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• Generalist Languages: Dying or Alive and Well?

  - by dsimcha

  Around here, it seems like there's somewhat of a consensus that generalist programming languages (that try to be good at everything, support multiple paradigms, support both very high- and very low-level programming), etc. are a bad idea, and that it's better to pick the right tool for the job and use lots of different languages. I see three major areas where this is flawed: Interfacing multiple languages is always at least a source of friction and is sometimes practically impossible. How severe a problem this is depends on how fine-grained the interfacing is. Near the boundary between the two languages, though, you're basically limited to the intersection of their features, and you have to care about things like binary interfaces that you usually wouldn't. Passing complex data structures (i.e. not just primitives and arrays of primitives) between languages is almost always a hassle. Furthermore, shifting between different syntaxes, different conventions, etc. can be confusing and annoying, though this is a fairly minor complaint. Requirements are never set in stone. I hate picking a language thinking it's the right tool for the job, then realizing that, when some new requirement surfaces, it's actually a terrible choice for that requirement. This has happened to me several times before, usually when working with languages that are very slow, very domain specific and/or has very poor concurrency/parallelism support. When you program in a language for a while, you start to build up a personal toolbox of small utility functions/classes/programs. The value of these goes drastically down if you're forced to use a different language than the one you've accumulated all this code in. What am I missing here? Why shouldn't more focus be placed on generalist languages? Are generalist languages as a category dying or alive and well?

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• What's the proper term for a function inverse to a constructor? Deconstructor, destructor, or something else?

  - by Petr Pudlák

  Edit: I'm rephrasing the question a bit. Apparently I caused some confusion because I didn't realize that the term destructor is used in OOP for something quite different - it's a function invoked when an object is being destroyed. In functional programming we (try to) avoid mutable state so there is no such equivalent to it. (I added the proper tag to the question.) Instead, I've seen that the record field for unwrapping a value (especially for single-valued data types such as newtypes) is sometimes called destructor or perhaps deconstructor. For example, let's have (in Haskell): newtype Wrap = Wrap { unwrap :: Int } Here Wrap is the constructor and unwrap is what? I've seen both, for example: ... Most often, one supplies smart constructors and destructors for these to ease working with them. ... at Haskell wiki, or ... The general theme here is to fuse constructor - deconstructor pairs like ... at Haskell wikibook (here it's probably meant in a bit more general sense). The questions are: How do we call unwrap in functional programming? Deconstructor? Destructor? Or by some other term? And to clarify, is this terminology applicable to other functional languages, or is it used just in the Has

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• Benefits of classic OOP over Go-like language

  - by tylerl

  I've been thinking a lot about language design and what elements would be necessary for an "ideal" programming language, and studying Google's Go has led me to question a lot of otherwise common knowledge. Specifically, Go seems to have all of the interesting benefits from object oriented programming without actually having any of the structure of an object oriented language. There are no classes, only structures; there is no class/structure inheritance -- only structure embedding. There aren't any hierarchies, no parent classes, no explicit interface implementations. Instead, type casting rules are based on a loose system similar to duck-typing, such that if a struct implements the necessary elements of a "Reader" or a "Request" or an "Encoding", then you can cast it and use it as one. Does such a system obsolete the concept of OOP? Or is there something about OOP as implemented in C++ and Java and C# that is inherently more capable, more maintainable, somehow more powerful that you have to give up when moving to a language like Go? What benefit do you have to give up to gain the simplicity that this new paradigm represents?

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• What can be done against language inertia?

  - by gerrit

  Often, projects use programming language X, but would use programming language Y if they were started from scratch. For example, big numerical models may be written entirely in Fortran. Whereas this might be a reasonable choice for the components that need to run fast (alternative would be C or C++), it might be a poor choice for components that either do not need to run fast (such as things dealing with human input or simple visualisations), or where runtime is not the limiting factor (such as I/O, particularly when from the network). Another example may be when a project is built using a propriety language (such as Matlab; no, FOSS clones are not good enough) and was started at a time when FOSS alternatives were not viable, but ten years later, they are; and it would be beneficial to migrate. However, due to language inertia, a migration does not happen. Code that works should not be touched, porting code is a time-consuming, expensive process, and programmers are familiar in language X but not necessarily in language Y. Still, in the long term, a migration would likely be beneficial. Can anything be done to mitigate the problems associated with language inertia? Are there any notable examples of big projects that have successfully overcome this problem? Or is a project bound to stick forever with the initial choices?

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• Uses of persistent data structures in non-functional languages

  - by Ray Toal

  Languages that are purely functional or near-purely functional benefit from persistent data structures because they are immutable and fit well with the stateless style of functional programming. But from time to time we see libraries of persistent data structures for (state-based, OOP) languages like Java. A claim often heard in favor of persistent data structures is that because they are immutable, they are thread-safe. However, the reason that persistent data structures are thread-safe is that if one thread were to "add" an element to a persistent collection, the operation returns a new collection like the original but with the element added. Other threads therefore see the original collection. The two collections share a lot of internal state, of course -- that's why these persistent structures are efficient. But since different threads see different states of data, it would seem that persistent data structures are not in themselves sufficient to handle scenarios where one thread makes a change that is visible to other threads. For this, it seems we must use devices such as atoms, references, software transactional memory, or even classic locks and synchronization mechanisms. Why then, is the immutability of PDSs touted as something beneficial for "thread safety"? Are there any real examples where PDSs help in synchronization, or solving concurrency problems? Or are PDSs simply a way to provide a stateless interface to an object in support of a functional programming style?

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• Where to Start?

