Object, HashMap<String, Object>>(); } /** * initialize the <code>DocumentBuilder</code> and read the XSD file * * @param docPath * @return the <code>Document</code> object representing the read XSD file */ private Document retrieveDoc(String docPath) { Document xsdDoc = null; File file = new File(docPath); try { DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder(); xsdDoc = builder.parse(file); } catch (Exception e) { appLogger.error(e.getMessage()); } return xsdDoc; } /** * perform the iteration/modification on the document * iterate to the level which contains all the elements (Single-Value, and Groups) and start processing each * * @param xsdDoc * @return */ private Document transformDoc(Document xsdDoc) { ArrayList<Object> newElementsList = new ArrayList<Object>(); HashMap<String, Object> docAttrMap = new HashMap<String, Object>(); Element sequenceElement = null; Element schemaElement = null; // get document's root element NodeList nodes = xsdDoc.getChildNodes(); for (int i = 0; i < nodes.getLength(); i++) { if (XSDTransformer.TAG_SCHEMA.equals(nodes.item(i).getNodeName())) { schemaElement = (Element) nodes.item(i); break; } } // process the document (change single-value elements, collect list of new elements to be added) for (int i1 = 0; i1 < schemaElement.getChildNodes().getLength(); i1++) { Node childLevel1 = (Node) schemaElement.getChildNodes().item(i1); // <ComplexType> element if (childLevel1.getNodeName().equals(XSDTransformer.TAG_COMPLEX_TYPE)) { // first, get the main attributes and put it in the csv file for (int i6 = 0; i6 < childLevel1.getChildNodes().getLength(); i6++) { Node child6 = childLevel1.getChildNodes().item(i6); if (XSDTransformer.TAG_ATTRIBUTE.equals(child6.getNodeName())) { if (child6.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME) != null) { String attrName = child6.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME).getNodeValue(); if (((Element) child6).getElementsByTagName(XSDTransformer.TAG_SIMPLE_TYPE).getLength() != 0) { Node simpleTypeElement = ((Element) child6).getElementsByTagName(XSDTransformer.TAG_SIMPLE_TYPE) .item(0); if (((Element) simpleTypeElement).getElementsByTagName(XSDTransformer.TAG_RESTRICTION).getLength() != 0) { Node restrictionElement = ((Element) simpleTypeElement).getElementsByTagName( XSDTransformer.TAG_RESTRICTION).item(0); if (((Element) restrictionElement).getElementsByTagName(XSDTransformer.TAG_MAX_LENGTH).getLength() != 0) { Node maxLengthElement = ((Element) restrictionElement).getElementsByTagName( XSDTransformer.TAG_MAX_LENGTH).item(0); HashMap<String, String> elementProperties = new HashMap<String, String>(); elementProperties.put(XSDTransformer.FIELD_TAG, attrName); elementProperties.put(XSDTransformer.FIELD_NUMBER, "0"); elementProperties.put(XSDTransformer.FIELD_DATA_TYPE, XSDTransformer.DATA_TYPE_XSD_STRING); elementProperties.put(XSDTransformer.FIELD_FMT, ""); elementProperties.put(XSDTransformer.FIELD_NAME, attrName); elementProperties.put(XSDTransformer.FIELD_SHORT_NAME, attrName); elementProperties.put(XSDTransformer.FIELD_COLUMN_NAME, attrName); elementProperties.put(XSDTransformer.FIELD_SINGLE_OR_MULTI, "S"); elementProperties.put(XSDTransformer.FIELD_LEN, maxLengthElement.getAttributes().getNamedItem( XSDTransformer.ATTR_VALUE).getNodeValue()); elementProperties.put(XSDTransformer.FIELD_INPUT_LEN, maxLengthElement.getAttributes() .getNamedItem(XSDTransformer.ATTR_VALUE).getNodeValue()); constructElementRow(elementProperties); // add the attribute as a column in the single-value table singleValueTableColumns.add(attrName + XSDTransformer.DELIMITER_COLUMN_TYPE + XSDTransformer.DATA_TYPE_XSD_STRING + XSDTransformer.DELIMITER_COLUMN_TYPE + maxLengthElement.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE).getNodeValue()); // add the attribute as a column in the single-values view sqlViewColumnsSingle.append(System.getProperty("line.separator") + attrName + ", "); sqlViewSelectSingle.append(System.getProperty("line.separator") + attrName + ", "); appLogger.debug("added attribute: " + attrName); } } } } } } // now, loop on the elements and process them for (int i2 = 0; i2 < childLevel1.getChildNodes().getLength(); i2++) { Node childLevel2 = (Node) childLevel1.getChildNodes().item(i2); // <Sequence> element if (childLevel2.getNodeName().equals(XSDTransformer.TAG_SEQUENCE)) { sequenceElement = (Element) childLevel2; for (int i3 = 0; i3 < childLevel2.getChildNodes().getLength(); i3++) { Node childLevel3 = (Node) childLevel2.getChildNodes().item(i3); // <Element> element if (childLevel3.getNodeName().equals(XSDTransformer.TAG_ELEMENT)) { // check if single element or group if (isGroup(childLevel3)) { processGroup(childLevel3, true, null, docAttrMap, xsdDoc, newElementsList); // insert a new comment node with the contents of the group tag sequenceElement.insertBefore(xsdDoc.createComment(serialize(childLevel3)), childLevel3); // remove the group tag sequenceElement.removeChild(childLevel3); } else { processElement(childLevel3); } } } } } } } // add new elements // this step should be after finishing processing the whole document. when you add new elements to the document // while you are working on it, those new elements will be included in the processing. We don't need that! for (int i = 0; i < newElementsList.size(); i++) { sequenceElement.appendChild((Element) newElementsList.get(i)); } // write the new required attributes to the schema element Iterator<String> attrIter = docAttrMap.keySet().iterator(); while(attrIter.hasNext()) { Element attr = (Element) docAttrMap.get(attrIter.next()); Element newAttrElement = xsdDoc.createElement(XSDTransformer.TAG_ATTRIBUTE); appLogger.debug("appending attr. [" + attr.getAttribute(XSDTransformer.ATTR_NAME) + "]..."); newAttrElement.setAttribute(XSDTransformer.ATTR_NAME, attr.getAttribute(XSDTransformer.ATTR_NAME)); newAttrElement.setAttribute(XSDTransformer.ATTR_TYPE, attr.getAttribute(XSDTransformer.ATTR_TYPE)); schemaElement.appendChild(newAttrElement); } return xsdDoc; } /** * check if the <code>element</code> sent is single-value element or group * element. the comparison depends on the children of the element. if found one of type * <code>ComplexType</code> then it's a group element, and if of type * <code>SimpleType</code> then it's a single-value element * * @param element * @return <code>true</code> if the element is a group element, * <code>false</code> otherwise */ private boolean isGroup(Node element) { for (int i = 0; i < element.getChildNodes().getLength(); i++) { Node child = (Node) element.getChildNodes().item(i); if (child.getNodeName().equals(XSDTransformer.TAG_COMPLEX_TYPE)) { // found a ComplexType child (Group element) return true; } else if (child.getNodeName().equals(XSDTransformer.TAG_SIMPLE_TYPE)) { // found a SimpleType child (Single-Value element) return false; } } return false; /* String attrName = null; if (element.getAttributes() != null) { Node attribute = element.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME); if (attribute != null) { attrName = attribute.getNodeValue(); } } if (attrName.startsWith("g")) { // group element return true; } else { // single element return false; } */ } /** * process a group element. recursively, process groups till no more group elements are found * * @param element * @param isFirstLevelGroup * @param attrMap * @param docAttrMap * @param xsdDoc * @param newElementsList */ private void processGroup(Node element, boolean isFirstLevelGroup, Node parentGroup, HashMap<String, Object> docAttrMap, Document xsdDoc, ArrayList<Object> newElementsList) { String elementName = null; HashMap<String, Object> groupAttrMap = new HashMap<String, Object>(); HashMap<String, Object> parentGroupAttrMap = new HashMap<String, Object>(); if (element.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME) != null) { elementName = element.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME).getNodeValue(); } appLogger.debug("processing group [" + elementName + "]..."); // get the attributes if a non-first-level-group // attributes are: groups's own attributes + parent group's attributes if (!isFirstLevelGroup) { // get the current element (group) attributes for (int i1 = 0; i1 < element.getChildNodes().getLength(); i1++) { if (XSDTransformer.TAG_COMPLEX_TYPE.equals(element.getChildNodes().item(i1).getNodeName())) { Node complexTypeNode = element.getChildNodes().item(i1); for (int i2 = 0; i2 < complexTypeNode.getChildNodes().getLength(); i2++) { if (XSDTransformer.TAG_ATTRIBUTE.equals(complexTypeNode.getChildNodes().item(i2).getNodeName())) { appLogger.debug("add group attr: " + ((Element) complexTypeNode.getChildNodes().item(i2)).getAttribute(XSDTransformer.ATTR_NAME)); groupAttrMap.put(((Element) complexTypeNode.getChildNodes().item(i2)).getAttribute(XSDTransformer.ATTR_NAME), complexTypeNode.getChildNodes().item(i2)); docAttrMap.put(((Element) complexTypeNode.getChildNodes().item(i2)).getAttribute(XSDTransformer.ATTR_NAME), complexTypeNode.getChildNodes().item(i2)); } } } } // now, get