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• Generic that takes only numeric types (int double etc)?

  - by brandon

  In a program I'm working on, I need to write a function to take any numeric type (int, short, long etc) and shove it in to a byte array at a specific offset. There exists a Bitconverter.GetBytes() method that takes the numeric type and returns it as a byte array, and this method only takes numeric types. So far I have: private void AddToByteArray<T>(byte[] destination, int offset, T toAdd) where T : struct { Buffer.BlockCopy(BitConverter.GetBytes(toAdd), 0, destination, offset, sizeof(toAdd)); } So basically my goal is that, for example, a call to AddToByteArray(array, 3, (short)10) would take 10 and store it in the 4th slot of array. The explicit cast exists because I know exactly how many bytes I want it to take up. There are cases where I would want a number that is small enough to be a short to really take up 4 bytes. On the flip side, there are times when I want an int to be crunched down to just a single byte. I'm doing this to create a custom network packet, if that makes any ideas pop in to your heads. If the where clause of a generic supported something like "where T : int || long || etc" I would be ok. (And no need to explain why they don't support that, the reason is fairly obvious) Any help would be greatly appreciated! Edit: I realize that I could just do a bunch of overloads, one for each type I want to support... but I'm asking this question because I want to avoid precisely that :)

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• [php,mysql] insert only adds upto 1000 records and ignoresall records after that.

  - by user560559

  Hello i have a large database where the client stores personal messages and fire email notifications [if allowed by the users]. certain users have the option of sending messages to their entire network of friends. some users have over 5000 friends in their network so if they select the whole network they'll be sending messages to over 5000 friends and system will store all the messages into a table. the problem is this that it does not insert more than 1000 records and ignores all inserts after the first 1000. i have increased the packet size, bulk_insert_buffer_size but still no luck. since the system stores some of the info in another table for reports, every insert returns its new message id. due to this i can not use the "insert into table (column1,column2) values (value1,value2) , (value1,value2)....etc." table engine is innodb, mysql version is 5.1.3 and is hosted on amazon web services. all i want is to fix this issue of inserting more than 1000 records at a time. as mentioned earlier, it works fine but only up to 1000 records and simply ignores all the records after that. i'm using php foreach(){} to insert message for each friend and if email is available, send notification to the user. this foreach(){} also inserts the same record in another table [with only 3 columns] for generating reports. thank you in advance for all the help and support. WMA.

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• Which are the most useful techniques for faster Bluetooth?

  - by Mike Howard

  Hi. I'm adding peer-to-peer bluetooth using GameKit to an iPhone shoot-em-up, so speed is vital. I'm sending about 40 messages a second each way, most of them with the faster GKSendDataUnreliable, all serializing with NSCoding. In testing between a 3G and 3GS, this is slowing the 3G down a lot more than I'd like. I'm wondering where I should concentrate my efforts to speed it up. How much slower is GKSendDataReliable? For the few packets that have to get there, would it be faster to send a GKSendDataUnreliable and have the peer send an acknowledgement so I can send again if I don't get the Ack within, say, 100ms? How much faster would it be to create the NSData instance using a regular C array rather than archiving with the NSCoding protocol? Is this serialization process (for about a dozen floats) just as slow as you'd expect from an object creation/deallocation overhead, or is something particularly slow happening? I heard that (for example) sending four seperate sets of data is much, much slower, than sending one piece of data four times the size. Would I make a significant saving by sending separate packets of data that wouldn't always go together in the same packet when they happen at the same time? Are there any other bluetooth performance secrets I've missed? Thanks for your help.

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• iPhone: Which are the most useful techniques for faster Bluetooth?

  - by Mike Howard

  Hi. I'm adding peer-to-peer bluetooth using GameKit to an iPhone shoot-em-up, so speed is vital. I'm sending about 40 messages a second each way, most of them with the faster GKSendDataUnreliable, all serializing with NSCoding. In testing between a 3G and 3GS, this is slowing the 3G down a lot more than I'd like. I'm wondering where I should concentrate my efforts to speed it up. How much slower is GKSendDataReliable? For the few packets that have to get there, would it be faster to send a GKSendDataUnreliable and have the peer send an acknowledgement so I can send again if I don't get the Ack within, say, 100ms? How much faster would it be to create the NSData instance using a regular C array rather than archiving with the NSCoding protocol? Is this serialization process (for about a dozen floats) just as slow as you'd expect from an object creation/deallocation overhead, or is something particularly slow happening? I heard that (for example) sending four seperate sets of data is much, much slower, than sending one piece of data four times the size. Would I make a significant saving by sending separate packets of data that wouldn't always go together in the same packet when they happen at the same time? Are there any other bluetooth performance secrets I've missed? Thanks for your help.

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• Insert only adds upto 1000 records and ignoresall records after that.

  - by user560559

  i have a large database where the client stores personal messages and fire email notifications [if allowed by the users]. certain users have the option of sending messages to their entire network of friends. some users have over 5000 friends in their network so if they select the whole network they'll be sending messages to over 5000 friends and system will store all the messages into a table. the problem is this that it does not insert more than 1000 records and ignores all inserts after the first 1000. i have increased the packet size, bulk_insert_buffer_size but still no luck. since the system stores some of the info in another table for reports, every insert returns its new message id. due to this i can not use the "insert into table (column1,column2) values (value1,value2) , (value1,value2)....etc." table engine is innodb, mysql version is 5.1.3 and is hosted on amazon web services. all i want is to fix this issue of inserting more than 1000 records at a time. as mentioned earlier, it works fine but only up to 1000 records and simply ignores all the records after that. i'm using php foreach(){} to insert message for each friend and if email is available, send notification to the user. this foreach(){} also inserts the same record in another table [with only 3 columns] for generating reports.