  - by freemann098

  my name is Chase. I've been programming for over 3 years now and I've made very little progress towards game development. I blame myself for it due to reasons. I have experience in many languages such as C++, C#, and Java. I have a little bit of knowledge in JavaScript/HTML and Python. My question is where to start on actually understanding jumping into game development. Whenever I watch game development tutorials it mostly makes sense until points of things like OpenGL or advanced topics that make no sense at all. An example is something like glOrhho Matrix or whatever. Videos either don't explain things like this or they're not explained very well. Do I not know enough basics? I find myself always copying code from a video but understanding very little of it. It's like i'm memorizing things I don't understand which makes it hard to program at all. If I were to want to get to the point where I could write my own game engine or just a game by myself in general in C++ using at the most documentation how would I start at mastering to that level. Should I learn C first, or get really good at basics in general with C++. I know there is a similar posted question on this site but it's not the same due to the fact the person asking the question has a well knowledge level in programming. I'm stuck in a loop of learning the same things but if I go farther I don't understand. I'm stuck in the same spot and need to make progress.

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• What's the proper term for a function inverse to a constructor - to unwrap a value from a data type?

  - by Petr Pudlák

  Edit: I'm rephrasing the question a bit. Apparently I caused some confusion because I didn't realize that the term destructor is used in OOP for something quite different - it's a function invoked when an object is being destroyed. In functional programming we (try to) avoid mutable state so there is no such equivalent to it. (I added the proper tag to the question.) Instead, I've seen that the record field for unwrapping a value (especially for single-valued data types such as newtypes) is sometimes called destructor or perhaps deconstructor. For example, let's have (in Haskell): newtype Wrap = Wrap { unwrap :: Int } Here Wrap is the constructor and unwrap is what? The questions are: How do we call unwrap in functional programming? Deconstructor? Destructor? Or by some other term? And to clarify, is this/other terminology applicable to other functional languages, or is it used just in the Haskell? Perhaps also, is there any terminology for this in general, in non-functional languages? I've seen both terms, for example: ... Most often, one supplies smart constructors and destructors for these to ease working with them. ... at Haskell wiki, or ... The general theme here is to fuse constructor - deconstructor pairs like ... at Haskell wikibook (here it's probably meant in a bit more general sense), or newtype DList a = DL { unDL :: [a] -> [a] } The unDL function is our deconstructor, which removes the DL constructor. ... in The Real World Haskell.

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• When can you call yourself good at language X?

  - by SoulBeaver

  This goes back to a conversation I've had with my girlfriend. I tried to tell her that I simply don't feel adequate enough in my programming language (C++) to call myself good. She then asked me, "Well, when do you consider yourself good enough?" That's an interesting question. I didn't know what to tell her. So I'm asking you. For any programming language, framework or the like, when do you reach a point were you sit back, look at what you've done and say, "Hey, I'm actually pretty good at this."? How do you define "good" so that you can tell others, honestly, "Yeah, I'm good at X". Additionally, do you reach these conclusions by comparing what others can do? Additional Info I have read the canonical paper on how it takes ten-thousand hours before you are an expert on the field. (Props to anybody that knows what this paper is called again) I have also read various articles from Coding Horror about interviewing people. Some people, it was said, "Cannot function outside of a framework." So they may be "good" for that framework, but not otherwise in the language. Is this true?

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• What are some ways to separate game logic from animations and the draw loop?

  - by TMV

  I have only previously made flash games, using MovieClips and such to separate out my animations from my game logic. Now I am getting into trying my hand at making a game for Android, but the game programming theory around separating these things still confuses me. I come from a background of developing non game web applications so I am versed in more MVC like patterns and am stuck in that mindset as I approach game programming. I want to do things like abstract my game by having, for example, a game board class that contains the data for a grid of tiles with instances of a tile class that each contain properties. I can give my draw loop access to this and have it draw the game board based on the properties of each tile on the game board, but I don't understand where exactly animation should go. As far as I can tell, animation sort of sits between the abstracted game logic (model) and the draw loop (view). With my MVC mindset, it's frustrating trying to decide where animation is actually supposed to go. It would have quite a bit of data associated with it like a model, but seemingly needs to be very closely coupled with the draw loop in order to have things like frame independent animation. How can I break out of this mindset and start thinking about patterns that make more sense for games?

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• What are some techniques I can use to refactor Object Oriented code into Functional code?

  - by tieTYT

  I've spent about 20-40 hours developing part of a game using JavaScript and HTML5 canvas. When I started I had no idea what I was doing. So it started as a proof of concept and is coming along nicely now, but it has no automated tests. The game is starting to become complex enough that it could benefit from some automated testing, but it seems tough to do because the code depends on mutating global state. I'd like to refactor the whole thing using Underscore.js, a functional programming library for JavaScript. Part of me thinks I should just start from scratch using a Functional Programming style and testing. But, I think refactoring the imperative code into declarative code might be a better learning experience and a safer way to get to my current state of functionality. Problem is, I know what I want my code to look like in the end, but I don't know how to turn my current code into it. I'm hoping some people here could give me some tips a la the Refactoring book and Working Effectively With Legacy Code. For example, as a first step I'm thinking about "banning" global state. Take every function that uses a global variable and pass it in as a parameter instead. Next step may be to "ban" mutation, and to always return a new object. Any advice would be appreciated. I've never taken OO code and refactored it into Functional code before.

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• Are specific types still necessary?