the parent's attributes parentGroupAttrMap = groupAttrs.get(parentGroup); if (parentGroupAttrMap != null) { Iterator<String> iter = parentGroupAttrMap.keySet().iterator(); while (iter.hasNext()) { String attrName = iter.next(); groupAttrMap.put(attrName, parentGroupAttrMap.get(attrName)); } } // put the attributes in the attributes map groupAttrs.put(element, groupAttrMap); } for (int i = 0; i < element.getChildNodes().getLength(); i++) { Node childLevel1 = (Node) element.getChildNodes().item(i); if (childLevel1.getNodeName().equals(XSDTransformer.TAG_COMPLEX_TYPE)) { for (int j = 0; j < childLevel1.getChildNodes().getLength(); j++) { Node childLevel2 = (Node) childLevel1.getChildNodes().item(j); if (childLevel2.getNodeName().equals(XSDTransformer.TAG_SEQUENCE)) { for (int k = 0; k < childLevel2.getChildNodes().getLength(); k++) { Node childLevel3 = (Node) childLevel2.getChildNodes().item(k); if (childLevel3.getNodeName().equals(XSDTransformer.TAG_ELEMENT)) { // check if single element or group if (isGroup(childLevel3)) { // another group element.. // unfortunately, a recursion is // needed here!!! :-( processGroup(childLevel3, false, element, docAttrMap, xsdDoc, newElementsList); } else { // reached a single-value element.. copy it under the // main sequence and apply the name-shorname // replacement processGroupElement(childLevel3, element, isFirstLevelGroup, xsdDoc, newElementsList); } } } } } } } appLogger.debug("finished processing group [" + elementName + "]."); } /** * process the sent <code>element</code> to extract/modify required * information: * 1. replace the <code>name</code> attribute with the <code>shortname</code>. * * @param element */ private void processElement(Node element) { String fieldShortName = null; String fieldColumnName = null; String fieldDataType = null; String fieldFormat = null; String fieldInputLength = null; String elementName = null; HashMap<String, String> elementProperties = new HashMap<String, String>(); if (element.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME) != null) { elementName = element.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME).getNodeValue(); } appLogger.debug("processing element [" + elementName + "]..."); for (int i = 0; i < element.getChildNodes().getLength(); i++) { Node childLevel1 = (Node) element.getChildNodes().item(i); if (childLevel1.getNodeName().equals(XSDTransformer.TAG_ANNOTATION)) { for (int j = 0; j < childLevel1.getChildNodes().getLength(); j++) { Node childLevel2 = (Node) childLevel1.getChildNodes().item(j); if (childLevel2.getNodeName().equals(XSDTransformer.TAG_APP_INFO)) { for (int k = 0; k < childLevel2.getChildNodes().getLength(); k++) { Node childLevel3 = (Node) childLevel2.getChildNodes().item(k); if (childLevel3.getNodeName().equals(XSDTransformer.TAG_HAS_PROPERTY)) { if (childLevel3.getAttributes() != null) { String attrName = null; Node attribute = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME); if (attribute != null) { attrName = attribute.getNodeValue(); elementProperties.put(attrName, childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue()); if (attrName.equals(XSDTransformer.FIELD_SHORT_NAME)) { fieldShortName = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue(); } else if (attrName.equals(XSDTransformer.FIELD_COLUMN_NAME)) { fieldColumnName = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue(); } else if (attrName.equals(XSDTransformer.FIELD_DATA_TYPE)) { fieldDataType = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue(); } else if (attrName.equals(XSDTransformer.FIELD_FMT)) { fieldFormat = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue(); } else if (attrName.equals(XSDTransformer.FIELD_INPUT_LEN)) { fieldInputLength = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue(); } } } } } } } } } if (element.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME) != null) { element.