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• Association Mapping Details confusion?

  - by AaronLS

  I have never understood why the associations in EntityFramework look the way they do in the Mapping Details window. When I select the line between 2 tables for an association, for example FK_ApplicationSectionsNodes_FormItems, it shows this: Association Maps to ApplicationSectionNodes FormItems (key symbol) FormItemId:Int32 <--> FormItemId:int ApplicationSectionNodes (key symbol) NodeId:Int32 <--> (key symbol) NodeId : int Fortunately this one was create automatically for me based on the foreign key constraints in my database, but whenever no constraints exist, I have a hard to creating associations manually(when the database doesn't have a diagram setup) because I don't understand the mapping details for associations. FormItems table has a primary key identity column FormItemId, and ApplicationSectionNodes contains a FormItemId column that is the foreign key and has NodeId as a primary key identity column. What really makes no sense to me is why the association has anything listed about the NodeId, when NodeId doesn't have anything to do with the foreign key relationship? (It's even more confusing with self referencing relationships, but maybe if I could understand the above case I'd have a better handle). CREATE TABLE [dbo].[ApplicationSectionNodes]( [NodeID] [int] IDENTITY(1,1) NOT NULL, [OutlineText] [varchar](5000) NULL, [ParentNodeID] [int] NULL, [FormItemId] [int] NULL, CONSTRAINT [PK_ApplicationSectionNodes] PRIMARY KEY CLUSTERED ( [NodeID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY], CONSTRAINT [UQ_ApplicationSectionNodesFormItemId] UNIQUE NONCLUSTERED ( [FormItemId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[ApplicationSectionNodes] WITH NOCHECK ADD CONSTRAINT [FK_ApplicationSectionNodes_ApplicationSectionNodes] FOREIGN KEY([ParentNodeID]) REFERENCES [dbo].[ApplicationSectionNodes] ([NodeID]) GO ALTER TABLE [dbo].[ApplicationSectionNodes] NOCHECK CONSTRAINT [FK_ApplicationSectionNodes_ApplicationSectionNodes] GO ALTER TABLE [dbo].[ApplicationSectionNodes] WITH NOCHECK ADD CONSTRAINT [FK_ApplicationSectionNodes_FormItems] FOREIGN KEY([FormItemId]) REFERENCES [dbo].[FormItems] ([FormItemId]) GO ALTER TABLE [dbo].[ApplicationSectionNodes] NOCHECK CONSTRAINT [FK_ApplicationSectionNodes_FormItems] GO FormItems Table: CREATE TABLE [dbo].[FormItems]( [FormItemId] [int] IDENTITY(1,1) NOT NULL, [FormItemType] [int] NULL, CONSTRAINT [PK_FormItems] PRIMARY KEY CLUSTERED ( [FormItemId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[FormItems] WITH NOCHECK ADD CONSTRAINT [FK_FormItems_FormItemTypes] FOREIGN KEY([FormItemType]) REFERENCES [dbo].[FormItemTypes] ([FormItemTypeId]) GO ALTER TABLE [dbo].[FormItems] NOCHECK CONSTRAINT [FK_FormItems_FormItemTypes] GO

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• iOS Switching an embedded view in storyboard

  - by Coyote6

  I have been trying to figure this out all day and I know it should be able to be done, but being new to iOS development using Objective-C and not Appcelerator I'm having newbie issues. What I am trying to accomplish is to have an embedded view in one of my other views, but to be able to switch which view is embedded through programming. I am using storyboards. When I tried to use the view container it displays the attached view, but I cannot attach multiple views to the container in the storyboard. I drew up an image, but to my annoyance I cannot post an image on here because I don't have enough "rep" points, so I posted it on my site: http://static.c6gx.com/images/iphone-embedded-views-diagram.jpg Later on I would like what appears to be a push segue, within that view container, but first I just want to be able to switch between embedded view 1, 2, 3, etc. Am I supposed to be using a view container to accomplish this, or some other type of controller? Then how would I call the transition to change the view? Thank you for any help you can provide.

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• How can I use SQL to select duplicate records, along with counts of related items?

  - by mipadi

  I know the title of this question is a bit confusing, so bear with me. :) I have a (MySQL) database with a Person record. A Person also has a slug field. Unfortunately, slug fields are not unique. There are a number of duplicate records, i.e., the records have different IDs but the same first name, last name, and slug. A Person may also have 0 or more associated articles, blog entries, and podcast episodes. If that's confusing, here's a diagram of the structure: I would like to produce a list of records that match this criteria: duplicate records (i.e., same slug field) for people who also have at least 1 article, blog entry, or podcast episode. I have a SQL query that will list all records with the same slug fields: SELECT id, first_name, last_name, slug, COUNT(slug) AS person_records FROM people_person GROUP BY slug HAVING (COUNT(slug) > 1) ORDER BY last_name, first_name, id; But this includes records for people that may not have at least 1 article, blog entry, or podcast. Can I tweak this to fit the second criteria?