  - by MKO

  One thing that occurred to me the other day, are specific types still necessary or a legacy that is holding us back. What I mean is: do we really need short, int, long, bigint etc etc. I understand the reasoning, variables/objects are kept in memory, memory needs to be allocated and therefore we need to know how big a variable can be. But really, shouldn't a modern programming language be able to handle "adaptive types", ie, if something is only ever allocated in the shortint range it uses fewer bytes, and if something is suddenly allocated a very big number the memory is allocated accordinly for that particular instance. Float, real and double's are a bit trickier since the type depends on what precision you need. Strings should however be able to take upp less memory in many instances (in .Net) where mostly ascii is used buth strings always take up double the memory because of unicode encoding. One argument for specific types might be that it's part of the specification, ie for example a variable should not be able to be bigger than a certain value so we set it to shortint. But why not have type constraints instead? It would be much more flexible and powerful to be able to set permissible ranges and values on variables (and properties). I realize the immense problem in revamping the type architecture since it's so tightly integrated with underlying hardware and things like serialization might become tricky indeed. But from a programming perspective it should be great no?

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• Spending a good fortune on a certificate holding Scrum Master or a Veteran XP coach?

  - by ashy_32bit

  There is a very prestigious company that delivers a well-sold software about financial systems. It has more that 20 years of history, and is staffed with about 20 programmers and much larger number of managerial staff. Dissatisfied customers have reported strange bugs and no one has a clue what is wrong, hard to read code, and customization is prohibitively expensive. In a word, the software is rotten. The company decided to spend a fortune and found the Agile thing as the remedy but they are stuck about what it is they need most urgently. Is it about the process or the developers or both? The challenge breaks down to the following options: They can hire a certificate holding Scrum Master to teach them Scrum. When asked about the value of doing it, the SM responded: "I will prepare them to embrace Agile and only then they can go Agile and save the product". They can as well hire a veteran XP coach. When posed with the same question he responded : "The most urgent problem is with the programmers and not the management, XP will save the product from rot and only then Scrum will make sense" Developers are far from capable of doing agile programming practices at the moment. No unit tests, no pair programmings, no CI (huh? what is it?) ... you get the idea. Some say they would be far better trying to improve their programming first (hire option 2) and then go with the process. Many say quite the opposite. Any insights ?

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• Laser range finder, what language to use? Beginner advice

  - by DrOnline

  I hope this is the right place. I am a programming beginner, and I want to make a laser range finder, and I need advice about how to proceed etc. In a few weeks I will get a lot of dirt cheap 3-5V lasers and some cheap usb webcams. I will point the laser and webcam in parallel, and somehow use trigonometry and programming to determined distance. I have seen online that others made done it this way, I have purposefully not looked at the details too much because I want to develop it on my own, and learn, but I know the general outline. I have a general idea of how to proceed. The program loads in a picture from the webcam, and I dunno how images work really, but I imagine there is a format that is basically an array of RGB values.. is this right? I will load in the red values, and find the most red one. I know the height difference between the laser and the cam. I know the center dot in the image, I know the redmost dot. I'm sure there's some way to figure out some range there. TO THE POINT: 1) Is my reasoning sound thus far, especially in terms of image analysis? I don't need complete solutions, just general points 2) What I need to figure out, is what platform to use. I have an arduino... apparently, I've read it's too weak to process images. Read that online. I know some C I know some Python I have Matlab. Which is the best option? I do not need high sampling rates, I have not decided on whether it should be automated or whether I should make a GUI with a button to press for samples. I will keep it simple and expand I think. I also do not need it to be super accurate, I'm just having fun here. Advice!

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• Can't connect to DeploymentShare$ from PC attempting to MDT, but can other PCs on the network

  - by Moman10

  I am in the process of setting up MDT and have run across a problem. MDT is installed on a Windows 2012 server, MDT version 6.2.5019.0. Using WDS as well. Active Directory domain, the server is up to date and on the network. I boot up the PC, it gets an address from DHCP, pulls down the LiteTouchPE_x64.wim image and goes into the MS Solution Accelerators screen, the Processing Bootstrap Settings box comes up and processes for a couple of seconds, then goes away, it sits there for another minute or so and then gives the error: A connection to the deployment share (\\Acme-MDT\DeploymentShare$) could not be made. Can not reach the DeployRoot. Possible Cause: Network Routing error or Network Configuration Error." I can then retry or cancel. I have seen this error online but so far nothing that helps fix it, but seems to be an issue with the FQDN. I verified that I am getting an IP address and that I can successfully ping the MDT server if I use the FQDN, but can not just by it's A record of Acme-MDT. I tried manually mapping the network share using net use and it works if I use the FQDN, but it fails with an error code 53, "Network path not found" if I just use the A record of Acme-MDT. Here is the net use command I'm using: net use * \\Acme-MDT\DeploymentShare$ /u:Domain\Administrator It gives the error System Error 53, Network path not found (and doesn't prompt for a password), but if I use the FQDN of \\Acme-MDT.domain.com\DeploymentShare$ it works fine to map the drive. I guess the problem is, when it tries to load the image, it is trying to start from \\Acme-MDT\DeploymentShare$ and I need it to start from \\Acme-MDT.domain.com\DeploymentShare$, but not sure how to get it to do that. I've put the fully qualified path in CustomSettings.ini and bootstrap, updated the deployment share, regenerated the boot image and replaced the boot wim in WDS. Or, if someone has an idea as to why it's acting this way and knows a way around it. The end result is what matters! :) I did verify in DNS that Acme-MDT is there, with the proper IP, and I can successfully use the net use command to map this drive from a couple other computers that are already on the network. I am assuming it has something to do with that computer not already being part of the domain, but I'm honestly at a loss as to how to fix it. Any ideas are appreciated, thanks in advance for your help!

