Re: possible dos / wsize affected frozen connection length (was: Re: 2.6.17.1: fails to fully get webpage)

2006-07-05 Thread linux-os \(Dick Johnson\)

On Tue, 4 Jul 2006, CaT wrote:

 On Fri, Jun 30, 2006 at 08:50:39AM +1000, CaT wrote:
 Another datapoint to this is that I've had this my netcat web test
 running since 8:42pm yesterday. It's 8:37am now. It hasn't progressed
 in any way. It hasn't quit. It hasn't timed out. It just sits there,
 hung. This leads me to consider the possibility of a DOS, either
 intentional or accidental (think about 2.6.17.x running on a mail server
 and someone mails/spams from a broken place).

 I'm just wondering if connections hanging around this long are normal.
 The above has now been running for 6 days. netstat is still reporting an
 established session. netcat has not timed out. It's all just sitting
 there doing nothing.

 --

To the extent that we overreact, we proffer the terrorists the
greatest tribute.
   - High Court Judge Michael Kirby

TCP/IP connections can continue forever. That's one of the reasons why
Berkeley sockets has SO_KEEPALIVE for a socket option. In the absence
of such an option, the physical connection can be broken for a week,
reconnected, then the session can continue.

In your case, you probably have a real error in which one end of the
connection crashed. However, until the other end shuts down that
socket, the connection is logically correct and should not be
forcefully terminated.

A DOS is unlikely because with no data being transferred, little
non-swapable resources are used. You can control the maximum number
of connections allowed from a host with your firewall software
(like iptables).

Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.86 BogoMips).
New book: http://www.AbominableFirebug.com/
_



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Re: Linux kernel and laws

2006-06-05 Thread linux-os \(Dick Johnson\)

On Mon, 5 Jun 2006, Adrian Bunk wrote:

 On Mon, Jun 05, 2006 at 08:52:35AM -0400, Jeff Garzik wrote:
 ...
 Paying attention to proper reverse engineering is good. Being
 overzealous is not.

 Being overzealous about merging drivers without first checking the legal
 ramifications is a good way to torpedo Linux.

 Far too many people have a careless U.S.A. laws suck, merge it anyway
 attitude.

 Independent of this issue:

 An interesting question is how to handle legal issues properly.

 Where is the borderline for rejecting code due to legal issues?
 Might not be 100% correct according to laws in the USA.
 Might not be 100% correct according to laws in Germany.
 Might not be 100% correct according to laws in Finland.
 Might not be 100% correct according to laws in Norway.
 Might not be 100% correct according to laws in Brasil.
 Might not be 100% correct according to laws in Japan.
 Might not be 100% correct according to laws in India.
 Might not be 100% correct according to laws in Russia.
 Might not be 100% correct according to laws in China.
 Might not be 100% correct according to laws in Saudi Arabia.
 Might not be 100% correct according to laws in Iran.

 For me living in Germany, none of these laws except for the German one
 has any relevance.

 I've never seen people on this list pointing to probable problems with
 Chinese laws although these laws are relevant for four times as many
 people as US laws.

 If someone would state a submission to the kernel might have issues
 according to Chinese laws, or Iranian laws, or Russian laws, would this
 be enough for keeping code out of the kernel?

 This might sound like a theoretical question, but e.g. considering that
 the kernel contains cryptography code it's a question that might have
 wide practical implications.

  Jeff

 cu
 Adrian

If the kernel represented simply a knowledge base, then the burden
about whether or not someone could use it used to rest entirely
upon the user. That's why some Pacific rim governments are reportedly
fire-walling information.

In most western cultures, knowledge was not a crime. For many years,
someone could write a book, telling you how to kill somebody and,
as long as he didn't carry it out, he could not be held culpable.

Recently, in the US and some other countries, knowledge has become
criminalized. If you know how to defeat copy protection, and
you are not in a protected industry, you could be tried and
convicted of a federal crime.

That's one of the reasons why there are now no general guidelines
about kernel code, or any intellectual property use, for that matter.
The conditions could occur where the government thinks that you
know too much and are, therefore, a threat to national security.