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME).setNodeValue(fieldShortName); } sqlViewColumnsSingle.append(System.getProperty("line.separator") + fieldColumnName + ", "); sqlViewSelectSingle.append(System.getProperty("line.separator") + fieldShortName + ", "); elementProperties.put(XSDTransformer.FIELD_SINGLE_OR_MULTI, "S"); constructElementRow(elementProperties); singleValueTableColumns.add(fieldShortName + XSDTransformer.DELIMITER_COLUMN_TYPE + fieldDataType + fieldFormat + XSDTransformer.DELIMITER_COLUMN_TYPE + fieldInputLength); appLogger.debug("finished processing element [" + elementName + "]."); } /** * process the sent <code>element</code> to extract/modify required * information: * 1. copy the element under the main sequence * 2. replace the <code>name</code> attribute with the <code>shortname</code>. * 3. add the attributes of the parent groups (if non-first-level-group) * * @param element */ private void processGroupElement(Node element, Node parentGroup, boolean isFirstLevelGroup, Document xsdDoc, ArrayList<Object> newElementsList) { String fieldShortName = null; String fieldColumnName = null; String fieldDataType = null; String fieldFormat = null; String fieldInputLength = null; String elementName = null; Element newElement = null; HashMap<String, String> elementProperties = new HashMap<String, String>(); ArrayList<String> tableColumns = new ArrayList<String>(); HashMap<String, Object> groupAttrMap = null; if (element.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME) != null) { elementName = element.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME).getNodeValue(); } appLogger.debug("processing element [" + elementName + "]..."); // 1. copy the element newElement = (Element) element.cloneNode(true); newElement.setAttribute(XSDTransformer.ATTR_MAX_OCCURS, "unbounded"); // 2. if non-first-level-group, replace the element's SimpleType tag with a ComplexType tag if (!isFirstLevelGroup) { if (((Element) newElement).getElementsByTagName(XSDTransformer.TAG_SIMPLE_TYPE).getLength() != 0) { // there should be only one tag of SimpleType Node simpleTypeNode = ((Element) newElement).getElementsByTagName(XSDTransformer.TAG_SIMPLE_TYPE).item(0); // create the new ComplexType element Element complexTypeNode = xsdDoc.createElement(XSDTransformer.TAG_COMPLEX_TYPE); complexTypeNode.setAttribute(XSDTransformer.ATTR_MIXED, "true"); // get the list of attributes for the parent group groupAttrMap = groupAttrs.get(parentGroup); Iterator<String> attrIter = groupAttrMap.keySet().iterator(); while(attrIter.hasNext()) { Element attr = (Element) groupAttrMap.get(attrIter.next()); Element newAttrElement = xsdDoc.createElement(XSDTransformer.TAG_ATTRIBUTE); appLogger.debug("adding attr. [" + attr.getAttribute(XSDTransformer.ATTR_NAME) + "]..."); newAttrElement.setAttribute(XSDTransformer.ATTR_REF, attr.getAttribute(XSDTransformer.ATTR_NAME)); newAttrElement.setAttribute(XSDTransformer.ATTR_USE, "optional"); complexTypeNode.appendChild(newAttrElement); } // replace the old SimpleType node with the new ComplexType node newElement.replaceChild(complexTypeNode, simpleTypeNode); } } // 3. replace the name with the shortname in the new element for (int i = 0; i < newElement.getChildNodes().getLength(); i++) { Node childLevel1 = (Node) newElement.getChildNodes().item(i); if (childLevel1.getNodeName().equals(XSDTransformer.TAG_ANNOTATION)) { for (int j = 0; j < childLevel1.getChildNodes().getLength(); j++) { Node childLevel2 = (Node) childLevel1.getChildNodes().item(j); if (childLevel2.getNodeName().equals(XSDTransformer.TAG_APP_INFO)) { for (int k = 0; k < childLevel2.getChildNodes().getLength(); k++) { Node childLevel3 = (Node) childLevel2.getChildNodes().item(k); if (childLevel3.getNodeName().equals(XSDTransformer.TAG_HAS_PROPERTY)) { if (childLevel3.getAttributes() != null) { String attrName = null; Node attribute = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_NAME); if (attribute != null) { attrName = attribute.getNodeValue(); elementProperties.put(attrName, childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue()); if (attrName.equals(XSDTransformer.FIELD_SHORT_NAME)) { fieldShortName = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue(); } else if (attrName.equals(XSDTransformer.FIELD_COLUMN_NAME)) { fieldColumnName = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue(); } else if (attrName.equals(XSDTransformer.FIELD_DATA_TYPE)) { fieldDataType = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE) .getNodeValue(); } else if (attrName.equals(XSDTransformer.FIELD_FMT)) { fieldFormat = childLevel3.getAttributes().getNamedItem(XSDTransformer.ATTR_VALUE)

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  • Cisco ASA and static IPv6 tunnel endpoint?