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• TCP/IP RST being sent differently in different browsers.

  - by Brian

  On Mac OS X (10.6), if I start a YouTube video download and pull the Ethernet cable for 5 or so seconds, then plug it back in, I get varying results depending on the browser. With Opera and Chrome, after I plug the cable back in the video continues to load. But with Safari and Firefox, it never does. Using Wireshark to look at the traffic, I found that Opera and Chrome simply ACK the first packet from YouTube after the cable has been plugged back in, but Safari and Firefox set the RST flag (0x4) in the TCP header and no more traffic follows. I can put a HUB in between the machine and the internet connection, the problem goes away and all four browsers continue loading the video when the cable is plugged back into the HUB. Again, looking at the Wireshark logs, it's evident that the machine doesn't see the Mulitcast connection close and there is simply a delay in the packets flowing through. So it seems that if Safari and Firefox sees a Multicast connection close, and then later see data on that same connection, they will send a RST. My question is why? What is the correct course of action, and why are 2/4 browsers doing it one way, while the other 2/4 are doing it another way? Is there somewhere in the code that I can see where this is happening in Firefox, for instance? Thank you very much.

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• How to detect a Socket disconnection?

  - by AngryHacker

  I've implemented a task using the async Sockets pattern in Silverlight 3. I started with Michael Schwarz's implementation and built on top of that. So basically, my Silverlight app establishes a persistent socket connection to a device and then data flows both ways as necessary between the device and the Silverlight app. One thing I am struggling with is how to detect disconnection. I could think of 2 approaches: Keep-Alive. I know this can be done at the Sockets level, but I am not sure how to do this in an async model. How would the Socket class let me know there has been a disconnection. Manual keep alive. Basically, I am having the Silverlight app send a dummy packet every 20 seconds or so. If it fails, I'd assume disconnection. However, incredibly, SocketAsyncEventArgs.SocketError always reports success, even if I simply unplug the device that the Silverlight app is connected to. I am not sure whether this is a bug or what or perhaps I need to upgrade to SL4. Any ideas, direction or implementation would be appreciated.

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• How to filter and intercept Linux packets by using net_dev_add() API?

  - by Khajavi

  I'm writing ethernet network driver for linux. I want to receive packets, edit and resend them. I know how to edit the packet in packet_interceptor function, but how can I drop incoming packets in this function?? #include <linux/netdevice.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <net/sock.h> struct packet_type my_proto; int packet_interceptor(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) { // I dont want certain packets go to upper in net_devices for further processing. // How can I drop sk_buff here?! return 0; } static int hello_init( void ) { printk(KERN_INFO "Hello, world!\n"); my_proto.type = htons(ETH_P_ALL); my_proto.dev = NULL; my_proto.func = packet_interceptor; dev_add_pack(&my_proto); return 0; } static void hello_exit(void) { dev_remove_pack(&my_proto); printk(KERN_INFO "Bye, world\n"); } module_init(hello_init); module_exit(hello_exit);

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• Ensure that my C# desktop application is making requests to my ASP .NET MVC action?

  - by Mathias Lykkegaard Lorenzen

  I've seen questions that are almost identical to this one, except minor but important differences that I would like to get detailed. Let's say that I have a controller and an action method in MVC which therefore accepts requests on the following URL: http://example.com/api/myapimethod?data=some-data-here. This URL is then being called regularly by 1000 clients or more spread out in the public. The reason for this is crowdsourcing. The clients around the globe help feed a global cache on my server, which makes it faster for the rest of the clients to fetch the data. Now, if I'm sneaky (and I am), I can go into Fiddler, Ethereal, Wireshark or any other packet sniffing tool and figure out which requests the program is making. By figuring that out, I can also replicate them, and fill the service with false corrupted data. What is the best approach to ensuring that the data received in my ASP .NET MVC action method is actually from the desktop client application, and not some falsely generated data that the user invented? Since it is all based on crowdsourcing, would it be a good idea for my users to be able to "vote" if some data is falsified, and then let an automatic cleanup commence if there are enough votes? I do not have access to a tool like SmartAssembly, so unfortunately my .NET program is fully decompilable. I realize this might be impossible to accomplish in an error-proof manner, but I would like to know where my best chances are.

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• Java: Cleaing up connection reset (but not by peer).

  - by Zombies

  There seems to be some confusion as well contradicting statements on various SO answers: http://stackoverflow.com/questions/585599/whats-causing-my-java-net-socketexception-connection-reset . You can see here that the accepted answer states that the connecteion was closed by other side. But this is not true, closing a connection doesn't cause a connection reset. It is cauesed by "an underlying TCP/IP error." What I want to know is if a SocketException: Connection reset means really besides "unerlying TCP/IP Error." What really causes this? As I doubt it has anything to do with the connection being closed (since closing a connection isn't an exception worthy flag, and reading from a closed connection is, but that isn't an "underlying TCP/IP error." My hypothesis is this Connection reset is caused from a server's failure to acknowledge an ACK packet (either wholly or just improperly as per TCP/IP). And that a SocketTimeoutException is generated only when no data is generated to be read (since this is thrown during a read after a certain duration, and read is waiting for data, but is not concerned with ACK packets). In other words, read() throws SocketTimeoutException if it didn't read any bytes of actual data (DATA LAYER) in its allotted time.