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• Complex SQL design, help/advice needed

  - by eugeneK

  Hi, i have few questions for SQL gurus in here ... Briefly this is ads management system where user can define campaigns for different countries, categories, languages. I have few questions in mind so help me with what you can. Generally i'm using ASP.NET and i want to cache all result set of certain user once he asks for statistics for the first time, this way i will avoid large round-trips to server. any help is welcomed Click here for diagram with all details you need for my questions 1.Main issue of this application is to show to the user how many clicks/impressions were and how much money he spent on campaign. What is the easiest way to get this information for him? I will also include filtering by date, date ranges and few other params in this statistics table. 2.Other issue is what happens when user will try to edit campaign. Old campaign will die this means if user set 0.01$ as campaignPPU (pay-per-unit) and next day updates it to 0.05$ all will be reset to 0.05$. 3.If you could re-design some parts of table design so it would be more flexible and easier to modify, how would you do it? Thanks... sorry for so large job but it may interest some SQL guys in here

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• Rails - Scalable calculation model

  - by H O

  I currently have a calculation structure in my rails app that has models metric, operand and operation_type. Presently, the metric model has many operands, and can perform calculations based on the operation_type (e.g. sum, multiply, etc.), and each operand is defined as being right or left (i.e. so that if the operation is division, the numerator and denominator can be identified). Presently, an operand is always an attribute of some model, e.g. @customer.sales.selling_price.sum. In order to make this scalable, in need to allow an operand to be either an attribute of some kind, or the results of a previous operation, i.e. an operand can be a metric. I have included a diagram of how my models currently look: Can anyone assist me with the most elegant way of allowing an operand to be an actual operand, or another metric? Thanks! EDIT: It seems based on the only answer so far that perhaps polymorphic associations are the way to go on this, but the answer is so brief I have no idea how they could be used in this way - can anyone elaborate? EDIT 2: OK, I think I'm getting somewhere - essentially i presently have a metric, which has_many operands, and an operand has_many metrics. I need a polymorphic self join, where a metric can also have many metrics - do I need to call this something else, perhaps calculated_metrics, so that the metric model can use itself? That would leave me with a situation where a metric has_many operands, and a metric has many calculated_metrics.

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• Classical task-scheduling assignment

  - by Bruno

  I am working on a flight scheduling app (disclaimer: it's for a college project, so no code answers, please). Please read this question w/ a quantum of attention before answering as it has a lot of peculiarities :( First, some terminology issues: You have planes and flights, and you have to pair them up. For simplicity's sake, we'll assume that a plane is free as soon as the flight using it prior lands. Flights are seen as tasks: They have a duration They have dependencies They have an expected date/time for beginning Planes can be seen as resources to be used by tasks (or flights, in our terminology). Flights have a specific type of plane needed. e.g. flight 200 needs a plane of type B. Planes obviously are of one and only one specific type, e.g., Plane Airforce One is of type C. A "project" is the set of all the flights by an airline in a given time period. The functionality required is: Finding the shortest possible duration for a said project The earliest and latest possible start for a task (flight) The critical tasks, with basis on provided data, complete with identifiers of preceding tasks. Automatically pair up flights and planes, so as to get all flights paired up with a plane. (Note: the duration of flights is fixed) Get a Gantt diagram with the projects scheduling, in which all flights begin as early as possible, showing all previously referred data graphically (dependencies, time info, etc.) So the questions is: How in the world do I achieve this? Particularly: We are required to use a graph. What do the graph's edges and nodes respectively symbolise? Are we required to discard tasks to achieve the critical tasks set? If you could also recommend some algorithms for us to look up, that'd be great.

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• "Finding" an object instance of a known class?

  - by Sean C

  My first post here (anywhere for that matter!), re. Cocoa/Obj-C (I'm NOT up to speed on either, please be patient!). I hope I haven't missed the answer already, I did try to find it. I'm an old-school procedural dog (haven't done any programming since the mid 80's, so I probably just can't even learn new tricks), but OOP has my head spinning! My question is: is there any means at all to "discover/find/identify" an instance of an object of a known class, given that some OTHER unknown process instantiated it? eg. somthing that would accomplish this scenario: (id) anObj = [someTarget getMostRecentInstanceOf:[aKnownClass class]]; for that matter, "getAnyInstance" or "getAllInstances" might do the trick too. Background: I'm trying to write a plugin for a commercial application, so much of the heavy lifting is being done by the app, behind the scenes. I have the SDK & header files, I know what class the object is, and what method I need to call (it has only instance methods), I just can't identify the object for targetting. I've spent untold hours and days going over Apples documentation, tutorials and lots of example/sample code on the web (including here at Stack Overflow), and come up empty. Seems that everything requires a known target object to work, and I just don't have one. Since I may not be expressing my problem as clearly as needed, I've put up a web page, with diagram & working sample pages to illustrate: http://www.nulltime.com/svtest/index.html Any help or guidance will be appreciated! Thanks.

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• Zend, slow load, "waiting for response" for 20-80 seconds on local site

  - by Tony C.

  So I have several sites running under the same zend setup. All of the sites run pretty normally except one. Upon loading or reloading this one site, reguardless of which page your on (excluding the 404 page explanation later...) you get a serious pause before any content begins to download. Using firebugs net panel you can see that the first request which is www.(siteaddress).com.local you see a "waiting for response" bar (purple) that is going for anywhere from 20 to sometimes 80+ seconds and this isn't on a dev site, this is on a local site under localhost. What I've managed to figure out so far is that all the pages do this except my 404 page. The reason the 404 page doesn't succumb to this is because it uses a seperate controller (the error controller) and therefore bypasses much of the controller and functions the other parts of the site use. Using exit statements I've manged to figure out that the problem happens somewhere between my post dispatch and my main (top most) controllers Init function. If i exit in the main controllers init the page loads (then exits instantly, no wait). If i do the same in the pre or post dispatch the page waits the 20-80 seconds then exits. Is there a diagram or explanation somewhere or a way for me to find out what events fire inbetween the post dispatch and the main controllers init function? Or does anyone have any clue what might cause this? Any help would be greatly appreciated...

