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  • how to allow certain packet with certian destination ports to forward using iptables?

    - by moataz metwally
    i have server and i virualized it into multiple windws vps's using kvm. i would like to make all vps behind the server firewall. to control all the ports of all vps's from the host server.i have tried to do this by that iptables file but it still blocking all the forward packets. when i remove -A FORWARD -j DROP from the file the vps will be out of the firewall control : # Generated by iptables-save v1.4.7 on Mon Oct 21 04:30:35 2013 *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [49:7546] -A OUTPUT -j ACCEPT -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT -p icmp -j DROP -A INPUT -i lo -j ACCEPT -A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT -A INPUT -p tcp -m state --state NEW -m tcp -m multiport --dports 5901:6010,4080:4085 -j ACCEPT -A FORWARD -p tcp -s 0/0 -d 0/0 --destination-port 3389 -j ACCEPT -A INPUT -j DROP -A FORWARD -j DROP COMMIT # Completed on Mon Oct 21 04:30:35 2013 and my ifconfig output: eth0 Link encap:Ethernet HWaddr 6C:62:6D:EF:B8:77 inet6 addr: fe80::6e62:XXX:feef:b877/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:4460000 errors:0 dropped:0 overruns:0 frame:0 TX packets:1825697 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:5461498823 (5.0 GiB) TX bytes:547852516 (522.4 MiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:6380 errors:0 dropped:0 overruns:0 frame:0 TX packets:6380 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:6481652 (6.1 MiB) TX bytes:6481652 (6.1 MiB) natbr2 Link encap:Ethernet HWaddr 52:54:00:48:72:53 inet addr:88.XXX.XXX.X53 Bcast:88.198.242.159 Mask:255.255.255.248 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1338720 errors:0 dropped:0 overruns:0 frame:0 TX packets:3570844 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:434791198 (414.6 MiB) TX bytes:4321751647 (4.0 GiB) viif1001 Link encap:Ethernet HWaddr FE:16:3E:0F:41:D8 inet6 addr: fe80::fc16:XXX:fe0f:41d8/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:358229 errors:0 dropped:0 overruns:0 frame:0 TX packets:479289 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:50127351 (47.8 MiB) TX bytes:261223068 (249.1 MiB) viif1002 Link encap:Ethernet HWaddr FE:16:3E:EA:65:FA inet6 addr: fe80::fc16:XXX:feea:65fa/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:575590 errors:0 dropped:0 overruns:0 frame:0 TX packets:1489296 errors:0 dropped:0 overruns:5412 carrier:0 collisions:0 txqueuelen:500 RX bytes:243629668 (232.3 MiB) TX bytes:1724640936 (1.6 GiB) viif1003 Link encap:Ethernet HWaddr FE:16:3E:2B:85:0E inet6 addr: fe80::fc16:XXX:fe2b:850e/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:413052 errors:0 dropped:0 overruns:0 frame:0 TX packets:1741801 errors:0 dropped:0 overruns:299 carrier:0 collisions:0 txqueuelen:500 RX bytes:147931054 (141.0 MiB) TX bytes:2338132498 (2.1 GiB) viifbr0 Link encap:Ethernet HWaddr 6C:62:6D:EF:B8:77 inet addr:176.XX.XX.X9 Bcast:176.9.0.95 Mask:255.255.255.224 inet6 addr: fe80::6e62:XXX:feef:b877/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:2685666 errors:0 dropped:0 overruns:0 frame:0 TX packets:1472089 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:4244043694 (3.9 GiB) TX bytes:523110523 (498.8 MiB)

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  • ufw portforwarding to virtualbox guest

    - by user85116
    My goal is to be able to connect using remote desktop on my desktop machine, to windows xp running in virtualbox on my linux server. My setup: server = debian squeeze, 64 bit, with a public IP address (host) virtualbox-ose 3.2.10 (from debian repo) windows xp running inside VBox as a guest; bridged networking mode in VBox, ip = 192.168.1.100 ufw as the firewall on debian, 3 ports are opened: 22 / ssh, 80 / apache, and 3389 for remote desktop My problem: If I try to use remote desktop on my home computer, I am unable to connect to the windows guest. If I first "ssh -X -C" into the debian server, then run "rdesktop 192.168.1.100", I am able to connect without issue. The windows firewall was configured to allow remote desktop connections, and I've even turned it off (as it is redundant here) to see if that was the problem but it made no difference. Since I am able to connect from inside the local subnet, I suspect that I have not setup my debian firewall correctly to handle connections from outside the LAN. Here is what I've done... First my ufw status: ufw status Status: active To Action From -- ------ ---- 22 ALLOW Anywhere 80 ALLOW Anywhere 3389 ALLOW Anywhere I edited /etc/ufw/sysctl.conf and added: net/ipv4/ip_forward=1 Edited /etc/default/ufw and added: DEFAULT_FORWARD_POLICY="ACCEPT" Edited /etc/ufw/before.rules and added: # setup port forwarding to forward rdp to windows VM *nat :PREROUTING - [0:0] -A PREROUTING -i eth0 -p tcp --dport 3389 -j DNAT --to-destination 192.168.1.100 -A PREROUTING -i eth0 -p udp --dport 3389 -j DNAT --to-destination 192.168.1.100 COMMIT # Don't delete these required lines, otherwise there will be errors *filter <snip> Restarted the firewall etc., but no connection. My log files on the debian host show this (my public ip address was removed for this posting but it is correct in the actual log): Feb 6 11:11:21 localhost kernel: [171991.856941] [UFW AUDIT] IN=eth0 OUT=eth0 SRC=aaa.bbb.ccc.dd DST=192.168.1.100 LEN=60 TOS=0x00 PREC=0x00 TTL=45 ID=27518 DF PROTO=TCP SPT=54201 DPT=3389 WINDOW=5840 RES=0x00 SYN URGP=0 Feb 6 11:11:21 localhost kernel: [171991.856963] [UFW ALLOW] IN=eth0 OUT=eth0 SRC=aaa.bbb.ccc.dd DST=192.168.1.100 LEN=60 TOS=0x00 PREC=0x00 TTL=45 ID=27518 DF PROTO=TCP SPT=54201 DPT=3389 WINDOW=5840 RES=0x00 SYN URGP=0 Feb 6 11:11:24 localhost kernel: [171994.856701] [UFW AUDIT] IN=eth0 OUT=eth0 SRC=aaa.bbb.ccc.dd DST=192.168.1.100 LEN=60 TOS=0x00 PREC=0x00 TTL=45 ID=27519 DF PROTO=TCP SPT=54201 DPT=3389 WINDOW=5840 RES=0x00 SYN URGP=0 Feb 6 11:11:24 localhost kernel: [171994.856723] [UFW ALLOW] IN=eth0 OUT=eth0 SRC=aaa.bbb.ccc.dd DST=192.168.1.100 LEN=60 TOS=0x00 PREC=0x00 TTL=45 ID=27519 DF PROTO=TCP SPT=54201 DPT=3389 WINDOW=5840 RES=0x00 SYN URGP=0 Feb 6 11:11:30 localhost kernel: [172000.856656] [UFW AUDIT] IN=eth0 OUT=eth0 SRC=aaa.bbb.ccc.dd DST=192.168.1.100 LEN=60 TOS=0x00 PREC=0x00 TTL=45 ID=27520 DF PROTO=TCP SPT=54201 DPT=3389 WINDOW=5840 RES=0x00 SYN URGP=0 Feb 6 11:11:30 localhost kernel: [172000.856678] [UFW ALLOW] IN=eth0 OUT=eth0 SRC=aaa.bbb.ccc.dd DST=192.168.1.100 LEN=60 TOS=0x00 PREC=0x00 TTL=45 ID=27520 DF PROTO=TCP SPT=54201 DPT=3389 WINDOW=5840 RES=0x00 SYN URGP=0 Although this is the current setup / configuration, I've also tried several variations of this; I thought maybe the ISP would be blocking 3389 for some reason and tried using different ports, but again there was no connection. Any ideas...? Did I forget to modify some file somewhere?