    - by Martijn Heemels
    I recently installed a Cisco ASA 5505 firewall on the edge of our LAN. The setup is simple: Internet <-- ASA <-- LAN I would like provide the hosts in the LAN with IPv6 connectivity by setting up a 6in4 tunnel to SixXS. It would be nice to have the ASA as tunnel endpoint so it can firewall both IPv4 and IPv6 traffic. Unfortunately the ASA apparently can't create a tunnel itself, and can't port-forward protocol 41 traffic, so I believe I would have to do one of the following instead: Set up a host with it's own IP outside the firewall, and have that function as tunnel-endpoint. The ASA can then firewall and route the v6 subnet to the LAN. Set up a host inside the firewall that functions as endpoint, separated via vlan or whatever, and loop the traffic back into the ASA where it can be firewalled and routed. This seems contrived, but would allow me to use a VM instead of a physical machine as endpoint. Any other way? What would you suggest is the optimal way to set this up? P.S. I do have a spare public IP address available if needed, and can spin up another VM in our VMware infrastructure.

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  • New Static Website with Hosted DNS alternating 502, 503 and Page Does Not Exist Errors

    - by Dave
    This has become an increasingly frustrating ordeal. I'm mostly a web developer, so forgive me if I am using improper terminology here. I have a client that had purchased a domain at JustHost. We built him a website and have it on our own server space. Now, I'm mostly used to dealing with godaddy and it is simple enough to manage dns records and point the A record to our server IP, where Apache on our end deals with the domains via name-based virtual hosts. But for some reason, in setting this up with JustHost, when attempting to go to the domain name, I either get a 502 or 503 error or "webpage does not exist". Now, I know that the basic functionality of the webpage must be working because I can access the the index etc straight through my servers www data (IE [server-ip]/website_folder). I was on the phone with technical support for over three hours yesterday with justhost and the best I could get was "That's really weird..." I've checked my logs and there doesn't seem to be anything coming through to my end. Does anybody have an idea of whats going on here? I would love for it to be a problem on my end, because justhost doesn't seem capable of helping further. Any help is greatly appreciated, thanks. I forgot to mention that we have several other sites up and running and completely accessible.

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  • Cisco ASA 5505 network route for static IP hosts

    - by TheCapn
    I've configured my internal VLAN using the most basic settings where ports 1-7 are assigned from a pool of addresses in the range 192.168.15.5 - 192.168.15.36. These hosts are given access to the internet and it works great. What I'm trying to set up now is allowing users who are connected to the device and specify their IP (say I connect and request 192.168.15.45) are given internet access and can still work alongside DHCP hosts. Those with a DHCP assigned address are blocked from the internet. Mostly the issue resides in that I am very new to working with the device. I feel that the solution is easy but I'm not looking in the right spots and don't have the correct terminology down to google it. Do I need to define access control lists? Group policies? a new VLAN? The rules that are set up seem to be specific to the entire /24 subnet but when I request a static IP outside of the DHCP range I get blocked from other hosts and the internet.

