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• Allied Telesis router: IP filtering for the LOCAL interface

  - by syneticon-dj

  Given an Allied Telesis router with an AlliedWare OS (2.9.1) I would like to disable access to all management services of the router except for a number of subnets (or alternatively have what is a "management VLAN" with other manufacturers' switch and router models). What I have tried so far: creating a new VLAN and an appropriate IP interface, setting the LOCAL IP into this subnet, creating an IP filter for the IP interface and specifying my exclusion subnets: it simply does not work as intended as I can access the LOCAL IP set from any of the other VLAN interfaces - the traffic is apparently not going through my defined filter set at all creating a new IP filter set and binding it to the LOCAL IP interface: this seems not to affect any kind of traffic at all, the counters for the filter set remain at zero packets setting the Remote Security Officer Level IP address range: this only restricts the ability for a user with the Security Officer privilege level to log in from any but the specified address ranges / subnets. Unfortunately, it does not prevent service availability (and thus DoS capacity) or the ability to log in as a less privileged user (e.g. a "manager") calling technical support: unfortunately no solution so far What I have not tried: creating a filter set for each and every IP interface defined on the router and excluding access to the router's management IP: I would like to reduce the overhead induced by IP filters as the router already is CPU-constrained at times. Setting up filters for every IP interface would mean that each and every traffic packet would have to pass the filters, thus consuming CPU cycles. If by any means possible, I would like to find a different solution.

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• iptables, forward traffic for ip not active on the host itself

  - by gucki

  I have kvm guest which's netword card is conntected to the host using a tap device. The tap device is part of a bridge on the host together with eth0 so it can access the public network. So far everything works, the guest can access the public network and it can be accessed from the public network. Now the kvm process on the host provides a vnc server for the guest which listens on 127.0.0.1:5901 on the host. Is there any way to make this vnc server accessible by the ip address which the guest is using (ex. 192.168.0.249), without interrupting the guest from using the same ip (port 5901 is not used by the guest)? It should also work when the guest is not using any ip address at all. So basically I just want to fake IP xx is on the host and only answer/ forward traffic to port 5901 to the host itself. I tried using this NAT rule on the host, but it doesn't work. Ip forwarding is enabled at the host. iptables -t nat -A PREROUTING -p tcp --dst 192.168.0.249 --dport 5901 -j DNAT --to-destination 127.0.0.1:5901 I assume this is because the IP 192.168.0.249 is not not bound to any interfaces and so no ARP requests for it get answered and so no packets for this IP arrive at the host. How can make it work? :)

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• DNAT from localhost (127.0.0.1)

  - by pts

  I'd like to set up a TCP DNAT from 127.0.0.1, port 4242 to 11.22.33.44, port 5353 on Linux 3.x (currently 3.2.52, but I can upgrade if needed). It looks like the simple DNAT rule setup doesn't work, telnet 127.0.0.1 4242 hangs for a minute in Trying 127.0.0.1..., and then it times out. Maybe it's because the kernel is discarding the returning packets (e.g. SYN+ACK), because it considers them Martian. I don't need an explanation why the simple solution doesn't work, I need a solution, even if it's complicated (e.g. it involves creating may rules). I could set up a usual DNAT from another local IP address, outside the 127.0.0.0/8 network, but now I need 127.0.0.1 as the destination address. I know that I can set up a user-level port forwarding process, but now I need a solution which can be set up using iptables and doesn't need helper processes. I was googling for this for an hour. It was asked multiple times, but I couldn't find any working solutions. Also there are many questions about DNAT to 127.0.0.1, but I don't need that, I need the opposite.

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• Tunnell network requests with Windows 7

  - by mark

  I've Windows 7 64bit Pro client in a private LAN behind a Netgear wgr614v7 router. I've also a remote Debian server machine outside. I'd like to tunnel all (or specified ports/protocols) over this outside server, so when I'm on the Windows machine and I request serverfault.com it would not appear from the wgr614v7 public IP but from the server. But it's not only about HTTP traffic, it's basically about everything I'd like to: other TCP ports, even UDP, etc. It must be transparent to the application, e.g. they shouldn't be aware of this. All their requests just appear as being from the server and the tunnel between them takes care about the packets. I'm aware of e.g. Putty and forwarding individual ports or using it as a socks proxy, however not many applications to support this and the support in windows itself looks non-existent to me. I might add it should be something "reasonable" easy to set up. I've heard about PPTP but I'm unsure about it's security implications (by design). Should I go for VPN? There seem to be two common solutions for Linux (OpenSwan and StrongSwan), why would I pick the one over the other? I also fear that setting up a VPN might be quite complex, OTOH maybe it's the only sane way to do the things right? Or is OpenVPN sufficient? I'm seeking for open (source) solutions, what other options to I have or which direction should I head to?

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• Windows Server don't connect to network share

  - by user104775

  Windows Server don't connect to network share. Network share is work. Ping Blockquote Pinging 109.123.146.223 with 32 bytes of data: Reply from 109.123.146.223: bytes=32 time<1ms TTL=63 Reply from 109.123.146.223: bytes=32 time<1ms TTL=63 Reply from 109.123.146.223: bytes=32 time<1ms TTL=63 Ping statistics for 109.123.146.223: Packets: Sent = 3, Received = 3, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms net view \shareaddress Blockquote System error 53 has occurred. The network path was not found. When network share was connected, I was got a error message: Blockquote \ "Mapped disk letter" refers to a location that is unavailable. It could be on a hard drive on this computer, or on a network. Check to make sure that the disk is properly inserted, or that you are connected to the Internet or your network, and then try again. If it still cannot be located, the information might have been moved to a different location Network share mounted via Group Policy. Any ideas?