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  • VIM does not detect syntax of .ssh/config

    - by Erik
    On a plain Ubuntu installation (12.04 in my case) when I have no ~/.vimrc VIM does not detect syntax of .ssh/config. Syntax highlighting works, but it does not set the correct filetype. vi ~/.ssh/config :set syn? >syntax=conf When I do: set syn=sshconfig Then the syntax highlighting is as it should be. Why isn't the filetype automatically identified? And how can it be set automatically?

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  • No Telnet login prompt when used over SSH tunnel

    - by SCO
    Hi there ! I have a device, let's call it d1, runnning a lightweight Linux. This device is NATed by my internet box/router, hence not reachable from the Internet. That device runs a telnet daemon on it, and only has root as user (no pwd). Its ip address is 192.168.0.126 on the private network. From the private network (let's say 192.168.0.x), I can do: telnet 192.168.0.126 Where 192.168.0.126 is the IP address in the private network. This works correctly. However, to allow administration, I'd need to access that device from outside of that private network. Hence, I created an SSH tunnel like this on d1 : ssh -R 4455:localhost:23 ussh@s1 s1 is a server somewhere in the private network (but this is for testing purposes only, it will endup somewhere in the Internet), running a standard Linux distro and on which I created a user called 'ussh'. s1 IP address is 192.168.0.48. When I 'telnet' with the following, let's say from c1, 192.168.0.19 : telnet -l root s1 4455 I get : Trying 192.168.0.48... Connected to 192.168.0.48. Escape character is '^]'. Connection closed by foreign host . The connection is closed after roughly 30 seconds, and I didn't log. I tried without the -l switch, without any success. I tried to 'telnet' with IP addresses instead of names to avoid reverse DNS issues (although I added to d1 /etc/hosts a line refering to s1 IP/name, just in case), no success. I tried on another port than 4455, no success. I gathered Wireshark logs from s1. I can see : s1 sends SSH data to c1, c1 ACK s1 performs an AAAA DNS request for c1, gets only the Authoritave nameservers. s1 performs an A DNS request, then gets c1's IP address s1 sends a SYN packet to c1, c1 replies with a RST/ACK s1 sends a SYN to c1, C1 RST/ACK (?) After 0.8 seconds, c1 sends a SYN to s1, s1 SYN/ACK and then c1 ACK s1 sends SSH content to d1, d1 sends an ACK back to s1 s1 retries AAAA and A DNS requests After 5 seconds, s1 retries a SYN to c1, once again it is RST/ACKed by c1. This is repeated 3 more times. The last five packets : d1 sends SSH content to s1, s1 sends ACK and FIN/ACK to c1, c1 replies with FIN/ACK, s1 sends ACK to c1. The connection seems to be closed by the telnet daemon after 22 seconds. AFAIK, there is no way to decode the SSH stream, so I'm really stuck here ... Any ideas ? Thank you !

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  • What does this rule mean

    - by Kenyana
    When I run $ sudo iptables -L This is what I get Chain INPUT (policy ACCEPT) target prot opt source destination REJECT tcp -- anywhere anywhere tcp dpt:www flags:FIN,SYN,RST,ACK/SYN #conn/32 > 20 reject-with tcp-reset Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination What does this mean? I am pretty new to the whole Ubuntu world. I cannot access webmin at times, keep getting The connection has timed out error.

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  • Using LINQ to search a byte array for all subarrays that start/stop with certain byte

    - by Joel B
    I'm dealing with a COM port application and we have a defined variable-length packet structure that I'm talking to a micro-controller with. The packet has delimiters for the start and stop bytes. The trouble is that sometimes the read buffer can contain extraneous characters. It seems like I'll always get the whole packet, just some extra chatter before/after the actual data. So I have a buffer that I append data to whenever new data is received from the COM port. What is the best way to search this buffer for any possible occurrences of my packet? For example: Say my packet delimiter is 0xFF and I have an array as such { 0x00, 0xFF, 0x02, 0xDA, 0xFF, 0x55, 0xFF, 0x04 } How can I create a function/LINQ-statment that returns all subarrays that start and end with the delimiter (almost like a sliding-correlator with wildcards)? The sample would return the following 3 arrays: {0xFF, 0x02, 0xDA, 0xFF}, {0xFF, 0x55, 0xFF}, and {0xFF, 0x02, 0xDA, 0xFF, 0x55, 0xFF}

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  • How to receive packets on the MCU's serial port?