So, again, see a lawyer. The fact that you sought and accepted
legal opinion may in the future be your only viable defense as
governments bring charges against you! Sorry state of affairs for
sure.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.88 BogoMips).
New book: http://www.AbominableFirebug.com/
_



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Re: Van Jacobson's net channels and real-time

2006-04-25 Thread linux-os \(Dick Johnson\)

On Mon, 24 Apr 2006, Auke Kok wrote:

 linux-os (Dick Johnson) wrote:
 On Mon, 24 Apr 2006, Auke Kok wrote:

 Ingo Oeser wrote:
 On Saturday, 22. April 2006 15:49, Jörn Engel wrote:
 That was another main point, yes.  And the endpoints should be as
 little burden on the bottlenecks as possible.  One bottleneck is the
 receive interrupt, which shouldn't wait for cachelines from other cpus
 too much.
 Thats right. This will be made a non issue with early demuxing
 on the NIC and MSI (or was it MSI-X?) which will select
 the right CPU based on hardware channels.
 MSI-X. with MSI you still have only one cpu handling all MSI interrupts and
 that doesn't look any different than ordinary interrupts. MSI-X will allow
 much better interrupt handling across several cpu's.

 Auke
 -

 Message signaled interrupts are just a kudge to save a trace on a
 PC board (read make junk cheaper still).

 yes. Also in PCI-Express there is no physical interrupt line anymore due to
 the architecture, so even classical interrupts are sent as message over the 
 bus.

 They are not faster and may even be slower.

 thus in the case of PCI-Express, MSI interrupts are just as fast as the
 ordinary ones. I have no numbers on whether MSI is faster or not then e.g.
 interrupts on PCI-X, but generally speaking, the PCI-Express bus is not
 designed to be low latency at all, at best it gives you X latency, where X
 is something like microseconds. The MSI message itself only takes 10-20
 nanoseconds though, but all the handling probably adds a large factor to that
 (1000 or so). No clue on classical interrupt line latency - anyone?


About 9 nanosecond per foot of FR-4 (G10) trace, plus the access time
through the gate-arrays (about 20 ns) so, from the time a device needs
the CPU, until it hits the interrupt pin, you have typically 30 to
50 nanoseconds. Of course the CPU is __much__ slower. However, these
physical latencies are in series, cannot be compensated for because
the CPU can't see into the future.


 They will not be the salvation of any interrupt latency problems.

 This is also not the problem - we really don't care that our 100.000 packets
 arrive 20usec slower per packet, just as long as the bus is not idle for those
 intervals. We would care a lot if 25.000 of those arrive directly at the
 proper CPU, without the need for one of the cpu's to arbitrate on every
 interrupt. That's the idea anyway.

It forces driver-writers to loop in ISRs to handle new status changes
that happened before an asserted interrupt even got to the CPU. This
is bad. You end up polled in the ISR, with the interrupts off. Turning
on the interrupts exacerbates the problem, you may never leave the
ISR! It becomes the new idle task. To properly use interrupts,
the hardware latency must be less than the CPUs response to the
hardware stimulus.


 Nowadays with irq throttling we introduce a lot of designed latency anyway,
 especially with network devices.

 The solutions for increasing networking speed,
 where the bit-rate on the wire gets close to the bit-rate on the
 bus, is to put more and more of the networking code inside the
 network board. The CPU get interrupted after most things (like
 network handshakes) are complete.

 That is a limited vision of the situation. You could argue that the current
 CPU's have so much power that they can easily do a lot of the processing
 instead of the hardware, and thus warm caches for userspace, setup sockets
 etc. This is the whole idea of Van Jacobsen's net channels. Putting more
 offloading into the hardware just brings so much problems with itself, that
 are just far easier solved in the OS.


 Cheers,

 Auke


Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_



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Re: Van Jacobson's net channels and real-time

2006-04-24 Thread linux-os \(Dick Johnson\)

On Mon, 24 Apr 2006, Auke Kok wrote:

 Ingo Oeser wrote:
 On Saturday, 22. April 2006 15:49, Jörn Engel wrote:
 That was another main point, yes.  And the endpoints should be as
 little burden on the bottlenecks as possible.  One bottleneck is the
 receive interrupt, which shouldn't wait for cachelines from other cpus
 too much.

 Thats right. This will be made a non issue with early demuxing
 on the NIC and MSI (or was it MSI-X?) which will select
 the right CPU based on hardware channels.

 MSI-X. with MSI you still have only one cpu handling all MSI interrupts and
 that doesn't look any different than ordinary interrupts. MSI-X will allow
 much better interrupt handling across several cpu's.