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• tc rules block traffic from some hosts at network

  - by user139430

  I have a problem I can not solve. The script, which sets the rules for traffic shaping is blocking the traffic from some hosts.If I remove all the rules, then it works. I can not understand why? Here is my script... #!/bin/sh cmdTC=/sbin/tc rateLANDl="60mbit" ceilLANDl="60mbit" rateLANUl="40mbit" ceilLANUl="40mbit" quantLAN="1514" # Nowaday bandwidth limit set to 100mbit. # We devide it with 60mbit download and 40mbit upload bandthes. rateHiDl="30mbit" ceilHiDl="60mbit" rateHiUl="20mbit" ceilHiUl="40mbit" quantHi="1514" rateLoDl="30mbit" ceilLoDl="60mbit" rateLoUl="20mbit" ceilLoUl="40mbit" quantLo="1514" devNIF=eth0 devFIF=ifb0 modprobe ifb ip link set $devFIF up 2>/dev/null #exit 0 ################################################################################################ # Remove discuiplines from network and fake interfaces ################################################################################################ $cmdTC qdisc del dev $devNIF root 2>/dev/null $cmdTC qdisc del dev $devFIF root 2>/dev/null $cmdTC qdisc del dev $devNIF ingress 2>/dev/null if [ "$1" = "down" ]; then exit 0 fi ################################################################################################ # Create discuiplines for network interface ################################################################################################ $cmdTC qdisc add dev $devNIF root handle 1:0 htb default 12 # Create classes for network interface $cmdTC class add dev $devNIF parent 1:0 classid 1:1 htb rate ${rateLANDl} ceil ${ceilLANDl} quantum ${quantLAN} $cmdTC class add dev $devNIF parent 1:1 classid 1:11 htb rate ${rateHiDl} ceil ${ceilHiDl} quantum ${quantHi} $cmdTC class add dev $devNIF parent 1:1 classid 1:12 htb rate ${rateLoDl} ceil ${ceilLoDl} quantum ${quantLo} $cmdTC qdisc add dev $devNIF parent 1:11 handle 111: sfq perturb 10 $cmdTC qdisc add dev $devNIF parent 1:12 handle 112: sfq perturb 10 # Create filters for network interface $cmdTC filter add dev $devNIF protocol all parent 1:0 u32 match ip dst 10.252.2.0/24 flowid 1:11 $cmdTC filter add dev $devNIF protocol all parent 111: handle 111 flow hash keys dst divisor 1024 baseclass 1:11 $cmdTC filter add dev $devNIF protocol all parent 112: handle 112 flow hash keys dst divisor 1024 baseclass 1:12 ################################################################################################ # Create discuiplines for fake interface ################################################################################################ $cmdTC qdisc add dev $devFIF root handle 1:0 htb default 12 # Create classes for network interface $cmdTC class add dev $devFIF parent 1:0 classid 1:1 htb rate ${rateLANUl} ceil ${ceilLANUl} quantum ${quantLAN} $cmdTC class add dev $devFIF parent 1:1 classid 1:11 htb rate ${rateHiUl} ceil ${ceilHiUl} quantum ${quantHi} $cmdTC class add dev $devFIF parent 1:1 classid 1:12 htb rate ${rateLoUl} ceil ${ceilLoUl} quantum ${quantLo} $cmdTC qdisc add dev $devFIF parent 1:11 handle 111: sfq perturb 10 $cmdTC qdisc add dev $devFIF parent 1:12 handle 112: sfq perturb 10 # Create filters for network interface $cmdTC filter add dev $devFIF protocol all parent 1:0 u32 match ip src 10.252.2.0/24 flowid 1:11 $cmdTC filter add dev $devFIF protocol all parent 111: handle 111 flow hash keys src divisor 1024 baseclass 1:11 $cmdTC filter add dev $devFIF protocol all parent 112: handle 112 flow hash keys src divisor 1024 baseclass 1:12 ################################################################################################ # Create redirect discuiplines from network to fake interface ################################################################################################ $cmdTC qdisc add dev $devNIF handle ffff:0 ingress $cmdTC filter add dev $devNIF parent ffff:0 protocol all u32 match u32 0 0 action mirred egress redirect dev $devFIF Here is my /etc/modules: loop ifb ppp_mppe nf_conntrack_pptp nt_conntrack_proto_gre nf_nat_pptp nf_nat_proto_gre The system is Linux wall 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64 GNU/Linux

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• Network switching issues with MacOS 10.7?

  - by Denis

  I'm having a wired problem and hope somebody can tip me, what way should I dig to. I'm using MacBookPro with Lion 10.7.3 both at my working place & at home. At working place, we have a domain-based network with 802.1x authorization (more than 400 computers) and to connect it I'm using Ethernet cable. IP range is 10.10.2.*. All network settings are setup automatically by DHCP. Also, in settings, I have Network Account Server setup in the User&Groups Settings for my work Domain server - and it is available only from corporate network. At home, I have an ADSL router, that shares Internet connection by WiFi in NAT mode. I'm using WiFi to connect it. Router gives out addresses from 192.168.1.* range and all settings are also set up by router's DHCP. So, my problem is the following. When I come back home from the office, I open my MacBook and AirPort automatically connects my WiFi network. After this, for about 1 minute I'm able to browse sites & ping hosts successfully. But after this minute, network connection is broken down. All pings return time-out. trace route to google.com stops on 192.168.1.1 (which is my router). This lasts for 3-4 minutes. After that network connection is automatically repaired and all pings go smoothly again. At the same time, when my MacBook return timeouts, I can successfully ping any host from my wife's MacBook - so this doesn't look like router issue. When I come to the office, I don't have any issues and Internet connection is available & stable moments after ethernet cable plugged in. Do anybody has any clues about this? What should I monitor & what settings look for resolving this issue? Please, ask, what additional information should I provide. Hoping for good advice & thanks in advance!