    - by itisravi
    Hello, Consider this code running on my microcontroller unit(MCU): while(1){ do_stuff; if(packet_from_PC) send_data_via_gpio(new_packet); //send via general purpose i/o pins else send_data_via_gpio(default_packet); do_other_stuff; } The MCU is also interfaced to a PC via a UART.Whenever the PC sends data to the MCU, the *new_packet* is sent, otherwise the *default_packet* is sent.Each packet can be 5 or more bytes with a pre defined packet structure. My question is: 1.Should i receive the entire packet from PC using inside the UART interrut service routine (ISR)? In this case, i have to implement a state machine inside the ISR to assemble the packet (which can be lengthy with if-else or switch-case blocks). 2.Detect a REQUEST command (one byte)from the PC in my ISR set a flag, diable UART interrupt alone and form the packet in my while(1) loop by polling the UART?

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  • pfSense router on a LAN with two gateways

    - by JohnCC
    I have a LAN with an ADSL modem/router on it. We have just gained an alternative high-speed internet connection at our location, and I want to connect the LAN to it, eventually dropping the ADSL. I've chosen to use a small PFSense box to connect the LAN to the new WAN connection. Two servers on the LAN run services accessible to the outside via NAT using the single ADSL WAN IP. We have DNS records which point to this IP. I want to do the same via the new connection, using the WAN IP there. That connection permits multiple IPs, so I have configured pfSense using virtual IP's, 1:1 NAT and appropriate firewall rules. When I change the servers' default gateway settings to the pfSense box, I can access the services via the new WAN IPs without a problem. However, I can no longer access them via the old WAN IP. If I set the servers' default gateway back to the ADSL router, then the opposite is true - I can access the services via the ADSL IP, but not via the new one. In the first case, I believe this is because an incoming SYN packet arrives at the ADSL WAN IP, and is NAT'd and sent to the internal IP of the server. The server responds with a SYN/ACK which it sends via its default gateway, the pfSense box. The pfSense box sees a SYN/ACK that it saw no SYN for and drops the packet. Is there any sensible way around this? I would like the services to be accessible via both IPs for a short period at least, since once I change the DNS it will take a while before everyone picks up the new address.

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  • Nginx proxy to IIS Connection Timeout

    - by MitMaro
    I am having an issue with random timeouts with a Nginx proxy connecting to an IIS machine. I have been watching a packet capture between the two servers and it seems that the IIS machine is receiving a SYN packet but is not responding with what I think should be an ACK response. Before the timeout occurs there seems to be a slower response from the IIS server. There is no unusual memory or processor usage on the IIS or Nginx machine. Some information on the servers and setup: Nginx Machine: Ubuntu 10.04 64bit Nginx 0.7.65 Amazon EC2 Windows Machine: Windows Server 2008 IIS 7 ASP.net Application in Integrated Mode Nginx Error: 2011/01/10 17:57:40 [error] 8297#0: *30 connect() failed (110: Connection timed out) while connecting to upstream, client: 209.***.***.***, server: secure.example.com, request: "GET /a/path/deliver.aspx HTTP/1.1", upstream: "http://***.***.***.****:****//another/path/deliver.aspx", host: "secure.example.com" WireShark Packets 6521.449528 10.***.***.*** -> 174.***.***.*** TCP 38695 > us-cli [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=477422103 TSER=0 WS=7 6524.443239 10.***.***.*** -> 174.***.***.*** TCP 38695 > us-cli [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=477422403 TSER=0 WS=7 6530.443241 10.***.***.*** -> 174.***.***.*** TCP 38695 > us-cli [SYN] Seq=0 Win=5840 Len=0 MSS=1460 TSV=477423003 TSER=0 WS=7

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  • Allow connections to only a specific URL via HTTPS with iptables, -m recent (potentially) and -m string (definitely)

    - by The Consumer
    Hello, Let's say that, for example, I want to allow connections only to subdomain.mydomain.com; I have it partially working, but it sometimes gets in a freaky loop with the client key exchange once the Client Hello is allowed. Ah, to make it even more annoying, it's a self-signed certificate, and the page requires authentication, and HTTPS is listening on a non-standard port... So the TCP/SSL Handshake experience will differ greatly for many users. Is -m recent the right route? Is there a more graceful method to allow the complete TCP stream once the string is seen? Here's what I have so far: #iptables -N SSL #iptables -A INPUT -i eth0 -p tcp -j SSL #iptables -A SSL -m recent --set -p tcp --syn --dport 400 #iptables -A SSL -m recent --update -p tcp --tcp-flags PSH,SYN,ACK SYN,ACK --sport 400 #iptables -A SSL -m recent --update -p tcp --tcp-flags PSH,SYN,ACK ACK --dport 400 #iptables -A SSL -m recent --remove -p tcp --tcp-flags PSH,ACK PSH,ACK --dport 400 -m string --algo kmp --string "subdomain.mydomain.com" -j ACCEPT Yes, I have tried to get around this with nginx tweaks, but I can't get nginx to return a 444 or abrupt disconnect before the client hello, if you can think of a way to achieve this instead, I'm all ears, err, eyes. (As suggested by a user, bringing this inquiry over from http://stackoverflow.com/questions/4628157/allow-connections-to-only-a-specific-url-via-https-with-iptables-m-recent-pote)

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  • There's a black hole in my server (TcpClient, TcpListener)

    - by Matías
    Hi, I'm trying to build a server that will receive files sent by clients over a network. If the client decides to send one file at a time, there's no problem, I get the file as I expected, but if it tries to send more than one I only get the first one. Here's the server code: I'm using one Thread per connected client public void ProcessClients() { while (IsListening) { ClientHandler clientHandler = new ClientHandler(listener.AcceptTcpClient()); Thread thread = new Thread(new ThreadStart(clientHandler.Process)); thread.Start(); } } The following code is part of ClientHandler class public void Process() { while (client.Connected) { using (MemoryStream memStream = new MemoryStream()) { int read; while ((read = client.GetStream().Read(buffer, 0, buffer.Length)) > 0) { memStream.Write(buffer, 0, read); } if (memStream.Length > 0) { Packet receivedPacket = (Packet)Tools.Deserialize(memStream.ToArray()); File.WriteAllBytes(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory), Guid.NewGuid() + receivedPacket.Filename), receivedPacket.Content); } } } } On the first iteration I get the first file sent, but after it I don't get anything. I've tried using a Thread.Sleep(1000) at the end of every iteration without any luck. On the other side I have this code (for clients) . . client.Connect(); foreach (var oneFilename in fileList) client.Upload(oneFilename); client.Disconnect(); . . The method Upload: public void Upload(string filename) { FileInfo fileInfo = new FileInfo(filename); Packet packet = new Packet() { Filename = fileInfo.Name, Content = File.ReadAllBytes(filename) }; byte[] serializedPacket = Tools.Serialize(packet); netStream.Write(serializedPacket, 0, serializedPacket.Length); netStream.Flush(); } netStream (NetworkStream) is opened on Connect method, and closed on Disconnect. Where's the black hole? Can I send multiple objects as I'm trying to do? Thanks for your time.