 Auke
 -

Message signaled interrupts are just a kudge to save a trace on a
PC board (read make junk cheaper still). They are not faster and
may even be slower. They will not be the salvation of any interrupt
latency problems. The solutions for increasing networking speed,
where the bit-rate on the wire gets close to the bit-rate on the
bus, is to put more and more of the networking code inside the
network board. The CPU get interrupted after most things (like
network handshakes) are complete.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_



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Re: Van Jacobson's net channels and real-time

2006-04-24 Thread linux-os \(Dick Johnson\)

On Mon, 24 Apr 2006, Rick Jones wrote:

 Thats right. This will be made a non issue with early demuxing
 on the NIC and MSI (or was it MSI-X?) which will select
 the right CPU based on hardware channels.

 MSI-X. with MSI you still have only one cpu handling all MSI interrupts and
 that doesn't look any different than ordinary interrupts. MSI-X will allow
 much better interrupt handling across several cpu's.

 Auke
 -


 Message signaled interrupts are just a kudge to save a trace on a
 PC board (read make junk cheaper still). They are not faster and
 may even be slower. They will not be the salvation of any interrupt
 latency problems. The solutions for increasing networking speed,
 where the bit-rate on the wire gets close to the bit-rate on the
 bus, is to put more and more of the networking code inside the
 network board. The CPU get interrupted after most things (like
 network handshakes) are complete.

 if the issue is bus vs network bitrates would offloading really buy that
 much?  i suppose that for minimum sized packets not DMA'ing the headers
 across the bus would be a decent win, but down at small packet sizes
 where headers would be 1/3 to 1/2 the stuff DMA'd around, I would think
 one is talking more about CPU path lengths than bus bitrates.

 and up and full size segments, since everyone is so fond of bulk
 transfer tests, the transfer saved by not shovig headers across the bus
 is what 54/1448 or ~3.75%

 spreading interrupts via MSI-X seems nice and all, but i keep wondering
 if the header field-based distribution that is (will be) done by the
 NICs is putting the cart before the horse - should the NIC essentially
 be telling the system the CPU on which to run the application, or should
 the CPU on which the application runs be telling networking where it
 should be happening?

 rick jones


Ideally, TCP/IP is so mature that one should be able to tell some
hardware state-machine Connect with 123.555.44.333, port 23 and
it signals via interrupt when that happens. Then one should be
able to say send these data to that address or fill this buffer
with data from that address. All the networking could be done
on the board, perhaps with a dedicated CPU (as is now done) or
all in silicon.

So, the driver end of the networking software just handles
buffers. There are interrupts that show status such as
completions or time-outs, trivial stuff.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_



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Re: Router stops routing after changing MAC Address

2006-03-14 Thread linux-os \(Dick Johnson\)

On Tue, 14 Mar 2006, Bart Samwel wrote:

 linux-os (Dick Johnson) wrote:
 On Mon, 13 Mar 2006, Greg Scott wrote:
 Bst... Not! There are not any MAC addresses associated with any
 of the intercity links, usually not even in WANs!  MAC is for
 Ethernet! Once you go to fiber, ATM, T-N, etc., there are no MAC addresses.

 Bt. According to WikiPedia:

 http://en.wikipedia.org/wiki/MAC_address

 MAC addresses are used for:

 - Token ring
 - 802.11 wireless networks
 - Bluetooth
 - FDDI
 - ATM (switched virtual connections only, as part of an NSAP address)
 - SCSI and Fibre Channel (as part of a World Wide Name)

 FDDI = fiber, ATM = ATM.

 --Bart


A name is NOT.  I can call my mail route number RFD#2 a MAC
address. Also token-ring is a form of Ethernet as are all
known wireless networks unless they use light. Even cable
modems use Ethernet, with FDM on the cable side and baseband
on the customer side. Calling SCSI MAC is absurd. All of the
above, except the ethernets are forms of point-to-point
communications links. IP (over/under or through) these
links uses a source and destination IP and any hardware
addressing scheme is incidental.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.15.4 on an i686 machine (5589.54 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_



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Re: Router stops routing after changing MAC Address

2006-03-13 Thread linux-os \(Dick Johnson\)

On Mon, 13 Mar 2006, Stephen Hemminger wrote:

 There still is a bug in the 3c59x driver.  It doesn't include any code
 to handle changing the mac address.  It will work if you take the device
 down, change address, then bring it up. But you shouldn't have to do that.

 Also, if the driver handles setting mac address, it could have prevented
 you from using a multicast address.

 Something like this is needed (untested, I don't have that hardware).