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• Week 21: FY10 in the Rear View Mirror

  - by sandra.haan

  FY10 is coming to a close and before we dive into FY11 we thought we would take a walk down memory lane and reminisce on some of our favorite Oracle PartnerNetwork activities. June 2009 brought One Red Network to partners offering access to the same virtual kickoff environment used by Oracle employees. It was a new way to deliver valuable content to key stakeholders (and without the 100+ degree temperatures). Speaking of hot, Oracle also announced in June new licensing options for our ISV partners. This model enables an even broader community of ISVs to build, deploy and manage SaaS applications on the same platform. While some people took the summer off, the OPN Program team was working away to deliver a brand new partner program - Oracle PartnerNetwork Specialized - at Oracle OpenWorld in October. Specialized. Recognized. Preferred. If you haven't gotten the message yet, we may need an emergency crew to pull you out from that rock you've been hiding under. But seriously, the announcement at the OPN Forum drew a big crowd and our FY11 event is shaping up to be just as exciting. OPN Specialized was announced in October and opened our doors for enrollment in December 2009. To mark our grand opening we held our first ever social webcast allowing partners from around the world to interact with us live throughout the day. We had a lot of great conversations and really enjoyed the chance to speak with so many of you. After a short holiday break we were back at it - just a small announcement - Oracle's acquisition of Sun. In case you missed it, here is a short field report from Ted Bereswill, SVP North America Alliances & Channels on the partner events to support the announcement: And while we're announcing things - did we mention that both Ted Bereswill and Judson Althoff were named Channel Chiefs by CRN? Not only do we have a couple of Channel Chiefs, but Oracle also won the Partner Program 5 Star Programs Award and took top honors at the CRN Channel Champion Awards for Financial Factors/Financial Performance in the category of Data and Information Management and the and Xchange Solution Provider event in March 2010. We actually caught up with Judson at this event for a quick recap of our participation: But awards aside, let's not forget our main focus in FY10 and that is Specialization. In April we announced that we had over 35 Specializations available for partners and a plan to deliver even more in FY11. We are just days away from the end of FY10 but hope you enjoyed our walk down memory lane. We are already planning lots of activity for our partners in FY11 starting with our Partner Kickoff event on June 29th. Join us to hear the vision and strategy for FY11 and interact with regional A&C leaders. We look forward to talking with you then. The OPN Communications Team

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• PPTP VPN connects via NM but goes down during SSH connection

  - by Andrea Olivato

  I setup a VPN PPTP connection via network manager and it connects correctly (I see the lock near the notification icon and the message "Vpn connection has been successfully...") As soon as I try to perform any SSH connection via the established tunnel the connection itself goes down with the message "Vpn connection failed". the SSH connection always fails at debug1: SSH2_MSG_KEXINIT sent I've looked into the system logs and this is the log Dec 12 12:25:00 ushuaia NetworkManager[1155]: <info> Starting VPN service 'pptp'... Dec 12 12:25:00 ushuaia NetworkManager[1155]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 7093 Dec 12 12:25:00 ushuaia NetworkManager[1155]: <info> VPN service 'pptp' appeared; activating connections Dec 12 12:25:00 ushuaia NetworkManager[1155]: <info> VPN plugin state changed: init (1) Dec 12 12:25:00 ushuaia NetworkManager[1155]: <info> VPN plugin state changed: starting (3) Dec 12 12:25:00 ushuaia NetworkManager[1155]: <info> VPN connection 'Redation' (Connect) reply received. Dec 12 12:25:05 ushuaia NetworkManager[1155]: <info> VPN connection 'Redation' (IP4 Config Get) reply received from old-style plugin. Dec 12 12:25:05 ushuaia NetworkManager[1155]: <info> VPN Gateway: 5.98.141.210 Dec 12 12:25:06 ushuaia NetworkManager[1155]: <info> VPN connection 'Redation' (IP Config Get) complete. Dec 12 12:25:06 ushuaia NetworkManager[1155]: <info> VPN plugin state changed: started (4) Dec 12 12:25:14 ushuaia NetworkManager[1155]: <info> VPN plugin state changed: stopping (5) Dec 12 12:25:14 ushuaia NetworkManager[1155]: <info> VPN plugin state changed: stopped (6) Dec 12 12:25:14 ushuaia NetworkManager[1155]: <info> VPN plugin state change reason: 0 Dec 12 12:25:15 ushuaia NetworkManager[1155]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active. Dec 12 12:25:20 ushuaia NetworkManager[1155]: <info> VPN service 'pptp' disappeared Please note that the same vpn is configured on my colleagues Windows 7 and works without problem when they use putty to connect via SSH

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• Problem getting GOBI 2000 HS to work

  - by Zypher

  I've been trying to get my integrated GOBI WWAN card to work under 10.10 for a while now. I was able to get the network manager to see the card after installing the gobi-loader package. I was able to setup the connection, but i cannot establish a connection to Verizon. Below is the output from /var/log/daemon.log as i try to connect. Oct 19 14:29:42 gbeech-x201 AptDaemon: INFO: Quiting due to inactivity Oct 19 14:29:42 gbeech-x201 AptDaemon: INFO: Shutdown was requested Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) starting connection 'Verizon connection' Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 3 -> 4 (reason 0) Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) scheduled... Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) started... Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 4 -> 6 (reason 0) Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) complete. Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) scheduled... Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) started... Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 6 -> 4 (reason 0) Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) complete. Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <warn> CDMA connection failed: (32) No service Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 4 -> 9 (reason 0) Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> Marking connection 'Verizon connection' invalid. Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <warn> Activation (ttyUSB0) failed. Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 9 -> 3 (reason 0) Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): deactivating device (reason: 0). Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> Policy set 'Auto SO-GUEST' (wlan0) as default for IPv4 routing and DNS. Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> Policy set 'Auto SO-GUEST' (wlan0) as default for IPv4 routing and DNS.