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  • UDP server doesnt accept calls from outside.

    - by rayman
    Hi, ive implement simple udp server on my Android device.(sdk 1.5) it works fine when i am runnning a local client on the phone sends through it trigger to my server. but when i try to get udp call from an outside server to my phone, it doesnt work. already make sure the outside server isnt blocked by firewall and it's sending the udp trigger to the right port, which my phone is listening to. i used natstat on the phone and checked that the phone is realy listening to the it's local ip and the port ive setted it to. here is my code of the server:(on the device) // server will listen to one client try { Thread udpServerThread = new Thread() { @Override public void run() { try { // Retrieve the ServerName InetAddress serverAddr = InetAddress .getByName("localhost"); Log.d("UDP", "S: Connecting..."); // Create new UDP-Socket socket = new DatagramSocket(SERVERPORT,serverAddr); byte[] buf = new byte[17]; // * Prepare a UDP-Packet that can contain the data we // * want to receive DatagramPacket packet = new DatagramPacket(buf, buf.length); Log.d("UDP", "S: Receiving..."); // wait to Receive the UDP-Packet socket.receive(packet); Log.d("UDP", "S: Received: '" + new String(packet.getData()) + "'"); acceptedMsg=new String(packet.getData()); notifyService(acceptedMsg); Log.d("UDP", "S: Done."); } catch (Exception e) { Log.e("UDP", "S: Error", e); } } }; udpServerThread.start(); } catch (Exception E) { Log.e("r",E.getMessage()) ; } so as i said, when i try it with local client(seperate thread) which sends udp trigger it works fine, but when i take this client implementation and put it on an outside real server, after UDP being sent, the phone doesnt respond to it. any idea? thanks, ray.

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  • Protocol specification in XML

    - by Mathijs
    Is there a way to specify a packet-based protocol in XML, so (de)serialization can happen automatically? The context is as follows. I have a device that communicates through a serial port. It sends and receives a byte stream consisting of 'packets'. A packet is a collection of elementary data types and (sometimes) other packets. Some elements of packets are conditional; their inclusion depends on earlier elements. I have a C# application that communicates with this device. Naturally, I don't want to work on a byte-level throughout my application; I want to separate the protocol from my application code. Therefore I need to translate the byte stream to structures (classes). Currently I have implemented the protocol in C# by defining a class for each packet. These classes define the order and type of elements for each packet. Making class members conditional is difficult, so protocol information ends up in functions. I imagine XML that looks like this (note that my experience designing XML is limited): <packet> <field name="Author" type="int32" /> <field name="Nickname" type="bytes" size="4"> <condition type="range"> <field>Author</field> <min>3</min> <max>6</min> </condition> </field> </packet> .NET has something called a 'binary serializer', but I don't think that's what I'm looking for. Is there a way to separate protocol and code, even if packets 'include' other packets and have conditional elements?

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  • Oracle Coherence, Split-Brain and Recovery Protocols In Detail