 --- linux-2.6/drivers/net/3c59x.c.orig2006-03-13 09:58:25.0 
 -0800
 +++ linux-2.6/drivers/net/3c59x.c 2006-03-13 09:52:47.0 -0800
 @@ -895,6 +895,7 @@ static void dump_tx_ring(struct net_devi
 static void update_stats(void __iomem *ioaddr, struct net_device *dev);
 static struct net_device_stats *vortex_get_stats(struct net_device *dev);
 static void set_rx_mode(struct net_device *dev);
 +static int set_rx_address(struct net_device *dev, void *addr);
 #ifdef CONFIG_PCI
 static int vortex_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);
 #endif
 @@ -1563,6 +1564,7 @@ static int __devinit vortex_probe1(struc
 #endif
   dev-ethtool_ops = vortex_ethtool_ops;
   dev-set_multicast_list = set_rx_mode;
 + dev-set_mac_address = set_rx_address;
   dev-tx_timeout = vortex_tx_timeout;
   dev-watchdog_timeo = (watchdog * HZ) / 1000;
 #ifdef CONFIG_NET_POLL_CONTROLLER
 @@ -3150,6 +3152,27 @@ static void set_rx_mode(struct net_devic
   iowrite16(new_mode, ioaddr + EL3_CMD);
 }

 +
 +static int set_rx_address(struct net_device *dev, void *p)
 +{
 + struct vortex_private *vp = netdev_priv(dev);
 + void __iomem *ioaddr = vp-ioaddr;
 + const struct sockaddr *addr = p;
 +
 + if (!is_valid_ether_addr(addr-sa_data))
 + return -EADDRNOTAVAIL;
 +
 + spin_lock_bh(vp-lock);
 + memcpy(dev-dev_addr, addr-sa_data, ETH_ALEN);
 +
 + EL3WINDOW(2);
 + for (i = 0; i  ETH_ALEN; i++)
 + iowrite8(dev-dev_addr[i], ioaddr + i);
 + spin_unlock_bh(vp-lock);
 +
 + return 0;
 +}
 +
 #if defined(CONFIG_VLAN_8021Q) || defined(CONFIG_VLAN_8021Q_MODULE)
 /* Setup the card so that it can receive frames with an 802.1q VLAN tag.
Note that this must be done after each RxReset due to some backwards
 -

Actually, it doesn't make any difference. Changing the IEEE station
(physical) address is not an allowed procedure even though hooks are
available in many drivers to do this. According to the IEEE 802
physical media specification, this 48-bit address must be unique and
must be one of a group assigned by IEEE. Failure to follow this
simple protocol can (will) cause an entire network to fail. If
you don't care, then you certainly don't care about multicast
bits either, basically let them set it to all ones as well.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.15.4 on an i686 machine (5589.54 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_



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RE: Router stops routing after changing MAC Address

2006-03-13 Thread linux-os \(Dick Johnson\)

On Mon, 13 Mar 2006, Greg Scott wrote:

 But in a failover scenario you want two devices to have the same IEEE
 (station) Address (or MAC Address or hardware address).  So many names
 for the same thing!

 When the primary unit fails, you want the backup unit to completely
 assume the failed unit's identity - right down to the MAC Address.  The
 other way to do it using gratuitous ARPs is not good enough because some
 cheap router someplace with an ARP cache of several hours will not
 listen and will never update its own ARP cache.

 I like to think of this as bending the rules a little bit, not really
 breaking them.  :)

 - Greg


Top posting, NotGood(tm). Anyway, if the device fails, you have
routers and hosts ARPing the interface, trying to establish a
route anyway.



 Actually, it doesn't make any difference. Changing the IEEE station
 (physical) address is not an allowed procedure even though hooks are
 available in many drivers to do this. According to the IEEE 802
 physical media specification, this 48-bit address must be unique
 and must be one of a group assigned by IEEE. Failure to follow this
 simple protocol can (will) cause an entire network to fail. If you
 don't care, then you certainly don't care about multicast bits either,
 basically let them set it to all ones as well.

 Cheers,
 Dick Johnson
 Penguin : Linux version 2.6.15.4 on an i686 machine (5589.54 BogoMips).
 Warning : 98.36% of all statistics are fiction, book release in April.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.15.4 on an i686 machine (5589.54 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_



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RE: Router stops routing after changing MAC Address

2006-03-13 Thread linux-os \(Dick Johnson\)

On Mon, 13 Mar 2006, Greg Scott wrote:

 Yup.