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• Coordinate system problem with the grid control

  - by Jason94

  In my WPF application im trying to visualize some temperature data. I have a list of temperatures for the 7 past days and want to make a point to point line diagram. My problem is with the different koordinatesystems and adjusting data to the grid. XAML: <Grid Height="167" HorizontalAlignment="Left" Margin="6,6,0,0" Name="grid1" VerticalAlignment="Bottom" Width="455" /> C# (draft): http://pastebin.com/6UWkMFj1 scale is a global variable that changes with a slider (1-10). How to i correct my application so the line always is centered? As it is now it starts out centeded but if i crank up the slider to 3-4 the line goes up and above the applicationwindow. I also would like to use the full height of the grid window not just a small piece like images below: http://img32.imageshack.us/i/002wtvu.jpg/ http://img691.imageshack.us/i/001tqco.jpg/ As you can see i have worked out my data so day 1 with temperature 62 F is lower then day 2 with temperature of 76 F but i have scaling issues and placementissues... could somebody straighten out my math? :-)

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• What does the Kernel Virtual Memory of each process contain?

  - by claws

  When say 3 programs (executables) are loaded into memory the layout might look something like this: I've following questions: Is the concept of Virtual Memory limited to user processes? Because, I am wondering where does the Operating System Kernel, Drivers live? How is its memory layout? I know its operating system specific make your choice (windows/linux). They say, on a 32 bit machine in a 4GB address space. Half of it (or more recently 1GB) is occupied by kernel. I can see in this diagram that "Kernel Virtual memory" is occupying 0xc0000000 - 0xffffffff (= 1 GB). Are they talking about this? or is it something else? Just want to confirm. What exactly does the Kernel Virtual Memory of each of these processes contain? What is its layout? When we do IPC we talk about shared memory. I don't see any memory shared between these processes. Where does it live? Resources (files, registries in windows) are global to all processes. So, the resource/file handle table must be in some global space. Which area would that be in? Where can I know more about this kernel side stuff.

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• Running Sitecore Production Site under a Virtual Directory

  - by danswain

  We are using Sitecore 6 on a Windows Server 2003 (32bit) dev machine. I know it's not recommended for the CMS editing site, but we've been told it is possible to get the front-end Sitecore websites to run from within a virtual directory. Here's the issue: we'd like to achieve what the below poor mans diagram shows. We have a website (.net 1.1) /WebSiteRoot (.net 1.1) | | |---- Custom .net 1.1 Web Application | |---- SiteCore frontend WebApplication (.net 2.0) | |---- Custom .net 2.0 WebApplication The Sitecore webApplication would contain the Sitecore pipeline in its web.config and we'd make use of the section to configure the virtual folder to allow for where our Sitecore app sits and point it to the appropriate place in the Content Tree. Is it possible to pull this off? This is just the customer facing website, there will be no CMS editing functionality on these servers, that will be done from a more standard Sitecore install inside the firewall on a different server. The errors we're encountering are centered around loading the the various config files in the App_Config folder. It seems to do a Server.MapPath on "/" initially (which is wrong for us) so we've tried putting absolute paths in the web.config and still no joy (I think there must be some hardcoded piece that looks for the Include directory). Any help would be greatly appreciated. Thanks

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• SINGLE SIGN ON SECURITY THREAT! FACEBOOK access_token broadcast in the open/clear