    - by Ricardo Ferreira
    This article provides a high level conceptual overview of Split-Brain scenarios in distributed systems. It will focus on a specific example of cluster communication failure and recovery in Oracle Coherence. This includes a discussion on the witness protocol (used to remove failed cluster members) and the panic protocol (used to resolve Split-Brain scenarios). Note that the removal of cluster members does not necessarily indicate a Split-Brain condition. Oracle Coherence does not (and cannot) detect a Split-Brain as it occurs, the condition is only detected when cluster members that previously lost contact with each other regain contact. Cluster Topology and Configuration In order to create an good didactic for the article, let's assume a cluster topology and configuration. In this example we have a six member cluster, consisting of one JVM on each physical machine. The member IDs are as follows: Member ID  IP Address  1  10.149.155.76  2  10.149.155.77  3  10.149.155.236  4  10.149.155.75  5  10.149.155.79  6  10.149.155.78 Members 1, 2, and 3 are connected to a switch, and members 4, 5, and 6 are connected to a second switch. There is a link between the two switches, which provides network connectivity between all of the machines. Member 1 is the first member to join this cluster, thus making it the senior member. Member 6 is the last member to join this cluster. Here is a log snippet from Member 6 showing the complete member set: 2010-02-26 15:27:57.390/3.062 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=main, member=6): Started DefaultCacheServer... SafeCluster: Name=cluster:0xDDEB Group{Address=224.3.5.3, Port=35465, TTL=4} MasterMemberSet ( ThisMember=Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) OldestMember=Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) ActualMemberSet=MemberSet(Size=6, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=5, Timestamp=2010-02-26 15:27:49.095, Address=10.149.155.79:8088, MachineId=1103, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:3229, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) RecycleMillis=120000 RecycleSet=MemberSet(Size=0, BitSetCount=0 ) ) At approximately 15:30, the connection between the two switches is severed: Thirty seconds later (the default packet timeout in development mode) the logs indicate communication failures across the cluster. In this example, the communication failure was caused by a network failure. In a production setting, this type of communication failure can have many root causes, including (but not limited to) network failures, excessive GC, high CPU utilization, swapping/virtual memory, and exceeding maximum network bandwidth. In addition, this type of failure is not necessarily indicative of a split brain. Any communication failure will be logged in this fashion. Member 2 logs a communication failure with Member 5: 2010-02-26 15:30:32.638/196.928 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=2): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=5, Timestamp=2010-02-26 15:27:49.095, Address=10.149.155.79:8088, MachineId=1103, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:3229, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) ) The Coherence clustering protocol (TCMP) is a reliable transport mechanism built on UDP. In order for the protocol to be reliable, it requires an acknowledgement (ACK) for each packet delivered. If a packet fails to be acknowledged within the configured timeout period, the Coherence cluster member will log a packet timeout (as seen in the log message above). When this occurs, the cluster member will consult with other members to determine who is at fault for the communication failure. If the witness members agree that the suspect member is at fault, the suspect is removed from the cluster. If the witnesses unanimously disagree, the accuser is removed. This process is known as the witness protocol. Since Member 2 cannot communicate with Member 5, it selects two witnesses (Members 1 and 4) to determine if the communication issue is with Member 5 or with itself (Member 2). However, Member 4 is on the switch that is no longer accessible by Members 1, 2 and 3; thus a packet timeout for member 4 is recorded as well: 2010-02-26 15:30:35.648/199.938 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=2): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) Member 1 has the ability to confirm the departure of member 4, however Member 6 cannot as it is also inaccessible. At the same time, Member 3 sends a request to remove Member 6, which is followed by a report from Member 3 indicating that Member 6 has departed the cluster: 2010-02-26 15:30:35.706/199.996 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=2): MemberLeft request for Member 6 received from Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) 2010-02-26 15:30:35.709/199.999 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=2): MemberLeft notification for Member 6 received from Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) The log for Member 3 determines how Member 6 departed the cluster: 2010-02-26 15:30:35.161/191.694 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=3): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) ) 2010-02-26 15:30:35.165/191.698 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=3): Member departure confirmed by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) ); removing Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) In this case, Member 3 happened to select two witnesses that it still had connectivity with (Members 1 and 2) thus resulting in a simple decision to remove Member 6. Given the departure of Member 6, Member 2 is left with a single witness to confirm the departure of Member 4: 2010-02-26 15:30:35.713/200.003 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=2): Member departure confirmed by MemberSet(Size=1, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) ); removing Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) In the meantime, Member 4 logs a missing heartbeat from the senior member. This message is also logged on Members 5 and 6. 2010-02-26 15:30:07.906/150.453 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=PacketListenerN, member=4): Scheduled senior member heartbeat is overdue; rejoining multicast group. Next, Member 4 logs a TcpRing failure with Member 2, thus resulting in the termination of Member 2: 2010-02-26 15:30:21.421/163.968 Oracle Coherence GE 3.5.3/465p2 <D4> (thread=Cluster, member=4): TcpRing: Number of socket exceptions exceeded maximum; last was "java.net.SocketTimeoutException: connect timed out"; removing the member: 2 For quick process termination detection, Oracle Coherence utilizes a feature called TcpRing which is a sparse collection of TCP/IP-based connections between different members in the cluster. Each member in the cluster is connected to at least one other member, which (if at all possible) is running on a different physical box. This connection is not used for any data transfer, only heartbeat communications are sent once a second per each link. If a certain number of exceptions are thrown while trying to re-establish a connection, the member throwing the exceptions is removed from the cluster. Member 5 logs a packet timeout with Member 3 and cites witnesses Members 4 and 6: 2010-02-26 15:30:29.791/165.037 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=5): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) 2010-02-26 15:30:29.798/165.044 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=5): Member departure confirmed by MemberSet(Size=2, BitSetCount=2 Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ); removing Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) Eventually we are left with two distinct clusters consisting of Members 1, 2, 3 and Members 4, 5, 6, respectively. In the latter cluster, Member 4 is promoted to senior member. The connection between the two switches is restored at 15:33. Upon the restoration of the connection, the cluster members immediately receive cluster heartbeats from the two senior members. In the case of Members 1, 2, and 3, the following is logged: 2010-02-26 15:33:14.970/369.066 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=1): The member formerly known as Member(Id=4, Timestamp=2010-02-26 15:30:35.341, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) has been forcefully evicted from the cluster, but continues to emit a cluster heartbeat; henceforth, the member will be shunned and its messages will be ignored. Likewise for Members 4, 5, and 6: 2010-02-26 15:33:14.343/336.890 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=4): The member formerly known as Member(Id=1, Timestamp=2010-02-26 15:30:31.64, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) has been forcefully evicted from the cluster, but continues to emit a cluster heartbeat; henceforth, the member will be shunned and its messages will be ignored. This message indicates that a senior heartbeat is being received from members that were previously removed from the cluster, in other words, something that should not be possible. For this reason, the recipients of these messages will initially ignore them. After several iterations of these messages, the existence of multiple clusters is acknowledged, thus triggering the panic protocol to reconcile this situation. When the presence of more than one cluster (i.e. Split-Brain) is detected by a Coherence member, the panic protocol is invoked in order to resolve the conflicting clusters and consolidate into a single cluster. The protocol consists of the removal of smaller clusters until there is one cluster remaining. In the case of equal size clusters, the one with the older Senior Member will survive. Member 1, being the oldest member, initiates the protocol: 2010-02-26 15:33:45.970/400.066 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=1): An existence of a cluster island with senior Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) containing 3 nodes have been detected. Since this Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) is the senior of an older cluster island, the panic protocol is being activated to stop the other island's senior and all junior nodes that belong to it. Member 3 receives the panic: 2010-02-26 15:33:45.803/382.336 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=3): Received panic from senior Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) caused by Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member 4, the senior member of the younger cluster, receives the kill message from Member 3: 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. In turn, Member 4 requests the departure of its junior members 5 and 6: 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. 2010-02-26 15:33:43.343/349.015 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=6): Received a Kill message from a valid Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer); stopping cluster service. Once Members 4, 5, and 6 restart, they rejoin the original cluster with senior member 1. The log below is from Member 4. Note that it receives a different member id when it rejoins the cluster. 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. 2010-02-26 15:33:46.921/369.468 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Service Cluster left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Invocation:InvocationService, member=4): Service InvocationService left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=OptimisticCache, member=4): Service OptimisticCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=ReplicatedCache, member=4): Service ReplicatedCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=DistributedCache, member=4): Service DistributedCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Invocation:Management, member=4): Service Management left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service Management with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service DistributedCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service ReplicatedCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service OptimisticCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service InvocationService with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member(Id=6, Timestamp=2010-02-26 15:33:47.046, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) left Cluster with senior member 4 2010-02-26 15:33:49.218/371.765 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=main, member=n/a): Restarting cluster 2010-02-26 15:33:49.421/371.968 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=n/a): Service Cluster joined the cluster with senior service member n/a 2010-02-26 15:33:49.625/372.172 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=n/a): This Member(Id=5, Timestamp=2010-02-26 15:33:50.499, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=1) joined cluster "cluster:0xDDEB" with senior Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=2) Cool isn't it?