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• Detecting TCP dropout over an unreliable network

  - by yx

  I am doing some experimentation over an unreliable radio network (home brewed) using very rudimentary java socket programming to transfer messages back and forth between the end nodes. The setup is as follows: Node A --- Relay Node --- Node B One problem I am constantly running into is that somehow the connection drops out and neither Node A or B knows that the link is dead, and yet continues to transmit data. The TCP connection does not time out either. I have added in a heartbeat message that causes a timeout after a while, but I still would like to know what is the underlying cause of why TCP does not time out. Here are the options I am enabling when setting up a socket: channel.socket().setKeepAlive(false); channel.socket().setTrafficClass(0x08); // for max throughput This behavior is strange since it is totally different than when I have a wired network. On a wired network, I can simulate a disconnected connection by pulling out the ethernet cord, however, once I plug the cord back in, the connection becomes restablished and messages begin to be passed through once more. On the radio network, the connection is never reestablished and once it silently dies, the messages never resume. Is there some other unknown java implentation or setting for a socket that I can use, also, why am I seeing this behavior in the first place? And yes, before anyone says anything, I know TCP is not the preffered choice over an unreliable network, but in this case I wanted to ensure no packet loss.

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• SYN receives RST,ACK very frequently

  - by user1289508

  Hi Socket Programming experts, I am writing a proxy server on Linux for SQL Database server running on Windows. The proxy is coded using bsd sockets and in C, and it is working just fine. When I use a database client (written in JAVA, and running on a Linux box) to fire queries (with a concurrency of 100 or more) directly to the Database server, not experiencing connection resets. But through my proxy I am experiencing many connection resets. Digging deeper I came to know that connection from 'DB client' to 'Proxy' always succeeds but when the 'Proxy' tries to connect to the DB server the connection fails, due to the SYN packet getting RST,ACK. That was to give some background. The question is : Why does sometimes SYN receives RST,ACK? 'DB client(linux)' to 'Server(windows)' ---- Works fine 'DB client(linux) to 'Proxy(Linux)' to 'Server(windows)' ----- problematic I am aware that this can happen in "connection refused" case but this definitely is not that one. SYN flooding might be another scenario, but that does not explain fine behavior while firing to Server directly. I am suspecting some socket option setting may be required, that the client does before connecting and my proxy does not. Please put some light on this. Any help (links or pointers) is most appreciated. Additional info: Wrote a C client that does concurrent connections, which takes concurrency as an argument. Here are my observations: - At 5000 concurrency and above, some connects failed with 'connection refused'. - Below 2000, it works fine. But the actual problem is observed even at a concurrency of 100 or more. Note: The problem is time dependent sometimes it never comes at all and sometimes it is very frequent and DB client (directly to server) works fine at all times .

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• Rewriting Live TCP/IP (Layer 4) Streams

  - by user213060

  I want to rewrite TCP/IP streams. Ettercap's etterfilter command lets you perform simple live replacements of TCP/IP data based on fixed strings or regexes. Example: if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "gzip")) { replace("gzip", " "); msg("whited out gzip\n"); } } if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "deflate")) { replace("deflate", " "); msg("whited out deflate\n"); } } http://ettercap.sourceforge.net/forum/viewtopic.php?t=2833 I would like to rewrite streams based on my own filter program instead of just simple string replacements. Anyone have an idea of how to do this? Is there anything other than Ettercap that can do live replacement like this, maybe as a plugin to a VPN software or something? The rewriting should occur at the transport layer (Layer 4) as it does in this example, instead of a lower layer packet-based approach. Thanks!

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• What are the C# equivalent of these C++ structs

  - by Otake

  typedef union _Value { signed char c; unsigned char b; signed short s; unsigned short w; signed long l; unsigned long u; float f; double *d; char *p; } Value; typedef struct _Field { WORD nFieldId; BYTE bValueType; Value Value; } Field; typedef struct _Packet { WORD nMessageType; WORD nSecurityType; BYTE bExchangeId; BYTE bMarketCenter; int iFieldCount; char cSymbol[20]; Field FieldArr[1]; } Packet; What are the C# equivalent of these C++ structs? I am migrating some code from C++ to C# and having problems to migrate these structures. I had tried a few things but I always ended up having marshalling problems.

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• Creating a assertClass() method in JUnit

  - by Mike

  Hi, I'm creating a test platform for a protocol project based on Apache MINA. In MINA when you receive packets the messageReceived() method gets an Object. Ideally I'd like to use a JUnit method assertClass(), however it doesn't exist. I'm playing around trying to work out what is the closest I can get. I'm trying to find something similar to instanceof. Currently I have: public void assertClass(String msg, Class expected, Object given) { if(!expected.isInstance(given)) Assert.fail(msg); } To call this: assertClass("Packet type is correct", SomePacket.class, receivedPacket); This works without issue, however in experimenting and playing with this my interest was peaked by the instanceof operator. if (receivedPacket instanceof SomePacket) { .. } How is instanceof able to use SomePacket to reference the object at hand? It's not an instance of an object, its not a class, what is it?! Once establishing what type SomePacket is at that point is it possible to extend my assertClass() to not have to include the SomePacket.class argument, instead favouring SomePacket?