  - by MOKANA

  Subsequent to my posting there was a remark made that this was not really a question but I thought I did indeed postulate one. So that there is no ambiquity here is the question with a lead in: Since there is no data sent from Facebook during the Canvas Load process that is not at some point divulged, including the access_token, session and other data that could uniquely identify a user, does any one see any other way other than adding one more layer, i.e., a password, sent over the wire via HTTPS along with the access_toekn, that will insure unique untampered with security by the user? Using Wireshark I captured the local broadcast while loading my Canvas Application page. I was hugely surprised to see the access_token broadcast in the open, viewable for any one to see. This access_token is appended to any https call to the Facebook OpenGraph API. Using facebook as a single click log on has now raised huge concerns for me. It is stored in a session object in memory and the cookie is cleared upon app termination and after reviewing the FB.Init calls I saw a lot of HTTPS calls so I assumed the access_token was always encrypted. But last night I saw in the status bar a call from what was simply an http call that included the App ID so I felt I should sniff the Application Canvas load sequence. Today I did sniff the broadcast and in the attached image you can see that there are http calls with the access_token being broadcast in the open and clear for anyone to gain access to. Am I missing something, is what I am seeing and my interpretation really correct. If any one can sniff and get the access_token they can theorically make calls to the Graph API via https, even though the call back would still need to be the site established in Facebook's application set up. But what is truly a security threat is anyone using the access_token for access to their own site. I do not see the value of a single sign on via Facebook if the only thing that was established as secure was the access_token - becuase for what I can see it clearly is not secure. Access tokens that never have an expire date do not change. Access_tokens are different for every user, to access to another site could be held tight to just a single user, but compromising even a single user's data is unacceptable. http://www.creatingstory.com/images/InTheOpen.png Went back and did more research on this: FINDINGS: Went back an re ran the canvas application to verify that it was not any of my code that was not broadcasting. In this call: HTTP GET /connect.php/en_US/js/CacheData HTTP/1.1 The USER ID is clearly visible in the cookie. So USER_ID's are fully visible, but they are already. Anyone can go to pretty much any ones page and hover over the image and see the USER ID. So no big threat. APP_ID are also easily obtainable - but . . . http://www.creatingstory.com/images/InTheOpen2.png The above file clearly shows the FULL ACCESS TOKEN clearly in the OPEN via a Facebook initiated call. Am I wrong. TELL ME I AM WRONG because I want to be wrong about this. I have since reset my app secret so I am showing the real sniff of the Canvas Page being loaded. Additional data 02/20/2011: @ifaour - I appreciate the time you took to compile your response. I am pretty familiar with the OAuth process and have a pretty solid understanding of the signed_request unpacking and utilization of the access_token. I perform a substantial amount of my processing on the server and my Facebook server side flows are all complete and function without any flaw that I know of. The application secret is secure and never passed to the front end application and is also changed regularly. I am being as fanatical about security as I can be, knowing there is so much I don’t know that could come back and bite me. Two huge access_token issues: The issues concern the possible utilization of the access_token from the USER AGENT (browser). During the FB.INIT() process of the Facebook JavaScript SDK, a cookie is created as well as an object in memory called a session object. This object, along with the cookie contain the access_token, session, a secret, and uid and status of the connection. The session object is structured such that is supports both the new OAuth and the legacy flows. With OAuth, the access_token and status are pretty much al that is used in the session object. The first issue is that the access_token is used to make HTTPS calls to the GRAPH API. If you had the access_token, you could do this from any browser: https://graph.facebook.com/220439?access_token=... and it will return a ton of information about the user. So any one with the access token can gain access to a Facebook account. You can also make additional calls to any info the user has granted access to the application tied to the access_token. At first I thought that a call into the GRAPH had to have a Callback to the URL established in the App Setup, but I tested it as mentioned below and it will return info back right into the browser. Adding that callback feature would be a good idea I think, tightens things up a bit. The second issue is utilization of some unique private secured data that identifies the user to the third party data base, i.e., like in my case, I would use a single sign on to populate user information into my database using this unique secured data item (i.e., access_token which contains the APP ID, the USER ID, and a hashed with secret sequence). None of this is a problem on the server side. You get a signed_request, you unpack it with secret, make HTTPS calls, get HTTPS responses back. When a user has information entered via the USER AGENT(browser) that must be stored via a POST, this unique secured data element would be sent via HTTPS such that they are validated prior to data base insertion. However, If there is NO secured piece of unique data that is supplied via the single sign on process, then there is no way to guarantee unauthorized access. The access_token is the one piece of data that is utilized by Facebook to make the HTTPS calls into the GRAPH API. it is considered unique in regards to BOTH the USER and the APPLICATION and is initially secure via the signed_request packaging. If however, it is subsequently transmitted in the clear and if I can sniff the wire and obtain the access_token, then I can pretend to be the application and gain the information they have authorized the application to see. I tried the above example from a Safari and IE browser and it returned all of my information to me in the browser. In conclusion, the access_token is part of the signed_request and that is how the application initially obtains it. After OAuth authentication and authorization, i.e., the USER has logged into Facebook and then runs your app, the access_token is stored as mentioned above and I have sniffed it such that I see it stored in a Cookie that is transmitted over the wire, resulting in there being NO UNIQUE SECURED IDENTIFIABLE piece of information that can be used to support interaction with the database, or in other words, unless there were one more piece of secure data sent along with the access_token to my database, i.e., a password, I would not be able to discern if it is a legitimate call. Luckily I utilized secure AJAX via POST and the call has to come from the same domain, but I am sure there is a way to hijack that. I am totally open to any ideas on this topic on how to uniquely identify my USERS other than adding another layer (password) via this single sign on process or if someone would just share with me that I read and analyzed my data incorrectly and that the access_token is always secure over the wire. Mahalo nui loa in advance.

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• What is the "right" way to make a modular ASP.NET page?

  - by Wayne Werner

  Hi, I'm writing an internal program using ASP.NET (Visual Studio 2008). The basic premise is that folks will connect to the page through their web browser, put in some data (which will be validated and sanitized of course), click "submit" and then a query will be run on a database. I told you that story so I can tell you this story - I want to make my program modular for the likelihood that this program will be updated later on, and probably extended. My initial thought is to compile the database handler as a dll and then use its functionality on my page (see my little diagram). But I can't figure out how to hook the dll into my page - My Google-fu has failed which leads me to my questions: 1) Is creating a dll the "right" solution? If so, continue to question 2, if not, what should I be doing? Any resources/tutorial links would be appreciated. 2) How do I attach a dll? Visual Studio tells me I can't Imports from an .aspx page, and I've tried <%@ Import namespace="MyDllName" % and a few other variations, none of which worked. Thanks!

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• how are association, aggregation and composition written?

  - by ajsie

  i have read some posts about the differences between these 3 relationships and i think i get the point. i just wonder, are all these written the same when coding? question 1: all 3 are just a value of the object type in a instance variable? class A { public $b = '' public function __construct($object) { $this->b = $object // <-- could be a association, aggregation or a composition relation? } } question 2: does it have to be an instance variable or can it be a static one? class A { public static $b = '' // <-- nothing changed? public function __construct($object) { $this->b = $object } } question 3: is there a difference in where the object is created? i tend to think that composition object is created inside the object: class A { public $b = '' public function __construct() { $this->b = new Object // is created inside the object } } and aggregation/association is passed through a constructor or another method: class A { public $b = '' public function __construct($object) { // passed through a method $this->b = $object } } question 4: why/when is this important to know. do i have to comment an object inside another what relation its about or do you do it in an UML diagram? could someone shed a light on these questions. thanks!

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• Howto display or view encrypted data in encrypted form?