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• Can't reach only certain websites from my Wifi (with macbook and iphone)

  - by mellin

  I can't access certain websites neither from my macbook nor from my iphone when connected to my Wifi. The same website can be opened from another windows computer connected to the same Wifi. This is what happens when I try to ping it: PING ilpost.it (151.1.175.113): 56 data bytes Request timeout for icmp_seq 0 Request timeout for icmp_seq 1 Request timeout for icmp_seq 2 ... And when I try to traceroute it: host-001:~ j$ traceroute www.ilpost.it traceroute to ilpost.it (151.1.175.113), 64 hops max, 52 byte packets 1 vodafonedslrouter (192.168.1.1) 2.965 ms 0.743 ms 0.745 ms 2 * 2.96.54.77.rev.vodafone.pt (77.54.96.2) 12.076 ms 10.871 ms 3 77.41.30.213.rev.vodafone.pt (213.30.41.77) 14.145 ms 10.693 ms 11.960 ms 4 85.205.11.49 (85.205.11.49) 9.658 ms 8.946 ms 9.085 ms 5 85.205.13.105 (85.205.13.105) 57.497 ms 57.621 ms 48.080 ms 6 188.111.129.17 (188.111.129.17) 49.483 ms 51.338 ms 48.852 ms 7 85.205.25.174 (85.205.25.174) 47.891 ms 49.219 ms 47.821 ms 8 * * * 9 * * * 10 * * * 11 * * * I've flushed my DNS cache but nothing changed. This is quite dramatic as it seems to depend on 85.205.25.174 hop and don't know how to avoid it. Any suggestions? I add that 3 days ago everything worked fine. Then it has stopped.

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• Can't reach only certain websites from my Wifi (with macbook and iphone)

  - by trampj

  I can't access certain websites neither from my macbook nor from my iphone when connected to my Wifi. The same website can be opened from another windows computer connected to the same Wifi. This is what happens when I try to ping it: PING ilpost.it (151.1.175.113): 56 data bytes Request timeout for icmp_seq 0 Request timeout for icmp_seq 1 Request timeout for icmp_seq 2 ... And when I try to traceroute it: host-001:~ j$ traceroute www.ilpost.it traceroute to ilpost.it (151.1.175.113), 64 hops max, 52 byte packets 1 vodafonedslrouter (192.168.1.1) 2.965 ms 0.743 ms 0.745 ms 2 * 2.96.54.77.rev.vodafone.pt (77.54.96.2) 12.076 ms 10.871 ms 3 77.41.30.213.rev.vodafone.pt (213.30.41.77) 14.145 ms 10.693 ms 11.960 ms 4 85.205.11.49 (85.205.11.49) 9.658 ms 8.946 ms 9.085 ms 5 85.205.13.105 (85.205.13.105) 57.497 ms 57.621 ms 48.080 ms 6 188.111.129.17 (188.111.129.17) 49.483 ms 51.338 ms 48.852 ms 7 85.205.25.174 (85.205.25.174) 47.891 ms 49.219 ms 47.821 ms 8 * * * 9 * * * 10 * * * 11 * * * I've flushed my DNS cache but nothing changed. This is quite dramatic as it seems to depend on 85.205.25.174 hop and don't know how to avoid it. Any suggestions? I add that 3 days ago everything worked fine. Then it has stopped.

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• Private subnet for VM server host-only network

  - by Derek Pressnall

  At my current job, we distribute a product based on a Linux server with multiple VMs defined (using KVM / libvirt). We are planning to expose limited ports to the customer's network, and use iptables to direct inbound traffic to the appropriate internal VM. My question: is there a class of private subnets that I can use for the internal host-only network that is least likely to conflict with a client IP subnet? Specifically, if I choose a /24 out of any of the RFC-1918 defined private subnets (such as 192.168.x.x), there is a chance of conflicting with a customer-used range. I noticed that several current VM implementations default to 192.168.122.x -- is this due to an RFC that I'm not familiar with, and therefore this is a safe range to use (that most network admins would avoid)? Or did the various VM vendors just pick that range randomly? I guess I'm looking for an IP range that is more private than the existing private (RFC1918) addresses. The only other thought I had was to use one of the "Test Net" IP ranges reserved for documentation purposes (RFC 5737). Note, that I'm not worried about a customer's network blocking these IPs, as this is only internal to our server (packets get NATted before leaving the box). However this does seem more unorthodox than just sticking with the default 192.168.122.x/24 subnet.

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• Is there a way to measure wifi traffic on a network from a client?