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• Java loop to collect the second and third elements every three in an array

  - by mhollander38

  I have a file with data in the form timestamp, coordinate, coordinate, seperated by spaces, as here; 14:25:01.215 370.0 333.0 I need to loop through and add the coordinates only to an array. The data from the file is read in and put into as String[] called info, from split(" "). I have two problems, I think the end of the file has a extra " " which I need to lose appropriately and I also want confirmation/suggestions of my loop, at the moment I am getting sporadic out of bounds exceptions. My loop is as follows; String[] info; info = dataHolder.split(" "); ArrayList<String> coOrds1 = new ArrayList<String>(); for (int counter = 0; counter < info.length; counter = counter+3) { coOrds1.add(info[counter+1]); coOrds1.add(info[counter+2]); } Help and suggestions appreciated. The text file is here but the class receives in a UDP packet from another class so I am unsure if this potentially adds " " at the end or not.

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• Authentication system - Return information that have to change every time

  - by paulohr

  I have a application (made in Delphi) that contains a Authentication system (login & password). This system is in PHP, and the application get results from PHP using HTTP GET method. The system returns 'OK' if login and password are correct, and 'NO' if not correct. Like this... procedure Check; var x: string; begin x:=Get('www.mywebsite.com/auth.php?user=xxxxxx&pass=zzzzzz'); if x='OK' then UnlockFeatures else MessageBox(0,'You're not VIP','Error',0); end; Well, it works fine, but it is very easy to circumvent this system with sniffers, packet editor or proxy. So, I want to get some information (in PHP) that changes every time, and that could be possible get the same information by my application. What can I do? I don't need codes. Just tips, suggestions, please... Thanks...

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• Encouter error "Linux ip -6 addr add failed" while setting up OpenVPN client

  - by Mickel

  I am trying to set up my router to use OpenVPN and have gotten quite far (I think), but something seems to be missing and I am not sure what. Here is my configuration for the client: client dev tun proto udp remote ovpn.azirevpn.net 1194 remote-random resolv-retry infinite auth-user-pass /tmp/password.txt nobind persist-key persist-tun ca /tmp/AzireVPN.ca.crt remote-cert-tls server reneg-sec 0 verb 3 OpenVPN client log: Nov 8 15:45:13 rc_service: httpd 15776:notify_rc start_vpnclient1 Nov 8 15:45:14 openvpn[27196]: OpenVPN 2.3.2 arm-unknown-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [MH] [IPv6] built on Nov 1 2013 Nov 8 15:45:14 openvpn[27196]: NOTE: the current --script-security setting may allow this configuration to call user-defined scripts Nov 8 15:45:14 openvpn[27196]: Socket Buffers: R=[116736->131072] S=[116736->131072] Nov 8 15:45:14 openvpn[27202]: UDPv4 link local: [undef] Nov 8 15:45:14 openvpn[27202]: UDPv4 link remote: [AF_INET]178.132.75.14:1194 Nov 8 15:45:14 openvpn[27202]: TLS: Initial packet from [AF_INET]178.132.75.14:1194, sid=44d80db5 8b36adf9 Nov 8 15:45:14 openvpn[27202]: WARNING: this configuration may cache passwords in memory -- use the auth-nocache option to prevent this Nov 8 15:45:14 openvpn[27202]: VERIFY OK: depth=1, C=RU, ST=Moscow, L=Moscow, O=Azire Networks, OU=VPN, CN=Azire Networks, name=Azire Networks, [email protected] Nov 8 15:45:14 openvpn[27202]: Validating certificate key usage Nov 8 15:45:14 openvpn[27202]: ++ Certificate has key usage 00a0, expects 00a0 Nov 8 15:45:14 openvpn[27202]: VERIFY KU OK Nov 8 15:45:14 openvpn[27202]: Validating certificate extended key usage Nov 8 15:45:14 openvpn[27202]: ++ Certificate has EKU (str) TLS Web Server Authentication, expects TLS Web Server Authentication Nov 8 15:45:14 openvpn[27202]: VERIFY EKU OK Nov 8 15:45:14 openvpn[27202]: VERIFY OK: depth=0, C=RU, ST=Moscow, L=Moscow, O=AzireVPN, OU=VPN, CN=ovpn, name=ovpn, [email protected] Nov 8 15:45:15 openvpn[27202]: Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key Nov 8 15:45:15 openvpn[27202]: Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Nov 8 15:45:15 openvpn[27202]: Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key Nov 8 15:45:15 openvpn[27202]: Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication Nov 8 15:45:15 openvpn[27202]: Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 2048 bit RSA Nov 8 15:45:15 openvpn[27202]: [ovpn] Peer Connection Initiated with [AF_INET]178.132.75.14:1194 Nov 8 15:45:17 openvpn[27202]: SENT CONTROL [ovpn]: 'PUSH_REQUEST' (status=1) Nov 8 15:45:17 openvpn[27202]: PUSH: Received control message: 'PUSH_REPLY,ifconfig-ipv6 2a03:8600:1001:4010::101f/64 2a03:8600:1001:4010::1,route-ipv6 2000::/3 2A03:8600:1001:4010::1,redirect-gateway def1 bypass-dhcp,dhcp-option DNS 194.1.247.30,tun-ipv6,route-gateway 178.132.77.1,topology subnet,ping 3,ping-restart 15,ifconfig 178.132.77.33 255.255.255.192' Nov 8 15:45:17 openvpn[27202]: OPTIONS IMPORT: timers and/or timeouts modified Nov 8 15:45:17 openvpn[27202]: OPTIONS IMPORT: --ifconfig/up options modified Nov 8 15:45:17 openvpn[27202]: OPTIONS IMPORT: route options modified Nov 8 15:45:17 openvpn[27202]: OPTIONS IMPORT: route-related options modified Nov 8 15:45:17 openvpn[27202]: OPTIONS IMPORT: --ip-win32 and/or --dhcp-option options modified Nov 8 15:45:17 openvpn[27202]: TUN/TAP device tun0 opened Nov 8 15:45:17 openvpn[27202]: TUN/TAP TX queue length set to 100 Nov 8 15:45:17 openvpn[27202]: do_ifconfig, tt->ipv6=1, tt->did_ifconfig_ipv6_setup=1 Nov 8 15:45:17 openvpn[27202]: /usr/sbin/ip link set dev tun0 up mtu 1500 Nov 8 15:45:18 openvpn[27202]: /usr/sbin/ip addr add dev tun0 178.132.77.33/26 broadcast 178.132.77.63 Nov 8 15:45:18 openvpn[27202]: /usr/sbin/ip -6 addr add 2a03:8600:1001:4010::101f/64 dev tun0 Nov 8 15:45:18 openvpn[27202]: Linux ip -6 addr add failed: external program exited with error status: 254 Nov 8 15:45:18 openvpn[27202]: Exiting due to fatal error Any ideas are most welcome!