  - by Brian Gianforcaro

  In the Wikipedia Article on Block Cipher Modes they have a neat little diagram of an unencrypted image, the same image encrypted using ECB mode and another version of the same image encrypted using another method. At university I have developed my own implementation of DES (you can find it here) and we must demo our implementation in a presentation. I would like to display a similar example as shown above using our implementation. However most image files have header blocks associated with them, which when encrypting the file with our implementation, also get encrypted. So when you go to open them in an image viewer, they are assumed to be corrupted and can't be viewed. I was wondering if anybody new of a simple header-less image format which we could use to display these? Or if anyone had any idea's as to how the original creator of the images above achieved the above result? Any help would be appreciated, Thanks Note: I realise rolling your own cryptography library is stupid, and DES is considered broken, and ECB mode is very flawed for any useful cryptography, this was purely an academic exercise for school. So please, no lectures, I know the drill.

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• Looking for home networking hardware and software advice

  - by phobos7

  Note: I originally wrote this up in a blog post. I've removed any affiliate links that I put in my original post to ensure I don't annoy anybody. I've recently moved home and I now need to go to the trouble of sorting out my home network yet again. We had Virgin broadband in Hertford but you can't get Virgin in the street we've moved to so I've had to go with O2 Broadband. Normally I prefer to use my own hardward, and previously used the DLink DIR-655 router which was great, but in this situation I am using the O2 Wirelss Box III since I only have an old Netgear DG834PN Wireless G modem router and I'd rather be using Wireless N. Anyway, the place we have moved into has only one phone point in the hallway, has the best TV point in one room and the best place to put the TV and other entertainment stuff in yet another room. So, networking the house up for Internet and TV is required. The diagram below shows the things that I'll have in my home network but there are three points where I'm not quite sure what hardware to us. Wireless Access Point/Bridge, that acts only as a wireless to wire bridge and not an AP, that links up a Media Centre/PC and a couple of consoles to the network. I'm pretty much settled on us an Acer Aspire Revo R3600 as my media PC, probably with Ubuntu or Windows and XBMC installed. Wireless Access Point/Bridge, that acts only as a wireless to wire bridge and not an AP, that links up a device that can decode and stream TV from a TV aerial across the network. The device that is connected to 2). At the moment I'm considering a HDHomeRun by SiliconDust. At the moment I'm considering either the TP LINK TL-WA701ND 150Mbps Wireless Lite N Access Point (very cheap at Amazon) or the Netgear 5 GHz Wireless-N HD Access Point/Bridge. I'd love to get some insight into what you would do in my situation. What Wireless Access Point/Bridge should I put at points 1) and 2)? What device should I choose for point 3) that can decode and stream a TV signal? Is the Acer Aspire Revo R3600 a good choice? ![alt text][6] Note 2: I've also posted this question on AVForums.

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• VPN iptables Forwarding: Net-to-net

  - by Mike Holler

  I've tried to look elsewhere on this site but I couldn't find anything matching this problem. Right now I have an ipsec tunnel open between our local network and a remote network. Currently, the local box running Openswan ipsec with the tunnel open can ping the remote ipsec box and any of the other computers in the remote network. When logged into on of the remote computers, I can ping any box in our local network. That's what works, this is what doesn't: I can't ping any of the remote computers via a local machine that is not the ipsec box. Here's a diagram of our network: [local ipsec box] ----------\ \ [arbitrary local computer] --[local gateway/router] -- [internet] -- [remote ipsec box] -- [arbitrary remote computer] The local ipsec box and the arbitrary local computer have no direct contact, instead they communicate through the gateway/router. The router has been set up to forward requests from local computers for the remote subnet to the ipsec box. This works. The problem is the ipsec box doesn't forward anything. Whenever an arbitrary local computer pings something on the remote subnet, this is the response: [user@localhost ~]# ping 172.16.53.12 PING 172.16.53.12 (172.16.53.12) 56(84) bytes of data. From 10.31.14.16 icmp_seq=1 Destination Host Prohibited From 10.31.14.16 icmp_seq=2 Destination Host Prohibited From 10.31.14.16 icmp_seq=3 Destination Host Prohibited Here's the traceroute: [root@localhost ~]# traceroute 172.16.53.12 traceroute to 172.16.53.12 (172.16.53.12), 30 hops max, 60 byte packets 1 router.address.net (10.31.14.1) 0.374 ms 0.566 ms 0.651 ms 2 10.31.14.16 (10.31.14.16) 2.068 ms 2.081 ms 2.100 ms 3 10.31.14.16 (10.31.14.16) 2.132 ms !X 2.272 ms !X 2.312 ms !X That's the IP for our ipsec box it's reaching, but it's not being forwarded. On the IPSec box I have enabled IP Forwarding in /etc/sysctl.conf net.ipv4.ip_forward = 1 And I have tried to set up IPTables to forward: *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [759:71213] -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT -A INPUT -p tcp -m state --state NEW -m tcp --dport 25 -j ACCEPT -A INPUT -p udp -m state --state NEW -m udp --dport 500 -j ACCEPT -A INPUT -p udp -m state --state NEW -m udp --dport 4500 -j ACCEPT -A INPUT -m policy --dir in --pol ipsec -j ACCEPT -A INPUT -p esp -j ACCEPT -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -s 10.31.14.0/24 -d 172.16.53.0/24 -j ACCEPT -A FORWARD -m policy --dir in --pol ipsec -j ACCEPT -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT Am I missing a rule in IPTables? Is there something I forgot? NOTE: All the machines are running CentOS 6.x Edit: Note 2: eth1 is the only network interface on the local ipsec box.