  - by millimoose

  Is there some way (preferrably one that comes with an existing tool) to measure the traffic going through the whole WiFi network from a computer connected to it? (That is, not from the AP or something between the modem and AP.) My situation is this: a few months back, the internet connection at my parent's place got really sluggish and laggy. (Lag spikes that cause page loads to time out etc, connections plain getting lost and dropping packets forever.) It's impossible to get mom's husband to do anything about this because he brushes this off with something like "just tell your sister to turn off torrents". Unfortunately the WiFi router's firmware doesn't do traffic logging. I'm not going to risk bricking it to put WRT on it; nor am I keen on rewiring the network to add a proxy to analyse the traffic. (I'm one of those people that make computers break just by looking at them, except machines I own.) I'd like to be able to find out roughly how much data is going over the air here while all the LAN wires are out of the router, all the computers accused of torrenting are off, etc. The idea is to either show that: Even if everything but my macbook is turned off, something is congesting the network. The husband is a systems developer and has a whole lot of mysterious hardware that's not to be touched around, one of them might be culprit. There is barely any traffic on the network, but the internet is still sluggish. Meaning this is likely a problem the ISP should solve. (Some hardware of theirs being glitchy, someone on an aggregated line hogging it constantly...) The network is encrypted, but I can temporarily set it to open for the sake of finding this out. So, in conclusion? Can this be done? Or is there some alternative way I could try to diagnose the problem?

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• Network using only switches

  - by mschultz

  So I'm not a network guy - but here's what I want to do - I have an existing network using wifi, which I like, and which is used to connect several computers to the internet. It is headed up by a router, which is in another part of the building. Three of those computers are in my office. All three have gigabit wired ethernet. I have a gigabit switch. Here's what I want to do: Build a 2nd network, out of just that switch, which allows all 3 computers to connect to each other (just to each other is fine, for this purpose, they need no internet). I have a distributed computing task (rendering high-quality fractal artwork, as it were), that requires the best connection speed to all 3 computers. I want them to be able to "talk to each other" as quickly as possible, with the fewest dropped packets (the dataflow over this network will be quite high). So how do I do this. I'm not a networking guy at all - I tried connecting them all, and nobody got an IP address (which I assume is because nobody is running a DNS server?). What all do I need to do to make this work? PS - two are running windows, one is running ubuntu.

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• Slow NFS and GFS2 performance