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  • C#: System.Lazy&lt;T&gt; and the Singleton Design Pattern

    - by James Michael Hare
    So we've all coded a Singleton at one time or another.  It's a really simple pattern and can be a slightly more elegant alternative to global variables.  Make no mistake, Singletons can be abused and are often over-used -- but occasionally you find a Singleton is the most elegant solution. For those of you not familiar with a Singleton, the basic Design Pattern is that a Singleton class is one where there is only ever one instance of the class created.  This means that constructors must be private to avoid users creating their own instances, and a static property (or method in languages without properties) is defined that returns a single static instance. 1: public class Singleton 2: { 3: // the single instance is defined in a static field 4: private static readonly Singleton _instance = new Singleton(); 5:  6: // constructor private so users can't instantiate on their own 7: private Singleton() 8: { 9: } 10:  11: // read-only property that returns the static field 12: public static Singleton Instance 13: { 14: get 15: { 16: return _instance; 17: } 18: } 19: } This is the most basic singleton, notice the key features: Static readonly field that contains the one and only instance. Constructor is private so it can only be called by the class itself. Static property that returns the single instance. Looks like it satisfies, right?  There's just one (potential) problem.  C# gives you no guarantee of when the static field _instance will be created.  This is because the C# standard simply states that classes (which are marked in the IL as BeforeFieldInit) can have their static fields initialized any time before the field is accessed.  This means that they may be initialized on first use, they may be initialized at some other time before, you can't be sure when. So what if you want to guarantee your instance is truly lazy.  That is, that it is only created on first call to Instance?  Well, there's a few ways to do this.  First we'll show the old ways, and then talk about how .Net 4.0's new System.Lazy<T> type can help make the lazy-Singleton cleaner. Obviously, we could take on the lazy construction ourselves, but being that our Singleton may be accessed by many different threads, we'd need to lock it down. 1: public class LazySingleton1 2: { 3: // lock for thread-safety laziness 4: private static readonly object _mutex = new object(); 5:  6: // static field to hold single instance 7: private static LazySingleton1 _instance = null; 8:  9: // property that does some locking and then creates on first call 10: public static LazySingleton1 Instance 11: { 12: get 13: { 14: if (_instance == null) 15: { 16: lock (_mutex) 17: { 18: if (_instance == null) 19: { 20: _instance = new LazySingleton1(); 21: } 22: } 23: } 24:  25: return _instance; 26: } 27: } 28:  29: private LazySingleton1() 30: { 31: } 32: } This is a standard double-check algorithm so that you don't lock if the instance has already been created.  However, because it's possible two threads can go through the first if at the same time the first time back in, you need to check again after the lock is acquired to avoid creating two instances. Pretty straightforward, but ugly as all heck.  Well, you could also take advantage of the C# standard's BeforeFieldInit and define your class with a static constructor.  It need not have a body, just the presence of the static constructor will remove the BeforeFieldInit attribute on the class and guarantee that no fields are initialized until the first static field, property, or method is called.   1: public class LazySingleton2 2: { 3: // because of the static constructor, this won't get created until first use 4: private static readonly LazySingleton2 _instance = new LazySingleton2(); 5:  6: // Returns the singleton instance using lazy-instantiation 7: public static LazySingleton2 Instance 8: { 9: get { return _instance; } 10: } 11:  12: // private to prevent direct instantiation 13: private LazySingleton2() 14: { 15: } 16:  17: // removes BeforeFieldInit on class so static fields not 18: // initialized before they are used 19: static LazySingleton2() 20: { 21: } 22: } Now, while this works perfectly, I hate it.  Why?  Because it's relying on a non-obvious trick of the IL to guarantee laziness.  Just looking at this code, you'd have no idea that it's doing what it's doing.  Worse yet, you may decide that the empty static constructor serves no purpose and delete it (which removes your lazy guarantee).  Worse-worse yet, they may alter the rules around BeforeFieldInit in the future which could change this. So, what do I propose instead?  .Net 4.0 adds the System.Lazy type which guarantees thread-safe lazy-construction.  Using System.Lazy<T>, we get: 1: public class LazySingleton3 2: { 3: // static holder for instance, need to use lambda to construct since constructor private 4: private static readonly Lazy<LazySingleton3> _instance 5: = new Lazy<LazySingleton3>(() => new LazySingleton3()); 6:  7: // private to prevent direct instantiation. 8: private LazySingleton3() 9: { 10: } 11:  12: // accessor for instance 13: public static LazySingleton3 Instance 14: { 15: get 16: { 17: return _instance.Value; 18: } 19: } 20: } Note, you need your lambda to call the private constructor as Lazy's default constructor can only call public constructors of the type passed in (which we can't have by definition of a Singleton).  But, because the lambda is defined inside our type, it has access to the private members so it's perfect. Note how the Lazy<T> makes it obvious what you're doing (lazy construction), instead of relying on an IL generation side-effect.  This way, it's more maintainable.  Lazy<T> has many other uses as well, obviously, but I really love how elegant and readable it makes the lazy Singleton.

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