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• migrating Solaris to RH: network latency issue, tcp window size & other tcp parameters

  - by Bastien

  Hello I have a client/server app (Java) that I'm migrating from Solaris to RH Linux. since I started running it in RH, I noticed some issues related to latency. I managed to isolate the problem that looks like this: client sends 5 messages (32 bytes each) in a row (same application timestamp) to the server. server echos messages. client receives replies and prints round trip time for each msg. in Solaris, all is well: I get ALL 5 replies at the same time, roughly 80ms after having sent original messages (client & server are several thousands miles away from each other: my ping RTT is 80ms, all normal). in RH, first 3 messages are echoed normally (they arrive 80ms after they've been sent), however the following 2 arrive 80ms later (so total 160ms RTT). the pattern is always the same. clearly looked like a TCP problem. on my solaris box, I had previously configured the tcp stack with 2 specific options: disable nagle algorithm globally set tcp_deferred_acks_max to 0 on RH, it's not possible to disable nagle globally, but I disabled it on all of my apps' sockets (TCP_NODELAY). so I started playing with tcpdump (on the server machine), and compared both outputs: SOLARIS: 22 2.085645 client server TCP 56150 > 6006 [PSH, ACK] Seq=111 Ack=106 Win=66672 Len=22 "MSG_1 RCV" 23 2.085680 server client TCP 6006 > 56150 [ACK] Seq=106 Ack=133 Win=50400 Len=0 24 2.085908 client server TCP 56150 > 6006 [PSH, ACK] Seq=133 Ack=106 Win=66672 Len=22 "MSG_2 RCV" 25 2.085925 server client TCP 6006 > 56150 [ACK] Seq=106 Ack=155 Win=50400 Len=0 26 2.086175 client server TCP 56150 > 6006 [PSH, ACK] Seq=155 Ack=106 Win=66672 Len=22 "MSG_3 RCV" 27 2.086192 server client TCP 6006 > 56150 [ACK] Seq=106 Ack=177 Win=50400 Len=0 28 2.086243 server client TCP 6006 > 56150 [PSH, ACK] Seq=106 Ack=177 Win=50400 Len=21 "MSG_1 ECHO" 29 2.086440 client server TCP 56150 > 6006 [PSH, ACK] Seq=177 Ack=106 Win=66672 Len=22 "MSG_4 RCV" 30 2.086454 server client TCP 6006 > 56150 [ACK] Seq=127 Ack=199 Win=50400 Len=0 31 2.086659 server client TCP 6006 > 56150 [PSH, ACK] Seq=127 Ack=199 Win=50400 Len=21 "MSG_2 ECHO" 32 2.086708 client server TCP 56150 > 6006 [PSH, ACK] Seq=199 Ack=106 Win=66672 Len=22 "MSG_5 RCV" 33 2.086721 server client TCP 6006 > 56150 [ACK] Seq=148 Ack=221 Win=50400 Len=0 34 2.086947 server client TCP 6006 > 56150 [PSH, ACK] Seq=148 Ack=221 Win=50400 Len=21 "MSG_3 ECHO" 35 2.087196 server client TCP 6006 > 56150 [PSH, ACK] Seq=169 Ack=221 Win=50400 Len=21 "MSG_4 ECHO" 36 2.087500 server client TCP 6006 > 56150 [PSH, ACK] Seq=190 Ack=221 Win=50400 Len=21 "MSG_5 ECHO" 37 2.165390 client server TCP 56150 > 6006 [ACK] Seq=221 Ack=148 Win=66632 Len=0 38 2.166314 client server TCP 56150 > 6006 [ACK] Seq=221 Ack=190 Win=66588 Len=0 39 2.364135 client server TCP 56150 > 6006 [ACK] Seq=221 Ack=211 Win=66568 Len=0 REDHAT: 17 2.081163 client server TCP 55879 > 6006 [PSH, ACK] Seq=111 Ack=106 Win=66672 Len=22 "MSG_1 RCV" 18 2.081178 server client TCP 6006 > 55879 [ACK] Seq=106 Ack=133 Win=5888 Len=0 19 2.081297 server client TCP 6006 > 55879 [PSH, ACK] Seq=106 Ack=133 Win=5888 Len=21 "MSG_1 ECHO" 20 2.081711 client server TCP 55879 > 6006 [PSH, ACK] Seq=133 Ack=106 Win=66672 Len=22 "MSG_2 RCV" 21 2.081761 client server TCP 55879 > 6006 [PSH, ACK] Seq=155 Ack=106 Win=66672 Len=22 "MSG_3 RCV" 22 2.081846 server client TCP 6006 > 55879 [PSH, ACK] Seq=127 Ack=177 Win=5888 Len=21 "MSG_2 ECHO" 23 2.081995 server client TCP 6006 > 55879 [PSH, ACK] Seq=148 Ack=177 Win=5888 Len=21 "MSG_3 ECHO" 24 2.082011 client server TCP 55879 > 6006 [PSH, ACK] Seq=177 Ack=106 Win=66672 Len=22 "MSG_4 RCV" 25 2.082362 client server TCP 55879 > 6006 [PSH, ACK] Seq=199 Ack=106 Win=66672 Len=22 "MSG_5 RCV" 26 2.082377 server client TCP 6006 > 55879 [ACK] Seq=169 Ack=221 Win=5888 Len=0 27 2.171003 client server TCP 55879 > 6006 [ACK] Seq=221 Ack=148 Win=66632 Len=0 28 2.171019 server client TCP 6006 > 55879 [PSH, ACK] Seq=169 Ack=221 Win=5888 Len=42 "MSG_4 ECHO + MSG_5 ECHO" 29 2.257498 client server TCP 55879 > 6006 [ACK] Seq=221 Ack=211 Win=66568 Len=0 so, I got confirmation things are not working correctly for RH: packet 28 is sent TOO LATE, it looks like the server is waiting for packet 27's ACK before doing anything. seems to me it's the most likely reason... then I realized that the "Win" parameters are different on Solaris & RH dumps: 50400 on Solaris, only 5888 on RH. that's another hint... I read the doc about the slide window & buffer window, and played around with the rcvBuffer & sendBuffer in java on my sockets, but never managed to change this 5888 value to anything else (I checked each time directly with tcpdump). does anybody know how to do this ? I'm having a hard time getting definitive information, as in some cases there's "auto-negotiation" that I might need to bypass, etc... I eventually managed to get only partially rid of my initial problem by setting the "tcp_slow_start_after_idle" parameter to 0 on RH, but it did not change the "win" parameter at all. the same problem was there for the first 4 groups of 5 messages, with TCP retransmission & TCP Dup ACK in tcpdump, then the problem disappeared altogether for all following groups of 5 messages. It doesn't seem like a very clean and/or generic solution to me. I'd really like to reproduce the exact same conditions under both OSes. I'll keep researching, but any help from TCP gurus would be greatly appreciated ! thanks !