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• Mac OS X Server Configure DHCP Options 66 and 67

  - by Paul Adams

  I need to configure Mountain Lion (10.8.2) OS X Server BOOTP to provide DHCP options 66 and 67 to provide PXE booting for PCs on my network. I have tried following the bootpd MAN pages, but they are not specific enough. I have also read conflicting information on the net, but nothing definitive for Mountain Lion DHCP. From bootpd man page: bootpd has a built-in type conversion table for many more options, mostly those specified in RFC 2132, and will try to convert from whatever type the option appears in the property list to the binary, packet format. For example, if bootpd knows that the type of the option is an IP address or list of IP addresses, it converts from the string form of the IP address to the binary, network byte order numeric value. If the type of the option is a numeric value, it converts from string, integer, or boolean, to the proper sized, network byte-order numeric value. Regardless of whether bootpd knows the type of the option or not, you can always specify the DHCP option using the data property list type <key>dhcp_option_128</key> <data> AAqV1Tzo </data> My TFTP server is 172.16.152.20 and the bootfile is pxelinux.0 I have edited /etc/bootpd.plist and added the following to the subnet dict: <key>dhcp_option_66</key> <data> LW4gLWUgrBCYFAo= </data> <key>dhcp_option_67</key> <data> LW4gLWUgcHhlbGludXguMAo= </data> According to the man page, the data elements are supposed to be Base64 encoded, but no matter what I try, I cannot get PXE clients to boot. I have tried encoding 172.16.152.20 using various methods: echo "172.16.152.20" | openssl enc -base64 returns MTcyLjE2LjE1Mi4yMAo= DHCP Option Code Utility (http://mac.softpedia.com/get/Internet-Utilities/DHCP-Option-Code-Utility.shtml) generating a string from 172.16.152.20 yields: LW4gLWUgMTcyLjE2LjE1Mi4yMAo= (used in the above example) DHCP Option Code Utility generating an IP Addresss from 172.16.152.20 yields: LW4gLWUgrBCYFAo= Encoding pxelinux.0 with the above methods likewise yields different encodings. I have tried using all three methods of encoding the data elements, but nothing seems to work i.e. my PXE boot clients do not get directed to my TFTP server. Can anyone help? Regards, Paul Adams.

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• My current iptable configuration doesn't work [on hold]

  - by Brad

  sudo chkconfig iptables off /etc/init.d/iptables on ### Clear/flush iptables sudo iptables -F sudo iptables -P INPUT ACCEPT sudo iptables -P OUTPUT ACCEPT sudo iptables -P FORWARD ACCEPT ### Allow SSH iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT ### Allow YUM updates sudo iptables -A OUTPUT -o eth0 -p tcp --dport 80 --match owner --uid-owner 0 --state NEW,ESTABLISHED -j ACCEPT sudo iptables -A OUTPUT -o eth0 -p tcp --dport 443 --match owner --uid-owner 0 --state NEW,ESTABLISHED -j ACCEPT ### Add your rules form the link above, here # ftp,smtp,imap,http,https,pop3,imaps,pop3s sudo iptables -A INPUT -i eth0 -p tcp -m multiport --dports 21,25,143,80,443,110,993,995 -m state --state NEW,ESTABLISHED -j ACCEPT sudo iptables -A OUTPUT -o eth0 -p tcp -m multiport --sports 21,25,143,80,110,443,993,995 -m state --state NEW,ESTABLISHED -j ACCEPT ## allow dns sudo iptables -A OUTPUT -p udp -o eth0 --dport 53 -j ACCEPT && sudo iptables -A INPUT -p udp -i eth0 --sport 53 -j ACCEPT # handling pings sudo iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT && sudo iptables -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT sudo iptables -A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT && sudo iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT # manage ddos attacks sudo iptables -A INPUT -p tcp --dport 80 -m limit --limit 25/minute --limit-burst 100 -j ACCEPT ## Implement some logging so that we know what's getting dropped sudo iptables -N LOGGING sudo iptables -A INPUT -j LOGGING sudo iptables -A LOGGING -m limit --limit 2/min -j LOG --log-prefix "IPTables Packet Dropped: " --log-level 7 sudo iptables -A LOGGING -j DROP # once a rule affects traffic then it is no longer managed # so if the traffic has not been accepted, block it sudo iptables -A INPUT -j DROP sudo iptables -I INPUT 1 -i lo -j ACCEPT sudo iptables -A OUTPUT -j DROP # allow only internal port forwarding sudo iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT sudo iptables -P FORWARD DROP # create an iptables config file sudo iptables-save > /root/dsl.fw ### Append the following to the rc.local file sudo nano /etc/rc.local ####--- /sbin/iptables-restore < sudo /root/dsl.fw ####--- /etc/init.d/iptables save ## check to see if this setting is working great. sudo service iptables restart ## log out/in testing sudo chkconfig iptables on What is the problem with this setup? If I restart the server it doesn't allow me back in SSH, and there may be a problem with Yum Original source of information: https://gist.github.com/Jonathonbyrd/1274837#file-instructions