  - by Tiago

  Recently I've designed and configured a 4 node cluster for a webapp that does lots of file handling. The cluster have been broken down into 2 main roles, webserver and storage. Each role is replicated to a second server using drbd in active/passive mode. The webserver does a NFS mount of the data directory of the storage server and the latter also has a webserver running to serve files to browser clients. In the storage servers I've created a GFS2 FS to hold the data which is wired to drbd. I've chose GFS2 mainly because the announced performance and also because the volume size which has to be pretty high. Since we entered production I've been facing two problems that I think are deeply connected. First of all, the NFS mount on the webservers keeps hanging for a minute or so and then resumes normal operations. By analyzing the logs I've found out that NFS stops answering for a while and outputs the following log lines: Oct 15 18:15:42 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:44 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:46 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:47 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:47 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:47 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:48 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:48 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:51 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:52 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:52 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:55 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:55 <server hostname> kernel: nfs: server active.storage.vlan not responding, still trying Oct 15 18:15:58 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK Oct 15 18:15:59 <server hostname> kernel: nfs: server active.storage.vlan OK In this case, the hang lasted for 16 seconds but sometimes it takes 1 or 2 minutes to resume normal operations. My first guess was this was happening due to heavy load of the NFS mount and that by increasing RPCNFSDCOUNT to a higher value, this would become stable. I've increased it several times and apparently, after a while, the logs started appearing less times. The value is now on 32. After further investigating the issue, I've came across a different hang, despite the NFS messages still appear in the logs. Sometimes, the GFS2 FS simply hangs which causes both the NFS and the storage webserver to serve files. Both stay hang for a while and then they resume normal operations. This hangs leaves no trace on client side (also leaves no NFS ... not responding messages) and, on the storage side, the log system appears to be empty, even though the rsyslogd is running. The nodes connect themselves through a 10Gbps non-dedicated connection but I don't think this is an issue because the GFS2 hang is confirmed but connecting directly to the active storage server. I've been trying to solve this for a while now and I've tried different NFS configuration options, before I've found out the GFS2 FS is also hanging. The NFS mount is exported as such: /srv/data/ <ip_address>(rw,async,no_root_squash,no_all_squash,fsid=25) And the NFS client mounts with: mount -o "async,hard,intr,wsize=8192,rsize=8192" active.storage.vlan:/srv/data /srv/data After some tests, these were the configurations that yielded more performance to the cluster. I am desperate to find a solution for this as the cluster is already in production mode and I need to fix this so that this hangs won't happen in the future and I don't really know for sure what and how I should be benchmarking. What I can tell is that this is happening due to heavy loads as I have tested the cluster earlier and this problems weren't happening at all. Please tell me if you need me to provide configuration details of the cluster, and which do you want me to post. As last resort I can migrate the files to a different FS but I need some solid pointers on whether this will solve this problems as the volume size is extremely large at this point. The servers are being hosted by a third-party enterprise and I don't have physical access to them. Best regards. EDIT 1: The servers are physical servers and their specs are: Webservers: Intel Bi Xeon E5606 2x4 2.13GHz 24GB DDR3 Intel SSD 320 2 x 120GB Raid 1 Storage: Intel i5 3550 3.3GHz 16GB DDR3 12 x 2TB SATA Initially there was a VRack setup between the servers but we've upgraded one of the storage servers to have more RAM and it wasn't inside the VRack. They connect through a shared 10Gbps connection between them. Please note that it is the same connection that is used for public access. They use a single IP (using IP Failover) to connect between them and to allow for a graceful failover. NFS is therefore over a public connection and not under any private network (it was before the upgrade, were the problem still existed). The firewall was configured and tested thoroughly but I disabled it for a while to see if the problem still occurred, and it did. From my knowledge the hosting provider isn't blocking or limiting the connection between either the servers and the public domain (at least under a given bandwidth consumption threshold that hasn't been reached yet). Hope this helps figuring out the problem. EDIT 2: Relevant software versions: CentOS 2.6.32-279.9.1.el6.x86_64 nfs-utils-1.2.3-26.el6.x86_64 nfs-utils-lib-1.1.5-4.el6.x86_64 gfs2-utils-3.0.12.1-32.el6_3.1.x86_64 kmod-drbd84-8.4.2-1.el6_3.elrepo.x86_64 drbd84-utils-8.4.2-1.el6.elrepo.x86_64 DRBD configuration on storage servers: #/etc/drbd.d/storage.res resource storage { protocol C; on <server1 fqdn> { device /dev/drbd0; disk /dev/vg_storage/LV_replicated; address <server1 ip>:7788; meta-disk internal; } on <server2 fqdn> { device /dev/drbd0; disk /dev/vg_storage/LV_replicated; address <server2 ip>:7788; meta-disk internal; } } NFS Configuration in storage servers: #/etc/sysconfig/nfs RPCNFSDCOUNT=32 STATD_PORT=10002 STATD_OUTGOING_PORT=10003 MOUNTD_PORT=10004 RQUOTAD_PORT=10005 LOCKD_UDPPORT=30001 LOCKD_TCPPORT=30001 (can there be any conflict in using the same port for both LOCKD_UDPPORT and LOCKD_TCPPORT?) GFS2 configuration: # gfs2_tool gettune <mountpoint> incore_log_blocks = 1024 log_flush_secs = 60 quota_warn_period = 10 quota_quantum = 60 max_readahead = 262144 complain_secs = 10 statfs_slow = 0 quota_simul_sync = 64 statfs_quantum = 30 quota_scale = 1.0000 (1, 1) new_files_jdata = 0 Storage network environment: eth0 Link encap:Ethernet HWaddr <mac address> inet addr:<ip address> Bcast:<bcast address> Mask:<ip mask> inet6 addr: <ip address> Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:957025127 errors:0 dropped:0 overruns:0 frame:0 TX packets:1473338731 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2630984979622 (2.3 TiB) TX bytes:1648430431523 (1.4 TiB) eth0:0 Link encap:Ethernet HWaddr <mac address> inet addr:<ip failover address> Bcast:<bcast address> Mask:<ip mask> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 The IP addresses are statically assigned with the given network configurations: DEVICE="eth0" BOOTPROTO="static" HWADDR=<mac address> ONBOOT="yes" TYPE="Ethernet" IPADDR=<ip address> NETMASK=<net mask> and DEVICE="eth0:0" BOOTPROTO="static" HWADDR=<mac address> IPADDR=<ip failover> NETMASK=<net mask> ONBOOT="yes" BROADCAST=<bcast address> Hosts file to allow for a graceful NFS failover in conjunction with NFS option fsid=25 set on both storage servers: #/etc/hosts <storage ip failover address> active.storage.vlan <webserver ip failover address> active.service.vlan As you can see, packet errors are down to 0. I've also ran ping for a long time without any packet loss. MTU size is the normal 1500. As there is no VLan by now, this is the MTU used to communicate between servers. The webservers' network environment is similar. One thing I forgot to mention is that the storage servers handle ~200GB of new files each day through the NFS connection, which is a key point for me to think this is some kind of heavy load problem with either NFS or GFS2. If you need further configuration details please tell me. EDIT 3: Earlier today we had a major filesystem crash on the storage server. I couldn't get the details of the crash right away because the server stop responding. After the reboot, I noticed the filesystem was extremely slow, and I was not being able to serve a single file through either NFS or httpd, perhaps due to cache warming or so. Nevertheless, I've been monitoring the server closely and the following error came up in dmesg. The source of the problem is clearly GFS, which is waiting for a lock and ends up starving after a while. INFO: task nfsd:3029 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. nfsd D 0000000000000000 0 3029 2 0x00000080 ffff8803814f79e0 0000000000000046 0000000000000000 ffffffff8109213f ffff880434c5e148 ffff880624508d88 ffff8803814f7960 ffffffffa037253f ffff8803815c1098 ffff8803814f7fd8 000000000000fb88 ffff8803815c1098 Call Trace: [<ffffffff8109213f>] ? wake_up_bit+0x2f/0x40 [<ffffffffa037253f>] ? gfs2_holder_wake+0x1f/0x30 [gfs2] [<ffffffff814ff42e>] __mutex_lock_slowpath+0x13e/0x180 [<ffffffff814ff2cb>] mutex_lock+0x2b/0x50 [<ffffffffa0379f21>] gfs2_log_reserve+0x51/0x190 [gfs2] [<ffffffffa0390da2>] gfs2_trans_begin+0x112/0x1d0 [gfs2] [<ffffffffa0369b05>] ? gfs2_dir_check+0x35/0xe0 [gfs2] [<ffffffffa0377943>] gfs2_createi+0x1a3/0xaa0 [gfs2] [<ffffffff8121aab1>] ? avc_has_perm+0x71/0x90 [<ffffffffa0383d1e>] gfs2_create+0x7e/0x1a0 [gfs2] [<ffffffffa037783f>] ? gfs2_createi+0x9f/0xaa0 [gfs2] [<ffffffff81188cf4>] vfs_create+0xb4/0xe0 [<ffffffffa04217d6>] nfsd_create_v3+0x366/0x4c0 [nfsd] [<ffffffffa0429703>] nfsd3_proc_create+0x123/0x1b0 [nfsd] [<ffffffffa041a43e>] nfsd_dispatch+0xfe/0x240 [nfsd] [<ffffffffa025a5d4>] svc_process_common+0x344/0x640 [sunrpc] [<ffffffff810602a0>] ? default_wake_function+0x0/0x20 [<ffffffffa025ac10>] svc_process+0x110/0x160 [sunrpc] [<ffffffffa041ab62>] nfsd+0xc2/0x160 [nfsd] [<ffffffffa041aaa0>] ? nfsd+0x0/0x160 [nfsd] [<ffffffff81091de6>] kthread+0x96/0xa0 [<ffffffff8100c14a>] child_rip+0xa/0x20 [<ffffffff81091d50>] ? kthread+0x0/0xa0 [<ffffffff8100c140>] ? child_rip+0x0/0x20