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• Eliminating code duplication in a single file

  - by Jon

  Sadly, a project that I have been working on lately has a large amount of copy-and-paste code, even within single files. Are there any tools or techniques that can detect duplication or near-duplication within a single file? I have Beyond Compare 3 and it works well for comparing separate files, but I am at a loss for comparing single files. Thanks in advance. Edit: Thanks for all the great tools! I'll definitely check them out. This project is an ASP.NET/C# project, but I work with a variety of languages including Java; I'm interested in what tools are best (for any language) to remove duplication.

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• Win8/7/XP print spooler not getting along with Zebra ZT230 via WIFI

  - by Jonathan M

  I have a graphics-intensive 4"x6" label I'm printing to the ZT230. I'm printing multiple (10) copies. When connected via USB, all goes well. However, when connected via wifi, I only get 2 of the labels. A wireshark capture shows that at some point in the process my computer (presumably my windows spooler) is sending a reset packet, which, I believe, would pretty much kill the print job. I'm getting the same results on Win8, Win7 and WinXP. The print job was originally generated on Zebra's ZebraDesigner2 software. For easier diagnosis, I captured it to a .prn file. The .prn file can be found here: https://drive.google.com/file/d/0BwxF_9SAkKzLLTF5bUJVT0lESUU/edit?usp=sharing And the wireshark capture file can be found here: https://drive.google.com/file/d/0BwxF_9SAkKzLTGpSS0ktZW1xV28/edit?usp=sharing And the printer configuration listing: https://docs.google.com/document/d/1zh1Tw4D4yNa2uljOIL1kO2z8se9HK859irpUEwyxlyY/edit?usp=sharing I've started a discussion with Zebra Tech Support, and they're working on it, but I thought I'd toss it out here for more ideas since we're getting kind of stumped. Any ideas why this may be happening?

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• Error calling webservice using JSONP + jquery with IE on remote domain

  - by Jay Heavner

  I have a .Net webservice on my app server that returns data formatted as JSONP. I have an HTML test client on that server which works fine using IE, Firefox, & Chrome. If I copy the same HTML to my workstation or deploy to my webserver it works with Firefox & Chrome but in IE I'm getting two javascript errors. Message: Object doesn't support this property or method Line: 1 Char: 1 Code: 0 URI: http://mydomain/WebServices/LyrisProxy/Services/Lyris/JSONP/Lyris.asmx/AddUser?lyrisInstance="1"&email="[email protected]"&fullName="My Name"&lyrisList="listname"&format=json&callback=jsonp1274109819864&_=1274109829665 Message: Member not found. Line: 59 Char: 209 Code: 0 URI: http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js I'm kind of at loss as to what to do to fix this.

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• How to debug .net error where message is masked in Ajax call

  - by Matt Thrower

  Hi, I'm currently working on a page which makes use of the MS Ajax UpdatePanel. However I've run into a strange problem. If I simply compile and view my page, one of the button click events results in an error. However, because the button affects items inside an UpdatePanel the actual exception is hidden from me: all I'm getting is a HTTP 500 error returned to me through the UpdatePanel Javascript. What's odd about this is that if I step through the code line by line in Visual Studio, I don't get the error. The button doesn't cause the behaviour I'm expecting, but it throws no errors. Because the step through isn't causing an error to be thrown, I'm at a loss how I can get to the actual exception message so I can find out where the error is being thrown and debug it. Suggestions gratefully received. Cheers, Matt

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• Alternate play / pause button for WordPress wpaudio soundmanager plugin

  - by j-man86

  Hello! I am using the wpaudio plugin to convert mp3 links into a javascript/flash audio player. My problem is that I use this plugin in two areas on my site: one on a black background, and one on a white background. I need to use an alternate set of play/pause buttons for each page (white buttons for the black background and vice versa). I am at a total loss on how to do this. I need to some how incorporate a "if page is..." statement into the wpaudio.js but I don't know how to do this with jQuery. Can anyone help? Thanks so much!