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  • Too much delay while sending object over UDP to server

    - by RomZes
    I'm getting 4 sec delay when sending objects over UDP. Working on small game and trying to implement multiplayer. For now just trying to synchronize movements of 2 balls on the screen. StartingPoint.java is my server(first player), that receiving serialized objects (coordinates). SecondPlayer.java is client that sending serialized objects to server. When I'm moving my first object it appears 4 seconds later on different screen. StartingPoint.java @Override public void run() { byte[] receiveData = new byte[256]; byte[] sendData = new byte[256]; // DatagramSocket socketS; try { socket = new DatagramSocket(5000); System.out.println("Socket created on "+ port + " port"); } catch (SocketException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } while(true){ b1.update(this); b3.update(); System.out.println("Starting server..."); //// Receiving and deserializing object try { //socket.setSoTimeout(1000); DatagramPacket packet = new DatagramPacket(buf, buf.length); socket.receive(packet); byte[] data = packet.getData(); ByteArrayInputStream in = new ByteArrayInputStream(data); ObjectInputStream is = new ObjectInputStream(in); // socket.setSoTimeout(300); b1 = (Ball) is.readObject(); } catch (IOException | ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } SecondPlayer.java @Override public void run() { while(true){ b.update(); networkSend(); repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } } public void networkSend(){ // Serialize to a byte array try { ByteArrayOutputStream bStream = new ByteArrayOutputStream(); ObjectOutputStream oo; oo = new ObjectOutputStream(bStream); oo.writeObject(b); oo.flush(); oo.close(); byte[] bufCar = bStream.toByteArray(); //socket = new DatagramSocket(); //socket.setSoTimeout(1000); InetAddress address = InetAddress.getByName("localhost"); DatagramPacket packet = new DatagramPacket(bufCar, bufCar.length, address, port); socket.send(packet); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }

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  • Java game applet development

    - by RomZes
    I'm getting 4 sec delay when sending objects over UDP. Working on small game and trying to implement multiplayer. For now just trying to synchronize movements of 2 balls on the screen. StartingPoint.java is my server(first player), that receiving serialized objects (coordinates). SecondPlayer.java is client that sending serialized objects to server. When I'm moving my first object it appears 4 seconds later on different screen. StartingPoint.java @Override public void run() { byte[] receiveData = new byte[256]; byte[] sendData = new byte[256]; // DatagramSocket socketS; try { socket = new DatagramSocket(5000); System.out.println("Socket created on "+ port + " port"); } catch (SocketException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } while(true){ b1.update(this); b3.update(); System.out.println("Starting server..."); //// Receiving and deserializing object try { //socket.setSoTimeout(1000); DatagramPacket packet = new DatagramPacket(buf, buf.length); socket.receive(packet); byte[] data = packet.getData(); ByteArrayInputStream in = new ByteArrayInputStream(data); ObjectInputStream is = new ObjectInputStream(in); // socket.setSoTimeout(300); b1 = (Ball) is.readObject(); } catch (IOException | ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } SecondPlayer.java @Override public void run() { while(true){ b.update(); networkSend(); repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } } public void networkSend(){ // Serialize to a byte array try { ByteArrayOutputStream bStream = new ByteArrayOutputStream(); ObjectOutputStream oo; oo = new ObjectOutputStream(bStream); oo.writeObject(b); oo.flush(); oo.close(); byte[] bufCar = bStream.toByteArray(); //socket = new DatagramSocket(); //socket.setSoTimeout(1000); InetAddress address = InetAddress.getByName("localhost"); DatagramPacket packet = new DatagramPacket(bufCar, bufCar.length, address, port); socket.send(packet); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }

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  • WOL for Asus M5A97 built in Realtek Network Adapter

    - by madphp
    I cant get wake on lan to work for my built in network adapter. Its a ASUS M5A97 motherboard, and the network adapter is a Realtek PCIe GBE. I have Shutdown WakeOnLan - Enabled Wake on Magic Packet - Enabled Wake on Pattern Match - Enabled WOL & Shutdown Link Speed - 10 Mbps First I have set up a magic packet client to listen, and the packet is getting through. I have also checked these in Power Management for the network adapter. Allow the computer to turn off this device to save power Allow this device to wake the computer Allow a magic packet to wake the computer.

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  • Can't join OS X Mavericks to AD Domain