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• Ubuntu 12 crashed and took down network

  - by Leopd

  We recently set up a new Ubuntu 12.04LTS server on our network. It's not fully configured so it's not doing much beyond sshd and a default apache2 install. But this evening it appears to have crashed. It wasn't responding to the network or the keyboard. But the worst part is, it took down the entire network. My knowledge of the network stack below OSI layer 3 is very limited, so the rest confuses me. When this machine was physically connected to the network, no other machine could connect to the outside internet. When things were broken, running arp showed that our gateway's IP address (10.0.1.1) was listed as "invalid." Unplugging the server from the network fixed the problem, and plugging it back in broke it again. So the crashed server was advertising itself as owning the gateway's IP address? There's nothing at all in syslog during the time when it was causing problems. Any ideas about how to figure out what went wrong or what we can do to prevent it from happening again? I'm hesitant to even put the machine back on the network right now. Update ** It crashed again, and I ran tcpdump -penn arp (thanks bahamat!) for several minutes and got this... (timestamps and duplicate lines removed) 00:1e:65:f8:dc:24 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 10.0.1.1 tell 10.0.2.191, length 46 00:1e:65:f8:dc:24 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 10.0.1.44 tell 10.0.2.191, length 46 60:d8:19:d4:71:d6 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 10.0.1.1 tell 10.0.2.125, length 46 d4:9a:20:04:e9:78 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Request who-has 192.168.1.1 tell 192.168.1.100, length 28 Update 2 ** When the network is functioning properly, arping -c4 10.0.1.1 returns this: ARPING 10.0.1.1 60 bytes from c0:c1:c0:77:25:8e (10.0.1.1): index=0 time=267.982 usec 60 bytes from c0:c1:c0:77:25:8e (10.0.1.1): index=1 time=422.955 usec 60 bytes from c0:c1:c0:77:25:8e (10.0.1.1): index=2 time=299.215 usec 60 bytes from c0:c1:c0:77:25:8e (10.0.1.1): index=3 time=366.926 usec --- 10.0.1.1 statistics --- 4 packets transmitted, 4 packets received, 0% unanswered (0 extra) When the bad server is plugged in, arping -c4 10.0.1.1 returns: ARPING 10.0.1.1 --- 10.0.1.1 statistics --- 4 packets transmitted, 0 packets received, 100% unanswered (0 extra) Context ** 10.0.x.x is the main subnet. 10.0.1.1 is the main internet gateway 10.0.1.44 is a printer 10.0.2.* devices are all laptops / workstations I have no idea what's using the 192.168.x.x subnet -- your guesses are at least as good as mine. A VM on a workstation? A misconfigured WAP? Somebody re-sharing wifi? A machine that failed to DHCP? The offending ubuntu server's MAC address ends in cd:80 so isn't listed in the dump. It should DHCP to 10.0.3.3 Thanks for any help. This ARP stuff is all voodoo to me. Packets just go to IP addresses, right? ;)

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• Proper network configuration for a KVM guest to be on the same networks at the host

  - by Steve Madsen

  I am running a Debian Linux server on Lenny. Within it, I am running another Lenny instance using KVM. Both servers are externally available, with public IPs, as well as a second interface with private IPs for the LAN. Everything works fine, except the VM sees all network traffic as originating from the host server. I suspect this might have something to do with the iptables-based firewall I'm running on the host. What I'd like to figure out is: how to I properly configure the host's networking such that all of these requirements are met? Both host and VMs have 2 network interfaces (public and private). Both host and VMs can be independently firewalled. Ideally, VM traffic does not have to traverse the host firewall. VMs see real remote IP addresses, not the host's. Currently, the host's network interfaces are configured as bridges. eth0 and eth1 do not have IP addresses assigned to them, but br0 and br1 do. /etc/network/interfaces on the host: # The primary network interface auto br1 iface br1 inet static address 24.123.138.34 netmask 255.255.255.248 network 24.123.138.32 broadcast 24.123.138.39 gateway 24.123.138.33 bridge_ports eth1 bridge_stp off auto br1:0 iface br1:0 inet static address 24.123.138.36 netmask 255.255.255.248 network 24.123.138.32 broadcast 24.123.138.39 # Internal network auto br0 iface br0 inet static address 192.168.1.1 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 bridge_ports eth0 bridge_stp off This is the libvirt/qemu configuration file for the VM: <domain type='kvm'> <name>apps</name> <uuid>636b6620-0949-bc88-3197-37153b88772e</uuid> <memory>393216</memory> <currentMemory>393216</currentMemory> <vcpu>1</vcpu> <os> <type arch='i686' machine='pc'>hvm</type> <boot dev='hd'/> </os> <features> <acpi/> <apic/> <pae/> </features> <clock offset='utc'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <devices> <emulator>/usr/bin/kvm</emulator> <disk type='file' device='cdrom'> <target dev='hdc' bus='ide'/> <readonly/> </disk> <disk type='file' device='disk'> <source file='/raid/kvm-images/apps.qcow2'/> <target dev='vda' bus='virtio'/> </disk> <interface type='bridge'> <mac address='54:52:00:27:5e:02'/> <source bridge='br0'/> <model type='virtio'/> </interface> <interface type='bridge'> <mac address='54:52:00:40:cc:7f'/> <source bridge='br1'/> <model type='virtio'/> </interface> <serial type='pty'> <target port='0'/> </serial> <console type='pty'> <target port='0'/> </console> <input type='mouse' bus='ps2'/> <graphics type='vnc' port='-1' autoport='yes' keymap='en-us'/> </devices> </domain> Along with the rest of my firewall rules, the firewalling script includes this command to pass packets destined for a KVM guest: # Allow bridged packets to pass (for KVM guests). iptables -A FORWARD -m physdev --physdev-is-bridged -j ACCEPT (Not applicable to this question, but a side-effect of my bridging configuration appears to be that I can't ever shut down cleanly. The kernel eventually tells me "unregister_netdevice: waiting for br1 to become free" and I have to hard reset the system. Maybe a sign I've done something dumb?)