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• OS X Keeps prompting me for SSH private key passphrase (OS X 10.6.8)

  - by Danny Englander

  I have a private key to ssh into my server and the connection works. In my hosts file I have: Host myhost HostName xxx.xxx.xxx.xx GlobalKnownHostsFile ~/.ssh/known_hosts port 22 User myuser IdentityFile ~/.ssh/mykey_dsa IdentitiesOnly yes .. and then I type ssh myhost Every time I connect, I get the Mac OS X keychain prompt and I tell OS X to remember the passphrase but then when I disconnect from ssh and re-connect, I am prompted to add the passphrase to the keychain again. This is only a recent problem so I suspect and issue with Keychain? To be clear, I can 're-add' to keychain every time and connect but this defats the purpose. The permissions on my dsa key are set at 600 or -rw-------@ I tried repairing disk permissions but that did no good. My Google-foo is also failing me, nothing of use came up. So I am not sure if this an OS X / keychain issue or an SSH issue. update: When I try ssh -vvv myhost, I think it reveals the issue: debug1: Trying private key: /Users/danny/.ssh/mykey_dsa debug1: PEM_read_PrivateKey failed debug1: read PEM private key done: type <unknown> debug3: Not a RSA1 key file /Users/danny/.ssh/mykey_dsa. debug1: read PEM private key done: type DSA Identity added: /Users/danny/.ssh/mykey_dsa (/Users/danny/.ssh/mykey_dsa) debug1: read PEM private key done: type DSA debug3: sign_and_send_pubkey debug2: we sent a publickey packet, wait for reply debug1: Authentication succeeded (publickey). ... and after that I get connected. I think this crux of the matter is: PEM_read_PrivateKey failed

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• How to monitor changes in the frequency of network latency spikes over time?

  - by dequis

  I'm currently trying to troubleshoot an issue with my network in which I get latency spikes up to 200 seconds (normally around 50 secs) in an apparently random way at apparently random moments of the day. While trying to find what part of my messy network needs to be blamed (outside of the scope of this question - discussed a bit on chat), I realized I have no reliable way to confirm that a change actually improved anything. So far, the main way in which i notice this is that irssi shows [Lag: 15 (??)] in the statusbar, increasing every 5 seconds, and all other connections seem to be affected too. Since this depends on my observations, it's not a very reliable method to know how often it really happens. Note that just sending ICMP pings is probably not enough, but that's just my guess. It might be a "bufferbloat" issue, it might be packet loss, it might only apply to persistent connections. I suspect this because a few months ago, when the issue started, I had a "ping" command running in background and it didn't show anything weird at all during the latency spikes. This seems to have changed now (pings don't go through), but still, I'd prefer something more robust.

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• Possible DNS issue after a reinstall of Windows Server 2000 (get off my lawn)

  - by cop1152

  I just replaced a drive on a Win2000 Server that replicates AD and issues out DHCP at one of our offices. I successfully joined it to the domain, setup range of IP's, etc, but am still having issues. I cannot RDC to it with name or IP. I can ping it, browse to it with Windows Explorer, and remote to it with some other software, but not RDC. The other issue is this: Users are unable to authenticate on it. They receive the message 'username or password incorrect' (or something like that). Changes made on the main domain controller seem to take forever to trickle down. The most significant entry in the DNS Server Log is Event ID 7062: The DNS Server Encountered a Packet Addressed to Itself. At least, I think its significant. The Directory Services Log shows numerous Event IDs 1265: The attempt to establish a replication link with parameters failed with the following status: The DSA operation is unable to proceed because of a DNS lookup failure. Does this make any sense to anyone? I feel like its something very simple that I am overlooking. Thanks in advance.

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• Memory leak in Qt signal and slots

  - by Ajay

  Hello, I am running valgrind on my Qt code,and even on successful exit of the application, get the following report from valgrind 8,832 bytes in 92 blocks are still reachable in loss record 12 of 12 at 0x4025390: operator new(unsigned int) (vg_replace_malloc.c:214) ==3339== by 0x4B75F05: QMutex::QMutex(QMutex::RecursionMode) (qmutex.cpp:123) ==3339== by 0x4B77602: QMutexPool::get(void const*) (qmutexpool.cpp:137) ==3339== by 0x4CA0EC2: signalSlotLock(QObject const*) (qobject.cpp:112) ==3339== by 0x4CA3939: QMetaObjectPrivate::connect(QObject const*, int, QObject const*, int, int, int*) (qobject.cpp:2900) ==3339== by 0x4CA5C00: QObject::connect(QObject const*, char const*, QObject const*, char const*, Qt::ConnectionType) (qobject.cpp:2599) I disconnect all signal connections and also delete the objects. The above mentioned leak increases if i increase the amount of signal and slot connections? Can anybody help with this?

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• High CPU Usage with WebGL?