    - by watkipet
    I'm attempting to join an OS X Mavericks (10.9) client to a Windows Server 2008 Active Directory domain, however the bind fails with this error in the OS X client's system.log: Oct 24 15:03:15 host.domain.com com.apple.preferences.users.remoteservice[5547]: -[ODCAddServerSheetController handleOtherActionError: gotError: Error Domain=com.apple.OpenDirectory Code=5202 "Authentication server encountered an error while attempting the requested operation." UserInfo=0x7f9e6cb3e180 {NSLocalizedDescription=Authentication server encountered an error while attempting the requested operation., NSLocalizedFailureReason=Authentication server encountered an error while attempting the requested operation.}, Authentication server encountered an error while attempting the requested operation. I've joined (bound) Ubuntu Linux clients to the same domain with net ads join in the past with no problems (using the same administrative user). I don't have access to any server logs. Here's the GUI error (from Directory Utility) on the OS X client: Here's the GUI error (from User's and Groups) in System Preferences on the OS X client: Update After some Wiresharking I've got some more info: OS X Client - KDC (over UDP): AS_REQ (no padata) OS X Client <- KDC (over UDP): KRB5KDC_ERR_PREAUTH_REQUIRED OS X Client - KDC (over UDP): AS_REQ (this time with PA-ENC-TIMESTAMP in padata) OS X Client <- KDC (over UDP): KRB5KDC_ERR_RESPONSE_TOO_BIG OS X Client - KDC (over TCP): AS_REQ (also with PA-ENC-TIMESTAMP in padata) OS X Client <- KDC (over TCP): KDC_ERR_ETYPE_NOSUPP ...and that's it. This is what I think is going on: The OS X client sends a kerberos request. The KDC says, "You need to pre-authenticate. Try again" The OS X client tries to pre-authenticate (all this so far is over UDP) Something gets lost on our network and the KDC says, "Oops something went wrong" The OS X client switches to TCP and tries again. Over TCP, the KDC says, "You're using an encryption type I don't support" Note that in its padata records, the OS X client is always using "aes256-cts-hmac-sha1-96" as its encryption type. However, in its KDC_REQ_BODY record it lists the aes256-cts-hmac-sha1-96, aes128-cts-hmac-sha1-96, des3-cbc-sha1, and rc4-hmac encryption types. When the KDC comes back with KDC_ERR_ETYPE_NOSUPP, it uses rc4-hmac as its encryption type in its padata record. I know next to nothing about Kerberos, but it seems to me that the OS X client should go ahead and try the rc4-hmac encryption type. However, it does nothing after this. Update 2 Here's the debug log from Directory Services on the OS X client. Sorry--it's long. 2013-10-25 14:19:13.219128 PDT - 10544.20463 - ODNodeCustomCall request, NodeID: 52A65FAE-4B24-455D-86EC-2199A780D234, Code: 80 2013-10-25 14:19:13.220409 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - client requested OU - 'CN=Computers,DC=domain,DC=com' 2013-10-25 14:19:13.220427 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - Binding using '[email protected]' for kerberos ID 2013-10-25 14:19:13.220571 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - new kerberos credential cache 'MEMORY:0x7fa713635470' for '[email protected]' 2013-10-25 14:19:13.220623 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: loop 1 2013-10-25 14:19:13.220639 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - KDC send 0 patypes 2013-10-25 14:19:13.220653 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - fast disabled, not doing any fast wrapping 2013-10-25 14:19:13.220699 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - Trying to find service kdc for realm DOMAIN.COM flags 0 2013-10-25 14:19:13.221275 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - submissing new requests to new host 2013-10-25 14:19:13.221326 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - connecting to host: udp 192.168.0.1:kerberos (192.168.0.1) tid: 00000001 2013-10-25 14:19:13.221373 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - writing packet: udp 192.168.0.1:kerberos (192.168.0.1) tid: 00000001 2013-10-25 14:19:13.222588 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - reading packet: udp 192.168.0.1:kerberos (192.168.0.1) tid: 00000001 2013-10-25 14:19:13.222617 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - host completed: udp 192.168.0.1:kerberos (192.168.0.1) tid: 00000001 2013-10-25 14:19:13.222665 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_sendto_context DOMAIN.COM done: 0 hosts 1 packets 1 wc: 0.001960 nr: 0.000000 kh: 0.000560 tid: 00000001 2013-10-25 14:19:13.222705 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: loop 2 2013-10-25 14:19:13.222737 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: processing input 2013-10-25 14:19:13.222752 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: got an KRB-ERROR from KDC 2013-10-25 14:19:13.222775 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: KRB-ERROR -1765328359/Additional pre-authentication required 2013-10-25 14:19:13.222791 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - KDC send 4 patypes 2013-10-25 14:19:13.222800 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - KDC send PA-DATA type: 19 2013-10-25 14:19:13.222808 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - KDC send PA-DATA type: 2 2013-10-25 14:19:13.222816 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - KDC send PA-DATA type: 16 2013-10-25 14:19:13.222825 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - KDC send PA-DATA type: 15 2013-10-25 14:19:13.222840 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: using ENC-TS with enctype 18 2013-10-25 14:19:13.222850 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: using default_s2k_func 2013-10-25 14:19:13.227443 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - fast disabled, not doing any fast wrapping 2013-10-25 14:19:13.227502 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - Trying to find service kdc for realm DOMAIN.COM flags 0 2013-10-25 14:19:13.228233 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - submissing new requests to new host 2013-10-25 14:19:13.228320 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - connecting to host: udp 192.168.0.1:kerberos (192.168.0.1) tid: 00010001 2013-10-25 14:19:13.228374 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - writing packet: udp 192.168.0.1:kerberos (192.168.0.1) tid: 00010001 2013-10-25 14:19:13.229930 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - reading packet: udp 192.168.0.1:kerberos (192.168.0.1) tid: 00010001 2013-10-25 14:19:13.229957 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - host completed: udp 192.168.0.1:kerberos (192.168.0.1) tid: 00010001 2013-10-25 14:19:13.229975 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_sendto trying over again (reset): 0 2013-10-25 14:19:13.230023 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - Trying to find service kdc for realm DOMAIN.COM flags 2 2013-10-25 14:19:13.230664 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - submissing new requests to new host 2013-10-25 14:19:13.230726 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - connecting to host: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00010002 2013-10-25 14:19:13.230818 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - connecting to 11: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00010002 2013-10-25 14:19:13.231101 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - writing packet: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00010002 2013-10-25 14:19:13.232743 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - reading packet: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00010002 2013-10-25 14:19:13.232777 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - host completed: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00010002 2013-10-25 14:19:13.232798 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_sendto_context DOMAIN.COM done: 0 hosts 2 packets 2 wc: 0.005316 nr: 0.000000 kh: 0.001339 tid: 00010002 2013-10-25 14:19:13.232856 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: loop 3 2013-10-25 14:19:13.232868 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: processing input 2013-10-25 14:19:13.232900 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: using keyproc 2013-10-25 14:19:13.232910 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: using default_s2k_func 2013-10-25 14:19:13.236487 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: extracting ticket 2013-10-25 14:19:13.236557 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_init_creds: wc: 0.015944 2013-10-25 14:19:13.237022 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - Trying to find service kdc for realm DOMAIN.COM flags 2 2013-10-25 14:19:13.237444 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - submissing new requests to new host 2013-10-25 14:19:13.237482 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - connecting to host: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00020001 2013-10-25 14:19:13.237551 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - connecting to 11: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00020001 2013-10-25 14:19:13.237900 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - writing packet: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00020001 2013-10-25 14:19:13.238616 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - reading packet: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00020001 2013-10-25 14:19:13.238645 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - host completed: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00020001 2013-10-25 14:19:13.238674 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_sendto_context DOMAIN.COM done: 0 hosts 1 packets 1 wc: 0.001656 nr: 0.000000 kh: 0.000409 tid: 00020001 2013-10-25 14:19:13.238839 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - Trying to find service kdc for realm DOMAIN.COM flags 2 2013-10-25 14:19:13.239302 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - submissing new requests to new host 2013-10-25 14:19:13.239360 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - connecting to host: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00030001 2013-10-25 14:19:13.239429 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - connecting to 11: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00030001 2013-10-25 14:19:13.239683 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - writing packet: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00030001 2013-10-25 14:19:13.240350 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - reading packet: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00030001 2013-10-25 14:19:13.240387 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - host completed: tcp 192.168.0.1:kerberos (192.168.0.1) tid: 00030001 2013-10-25 14:19:13.240415 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_sendto_context DOMAIN.COM done: 0 hosts 1 packets 1 wc: 0.001578 nr: 0.000000 kh: 0.000445 tid: 00030001 2013-10-25 14:19:13.240514 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - krb5_credential - krb5_get_credentials_with_flags: DOMAIN.COM wc: 0.003615 2013-10-25 14:19:13.240537 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - valid credentials for [email protected] 2013-10-25 14:19:13.240541 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - switching to cache 'MEMORY:0x7fa713635470' 2013-10-25 14:19:13.240545 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - switching GSS to cache 'MEMORY:0x7fa713635470 2013-10-25 14:19:13.240555 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - Bind Step 5 - Bind/Join computer to domain - 'domain.com' 2013-10-25 14:19:13.241345 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - resolving 'server.domain.com' 2013-10-25 14:19:13.241646 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - added socket 12 for host 'server.domain.com:389' address '192.168.0.2' to kqueue list 2013-10-25 14:19:13.241930 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - Setting kerberos server for 'Kerberos:DOMAIN.COM' to 'server.domain.com' 2013-10-25 14:19:13.241962 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - switching to cache 'MEMORY:0x7fa713635470' 2013-10-25 14:19:13.241969 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - switching GSS to cache 'MEMORY:0x7fa713635470 2013-10-25 14:19:13.242231 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - GSSAPI allow Confidentiality 2013-10-25 14:19:13.242234 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - setting realm 'DOMAIN.COM' for node '/Active Directory/domain.com' 2013-10-25 14:19:13.242239 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - GSSAPI allow Integrity (signing) 2013-10-25 14:19:13.242274 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - GSSAPI using hostname 'server.domain.com' 2013-10-25 14:19:13.242282 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - GSSAPI using initiator credential '[email protected]' 2013-10-25 14:19:13.250771 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - Authenticate to LDAP using Kerberos credential - 0 2013-10-25 14:19:13.250784 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - verified connectivity to '192.168.0.2' with socket 12 2013-10-25 14:19:13.251513 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - locating site using domain domain.com using CLDAP 2013-10-25 14:19:13.252145 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - using site of 'DOMAINGROUP' from CLDAP 2013-10-25 14:19:13.253626 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - resolving 'server2.domain.com' 2013-10-25 14:19:13.253933 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - added socket 13 for host 'server2.domain.com:389' address '192.168.0.1' to kqueue list 2013-10-25 14:19:13.254428 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - Setting kerberos server for 'Kerberos:DOMAIN.COM' to 'server2.domain.com' 2013-10-25 14:19:13.254462 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - switching to cache 'MEMORY:0x7fa713635470' 2013-10-25 14:19:13.254468 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - switching GSS to cache 'MEMORY:0x7fa713635470 2013-10-25 14:19:13.254617 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - setting realm 'DOMAIN.COM' for node '/Active Directory/domain.com' 2013-10-25 14:19:13.254661 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - GSSAPI allow Confidentiality 2013-10-25 14:19:13.254670 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - GSSAPI allow Integrity (signing) 2013-10-25 14:19:13.254689 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - GSSAPI using hostname 'server2.domain.com' 2013-10-25 14:19:13.254695 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - GSSAPI using initiator credential '[email protected]' 2013-10-25 14:19:13.262092 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - Authenticate to LDAP using Kerberos credential - 0 2013-10-25 14:19:13.262108 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - verified connectivity to '192.168.0.1' with socket 13 2013-10-25 14:19:13.262982 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - Computer account either already exists or DC is already Read/Write 2013-10-25 14:19:13.264968 PDT - 10544.20463, Node: /Active Directory, Module: ActiveDirectory - Adding record 'cn=spike,CN=Computers,DC=domain,DC=com' in 'domain.com' The failure point seems to be Computer account either already exists or DC is already Read/Write, however, I can search for 'spike' on the Active Directory server using Active Directory Explorer and it's not there. If I do the same search for the Linux and Windows PCs I added previously, I can find them.