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• Configuring VLAN's on two HP procurve switches

  - by pan

  Trying to route a new ISP (Microwave link) from one of my out buildings to my computer room and hence my firewall. Old ISP came direct into firewall. In the outbuilding the Microwave modem connects with cat5 to HP Procurve 2524 switch. Because this ISP is coming through my internal network, I plan on using a new vlan called "airspeed" only for this ISP traffic. Up until now I've just been using the Default_vlan on both HP switches (4108 + 2524). So far I've been unable to ping from my laptop to the ISP modem both of which are on the new vlan 2 ("Airspeed"). No traffic needs to cross from vlan 2 to vlan 1 so I've left the ports as untagged. I've used the subnet provide from my ISP as the new vlan 2 subnet. Can anybody see what I'm doing wrong here? I've added the configuration of both switch below. Rough diagram: Microwave modem (Gateway IP 77.75.00.49) | HP 2524 switch (port 24) | HP 2524 switch fibre link | HP 4108GL switch fibre link | HP 4108GL switch (port D1) | Laptop configured with IP 77.75.00.50 (for testing but will be connected to firewall) And my 4108GL config: ; J4865A Configuration Editor; Created on release #G.07.21 hostname "HP ProCurve Switch 4108GL" cdp run module 1 type J4864A module 2 type J4862B module 3 type J4862B module 4 type J4862B ip default-gateway 128.1.146.50 snmp-server community "public" Unrestricted snmp-server host 128.1.146.51 "public" Not-INFO snmp-server host 128.1.146.38 "public" vlan 1 name "DEFAULT_VLAN" untagged A1-A3,B1-B24,C1-C24,D2-D24 ip address 128.1.146.203 255.255.0.0 no untagged D1 exit vlan 2 name "Airspeed" untagged D1 ip address 77.75.00.51 255.255.255.248 exit Finally my 2524 config: ; J4813A Configuration Editor; Created on release #F.04.08 hostname "HP ProCurve Switch 2524" cdp run ip default-gateway 0.0.0.0 snmp-server community "public" Unrestricted snmp-server host 128.1.146.51 "public" Not-INFO snmp-server host 128.1.146.51 "public" snmp-server host 128.1.146.38 "public" vlan 1 name "DEFAULT_VLAN" untagged 1-23,25-26 no untagged 24 ip address 128.1.146.204 255.255.0.0 exit vlan 2 name "Airspeed" untagged 24 ip address 77.75.00.51 255.255.255.248 exit no aaa port-access authenticator active

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• Does a router have a receiving range?

  - by Aadit M Shah

  So my dad bought a TP-Link router (Model No. TL-WA7510N) which apparently has a transmitting range of 1km; and he believes that it also has a receiving range of 1km. So he's arguing with me that the router (which is a trans-receiver) can communicate with any device in the range of 1km whether or not that device has a transmitting range of 1km. To put it graphically: +----+ 1km +----+ | |------------------------------------------------->| | | TR | | TR | | | <----| | +----+ 100m+----+ So here's the problem: The two devices are 1km apart. The first device has a transmitting range of 1km. The second device only has a transmitting range of 100m. According to my dad the two devices can talk to each other. He says that the first device has a transmitting and a receiving range of 1km which means that it can both send data to devices 1km away and receive data from devices 1km away. To me this makes no sense. If the second device can only send data to devices 100m away then how can the first device catch the transmission? He further argues that for bidirectional communication both the sender and the reciver should have overlapping areas of transmission: According to him if two devices have an overlapping area of transmission then they can communicate. Here neither device has enough transmission power to reach the other. However they have enough receiving power to capture the transmission. Obviously this makes absolutely no sense to me. How can a device sense a transmission which hasn't even reached it yet and go out, capture it and bring it back it. To me a trans-receiver only has a transmission power. It has zero receiving power. Hence for two devices to be able to communicate bidirectionally, the diagram should look like: Hence, from my point of view, both the devices should have a transmission range far enough to reach the other for bidirectional communication to be possible; but no matter how much I try to explain to my dad he adamantly disagrees. So, to put an end to this debate once and for all, who is correct? Is there even such a thing as a receiving range? Can a device fetch a transmission that would otherwise never reach it? I would like a canonical answer on this.

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• Forwarding RDP via a Linux machine using iptables: Not working

  - by Nimmy Lebby

  I have a Linux machine and a Windows machine behind a router that implements NAT (the diagram might be overkill, but was fun to make): I am forwarding RDP port (3389) on the router to the Linux machine because I want to audit RDP connections. For the Linux machine to forward RDP traffic, I wrote these iptables rules: iptables -t nat -A PREROUTING -p tcp --dport 3389 -j DNAT --to-destination win-box iptables -A FORWARD -p tcp --dport 3389 -j ACCEPT The port is listening on the Windows machine: C:\Users\nimmy>netstat -a Active Connections Proto Local Address Foreign Address State (..snip..) TCP 0.0.0.0:3389 WIN-BOX:0 LISTENING (..snip..) And the port is forwarding on the Linux machine: # tcpdump port 3389 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes 01:33:11.451663 IP shieldsup.grc.com.56387 > linux-box.myapt.lan.ms-wbt-server: Flags [S], seq 94663035, win 8192, options [mss 1460], length 0 01:33:11.451846 IP shieldsup.grc.com.56387 > win-box.myapt.lan.ms-wbt-server: Flags [S], seq 94663035, win 8192, options [mss 1460], length 0 However, I am not getting any successful RDP connections from the outside. The port is not even responding: C:\Users\outside-nimmy>telnet example.com 3389 Connecting To example.com...Could not open connection to the host, on port 3389: Connect failed Any ideas? Update Per @Zhiqiang Ma, I looked at nf_conntrack proc file during a connection attempt and this is what I see (192.168.3.1 = linux-box, 192.168.3.5 = win-box): # cat /proc/net/nf_conntrack | grep 3389 ipv4 2 tcp 6 118 SYN_SENT src=4.79.142.206 dst=192.168.3.1 sport=43142 dport=3389 packets=6 bytes=264 [UNREPLIED] src=192.168.3.5 dst=4.79.142.206 sport=3389 dport=43142 packets=0 bytes=0 mark=0 secmark=0 zone=0 use=2 2nd update Got tcpdump on the router and it seems that win-box is sending an RST packet: 21:20:24.767792 IP shieldsup.grc.com.45349 > linux-box.myapt.lan.3389: S 19088743:19088743(0) win 8192 <mss 1460> 21:20:24.768038 IP shieldsup.grc.com.45349 > win-box.myapt.lan.3389: S 19088743:19088743(0) win 8192 <mss 1460> 21:20:24.770674 IP win-box.myapt.lan.3389 > shieldsup.grc.com.45349: R 721745706:721745706(0) ack 755785049 win 0 Why would Windows be doing this?