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• Using WKA in Large Coherence Clusters (Disabling Multicast)

  - by jpurdy

  Disabling hardware multicast (by configuring well-known addresses aka WKA) will place significant stress on the network. For messages that must be sent to multiple servers, rather than having a server send a single packet to the switch and having the switch broadcast that packet to the rest of the cluster, the server must send a packet to each of the other servers. While hardware varies significantly, consider that a server with a single gigabit connection can send at most ~70,000 packets per second. To continue with some concrete numbers, in a cluster with 500 members, that means that each server can send at most 140 cluster-wide messages per second. And if there are 10 cluster members on each physical machine, that number shrinks to 14 cluster-wide messages per second (or with only mild hyperbole, roughly zero). It is also important to keep in mind that network I/O is not only expensive in terms of the network itself, but also the consumption of CPU required to send (or receive) a message (due to things like copying the packet bytes, processing a interrupt, etc). Fortunately, Coherence is designed to rely primarily on point-to-point messages, but there are some features that are inherently one-to-many: Announcing the arrival or departure of a member Updating partition assignment maps across the cluster Creating or destroying a NamedCache Invalidating a cache entry from a large number of client-side near caches Distributing a filter-based request across the full set of cache servers (e.g. queries, aggregators and entry processors) Invoking clear() on a NamedCache The first few of these are operations that are primarily routed through a single senior member, and also occur infrequently, so they usually are not a primary consideration. There are cases, however, where the load from introducing new members can be substantial (to the point of destabilizing the cluster). Consider the case where cluster in the first paragraph grows from 500 members to 1000 members (holding the number of physical machines constant). During this period, there will be 500 new member introductions, each of which may consist of several cluster-wide operations (for the cluster membership itself as well as the partitioned cache services, replicated cache services, invocation services, management services, etc). Note that all of these introductions will route through that one senior member, which is sharing its network bandwidth with several other members (which will be communicating to a lesser degree with other members throughout this process). While each service may have a distinct senior member, there's a good chance during initial startup that a single member will be the senior for all services (if those services start on the senior before the second member joins the cluster). It's obvious that this could cause CPU and/or network starvation. In the current release of Coherence (3.7.1.3 as of this writing), the pure unicast code path also has less sophisticated flow-control for cluster-wide messages (compared to the multicast-enabled code path), which may also result in significant heap consumption on the senior member's JVM (from the message backlog). This is almost never a problem in practice, but with sufficient CPU or network starvation, it could become critical. For the non-operational concerns (near caches, queries, etc), the application itself will determine how much load is placed on the cluster. Applications intended for deployment in a pure unicast environment should be careful to avoid excessive dependence on these features. Even in an environment with multicast support, these operations may scale poorly since even with a constant request rate, the underlying workload will increase at roughly the same rate as the underlying resources are added. Unless there is an infrastructural requirement to the contrary, multicast should be enabled. If it can't be enabled, care should be taken to ensure the added overhead doesn't lead to performance or stability issues. This is particularly crucial in large clusters.

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• SSH / SFTP connection issue using Tamir.SharpSsh

  - by jinsungy

  This is my code to connect and send a file to a remote SFTP server. public static void SendDocument(string fileName, string host, string remoteFile, string user, string password) { Scp scp = new Scp(); scp.OnConnecting += new FileTansferEvent(scp_OnConnecting); scp.OnStart += new FileTansferEvent(scp_OnProgress); scp.OnEnd += new FileTansferEvent(scp_OnEnd); scp.OnProgress += new FileTansferEvent(scp_OnProgress); try { scp.To(fileName, host, remoteFile, user, password); } catch (Exception e) { throw e; } } I can successfully connect, send and receive files using CoreFTP. Thus, the issue is not with the server. When I run the above code, the process seems to stop at the scp.To method. It just hangs indefinitely. Anyone know what might my problem be? Maybe it has something to do with adding the key to the a SSH Cache? If so, how would I go about this? EDIT: I inspected the packets using wireshark and discovered that my computer is not executing the Diffie-Hellman Key Exchange Init. This must be the issue. EDIT: I ended up using the following code. Note, the StrictHostKeyChecking was turned off to make things easier. JSch jsch = new JSch(); jsch.setKnownHosts(host); Session session = jsch.getSession(user, host, 22); session.setPassword(password); System.Collections.Hashtable hashConfig = new System.Collections.Hashtable(); hashConfig.Add("StrictHostKeyChecking", "no"); session.setConfig(hashConfig); try { session.connect(); Channel channel = session.openChannel("sftp"); channel.connect(); ChannelSftp c = (ChannelSftp)channel; c.put(fileName, remoteFile); c.exit(); } catch (Exception e) { throw e; } Thanks.