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• Two network interfaces and two IP addresses on the same subnet in Linux

  - by Scott Duckworth

  I recently ran into a situation where I needed two IP addresses on the same subnet assigned to one Linux host so that we could run two SSL/TLS sites. My first approach was to use IP aliasing, e.g. using eth0:0, eth0:1, etc, but our network admins have some fairly strict settings in place for security that squashed this idea: They use DHCP snooping and normally don't allow static IP addresses. Static addressing is accomplished by using static DHCP entries, so the same MAC address always gets the same IP assignment. This feature can be disabled per switchport if you ask and you have a reason for it (thankfully I have a good relationship with the network guys and this isn't hard to do). With the DHCP snooping disabled on the switchport, they had to put in a rule on the switch that said MAC address X is allowed to have IP address Y. Unfortunately this had the side effect of also saying that MAC address X is ONLY allowed to have IP address Y. IP aliasing required that MAC address X was assigned two IP addresses, so this didn't work. There may have been a way around these issues on the switch configuration, but in an attempt to preserve good relations with the network admins I tried to find another way. Having two network interfaces seemed like the next logical step. Thankfully this Linux system is a virtual machine, so I was able to easily add a second network interface (without rebooting, I might add - pretty cool). A few keystrokes later I had two network interfaces up and running and both pulled IP addresses from DHCP. But then the problem came in: the network admins could see (on the switch) the ARP entry for both interfaces, but only the first network interface that I brought up would respond to pings or any sort of TCP or UDP traffic. After lots of digging and poking, here's what I came up with. It seems to work, but it also seems to be a lot of work for something that seems like it should be simple. Any alternate ideas out there? Step 1: Enable ARP filtering on all interfaces: # sysctl -w net.ipv4.conf.all.arp_filter=1 # echo "net.ipv4.conf.all.arp_filter = 1" >> /etc/sysctl.conf From the file networking/ip-sysctl.txt in the Linux kernel docs: arp_filter - BOOLEAN 1 - Allows you to have multiple network interfaces on the same subnet, and have the ARPs for each interface be answered based on whether or not the kernel would route a packet from the ARP'd IP out that interface (therefore you must use source based routing for this to work). In other words it allows control of which cards (usually 1) will respond to an arp request. 0 - (default) The kernel can respond to arp requests with addresses from other interfaces. This may seem wrong but it usually makes sense, because it increases the chance of successful communication. IP addresses are owned by the complete host on Linux, not by particular interfaces. Only for more complex setups like load- balancing, does this behaviour cause problems. arp_filter for the interface will be enabled if at least one of conf/{all,interface}/arp_filter is set to TRUE, it will be disabled otherwise Step 2: Implement source-based routing I basically just followed directions from http://lartc.org/howto/lartc.rpdb.multiple-links.html, although that page was written with a different goal in mind (dealing with two ISPs). Assume that the subnet is 10.0.0.0/24, the gateway is 10.0.0.1, the IP address for eth0 is 10.0.0.100, and the IP address for eth1 is 10.0.0.101. Define two new routing tables named eth0 and eth1 in /etc/iproute2/rt_tables: ... top of file omitted ... 1 eth0 2 eth1 Define the routes for these two tables: # ip route add default via 10.0.0.1 table eth0 # ip route add default via 10.0.0.1 table eth1 # ip route add 10.0.0.0/24 dev eth0 src 10.0.0.100 table eth0 # ip route add 10.0.0.0/24 dev eth1 src 10.0.0.101 table eth1 Define the rules for when to use the new routing tables: # ip rule add from 10.0.0.100 table eth0 # ip rule add from 10.0.0.101 table eth1 The main routing table was already taken care of by DHCP (and it's not even clear that its strictly necessary in this case), but it basically equates to this: # ip route add default via 10.0.0.1 dev eth0 # ip route add 130.127.48.0/23 dev eth0 src 10.0.0.100 # ip route add 130.127.48.0/23 dev eth1 src 10.0.0.101 And voila! Everything seems to work just fine. Sending pings to both IP addresses works fine. Sending pings from this system to other systems and forcing the ping to use a specific interface works fine (ping -I eth0 10.0.0.1, ping -I eth1 10.0.0.1). And most importantly, all TCP and UDP traffic to/from either IP address works as expected. So again, my question is: is there a better way to do this? This seems like a lot of work for a seemingly simple problem.