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• High I/O latency with software RAID, LUKS encrypted and LVM partitioned KVM setup

  - by aef

  I found out a performance problems with a Mumble server, which I described in a previous question are caused by an I/O latency problem of unknown origin. As I have no idea what is causing this and how to further debug it, I'm asking for your ideas on the topic. I'm running a Hetzner EX4S root server as KVM hypervisor. The server is running Debian Wheezy Beta 4 and KVM virtualisation is utilized through LibVirt. The server has two different 3TB hard drives as one of the hard drives was replaced after S.M.A.R.T. errors were reported. The first hard disk is a Seagate Barracuda XT ST33000651AS (512 bytes logical, 4096 bytes physical sector size), the other one a Seagate Barracuda 7200.14 (AF) ST3000DM001-9YN166 (512 bytes logical and physical sector size). There are two Linux software RAID1 devices. One for the unencrypted boot partition and one as container for the encrypted rest, using both hard drives. Inside the latter RAID device lies an AES encrypted LUKS container. Inside the LUKS container there is a LVM physical volume. The hypervisor's VFS is split on three logical volumes on the described LVM physical volume: one for /, one for /home and one for swap. Here is a diagram of the block device configuration stack: sda (Physical HDD) - md0 (RAID1) - md1 (RAID1) sdb (Physical HDD) - md0 (RAID1) - md1 (RAID1) md0 (Boot RAID) - ext4 (/boot) md1 (Data RAID) - LUKS container - LVM Physical volume - LVM volume hypervisor-root - LVM volume hypervisor-home - LVM volume hypervisor-swap - … (Virtual machine volumes) The guest systems (virtual machines) are mostly running Debian Wheezy Beta 4 too. We have one additional Ubuntu Precise instance. They get their block devices from the LVM physical volume, too. The volumes are accessed through Virtio drivers in native writethrough mode. The IO scheduler (elevator) on both the hypervisor and the guest system is set to deadline instead of the default cfs as that happened to be the most performant setup according to our bonnie++ test series. The I/O latency problem is experienced not only inside the guest systems but is also affecting services running on the hypervisor system itself. The setup seems complex, but I'm sure that not the basic structure causes the latency problems, as my previous server ran four years with almost the same basic setup, without any of the performance problems. On the old setup the following things were different: Debian Lenny was the OS for both hypervisor and almost all guests Xen software virtualisation (therefore no Virtio, also) no LibVirt management Different hard drives, each 1.5TB in size (one of them was a Seagate Barracuda 7200.11 ST31500341AS, the other one I can't tell anymore) We had no IPv6 connectivity Neither in the hypervisor nor in guests we had noticable I/O latency problems According the the datasheets, the current hard drives and the one of the old machine have an average latency of 4.12ms.

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• Automatic layout of manual network mapping

  - by Paul

  So I have a small business network mainly consisting of two routed layer-2 domains with a total of ca. 100 devices spread over ca. 2000m² production and office spaces. Typical problems to solve using the graph would be: Over what (cable) path is a PC connected to the server? Where to expect devices connected to a switch port? I want to generate a graph of the physical network topology: Nodes are endpoint devices, switch ports, wall outlets, patch panel ports etc. Edges are cable connections. Ideally, grouping edges (or segments) that pass through the same bundle could be grouped. Also I would like to augment the graph data with automatically gathered data (monitoring state, MAC address, Switch port <- MAC entries to build up parts of the map). At the moment I use graphviz for this inside a Confluence wiki like that: layout = "neato" overlap = scale subgraph { rankdir = "TB" subgraph cluster_r1pf1 { r1pf1 [label="{ Rack 1 PF 1 | { <p1>P1 | <p2>P2 | <p3>P3} }", shape=record] } subgraph cluster_switch1 { switch1 [label="{ Rack 1 Switch 1 | { <p1> P1 | <p1> P1 | <p3> P3} }", shape=record] } r1pf1:p1 -> switch1:p1 (obviously there are dozens of entries omitted here) Problem is: I have a hard time to influence graphviz to generate a bearable layout. Edges overlap so bad that you can't read the diagram anymore. The question is: What other tools (be it interactive like Visio, Omnigraffle or I/O-oriented like graphviz) exist that would allow an easily versionable (as in: Operates on a text file) documentation that is both machine and human readable and editable? Why not OmniGraffle or Visio? Well we don't have Macs and Visio is not available at the moment. To buy it I would need good arguments. Automation would be one of that. But last time I looked, versioning Visio files or even thinking about automatic handling was a nightmare. Related: Network Mapping Tools basically asks the same with a focus on generating the complete graph automatically (but without the need to document cabling connections) Recommendations for automatic computer inventory brings up links of "all-in-one" solutions

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• Building an SSL server farm