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• Decoding ima4 audio format

  - by MrDatabase

  To reduce the download size of an iPhone application I'm compressing some audio files. Specifically I'm using afconvert on the command line to change .wav format to .caf format w/ ima4 compression. I've read this (wooji-juice.com) awesome post about this exact topic. I'm having trouble w/ the "decoding ima4 packets" step. I've looked at their sample code and I'm stuck. Please help w/ some pseudo code or sample code that can guide me in the right direction. Thanks! Additional info: Here is what I've completed and where I'm having trouble... I can play .wav files in both the simulator and on the phone. I can compress .wav files to .caf w/ ima4 compression using afconvert on the command line. I'm using the SoundEngine that came w/ CrashLanding (I fixed one memory leak). I modified the SoundEngine code to look for the mFormatID 'ima4'. I don't understand the blog post linked above starting w/ "Calculating the size of the unpacked data". Why do I need to do this? Also, what does the term "packet" refer to? I'm very new to any sort of audio programming.

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• Socket error 10052 on UDP socket

  - by Jesper

  We have a .NET 2.0 desktop application which sends and receives network packets over UDP. Several users have reported an occasional socket error 10052 which happens when the code calls socket.BeginReceiveFrom on a the UDP socket. What does this mean? The official MS documentation for socket error 10052 says - quote: "WSAENETRESET (10052) Network dropped connection on reset . The connection has been broken due to keep-alive activity detecting a failure while the operation was in progress. It can also be returned by setsockopt if an attempt is made to set SO_KEEPALIVE on a connection that has already failed." This just doesn't make much sense for a UDP socket since UDP is a connectionless protocol. I know that another close error code 10054 in connection with UDP sockets means that an ICMP message "Port Unreachable" was received, and I am wondering if 10052 might map to another ICMP message? I have googled this for months, read network books, etc. but can't find anything. Please help - what does socket error 10052 on a UDP socket mean? Thanks in advance

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• ASIHTTPRequest POST splits up header + data?

  - by chris.o.

  Hi, I am using ASIHTTPRequest to POST data to a remote server on iPhone 4.2.1. When I make the following post request to our server, I get a 400 response (I removed the IP address): NSString dataString = @"data1=00&data2=00&data3=00"; ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:<ipremoved>]]]; [request appendPostData:[dataString dataUsingEncoding:NSUTF8StringEncoding]]; [request setRequestMethod:@"POST"]; [request addRequestHeader:@"User-Agent" value:@"iphone app"]; [request addRequestHeader:@"Content-Type" value:@"application/octet-stream"]; request.delegate = self; [request startAsynchronous]; When I send the same data using curl, I receive a 200 response: curl -H "User-Agent: iphone app" -H "Accept:" -H "Content-Type:application/octet-stream" --data-ascii "data1=00&data2=00&data3=00" --location <ipremoved> -v My colleague is stating that, in the failure case, the ASIHTTPRequest requires two socket reads: one for the header and one for the data. Apparently the server is not presently equipped to parse this correctly, so I am trying to work around it. If I setup a proxy between iPhone and my Mac and run Paros (to see packets), the problem goes away. Paros combine the header and data so that it is all acquired by the server in a single socket read. I've tried a few things suggested in other posts including disabling persistent connections, but I am not having any luck. I've also tried doing a ASIHTTPFormRequest, but the server does not like the generated data format. Any suggestions would be appreciated. Thanks.

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• Proggraming a VPN, Authontication stage - RFC not clear enough

  - by John

  I have a custom build of a unix OS. My task: Adding an IPSec to the OS. I am working on Phase I, done sending the first 2 packets. what I am trying to do now is making the Identefication Payload. I've been reading RFC 2409 (Apendix B) which discuss the keying materials (SKEYID, SKEYID_d, SKEYID_a, SKEYID_e and the IV making). Now, I use SHA1 for authontication and thus I use HMAC-SHA1 & my encryption algorithem is AES 256bit. The real problem is that the RFC is not clear enough of what should I do regarding the PRF. It says: "Use of negotiated PRFs may require the PRF output to be expanded due to the PRF feedback mechanism employed by this document." I use SHA1, does it mean I do not negotiate a PRF? In my opinion, AES is the only algorithm that needs expention (a fixed length of 256bit), so, do i need to expand only the SKEYID_e? If you happen to know a clearer, though relible, source then the RFC please post a link. Thanks in advance!