  - by shoosh

  I'm checking out the nightly builds of Firefox and Chromium with support of WebGL with a few demos and tutorials and I can't help but wonder about the extremely high CPU load they cause. A simple demo like this one runs at a sustained 60% of my dual core. The large version of this one maxes out the CPU to 100% and has some visible frame loss. Chromium seems to be slightly better than firefox but not by much. I'm pretty sure that if these were desktop application the CPU load would be negligible. So what's going on here? what is it doing? Running the simple scripts of these can't be that demanding. Is it the extra layer of security or something?

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• OpenVPN: ifup tap0 drops all connections

  - by raspi

  I'm trying to create star shaped "virtual" LAN with OpenVPN which is not connected to physical network. ie. tap0 packets should not go to eth0. Packet should only go through OpenVPN to connected clients. This setup works with my OpenVPN testing machine which runs Virtual Box but not on my actual server which is running on top of Xen. Both servers are running Ubuntu Intrepid. /etc/network/interfaces: iface tap0 inet manual address 10.10.10.1 netmask 255.255.255.0 gateway 10.10.10.1 /etc/openvpn/server.conf mode server tls-server port 1194 proto udp dev tap client-to-client ca /etc/openvpn/easy-rsa/keys/ca.crt cert /etc/openvpn/easy-rsa/keys/servername.crt key /etc/openvpn/easy-rsa/keys/servername.key dh /etc/openvpn/easy-rsa/keys/dh384.pem ifconfig-pool-persist ipp.txt server-bridge 10.10.10.1 255.255.255.0 10.10.10.128 10.10.10.250 push .route 10.10.10.1 255.255.255.0 keepalive 5 60 comp-lzo persist-key persist-tun status /var/log/openvpn-status.log log-append /var/log/openvpn.log verb 3 user nobody group nogroup ifup tap0 on Virtual Box: everything ok, SSH keeps running. But on Xen SSH connection drops and I have to reboot whole machine. What I'm missing?

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• OpenVPN bad source address from client

  - by Bogdan

  I have one problem with OpenVPN. There are a lot drops records in the openvpn log file on the server: Mon Oct 22 10:14:41 2012 us=726541 laptop/???:1194 MULTI: bad source address from client [192.168.1.107], packet dropped grep -E "^[a-z]" server.conf ----- port 1194 proto udp dev tun ca data/ca.crt cert data/server.crt key data/server.key dh data/dh1024.pem tls-server tls-auth data/ta.key 0 remote-cert-tls client cipher AES-256-CBC tun-mtu 1200 server 10.10.10.0 255.255.255.0 ifconfig-pool-persist ipp.txt push "redirect-gateway def1 bypass-dhcp" push "dhcp-option DNS 8.8.8.8" client-to-client client-config-dir /etc/openvpn/ccd route 10.10.10.0 255.255.255.0 keepalive 10 120 comp-lzo persist-key persist-tun max-clients 5 status /var/log/status-openvpn.log log /var/log/openvpn.log verb 4 auth-user-pass-verify /etc/openvpn/verify.sh via-file tmp-dir /tmp script-security 2 ----- cat ccd/laptop ----- iroute 10.10.10.0 255.255.255.0 ----- cat client.conf ----- remote server ip 1194 client dev tun ping 10 comp-lzo proto udp tls-client tls-auth data/ta.key 1 pkcs12 data/vpn.laptop.p12 remote-cert-tls server #ns-cert-type server persist-key persist-tun cipher AES-256-CBC verb 3 pull auth-user-pass /home/user/.openvpn/users.db ----- According to "Jan Just Keijser - OpenVPN 2 Cookbook" root of the problem is incorrect config options.see the screenshot But, as you see, my config has such options. Could you please help me to solve this problem. @week Verb leverl=6; client log. Mon Oct 22 16:06:02 2012 do_ifconfig, tt->ipv6=0, tt->did_ifconfig_ipv6_setup=0 Mon Oct 22 16:06:02 2012 /sbin/ifconfig tun0 10.10.10.3 pointopoint 10.10.10.5 mtu 1500 Mon Oct 22 16:06:02 2012 /sbin/route add -net xxxx netmask 255.255.255.255 gw 192.168.1.1 Mon Oct 22 16:06:02 2012 /sbin/route add -net 0.0.0.0 netmask 128.0.0.0 gw 10.10.10.5 Mon Oct 22 16:06:02 2012 /sbin/route add -net 128.0.0.0 netmask 128.0.0.0 gw 10.10.10.5 Mon Oct 22 16:06:02 2012 Initialization Sequence Completed cat ccd/latop iroute 10.10.10.0 255.255.255.0 ifconfig-push 10.10.10.3 10.10.10.5

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• JPA Cascading Delete: Setting child FK to NULL on a NOT NULL column

  - by JBristow

  I have two tables: t_promo_program and t_promo_program_param. They are represented by the following JPA entities: @Entity @Table(name = "t_promo_program") public class PromoProgram { @Id @Column(name = "promo_program_id") private Long id; @OneToMany(cascade = {CascadeType.REMOVE}) @JoinColumn(name = "promo_program_id") private List<PromoProgramParam> params; } @Entity @Table(name = "t_promo_program_param") public class PromoProgramParam { @Id @Column(name = "promo_program_param_id") private Long id; //@NotNull // This is a Hibernate annotation so that my test db gets created with the NOT NULL attribute, I'm not married to this annotation. @ManyToOne @JoinColumn(name = "PROMO_PROGRAM_ID", referencedColumnName = "promo_program_id") private PromoProgram promoProgram; } When I delete a PromoProgram, Hibernate hits my database with: update T_PROMO_PROGRAM_PARAM set promo_program_id=null where promo_program_id=? delete from t_promo_program where promo_program_id=? and last_change=? I'm at a loss for where to start looking for the source of the problem.