  - by dan

  I'm interested in building the the architecture in the article referenced below. I currently have a modestly-priced layer-4 load balancer and my application servers are the SSL endpoints. I want to put an SSL server farm in between my load balancer and my app servers. Then I will put another inexpensive load balancer between the SSL farm and my app servers, to do layer-7 routing. My web application has a fairly high amount of consumer traffic, that 6 servers can handle at about 50% capacity. Additionally, I have infrastructure traffic that is several orders of magnitude heavier than my consumer traffic. This is data coming in from all over the world that must integrate with my web application in real time. In total I have 18 app servers to handle all the traffic, plus 6 database servers. I will be adding 6 more app servers over the next 2 weeks and another 6 the 2 weeks after that. Conservatively, I estimate I will need to scale to 120 servers by the end of the year. My motivation right now is to separate the consumer traffic from the infrastructure traffic. The consumer traffic is higher priority than the infrastructure traffic and I cannot allow a stampede on the infrastructure side to take down my consumer-facing servers. Having a website that is always up is the top priority. However if there is a failure in one of the consumer app servers, I want to route that traffic to the servers designated for infrastructure traffic. The complication is that all the traffic is addressed using the same hostname and is nearly 100% https. The only way in my case to distinguish infrastructure from consumer traffic is by URL (poor architecture I inherited), so I need a layer 7 load balancer to be able to route. However for that to work I need either a fancy hardware-based SSL terminator or an SSL server farm as described above. Because my user base is rapidly scaling, I worry that if I go down the hardware path it will become very expensive very fast, especially since I will need 4 of everything for high availability (2 identical setups in 2 facilities). Meanwhile, the above diagram seems very flexible and more horizontally scalable. Has anyone built this before? Are there pre-built configurations? What considerations should I make and what software should I use (I've heard of people using apache with mod-ssl, nginx, and stunnel)? Also, when does it make sense to buy an expensive load balancer vs building an SSL server farm? http://1wt.eu/articles/2006_lb/index_05.html

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• What are the most likely bottlenecks determining the performance of CamStudio screen recording?

  - by Steve314

  When doing screen recording, I can get a frame rate of maybe 15 frames per second for the full screen on my 1080p monitor using the XVID codec. I can increase the speed a bit by recording a region, changing screen modes, and tweaking other settings, but I'm curious what hardware upgrades might give me the biggest bang for my buck. My PC is budget, but modern... Athlon 2 X4 645 (3.1GHz, quad core, limited cache) processor. 4GB single channel DDR3 1066 RAM. ASRock motherboard with NVidia GeForce 7025/nForce 630a Chipset. ATI Radeon HD 5450 graphics card - 512MB on board, not configured to steal system RAM. I dual-boot Windows XP and Windows 7. For the moment, XP is my bigger performance concern as it's still my getting-things-done O/S as opposed to my browser-host O/S. My goal is to make a few programming-related tutorials. For a lot of that I don't need screen recording - I can make up some slides, record audio with the PC switched off, yada yada. When I do need screen recording, I'll mostly be recording Notepad++, Visual Studio or a command prompt. Occasionally, I may be recording some kind of graphics or diagram program and using my pre-Bamboo cheap Wacom tablet - I have the CS2 versions of Photoshop and Illustrator, but I'd much more likely be using Microsoft Paint. Basically, what I'll be recording won't be making huge demands on the machine - but recording a fair number of pixels (720p preferred) will be useful. What's particularly wierd - not so long ago I still had a five-year-old Pentium 4 based PC. And (with the same 1080p monitor) it could record at not far from the same frame rate. So clearly the performance issues are more subtle than just throw-money-at-it. My first guess would be that the main bottleneck is the bandwidth for transferring data to/from the graphics card. Is that likely to be correct? In support of that, see this [Radeon HD 5450 review][1] - the memory bandwidth is only 12.8 GB/s. If you can't get data out of graphics memory quickly, you can't transfer it back to the system memory quickly. Apparently, that's slower than some top-end cards in 2002.

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• Enterprise IPv6 Migration - End of proxypac ? Start of Point-to-Point ? +10K users

  - by Yohann

  Let's start with a diagram : We can see a "typical" IPv4 company network with : An Internet acces through a proxy An "Others companys" access through an dedicated proxy A direct access to local resources All computers have a proxy.pac file that indicates which proxy to use or whether to connect directly. Computers have access to just a local DNS (no name resolution for google.com for example.) By the way ... The company does not respect the RFC1918 internally and uses public addresses! (historical reason). The use of internet proxy explicitly makes it possible to not to have problem. What if we would migrate to IPv6? Step 1 : IPv6 internet access Internet access in IPv6 is easy. Indeed, just connect the proxy in Internet IPv4 and IPv6. There is nothing to do in internal network : Step 2 : IPv6 AND IPv4 in internal network And why not full IPv6 network directly? Because there is always the old servers that are not compatible IPv6 .. Option 1 : Same architecture as in IPv4 with a proxy pac This is probably the easiest solution. But is this the best? I think the transition to IPv6 is an opportunity not to bother with this proxy pac! Option 2 : New architecture with transparent proxy, whithout proxypac, recursive DNS Oh yes! In this new architecture, we have: Explicit Internet Proxy becomes a Transparent Internet Proxy Local DNS becomes a Normal Recursive DNS + authorative for local domains No proxypac Explicit Company Proxy becomes a Transparent Company Proxy Routing Internal Routers reditect IP of appx.ext.example.com to Company Proxy. The default gateway is the Transparent Internet proxy. Questions What do you think of this architecture IPv6? This architecture will reveal the IP addresses of our internal network but it is protected by firewalls. Is this a real big problem? Should we keep the explicit use of a proxy? -How would you make for this migration scenario? -And you, how do you do in your company? Thanks! Feel free to edit my post to make it better.

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