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• Unable to mount XP share using fs-cifs from Linux

  - by MetalSearGolid

  I have a head unit that runs Linux that is connected to my PC via an Ethernet cable. I have a Windows XP share on this PC that the head unit needs to be able to mount, however, when mounting using the following command, it fails. Here is the command that fails, along with the verbose output: # fs-cifs -vvvvvvvvv -l //CUMBRIA-XP:192.168.1.2:/hnet /mnt/net cifs[2158679-1]: starting... cifs[2158679-1]: user is to input both name & passwd. cifs[2158679-1]: server [192.168.1.2] share [hnet] prefix [/mnt/net] user [nu ll] passwd [null] Welcome: 192.168.1.2(:/hnet) -> /mnt/net Username:headunit cifs[2158679-1]: user name: headunit length 8 cifs[2158679-1]: new server Password: cifs[2158679-1]: establishing connection to (192.168.1.2)CUMBRIA-XP cifs[2158679-1]: session request: 192.168.1.2:CUMBRIA-XP -> localhost cifs[2158679-1]: negotiating smb dialect cifs[2158679-1]: skey(idx=2): 00000000, challenge:(8), 6137bfa2 f2d7803b cifs[2158679-1]: negotiation: success with dialect=2 cifs[2158679-1]: logging headunit on 192.168.1.2 cifs[2158679-1]: new packet cifs[2158679-1]: returning: mid 0 status= 0 cifs[2158679-1]: smb_logon successful: dialect 2 enpass 1 cifs[2158679-1]: mounting 192.168.1.2:/hnet cifs[2158679-1]: returning: mid 1 status= 13 cifs[2158679-1]: smb_mount: Bad file descriptor cifs[2158679-1]: try upper case share. cifs[2158679-1]: session request: 192.168.1.2:CUMBRIA-XP -> localhost cifs[2158679-1]: negotiating smb dialect cifs[2158679-1]: skey(idx=2): 00000000, challenge:(8), 2d3e910f e3e148c4 cifs[2158679-1]: negotiation: success with dialect=2 cifs[2158679-1]: logging headunit on 192.168.1.2 cifs[2158679-1]: returning: mid 2 status= 0 cifs[2158679-1]: smb_logon successful: dialect 2 enpass 1 cifs[2158679-1]: mounting 192.168.1.2:/HNET cifs[2158679-1]: returning: mid 3 status= 13 cifs[2158679-1]: smb_mount: Bad file descriptor cifs[2158679-1]: mount failed. cifs[2158679-1]: io_mount: smb_connection failed: Bad file descriptor io_mount: Bad file descriptor cifs[2158679-1]: user is to input both name & passwd. fs-cifs: missing arguments, or all mount attempts failed. run "use fs-cifs" or "fs-cifs -h" for help. Any ideas? It is worthy to note that /mnt does not exist on the filesystem, but I was told by the company who gave us these units that fs-cifs should automatically create the /mnt/net folders if they don't exist.

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• Can't ssh tunnel to access a remote mysql server