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• NetworkManager Applet shows no networks

  - by Kkelk

  I am "the friend" referred to in the questions here and here. I decided to come and ask a question myself, as I can still not connect to the wireless network. I downloaded Keryx, as suggested here, and managed to download the necessary package and its dependencies. When I attempted to install the packages on Ubuntu using Keryx, Keryx just closed. Following this, I installed the packages manually using dpkg, and as far as I can tell, this was successful: kieran@ubuntu:~$ cd /host/wifi/Keryx/keryx/projects/Kieran/packages kieran@ubuntu:/host/wifi/Keryx/keryx/projects/Kieran/packages$ sudo dpkg -i *.deb [sudo] password for kieran: Selecting previously deselected package bcmwl-kernel-source. (Reading database ... 118296 files and directories currently installed.) Unpacking bcmwl-kernel-source (from bcmwl-kernel-source_5.60.48.36+bdcom-0ubuntu5_i386.deb) ... Selecting previously deselected package dkms. Unpacking dkms (from dkms_2.1.1.2-3ubuntu1.1_all.deb) ... Selecting previously deselected package fakeroot. Unpacking fakeroot (from fakeroot_1.14.4-1ubuntu1_i386.deb) ... Selecting previously deselected package linux-image. Unpacking linux-image (from linux-image_2.6.35.22.23_i386.deb) ... Selecting previously deselected package menu. Unpacking menu (from menu_2.1.44ubuntu1_i386.deb) ... Selecting previously deselected package patch. Unpacking patch (from patch_2.6-2ubuntu1_i386.deb) ... Setting up fakeroot (1.14.4-1ubuntu1) ... update-alternatives: using /usr/bin/fakeroot-sysv to provide /usr/bin/fakeroot (fakeroot) in auto mode. Setting up linux-image (2.6.35.22.23) ... Setting up menu (2.1.44ubuntu1) ... Setting up patch (2.6-2ubuntu1) ... Processing triggers for man-db ... Setting up dkms (2.1.1.2-3ubuntu1.1) ... Setting up bcmwl-kernel-source (5.60.48.36+bdcom-0ubuntu5) ... Loading new bcmwl-5.60.48.36+bdcom DKMS files... First Installation: checking all kernels... Building only for 2.6.35-22-generic Building for architecture i686 Building initial module for 2.6.35-22-generic Done. wl.ko: Running module version sanity check. - Original module - No original module exists within this kernel - Installation - Installing to /lib/modules/2.6.35-22-generic/updates/dkms/ depmod..... DKMS: install Completed. update-initramfs: deferring update (trigger activated) Processing triggers for install-info ... Processing triggers for doc-base ... Processing 31 changed 1 added doc-base file(s)... Registering documents with scrollkeeper... Processing triggers for menu ... Processing triggers for initramfs-tools ... update-initramfs: Generating /boot/initrd.img-2.6.35-22-generic Warning: No support for locale: en_GB.utf8 After rebooting, however, there were still no wireless networks in the NetworkManager Applet list. I opened the file /var/lib/NetworkManager/NetworkManager.state, and both NetworkEnabled and WirelessEnabled were set to True. While i'm very concious I may be asking a stupid question here, both my friend and I have nothing left to suggest, and as such - I would be very grateful for any answers as to how to get wireless working.

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• what differs a computer scientist/software engineer to regular people who learn programming language and APIs?

  - by Amumu

  In University, we learn and reinvent the wheel a lot to truly learn the programming concepts. For example, we may learn assembly language to understand, what happens inside the box, and how the system operates, when we execute our code. This helps understanding higher level concepts deeper. For example, memory management like in C is just an abstraction of manually managed memory contents and addresses. The problem is, when we're going to work, usually productivity is required more. I could program my own containers, or string class, or date/time (using POSIX with C system call) to do the job, but then, it would take much longer time to use existing STL or Boost library, which abstract all of those thing and very easy to use. This leads to an issue, that a regular person doesn't need to get through all the low level/under the hood stuffs, who learns only one programming language and using language-related APIs. These people may eventually compete with the mainstream graduates from computer science or software engineer and call themselves programmers. At first, I don't think it's valid to call them programmers. I used to think, a real programmer needs to understand the computer deeply (but not at the electronic level). But then I changed my mind. After all, they get the job done and satisfy all the test criteria (logic, performance, security...), and in business environment, who cares if you're an expert and understand how computer works or not. You may get behind the "amateurs" if you spend to much time learning about how things work inside. It is totally valid for those people to call themselves programmers. This makes me confuse. So, after all, programming should be considered an universal skill? Does programming language and concepts matter or the problems we solve matter? For example, many C/C++ vs Java and other high level language, one of the main reason is because C/C++ features performance, as well as accessing low level facility. One of the main reason (in my opinion), is coding in C/C++ seems complex, so people feel good about it (not trolling anyone, just my observation, and my experience as well. Try to google "C hacker syndrome"). While Java on the other hand, made for simplifying programming tasks to help developers concentrate on solving their problems. Based on Java rationale, if the programing language keeps evolve, one day everyone can map their logic directly with natural language. Everyone can program. On that day, maybe real programmers are mathematicians, who could perform most complex logic (including business logic and academic logic) without worrying about installing/configuring compiler, IDEs? What's our job as a computer scientist/software engineer? To solve computer specific problems or to solve problems in general? For example, take a look at this exame: http://cm.baylor.edu/ICPCWiki/attach/Problem%20Resources/2010WorldFinalProblemSet.pdf . The example requires only basic knowledge about the programming language, but focus more on problem solving with the language. In sum, what differs a computer scientist/software engineer to regular people who learn programming language and APIs? A mathematician can be considered a programmer, if he is good enough to use programming language to implement his formula. Can we programmer do this? Probably not for most of us, since we specialize about computer, not math. An electronic engineer, who learns how to use C to program for his devices, can be considered a programmer. If the programming languages keep being simplified, may one day the software engineers, who implements business logic and create softwares, be obsolete? (Not for computer scientist though, since many of the CS topics are scientific, and science won't change, but technology will).

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• W006.15 isp or T-mobile Network Error.

  - by Mike Koerner

  I just bought a new T-Mobile G2.  I wanted to turn on Wifi calling but kept receiving "W006.15 isp or T-mobile Network Error" and asking me to register.  After doing some research I looked at my cable modem/router logs and config.  There were fragmented packets originating from the phone and the incoming fragmented packets were blocked.  I disabled the "Block fragmented packets" setting and the phone was able to connect for Wifi calling

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