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  • IP address spoofing using Source Routing

    - by iamrohitbanga
    With IP options we can specify the route we want an IP packet to take while connecting to a server. If we know that a particular server provides some extra functionality based on the IP address can we not utilize this by spoofing an IP packet so that the source IP address is the privileged IP address and one of the hosts on the Source Routing is our own. So if the privileged IP address is x1 and server IP address is x2 and my own IP address is x3. I send a packet from x1 to x2 which is supposed to pass through x3. x1 does not actually send the packet. It is just that x2 thinks the packet came from x1 via x3. Now in response if x2 uses the same routing policy (as a matter of courtesy to x1) then all packets would be received by x3. Will the destination typically use the same IP address sequences as specified in the routing header so that packets coming from the server pass through my IP where I can get the required information? Can we not spoof a TCP connection in the above case? Is this attack used in practice?

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  • How is the MTU is 65535 in UDP but ethernet does not allow frame size more than 1500 bytes

    - by nikku
    I am using a fast ethernet of 100 Mbps, whose frame size is less than 1500 bytes (1472 bytes for payload as per my textbook). In that, I was able to send and receive a UDP packet of message size 65507 bytes, which means the packet size was 65507 + 20 (IP Header) + 8 (UDP Header) = 65535. If the frame's payload size itself is maximum of 1472 bytes (as per my textbook), how can the packet size of IP be greater than that which here is 65535? I used sender code as char buffer[100000]; for (int i = 1; i < 100000; i++) { int len = send (socket_id, buffer, i); printf("%d\n", len); } Receiver code as while (len = recv (socket_id, buffer, 100000)) { printf("%d\n". len); } I observed that send returns -1 on i > 65507 and recv prints or receives a packet of maximum of length 65507.

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  • What is Allow multicast from Broadband Network?

    - by PeanutsMonkey
    If a wireless modem router has the option Allow multicast from Broadband Network, what does this mean exactly? What risks are there to leaving it enabled and why would you have it enabled? I understand that a broadcast is sending a packet to every device on the network and a multicast is send a packet to a specified set of addresses. A multicast packet can cross routers whereas a broadcast cannot although I don't quite understand how these "set of addresses are specified"

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  • VPN with client-to-client direct connectivity?

    - by Johannes Ernst
    When setting up a VPN, clients (say client1 and client2) usually authenticate to a server, and together the three constitute the VPN. When client1 wishes to send a packet to client2, this packet usually gets routed by way of server. Are there products / configuration blueprints for products where it is possible to send packets directly from client1 to client2 without going though server? (if the underlying network topology permits it, e.g. no firewalls in the way) If not, is there a way by which client1 can send a packet to client2 by way of server, without the server being able to snoop on the content of the packet? (E.g. because the packet is encrypted with the public key of client2) I just asked in the OpenVPN forum, and the answer I got was "not with OpenVPN". So my question is: are there other products with which this is possible? Open-source preferred ... One use case: client1 and client2, typically in separate offices, find themselves both at headquarters. Do they still need to talk to each other via the public internet? Links appreciated. Thank you.

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