  - by hobbes3

  I can't seem to figure out why I can't use ssh tunnel to connect to my remote MySQL server. I do ssh tunnel with [hobbes3@hobbes3] ~ $ ssh linode -L 3307:localhost:3306 Then on another terminal, I try [hobbes3@hobbes3] ~ $ mysql -h localhost -P 3307 -u root --protocol=tcp -p Enter password: ERROR 2013 (HY000): Lost connection to MySQL server at 'reading initial communication packet', system error: 2 On the server, it shows this: root@li534-120 ~ # channel 4: open failed: connect failed: Connection refused Here is my my.cnf on the server: [mysqld] # Settings user and group are ignored when systemd is used (fedora >= 15). # If you need to run mysqld under different user or group, # customize your systemd unit file for mysqld according to the # instructions in http://fedoraproject.org/wiki/Systemd user=mysql datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock # Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links=0 # Semisynchronous Replication # http://dev.mysql.com/doc/refman/5.5/en/replication-semisync.html # uncomment next line on MASTER ;plugin-load=rpl_semi_sync_master=semisync_master.so # uncomment next line on SLAVE ;plugin-load=rpl_semi_sync_slave=semisync_slave.so # Others options for Semisynchronous Replication ;rpl_semi_sync_master_enabled=1 ;rpl_semi_sync_master_timeout=10 ;rpl_semi_sync_slave_enabled=1 # http://dev.mysql.com/doc/refman/5.5/en/performance-schema.html ;performance_schema [mysqld_safe] log-error=/var/log/mysqld.log pid-file=/var/run/mysqld/mysqld.pid [mysqld] port = 3306 socket=/var/lib/mysql/mysql.sock skip-external-locking key_buffer_size = 64M max_allowed_packet = 128M sort_buffer_size = 512K net_buffer_length = 8K read_buffer_size = 256K read_rnd_buffer_size = 512K myisam_sort_buffer_size = 8M thread_cache = 8 max_connections = 25 query_cache_size = 16M table_open_cache = 1024 table_definition_cache = 1024 tmp_table_size = 32M max_heap_table_size = 32M bind-address = 0.0.0.0 Now sure if this helps but here is the MySQL user list: mysql> select * from mysql.user; +-----------+------+-------------------------------------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+------------------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+--------+-----------------------+ | Host | User | Password | Select_priv | Insert_priv | Update_priv | Delete_priv | Create_priv | Drop_priv | Reload_priv | Shutdown_priv | Process_priv | File_priv | Grant_priv | References_priv | Index_priv | Alter_priv | Show_db_priv | Super_priv | Create_tmp_table_priv | Lock_tables_priv | Execute_priv | Repl_slave_priv | Repl_client_priv | Create_view_priv | Show_view_priv | Create_routine_priv | Alter_routine_priv | Create_user_priv | Event_priv | Trigger_priv | Create_tablespace_priv | ssl_type | ssl_cipher | x509_issuer | x509_subject | max_questions | max_updates | max_connections | max_user_connections | plugin | authentication_string | +-----------+------+-------------------------------------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+------------------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+--------+-----------------------+ | localhost | root | *664328D3C5E263F4FB25185681AAE7E92B01B2B0 | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | | | | | 0 | 0 | 0 | 0 | | | | 127.0.0.1 | root | *664328D3C5E263F4FB25185681AAE7E92B01B2B0 | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | | | | | 0 | 0 | 0 | 0 | | | | ::1 | root | *664328D3C5E263F4FB25185681AAE7E92B01B2B0 | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | | | | | 0 | 0 | 0 | 0 | | | +-----------+------+-------------------------------------------+-------------+-------------+-------------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+-----------------+------------+------------+--------------+------------+-----------------------+------------------+--------------+-----------------+------------------+------------------+----------------+---------------------+--------------------+------------------+------------+--------------+------------------------+----------+------------+-------------+--------------+---------------+-------------+-----------------+----------------------+--------+-----------------------+ 3 rows in set (0.00 sec) I read about how MySQL treats localhost vs 127.0.0.1 as connecting via a socket or TCP, respectively. But I'm starting to get confused on what's really going on or if socket vs TCP is even the issue. Thanks in advance and I'm open for any tips and suggestions! Some more info: My MySQL client, running OS X 10.8.4, is mysql Ver 14.14 Distrib 5.6.10, for osx10.8 (x86_64) using EditLine wrapper My MySQL server, running on CentOS 6.4 32-bit, is mysql> SHOW VARIABLES LIKE "%version%"; +-------------------------+--------------------------------------+ | Variable_name | Value | +-------------------------+--------------------------------------+ | innodb_version | 1.1.8 | | protocol_version | 10 | | slave_type_conversions | | | version | 5.5.28 | | version_comment | MySQL Community Server (GPL) by Remi | | version_compile_machine | i686 | | version_compile_os | Linux | +-------------------------+--------------------------------------+ 7 rows in set (0.00 sec)

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• DNS "recursion not available" using a Cisco AnyConnect VPN connection

  - by codeape

  Does anyone have experience with configuring Cisco AnyConnect VPN? We have a problem with client DNS name resolution when connected over VPN. To me, it looks as if the Cisco AnyConnect VPN client intercepts DNS queries from the clients. Can someone confirm that the AnyConnect VPN client in fact does this (intercepts DNS traffic)? Where is this configured on the VPN server? EDIT: Here's how the routing table changes when I connect to the VPN: [~] $ diff -u /tmp/route_normal /tmp/route_vpn --- /tmp/route_normal 2010-01-20 19:23:47.000000000 +0100 +++ /tmp/route_vpn 2010-01-20 19:24:46.000000000 +0100 @@ -1,6 +1,10 @@ Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface +xxx.xxx.xx.xx.i 10.0.0.1 255.255.255.255 UGH 0 0 0 ath0 172.16.53.0 * 255.255.255.0 U 0 0 0 vmnet1 10.0.0.0 * 255.255.255.0 U 0 0 0 ath0 +172.17.20.0 * 255.255.255.0 U 0 0 0 cscotun 0 +192.168.111.0 172.17.20.212 255.255.255.0 UG 0 0 0 cscotun 0 172.16.140.0 * 255.255.255.0 U 0 0 0 vmnet8 +172.16.0.0 172.17.20.212 255.255.0.0 UG 0 0 0 cscotun 0 default 10.0.0.1 0.0.0.0 UG 0 0 0 ath0 EDIT 2: The IT guy has done "something" on the VPN endpoint. Now I get "recursion not available" when doing nslookup. The DNS servers have recursion enabled. So it must be the Cisco VPN DNS interception messing this up. ubuntu@domU-12-31-39-00-ED-14:~$ /opt/cisco/vpn/bin/vpn connect xxx.xxxxxx.xx ... >> Please enter your username and password ... >> notice: Establishing VPN... >> state: Connected >> notice: VPN session established to ... ubuntu@domU-12-31-39-00-ED-14:~$ nslookup www.vg.no ;; Got recursion not available from ..., trying next server ;; Got recursion not available from ..., trying next server ;; Got recursion not available from ..., trying next server ;; Got recursion not available from ..., trying next server Server: 172.16.0.23 Address: 172.16.0.23#53 ** server can't find www.vg.no.compute-1.internal: REFUSED ubuntu@domU-12-31-39-00-ED-14:~$ ping 195.88.55.16 PING 195.88.55.16 (195.88.55.16) 56(84) bytes of data. 64 bytes from 195.88.55.16: icmp_seq=1 ttl=240 time=110 ms 64 bytes from 195.88.55.16: icmp_seq=2 ttl=240 time=111 ms 64 bytes from 195.88.55.16: icmp_seq=3 ttl=240 time=109 ms ^C --- 195.88.55.16 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2017ms rtt min/avg/max/mdev = 109.953/110.379/111.075/0.496 ms