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• NETKEY IPsec and ARP

  - by Shawn J. Goff

  I'm wondering if I have the correct routing setup for an IPsec tunnel. I have control over the IPsec endpoints and the hosts connected to one side. These hosts are connecting to the tunnel so that they have access to the network on the other side of what I will call the IPsec server. I don't have control of the network upstream of this server. Normally, the IPsec server will not respond to ARP requests for the hosts on the other side of the tunnel. So when a packet arrives for one of my hosts the server gets ARP requests, but the upstream router gets no response, and cannot construct the ethernet frame to send me the packets. If I was using one of the swan stacks, I would have a separate interface, and I'd probably just need to turn on proxyarp, but I'm using NETKEY, which doesn't use a separate interface for the tunnel. To solve the problem for now, I have added an eth0.5 vlan to the IPsec server, turned on proxyarp for that interface, and added all routes my hosts addresses to that interface so that it will respond to those ARP requests (and will therefore get relevant packets routed to it). This works, but it feels wrong. What is the correct way to get the upstream router to send me the traffic for these hosts?

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• Cisco router not receiving OSPF updates

  - by WebDevHobo

  Or at least, that's what I think is happening. There doesn't appear to be a debug command for this, or to see if something is in the routing table. I'm testing out this setup in Packet Tracer. I have 3 routers and a webserver From left to right, you have: Webserver - Router1 - Router2 - Router3 Router1 and Router2 can succesfully ping WebServer. Router3 cannot. Router2 has a default gateway set, to send all not-recognized data through its serial interface to Router1. Like this: ip route 0.0.0.0 0.0.0.0 Serial 0/0/1 Serial 0/0/1 being the connection to Router1 Router2 and Router3 have OSPF configured. From their "show run": Router2: router ospf 1 log-adjacency-changes passive-interface Serial0/0/1 network 10.1.1.0 0.0.0.3 area 0 default-information originate ! Router3: router ospf 1 log-adjacency-changes network 10.1.1.0 0.0.0.3 area 0 passive-interface FastEthernet0/0 ! I was under the assumption that setting default-information originate on Router2 would give Router3 the needed information. What's going wrong here? The interfaces are up. Ip addresses are with mask-range, clock rate is set at correct end. I don't know what else to check.

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• Why am I seeing MailSlot Browse messages on unrouted ports of my Linux box?

  - by nmichaels

  I have a Linux box (Debian squeeze) with several NICs. The ones of interest are: eth3 - my main link to the network (dhcp on 10.20.30.0/24) eth0 - the first connection to my test network (static: 192.168.1.2) eth4 - the second connection to my test network (static: 192.168.1.1) My routing table looks like this: $ sudo route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.20.30.0 * 255.255.255.0 U 0 0 0 eth3 default 10.20.30.254 0.0.0.0 UG 0 0 0 eth3 I have the 2 test net ports connected to each other with a crossover cable and an instance of wireshark running on each port. Every once in a while, I'll see a packet like the following show up. Who could be doing this, and how do I convince them to stop? I do have Samba running on the machine (for a cifs mount) but don't see why it would be sending packets out to unrouted ports. I had a Windows VM running in VMWare Client and thought that might be causing it, but it still happens without it. What I want is totally silent interfaces so I can run some tests with Scapy over them.

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• How to stop NpgsqlDataReader from blocking?

  - by Swingline Rage

  Running the following code against a large PostgreSQL table, the NpgsqlDataReader object blocks until all data is fetched. NpgsqlCommand cmd = new NpgsqlCommand(strQuery, _conn); NpgsqlDataReader reader = cmd.ExecuteReader(); // <-- takes 30 seconds How can I get it to behave such that it doesn't prefetch all the data? I want to step through the resultset row by row without having it fetch all 15 GB into memory at once. I know there were issues with this sort of thing in Npgsql 1.x but I'm on 2.0. This is against a PostgreSQL 8.3 database on XP/Vista/7. I also don't have any funky "force Npgsql to prefetch" stuff in my connection string. I'm at a complete loss for why this is happening.

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• Problem with PXE boot

  - by user70523

  I followed the following link for PXE boot, http://www.howtoforge.com/setting-up-a-pxe-install-server-on-ubuntu-9.10-p3 and I was able to ping the client from the server and also when I booted up the client It is getting the IP address from the server. But later,I got this error PXELinux 3.82 2009-06-09 . . . [other informations] !PXE Entry point found (we hope) at 9D3B:0109 via plan A UNDI code segment at 9D3B len 16C2 UNDI data segment at 933B len A000 Getting cached packet 01 02 03 . . . [other informations] TFTP prefix: Trying to load: pxelinux.cfg/ec5db4c0-74fe-d511-b9e7-3d9235afe5a1 Trying to load: pxelinux.cfg/01-00-17-31-b6-5e-a8 Trying to load: pxelinux.cfg/0A64491E Trying to load: pxelinux.cfg/0A64491 Trying to load: pxelinux.cfg/0A6449 Trying to load: pxelinux.cfg/0A644 Trying to load: pxelinux.cfg/0A64 Trying to load: pxelinux.cfg/0A6 Trying to load: pxelinux.cfg/0A Trying to load: pxelinux.cfg/0 Trying to load: pxelinux.cfg/default Unable to locate configuration file Boot failed: press a key to retry or wait for reset I have put all the files mentioned in the link in tftpboot. Can anyone explain what could be the problem. Thanks in advance