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• Browser Based Streaming Video/Audio (not progressive download)

  - by Josh

  Hello, I am trying to understand conceptually the best way to deliver real streaming audio and video content. I would want it to be consumed with a web browser, utilizing the least amount of proprietary technology. I wouldn't be serving static files and using progressive download, this would be real audio streams being captured live. How does one broadcast a stream that will be reasonably in sync with the source? What kind of protocol is suitable? Edit: In research I've found that there are a few protocols: RTSP, HTTP Streaming, RTMP, and RTP. HTTP streaming is somewhat unsuitable if you are streaming a live performance/communication of some kind because it relies on TCP (as its HTTP based) and you don't lose packets. In a low bandwidth situation, the client can get significantly behind in playback. ref RTMP is a proprietary technology, requiring flash media server. Crap on that. The reason I looked at flash is because they are extremely flexible as far as user experience goes. SoundManager2 provides an excellent javascript interface for playing media with flash. This is what I would look for in a client application. RTSP/RTP is what Microsoft switched to using, deprecating their MMS protocol. RTSP is the control protocol. Its similar to HTTP with a few distinct difference -- server can also talk to the client, and there are additional commands, like PAUSE. Its also a stateful protocol, which is maintained with a session id. RTP is the protocol for delivering the payload (encoded audio or video). There are a few open sourced projects, one of them being supported by apple here. It seems like this might do what I want it to, and it looks like quite a few players support it. It sounds like it would be suitable for a "live" broadcast from this page here. Thanks, Josh

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• Flash movies in inactive browser tabs pause or don't execute in real time

  - by ZenBlender

  I'm noticing some unexpected behavior. Some time in the last few months, a change in either Firefox, the Flash player, or both, has made it so that Flash movies that are in inactive browser tabs no longer execute in real time. They appear to still execute, but only in bursts, and not in a predictable way. This is a problem because I develop a Flash-based (Actionscript 2.0, Flash CS3) multiplayer game that maintains a network connection and allows players to chat, etc. Many of our players complain about Firefox crashing while playing the game. I have noticed it too, not too frequently, but it crashes several times a week. (Firefox crashes, I do not get a message from Flash player that indicates an infinite loop or problem in my code) My theory is that this new behavior is causing crashes when there is a lot of activity in my game, leading to lots of unhandled network traffic for my game getting buffered before Firefox/Flash will give it a chance to execute. Maybe this leads to a buffer overflow or missing packets, and as a result, something crashes. At times I will switch back to the tab that is running my game and discover a display bug, which looks as though Flash has simply failed to execute something that it was supposed to. I would assume this new behavior is on purpose, for example to prevent all the Flash-based advertisements in inactive tabs from executing and therefore killing performance. In a quick test on Chrome (5.0.342.9 beta), this "pausing" of Flash seems to be there as well, but somehow it seems much less of a problem. My users have only complained about Firefox crashing, not other browsers. My machine: Windows 7 x64 Firefox 3.6.3 Flash Player 10.1.50.426 My game: triplejack.com Any ideas? Ideally I'd like to disable this behavior for my Flash game so it can execute in real time even when in an inactive tab. Thanks for any help!

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• Problem with XML encoding of database contents with Latin characters

  - by user89691

  I have an ASP Access database that contains strings in various European languages. The database was populated prior by agents in the respective countries. It contains entries with accented etc characters as you would expect. If I open the database with MS Access these characters show up fine. For example the the German equivalent of "Open" shows as "Öffnen" (hopefully you can see an "O" with 2 dots above it!). I have ASP code that reads the database and returns records in XML. The text is passed to XMLEncode to construct the XML, but that only seems to deal with the 5 specials like "<", "&", etc. If I dump the XML the accented characters are unchanged. <English>Open</English> <German>Öffnen</German> If I look at the raw packets with Wireshark I see that the "Ö" byte is hex D6, which appears to be it's decimal Unicode and ISO 8859-1 value. The problem starts when I try to parse the XML in client-side JS. I get: "An invalid character was found in text content" from IE. FF and Chrome happily accept the XML without hiccup but the browser shows the "Ö" character as a diamond with a question mark inside. http://www.validome.org/xml/validate/ reports "encoding error." http://www.w3schools.com/dom/dom_validate.asp thinks it is fine. The XML is UTF-8 encoded. What do I need to do to have IE accept my XML without complaint? What do I need to do to have browsers display the stuff correctly?

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• How does XMPP work with perl?

  - by TheGNUGuy

  Hey everybody, I am trying to make my own jabber bot but i have run into a little trouble. I have gotten my bot to respond to messages, however, if I try to change the bot's presence then it seems as though all of the messages you send to the bot get delayed. What I mean is when I run the script I change the presence so I can see that it is online. Then When I send it a message it takes 3 before the callback subroutine i have set up for messages gets called. After the 3rd message is sent and the chat subroutine is called it still process the first message I sent. This really doesn't pose TOO much of a problem except that I have it set up to log out when I send the message "logout" and it has to be followed by two more messages in order to log out. I am not sure what it is that I have to do to fix this but i think it has something to do with iq packets because I have an iq callback set as well and it gets called 2 times after setting the presence. Here is my source code: http://pastebin.com/MgKMhTML Thanks for your help!