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• iptables (NAT/PAT) setup for SSH & Samba

  - by IanVaughan

  I need to access a Linux box via SSH & Samba that is hidden/connected behind another one. Setup :- A switch B C |----| |---| |----| |----| |eth0|----| |----|eth0| | | |----| |---| |eth1|----|eth1| |----| |----| Eg, SSH/Samba from A to C How does one go about this? I was thinking that it cannot be done via IP alone? Or can it? Could B say "hi on eth0, if your looking for 192.168.0.2, its here on eth1"? Is this NAT? This is a large private network, so what about if another PC has that IP?! More likely it would be PAT? A would say "hi 192.168.109.15:1234" B would say "hi on eth0, traffic for port 1234 goes on here eth1" How could that be done? And would the SSH/Samba demons see the correct packet header info and work?? IP info :- A - eth0 - 192.168.109.2 B - eth0 - B1 = 192.168.109.15 B2 = 172.24.40.130 - eth1 - 192.168.0.1 C - eth1 - 192.168.0.2 A, B & C are RHEL (RedHat) But Windows computers can be connected to the switch. I configured the 192.168.0.* IPs, they are changeable. Update after response from Eddie Few problems (and Machines' B IP is different!) From A :- ssh 172.24.40.130 works ok, (can get to B2) but ssh 172.24.40.130 -p 2022 -vv times out with :- OpenSSH_4.3p2, OpenSSL 0.9.8e-fips-rhel5 01 Jul 2008 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to 172.24.40.130 [172.24.40.130] port 2022. ...wait ages... debug1: connect to address 172.24.40.130 port 2022: Connection timed out ssh: connect to host 172.24.40.130 port 2022: Connection timed out From B2 :- $ service iptables status Table: filter Chain INPUT (policy ACCEPT) num target prot opt source destination Chain FORWARD (policy ACCEPT) num target prot opt source destination 1 ACCEPT tcp -- 0.0.0.0/0 192.168.0.2 tcp dpt:22 Chain OUTPUT (policy ACCEPT) num target prot opt source destination Table: nat Chain PREROUTING (policy ACCEPT) num target prot opt source destination 1 DNAT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:2022 to:192.168.0.2:22 Chain POSTROUTING (policy ACCEPT) num target prot opt source destination Chain OUTPUT (policy ACCEPT) num target prot opt source destination And ssh from B2 to C works fine :- $ ssh 192.168.0.2 Route info :- $ route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.0.0 * 255.255.255.0 U 0 0 0 eth1 172.24.40.0 * 255.255.255.0 U 0 0 0 eth0 169.254.0.0 * 255.255.0.0 U 0 0 0 eth1 default 172.24.40.1 0.0.0.0 UG 0 0 0 eth0 $ ip route 192.168.0.0/24 dev eth1 proto kernel scope link src 192.168.0.1 172.24.40.0/24 dev eth0 proto kernel scope link src 172.24.40.130 169.254.0.0/16 dev eth1 scope link default via 172.24.40.1 dev eth0 So I just dont know why the port forward doesnt work from A to B2?

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• Windows Server 2003 IPSec Tunnel Connected, But Not Working (Possibly NAT/RRAS Related)

  - by Kevinoid

  Configuration I have setup a "raw" IPSec tunnel between a Windows Server 2003 (SBS) machine and a Netgear FVG318 according to the instructions in Microsoft KB816514. The configuration is as follows (using the same conventions as the article): NetA | SBS2003 | FVG318 | NetB 10.0.0.0/24 | 216.x.x.x | 69.y.y.y | 10.0.254.0/24 Both the Main Mode and Quick Mode Security Associations are successfully completed and appear in the IP Security Monitor. I am also able to ping the SBS2003 server on its private address from any computer on NetB. The Problem Any traffic sent from a computer on NetA to NetB, or from SBS2003 to NetB (excluding ICMP Ping responses), is sent out on the public network interface outside the IPSec tunnel (no encryption or header authentication, as if the tunnel were not there). Pings sent from a computer on NetB to a computer on NetA successfully reach computers on NetA, but the responses are silently discarded by SBS2003 (they do not go out in the clear and do not generate any encrypted traffic). Possible Solutions Incorrect Configuration I could have mistyped something, somewhere, or KB816514 could be incorrect in some way. I have tried very hard to eliminate the first option. Have re-created the configuration several times, tried tweaking and adjusting all the settings I could without success (most prevent the SA from being established). NAT/RRAS I have seen multiple posts elsewhere suggesting that this could be due to interaction between NAT and the IPSec filters. Possibly the NetA private addresses get rewritten to 216.x.x.x before being compared with the Quick Mode IPSec filters and don't get tunneled because of the mismatch. In fact, The Cable Guy article from June 2005 "TCP/IP Packet Processing Paths" suggests that this is the case, (see step 2 and 4 of the Transit Traffic path). If this is the case, is there a way to exclude NetA-NetB traffic from NAT? Any thoughts, ideas, suggestions, and/or comments are appreciated. Update (2011-06-26) After failing to solve the problem, I resorted to paid Microsoft support. They were unable to solve the problem. Since then I have implemented a solution based on Linux that is working quite well. I will attempt to evaluate any proposed answers as best I can, but current configurations and time constraints will make this slow...

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