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• Firefox is very slow when establish SSL sessions

  - by yanglei

  Using wireshark, I discovered that Firefox v3.0 gets stuck every time before "client key exchange, change cipher spec" stage when establishing a SSL session. Specifically, it takes 0.8~1.8 second before Firefox send "Client Key Exchange" request. This is unacceptable since our application is HTTPS only. I tested this on IE6 and IE8, both works well. Any clues? [Update] Finally, I found the reason of 1 ~ 2 seconds stuck by displaying all captured packets in Wireshark. After the "server hello" stage, Firefox makes a request to ocsp.verisign.com combined with an additional DNS lookup for that domain. Firefox must wait the revocation status from OCSP before entering the next stage of SSL. Depends on whether DNS cache is in effect, this process takes 1 ~ 2 seconds. A interesting observation is that the IP packet contains "client key exchange" has a high possibility to get lost and thus a TCP retransmission is necessary. When this happens, the process can take 3 seconds at worst. I'm not sure if this is a coincidence or a bug. Anyway, here is the result from Wireshark: (delta-time) 0.369296 src-ip dst-ip TCP [ACK] Seq=161 Ack=2741 Win=65340 Len=0 2.538835 src-ip dst-ip TLSv1 Client Key Exchange, Change Cipher Spec, Finished 2.987034 src-ip dst-ip TLSv1 [TCP Retransmission] Client Key Exchange, Change Cipher Spec, Finished The difference between Firefox and IE is this: Firefox 3 enables OCSP checking by default where as IE only supports it. So, there is no problem with both IE6 and IE8. This is indeed a "certificate revoke" problem. Thanks

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• C++ Multithreading with pthread is blocking (including sockets)

  - by Sebastian Büttner

  I am trying to implement a multi threaded application with pthread. I did implement a thread class which looks like the following and I call it later twice (or even more), but it seems to block instead of execute the threads parallel. Here is what I got until now: The Thread Class is an abstract class which has the abstract method "exec" which should contain the thread code in a derive class (I did a sample of this, named DerivedThread) Thread.hpp #ifndef THREAD_H_ #define THREAD_H_ #include <pthread.h> class Thread { public: Thread(); void start(); void join(); virtual int exec() = 0; int exit_code(); private: static void* thread_router(void* arg); void exec_thread(); pthread_t pth_; int code_; }; #endif /* THREAD_H_ */ And Thread.cpp #include <iostream> #include "Thread.hpp" /*****************************/ using namespace std; Thread::Thread(): code_(0) { cout << "[Thread] Init" << endl; } void Thread::start() { cout << "[Thread] Created Thread" << endl; pthread_create( &pth_, NULL, Thread::thread_router, reinterpret_cast<void*>(this)); } void Thread::join() { cout << "[Thread] Join Thread" << endl; pthread_join(pth_, NULL); } int Thread::exit_code() { return code_; } void Thread::exec_thread() { cout << "[Thread] Execute" << endl; code_ = exec(); } void* Thread::thread_router(void* arg) { cout << "[Thread] exec_thread function in thread" << endl; reinterpret_cast<Thread*>(arg)->exec_thread(); return NULL; } DerivedThread.hpp #include "Thread.hpp" class DerivedThread : public Thread { public: DerivedThread(); virtual ~DerivedThread(); int exec(); void Close() = 0; DerivedThread.cpp [...] #include "DerivedThread.cpp" [...] int DerivedThread::exec() { //code to be executed do { cout << "Thread executed" << endl; usleep(1000000); } while (true); //dummy, just to let it run for a while } [...] Basically, I am calling this like the here: DerivedThread *thread; cout << "Creating Thread" << endl; thread = new DerivedThread(); cout << "Created thread, starting..." << endl; thread->start(); cout << "Started thread" << endl; cout << "Creating 2nd Thread" << endl; thread = new DerivedThread(); cout << "Created 2nd thread, starting..." << endl; thread->start(); cout << "Started 2nd thread" << endl; What is working great if I am only starting one of these Threads , but if I start multiple which should run together (not synced, only parallel) . But I discovered, that the thread is created, then as it tries to execute it (via start) the problem seems to block until the thread has closed. After that the next Thread is processed. I thought that pthread would do it unblocked for me, so what did I wrong? A sample output might be: Creating Thread [Thread] Thread Init Created thread, starting... [Thread] Created thread [Thread] exec_thread function in thread [Thread] Execute Thread executed Thread executed Thread executed Thread executed Thread executed Thread executed Thread executed .... Until Thread 1 is not terminated, a Thread 2 won't be created not executed. The process above is executed in an other class. Just for the information: I am trying to create a multi threaded server. The concept is like this: MultiThreadedServer Class has a main loop, like this one: ::inet::ServerSock *sock; //just a simple self made wrapper class for sockets DerivedThread *thread; for (;;) { sock = new ::inet::ServerSock(); this->Socket->accept( *sock ); cout << "Creating Thread" << endl; //Threads (according to code sample above) thread = new DerivedThread(sock); //I did not mentoine the parameter before as it was not neccesary, in fact, I pass the socket handle with the connected socket to the thread cout << "Created thread, starting..." << endl; thread->start(); cout << "Started thread" << endl; } So I thought that this would loop over and over and wait for new connections to accept. and when a new client arrives, I am creating a new thread and give the thread the connected socket as a parameter. In the DerivedThread::exec I am doing the handling for the connected client. Like: [...] do { [...] if (this-sock_-read( Buffer, sizeof(PacketStruc) ) 0) { cout << "[Handler_Base] Recv Packet" << endl; //handle the packet } else { Connected = false; } delete Buffer; } while ( Connected ); So I loop in the created thread as long as the client keeps the connection. I think, that the socket may cause the blocking behaviour. Edit: I figured out, that it is not the read() loop in the DerivedThread Class as I simply replaced it with a loop over a simple cout-usleep part. It did also only execute the first one and after first thread finished, the 2nd one was executed. Many thanks and best regards, Sebastian