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• SharpPcap issue

  - by Eyla

  This is my first time to use SharpPcap library. I created new project with VC# 2008 and I added SharpPcap as a reference to my project. I post a sample code to get interface of my pc but I'm getting this error: Error 1 The type or namespace name 'PcapDeviceList' could not be found (are you missing a using directive or an assembly reference?) C:\Users\Ali\Documents\Visual Studio 2008\Projects\Pcap\Pcap\Form1.cs 28 13 Pcap please advice to solve this problem. here is my code: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using SharpPcap; using SharpPcap.Packets; using SharpPcap.Protocols; using SharpPcap.Util; namespace Pcap { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { /* Retrieve the device list */ PcapDeviceList devices = SharpPcap.GetAllDevices(); /*If no device exists, print error */ if (devices.Count < 1) { Console.WriteLine("No device found on this machine"); return; } int i = 0; /* Scan the list printing every entry */ foreach (PcapDevice dev in devices) { /* Description */ label1.Text = "{0}) {1}" + i + dev.PcapDescription +"\n"+ /* Name */ "\tName:\t{0}" + dev.PcapName+"\n"+ /* IP Address */ "\tIP Address: \t\t{0}"+ dev.PcapIpAddress+"\n"+ /* Is Loopback */ "\tLoopback: \t\t{0}"+ dev.PcapLoopback; i++; } } } }

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• MSMQ on Win2008 R2 won’t receive messages from older clients

  - by Graffen

  Hi all I'm battling a really weird problem here. I have a Windows 2008 R2 server with Message Queueing installed. On another machine, running Windows 2003 is a service that is set up to send messages to a public queue on the 2008 server. However, messages never show up on the server. I've written a small console app that just sends a "Hello World" message to a test queue on the 2008 machine. Running this app on XP or 2003 results in absolutely nothing. However, when I try running the app on my Windows 7 machine, a message is delivered just fine. I've been through all sorts of security settings, disabled firewalls on all machines etc. The event log shows nothing of interest, and no exceptions are being thrown on the clients. Running a packet sniffer (WireShark) on the server reveals only a little. When trying to send a message from XP or 2003 I only see an ICMP error "Port Unreachable" on port 3527 (which I gather is an MQPing packet?). After that, silence. Wireshark shows a nice little stream of packets when I try from my Win7 client (as expected - messages get delivered just fine from Win7). I've enabled MSMQ End2End logging on the server, but only entries from the messages sent from my Win7 machine are appearing in the log. So somehow it seems that messages are being dropped silently somewhere along the route from XP or 2003 to my 2008 server. Does anyone have any clues as to what might be causing this mysterious behaviour? -- Jesper

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• How do I get uri of HTTP packet with winpcap?

  - by Gtker

  Based on this article I can get all incoming packets. /* Callback function invoked by libpcap for every incoming packet */ void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data) { struct tm *ltime; char timestr[16]; ip_header *ih; udp_header *uh; u_int ip_len; u_short sport,dport; time_t local_tv_sec; /* convert the timestamp to readable format */ local_tv_sec = header->ts.tv_sec; ltime=localtime(&local_tv_sec); strftime( timestr, sizeof timestr, "%H:%M:%S", ltime); /* print timestamp and length of the packet */ printf("%s.%.6d len:%d ", timestr, header->ts.tv_usec, header->len); /* retireve the position of the ip header */ ih = (ip_header *) (pkt_data + 14); //length of ethernet header /* retireve the position of the udp header */ ip_len = (ih->ver_ihl & 0xf) * 4; uh = (udp_header *) ((u_char*)ih + ip_len); /* convert from network byte order to host byte order */ sport = ntohs( uh->sport ); dport = ntohs( uh->dport ); /* print ip addresses and udp ports */ printf("%d.%d.%d.%d.%d -> %d.%d.%d.%d.%d\n", ih->saddr.byte1, ih->saddr.byte2, ih->saddr.byte3, ih->saddr.byte4, sport, ih->daddr.byte1, ih->daddr.byte2, ih->daddr.byte3, ih->daddr.byte4, dport); } But how do I extract URI information in packet_handler?

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• Are Large iPhone Ping Times Indicative of Application Latency?

  - by yar

  I am contemplating creating a realtime app where an iPod Touch/iPhone/iPad talks to a server-side component (which produces MIDI, and sends it onward within the host). When I ping my iPod Touch on Wifi I get huge latency (and a enormous variance, too): 64 bytes from 192.168.1.3: icmp_seq=9 ttl=64 time=38.616 ms 64 bytes from 192.168.1.3: icmp_seq=10 ttl=64 time=61.795 ms 64 bytes from 192.168.1.3: icmp_seq=11 ttl=64 time=85.162 ms 64 bytes from 192.168.1.3: icmp_seq=12 ttl=64 time=109.956 ms 64 bytes from 192.168.1.3: icmp_seq=13 ttl=64 time=31.452 ms 64 bytes from 192.168.1.3: icmp_seq=14 ttl=64 time=55.187 ms 64 bytes from 192.168.1.3: icmp_seq=15 ttl=64 time=78.531 ms 64 bytes from 192.168.1.3: icmp_seq=16 ttl=64 time=102.342 ms 64 bytes from 192.168.1.3: icmp_seq=17 ttl=64 time=25.249 ms Even if this is double what the iPhone-Host or Host-iPhone time would be, 15ms+ is too long for the app I'm considering. Is there any faster way around this (e.g., USB cable)? If not, would building the app on Android offer any other options? Traceroute reports more workable times: traceroute to 192.168.1.3 (192.168.1.3), 64 hops max, 52 byte packets 1 192.168.1.3 (192.168.1.3) 4.662 ms 3.182 ms 3.034 ms can anyone decipher this difference between ping and traceroute for me, and what they might mean for an application that needs to talk to (and from) a host?

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