 I had a situation 2 weeks ago where a customer connected a system to the
 Internet with an IP Address he should not have used.  And the little
 Cisco router on the frontend dutifully recorded it in its ARP cache -
 forever, with no TTL!  This took down their webmail for most of a day
 until we finally had to cycle the power on that nasty little Cisco 678.

 Bigger routers do it too.  I've had several situations over the years
 where I replaced an older firewall with a newer one with the same IP
 Addresses.  All the internal servers find it soon enough.  But I've
 waited literally hours for the routers to finally purge their ARP caches
 so they would see my replacement systems - often with the customer
 looking over my shoulders getting more and more nervous by the minute.

 And sometimes the routers are not accessible - you can't cycle them even
 if you had permission.  Consider the cases of bridged DSL service -

Bst... Not! There are not any MAC addresses associated with any
of the intercity links, usually not even in WANs!  MAC is for
Ethernet! Once you go to fiber, ATM, T-N, etc., there are no
MAC addresses. That's why there are bridges and routers, you
got to connect your tiny time-slot to your LAN and that
first device contains the MAC address that all your other stuff
talks to.

 where the real router could be on the other side of the country.  Try
 calling an ISP and asking the tech on the other end to purge an ARP
 cache on a router.  So the same IP Addresses but different MAC
 addresses, all you can do is wait for the passage of (lots of) time.
 That happened to me in my own network once.  I accidently took down my
 email server for something like 4 hours one time when I got careless.

 Indeed, there is a large onus on the software doing the MAC
 override to make sure it does not break the required uniqueness.
 Just as if one were using locally administered MAC addresses.

 Yes.  My 12:34:56 OUI scheme will work for this project but it is
 definitely not good for the long term.  I really really hope I have to
 spend some money with the IEEE soon to support lots and lots of
 rollouts.  :)

 - Greg Scott



 -Original Message-
 From: Rick Jones [mailto:[EMAIL PROTECTED]
 Sent: Monday, March 13, 2006 3:50 PM
 To: linux-os (Dick Johnson)
 Cc: Greg Scott; Chuck Ebbert; linux-kernel; netdev@vger.kernel.org; Bart
 Samwel; Alan Cox; Simon Mackinlay
 Subject: Re: Router stops routing after changing MAC Address

  Anyway, if the device fails, you have
 routers and hosts ARPing the interface, trying to establish a route
 anyway.

 But only after what may be a much longer time than the customer is
 willing to accept or able to configure.  I know of a number of HA
 situations where the new device is given the old MAC just to avoid
 that speicific situation of ARP caches not being updated except after
 quite some time.  Not necessarily on the end-systems, the issue can be
 with intermediate devices (routers).

 And if one has to work with static ARP entries to deal (however
 imperfectly) with ARP poisioning or whatnot...

 Indeed, there is a large onus on the software doing the MAC override to
 make sure it does not break the required uniqueness.  Just as if one
 were using locally administered MAC addresses.

 rick jones
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Cheers,
Dick Johnson
Penguin : Linux version 2.6.15.4 on an i686 machine (5589.54 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_



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Re: [RFC] ip / ifconfig redesign

2005-12-02 Thread linux-os \(Dick Johnson\)

On Fri, 2 Dec 2005, Al Boldi wrote:

 The current ip / ifconfig configuration is arcane and inflexible.  The reason
 being, that they are based on design principles inherited from the last
 century.

 In a GNU/OpenSource environment, OpenMinds should not inhibit themselves
 achieving new design-goals to enable a flexible non-redundant configuration.

 Specifically, '# ip addr ' exhibits this issue clearly, by requiring to
 associate the address to a link instead of the other way around.

 Consider this new approach for better address management:
 1. Allow the definition of an address pool
 2. Relate links to addresses
 3. Implement to make things backward-compatible.

 The obvious benefit here, would be the transparent ability for apps to bind
 to addresses, regardless of the link existence.


A link needs to exist for it to have an address.

 Another benefit includes the ability to scale the link level transparently,
 regardless of the application bind state.


That doesn't make any sense. Multiple applications can bind to the
same address. Then can't bind to the same port because they won't
get all their data.

 And there may be many other benefits... (i.e. 100% OSI compliance)

What does Open Source Initiative have to do with this at all???
You are just spewing stuff out.

 --
 Al

Also, how does this involve the kernel? The interface to the kernel
for hardware configuration is via ioctl(). For logic, sockets.

If the user-level tools suck, then they should be fixed. It
really doesn't have anything to do with the kernel.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.44 BogoMips).
Warning : 98.36% of all statistics are fiction.
.


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