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• PHP Form Validation Regular Expression, no symbols or numbers

  - by MrEnder

  Ok I am trying to get the users First Name the form gets their name perfectly fine and posts it into a variable. Now I am trying to do error checking else if(!preg_match("/^[\w-]+$/", $firstNameSignup)) { $firstNameSignupError = "Your first name cannot contain numbers or symbols, you entered " . $firstNameSignup; $firstNameSignup = ""; } I tried the above code and it does not like me but my if statement if(!isset($firstNameSignup) || $firstNameSignup == "") { $firstNameSignupError = "You must enter your first name"; } works fine so I know that the error is in that else if statement... most likely in my regular expression any help??? I'm totally at a loss (really new to PHP and regular expressions) Thanks Shelby

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• VPN from Windows XP to OpenSwan: correct setup?

  - by Gnudiff

  Main question is what I am doing wrong in my OpenSwan or L2TP client setup? I am trying to create a Linux OpenSwan VPN connection from Windows XP machine, using preshared key and the builtin Windows XP L2TP IPsec option. I have followed the instructions in Linux Home networking Wiki for setting up OpenSwan and a guide to making it work with the Windows XP client, but am now stuck. The net setup is as follows: [my windows client, private IP A]<->[f/wall B]<-internet->[g/w X]<->[Linux OpenSwan server Y] A - private subnet /24 B - internet address X - internet address /24 Y - internet address on same subnet as X What I essentially want is for computer with A address to feel and work, as if it was in X subnet for purposes of outgoing and incoming TCP and UDP connections. My OpenSwan setup is as follows: /etc/ipsec.conf (AAA and YYY indicates ip address parts of A and Y addresses): conn net-to-net authby=secret left=B leftsubnet=AAA.AAA.AAA.0/24 leftnexthop=%defaultroute right=Y rightsubnet=YYY.YYY.YYY.0/24 rightnexthop=B auto=start the secret in /etc/ipsec.secrets is listed as: B Y : PSK "0xMysecretkey" where B & Y stand for respective IP adresses of gateway B and linux server Y My L2TP WinXP setup is: IP of destination: Y don't prompt for username security options: typical, require secured pass, don't require data encryption, IPSec PSK set to 0xMysecretkey networking options: VPN Type: L2TP IPSec VPN; TCPIP protocol (with automatic IP address assignment) and QOS packet schedulers enabled The error I get from Windows client is 789: "error during initial negotiation"

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• Debugging "clogged" TCP connections

  - by Nikratio

  I'm having trouble with an internet connection that seems to randomly "freeze" arbitrary tcp connections. The connections stay established, but no data is coming through. When this happens, netstat still shows the connection status as ESTABLISHED on both the local computer: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name Timer tcp 0 53 192.168.0.10:41129 173.255.235.238:143 ESTABLISHED 8219/gnutls-cli on (79.31/13/0) ..and the remote server: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name Timer tcp 0 0 173.255.235.238:143 68.5.174.98:41129 ESTABLISHED 5303/imapd off (0.00/0/0) However, it seems that no data at all is transferred. If I run strace on the local and remote process, both just show a repeating sequence of select calls (with different fds of course), e.g. select(6, [0 5], NULL, NULL, {0, 50000}) = 0 (Timeout) select(6, [0 5], NULL, NULL, {0, 50000}) = 0 (Timeout) select(6, [0 5], NULL, NULL, {0, 50000}) = 0 (Timeout) The internet connection overall does not seem affected, I can still establish new connections to the same service on the same server without any problems. However, the affected local applications seem to be unaware of the problem and just hang. When I look at a packet capture of this connection on the client side, the last thing that happens is that the client transmits some data, then nothing happens for about 1100 seconds, and then several TCP Retransmission requests go out, with intervals increasing from 4 seconds to 130 seconds. No activity is captured after that. After about 10 minutes, the connection on the remote end disappears from the netstat (I wasn't able to catch any intermediate state), but still stays ESTABLISHED on the local end. Finally, after some more minutes, the local application aborts with a timeout and disappears from the local netstat output as well. Does anyone have a suggestion of how I could debug this further to find out where the problem lies and how to fix it? Additionaly and/or as a temporary workaround: is is there some way to globally reduce the timeout on client and/or server to reduce the time before the local application aborts?

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• WCF timeout exception detailed investigation

  - by Jason Kealey

  We have an application that has a WCF service (*.svc) running on IIS7 and various clients querying the service. The server is running Win 2008 Server. The clients are running either Windows 2008 Server or Windows 2003 server. I am getting the following exception, which I have seen can in fact be related to a large number of potential WCF issues. System.TimeoutException: The request channel timed out while waiting for a reply after 00:00:59.9320000. Increase the timeout value passed to the call to Request or increase the SendTimeout value on the Binding. The time allotted to this operation may have been a portion of a longer timeout. ---> System.TimeoutException: The HTTP request to 'http://www.domain.com/WebServices/myservice.svc/gzip' has exceeded the allotted timeout of 00:01:00. The time allotted to this operation may have been a portion of a longer timeout. I have increased the timeout to 30min and the error still occurred. This tells me that something else is at play, because the quantity of data could never take 30min to upload or download. The error comes and goes. At the moment, it is more frequent. It does not seem to matter if I have 3 clients running simultaneously or 100, it still occurs once in a while. Most of the time, there are no timeouts but I still get a few per hour. The error comes from any of the methods that are invoked. One of these methods does not have parameters and returns a bit of data. Another takes in lots of data as a parameter but executes asynchronously. The errors always originate from the client and never reference any code on the server in the stack trace. It always ends with: at System.Net.HttpWebRequest.GetResponse() at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout) On the server: I've tried (and currently have) the following binding settings: maxBufferSize="2147483647" maxReceivedMessageSize="2147483647" maxBufferPoolSize="2147483647" It does not seem to have an impact. I've tried (and currently have) the following throttling settings: <serviceThrottling maxConcurrentCalls="1500" maxConcurrentInstances="1500" maxConcurrentSessions="1500"/> It does not seem to have an impact. I currently have the following settings for the WCF service. [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Single)] I ran with ConcurrencyMode.Multiple for a while, and the error still occurred. I've tried restarting IIS, restarting my underlying SQL Server, restarting the machine. All of these don't seem to have an impact. I've tried disabling the Windows firewall. It does not seem to have an impact. On the client, I have these settings: maxReceivedMessageSize="2147483647" <system.net> <connectionManagement> <add address="*" maxconnection="16"/> </connectionManagement> </system.net> My client closes its connections: var client = new MyClient(); try { return client.GetConfigurationOptions(); } finally { client.Close(); } I have changed the registry settings to allow more outgoing connections: MaxConnectionsPerServer=24, MaxConnectionsPer1_0Server=32. I have now just recently tried SvcTraceViewer.exe. I managed to catch one exception on the client end. I see that its duration is 1 minute. Looking at the server side trace, I can see that the server is not aware of this exception. The maximum duration I can see is 10 seconds. I have looked at active database connections using exec sp_who on the server. I only have a few (2-3). I have looked at TCP connections from one client using TCPview. It usually is around 2-3 and I have seen up to 5 or 6. Simply put, I am stumped. I have tried everything I could find, and must be missing something very simple that a WCF expert would be able to see. It is my gut feeling that something is blocking my clients at the low-level (TCP), before the server actually receives the message and/or that something is queuing the messages at the server level and never letting them process. If you have any performance counters I should look at, please let me know. (please indicate what values are bad, as some of these counters are hard to decypher). Also, how could I log the WCF message size? Finally, are there any tools our there that would allow me to test how many connections I can establish between my client and server (independently from my application) Thanks for your time! Extra information added June 20th: My WCF application does something similar to the following. while (true) { Step1GetConfigurationSettingsFromServerViaWCF(); // can change between calls Step2GetWorkUnitFromServerViaWCF(); DoWorkLocally(); // takes 5-15minutes. Step3SendBackResultsToServerViaWCF(); } Using WireShark, I did see that when the error occurs, I have a five TCP retransmissions followed by a TCP reset later on. My guess is the RST is coming from WCF killing the connection. The exception report I get is from Step3 timing out. I discovered this by looking at the tcp stream "tcp.stream eq 192". I then expanded my filter to "tcp.stream eq 192 and http and http.request.method eq POST" and saw 6 POSTs during this stream. This seemed odd, so I checked with another stream such as tcp.stream eq 100. I had three POSTs, which seems a bit more normal because I am doing three calls. However, I do close my connection after every WCF call, so I would have expected one call per stream (but I don't know much about TCP). Investigating a bit more, I dumped the http packet load to disk to look at what these six calls where. 1) Step3 2) Step1 3) Step2 4) Step3 - corrupted 5) Step1 6) Step2 My guess is two concurrent clients are using the same connection, that is why I saw duplicates. However, I still have a few more issues that I can't comprehend: a) Why is the packet corrupted? Random network fluke - maybe? The load is gzipped using this sample code: http://msdn.microsoft.com/en-us/library/ms751458.aspx - Could the code be buggy once in a while when used concurrently? I should test without the gzip library. b) Why would I see step 1 & step 2 running AFTER the corrupted operation timed out? It seems to me as if these operations should not have occurred. Maybe I am not looking at the right stream because my understanding of TCP is flawed. I have other streams that occur at the same time. I should investigate other streams - a quick glance at streams 190-194 show that the Step3 POST have proper payload data (not corrupted). Pushing me to look at the gzip library again.

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