Tag Archives: Network

cURL and libcurl, Network

shorter HTTP requests for curl

Starting in curl 7.26.0 (due to be released at the end of May 2012), we will shrink the User-agent: header that curl sends by default in HTTP(S) requests to something much shorter! I suspect that this will raise some eyebrows out there so even though I’ve emailed about it to the curl-users list before I thought I’d better write it up and elaborate.

A default ‘curl localhost’ on Debian Linux makes 170 bytes get sent in that single request:

GET / HTTP/1.1
User-Agent: curl/7.24.0 (i486-pc-linux-gnu) libcurl/7.24.0 OpenSSL/1.0.0g zlib/1.2.6 libidn/1.23 libssh2/1.2.8 librtmp/2.3
Host: localhost
Accept: */*

As you can see, the user-agent description takes up a large portion of that request, and this for really no good reason at all. Without sacrificing any functionality I shrunk the same request down to 71 bytes:

GET / HTTP/1.1
User-Agent: curl/7.24.0
Host: localhost
Accept: */*

That means we shrunk it down to 41% of the original size. I’ll admit the example is a bit extreme and most other normal use cases will use longer host names and longer paths, but even for a URL like “https://daniel.haxx.se/docs/curl-vs-wget.html” we’re down to 50% of the original request size (100 vs 199).

Can we shrink it even more? Sure, we could leave out the version number too. I left it in there now only to allow some kind of statistics to get extracted. We can’t remove the entire header, we need to include a user-agent in requests since there are too many servers who won’t function properly otherwise.

And before anyone asks: this change is only for the curl command line tool and not for libcurl, the library. libcurl does in fact not send any user-agent at all by default…

Network, Technology

Digging the fiber

1 Comment

Finally the installation of my open fiber is moving along.

Roughly two weeks ago the team responsible for getting the thing from the boundary of my estate to my house arrived. They spent a great deal of time trying to piggyback the existing tube already running under my driveway for the telephone cable – until they gave up and had to use their shovels to dig a ditch through my garden. Apparently the existing tube was too tight and already too filled up with the existing cables. A little strike of bad luck I think since now they instead had to make a mess of my garden. Here’s a little picture of the dig work they did:

a ditch for the fiber through the garden

They aim at a depth of 25 cm for the cable while going through people’s estates, while outside of my garden they need 50 cm depth underneath the road and sidewalk down my little suburb street.

Once they were done we could see this orange cable sticking up next to my mailbox:

the outer end of the cable by my mailbox

… and the other end is sticking up here next to my front door. I expect the next team to get here and do the installation from here and pull it in through my wall and install the media converter etc possibly in the closet next to my front door. We’ll see…

the end of the cable next to the stairs by my front door

Today, when I arrived home after work the team that were digging up the sidewalk had already connected the cable side that was previously sticking out next to my mailbox (the middle picture).

Of course, they did their best at putting things (like soil) back as it was but I’ll admit that my better half used some rather colorful expressions to describe her sentiments about getting the garden remade like this.

I’ll get back with more reports later on when I get things installed internally and when the garden starts to repair.

Network

Network hardware deaths

6 Comments

Things went southwards already this morning. My wife was about to work from home and called me before 8am asking for help to get online as the wireless Internet access setup didn’t work for her.

As this has happened at some occasions before she knew she might need to reboot the wifi router to get things running again. So she did. Only this time, when she inserted the power plug again there was not a single LED turning on. None. She yanked it out again and re-inserted it. Nothing.

Okay, so she was not able to use the wifi and the router was dead.

At lunch, I took a short walk in the sunshine to my nearest “Kjell & Co” and got myself a new wifi router and brought it back with me home after work and immediately replaced the dead one with the new shiny one. I ran upstairs (most of my network gear is under the staircase on the bottom floor while my main computer andlink DIR 635d work space is on the upper floor), configured the new router with the static IP and those things that need to be there and…

…weird, I still can’t access the Internet!

I then decided to do the power recycle dance with the ADSL modem as well. I could see how the “WAN” led blinked, turned stable and then I could actually successfully send several ping packets (that got responses) before the connection broke again and the WAN led on the modem was again switched off. I retried the power cycle procedure but the led stayed off.

I called customer support for my ADSL service (Bredbandsbolaget) and they immediately spotted how old my modem is, indicating that it was probably the reason for the failure and set me up to receive a free replacement unit within 2-3 days.

This left me with several problems still nudging my brain:

  1. Why would suddenly two devices standing next to each other, connected with a cat5, break on the same day when they both have been running flawlessly like this for years? I had perfect network access when I went to bed last night and there were no power outages, lightning strikes or similar.
  2. Why and how could the customer service so quickly judge that the reason was the age of my modem? I get the sense they just knee-jerk the replacement unit because of the age of mine and there’s a rather big risk that when I plug in the new modem in a few days it will show the same symptoms…
  3. 2-3 days!! Gaaaah. Thank God I can tether with my phone, but man 3G may be nice and all but its not like my trusty old 12mbit ADSL I tend to get. Not to mention that the RTT is much worse and that’s a factor for me who use quite a lot of SSH to remote machines.

I guess I will find out when the new hardware arrives. I may get reason to write a follow-up then. I hope not!

Update on September 23rd:

A new ADSL modem arrived just two days after my call and yay, it could sync and I could use internet. Unfortunately something was still wrong though as my telephone didn’t work (I have a IP-telephony service that goes through the ADSL box). I took me until Sunday to call customer service again, and on Tuesday a second replace modem arrived which I installed on Thursday and… now even the phone works!

I never figured out why both devices died, but the end result is that my 802.11n wifi works properly with speeds above 6.5MB/sec in my house.

Network, Security

What SOCKS is good for

4 Comments

You ever wondered what SOCKS is good for these days?

To help us use the Internet better without having the surrounding be able to watch us as much as otherwise!

There’s basically two good scenarios and use areas for us ordinary people to use SOCKS:

  1. You’re a consultant or you’re doing some kind of work and you are physically connected to a customer’s or a friend’s network. You access the big bad Internet via their proxy or entirely proxy-less using their equipment and cables. This allows the network admin(s) to capture and snoop on your network traffic, be it on purpose or by mistake, as long as you don’t use HTTPS or other secure mechanisms. When surfing the web, it is very easily made to drop out of HTTPS and into HTTP by mistake. Also, even if you HTTPS to the world, the name resolves and more are still done unencrypted and will leak information.
  2. You’re using an open wifi network that isn’t using a secure encryption. Anyone else on that same area can basically capture anything you send and receive.

What you need to set it up? You run

ssh -D 8080 myname@myserver.example.com

… and once you’ve connected, you make sure that you change the network settings of your favourite programs (browsers, IRC clients, mail reader, etc) to reach the Internet using the SOCKS proxy on localhost port 8080. Now you’re done.

Now all your traffic will reach the Internet via your remote server and all traffic between that and your local machine is sent encrypted and secure. This of course requires that you have a server running OpenSSH somewhere, but don’t we all?

If you are behind another proxy in the first place, it gets a little more complicated but still perfectly doable. See my separate SSH through or over proxy document for details.

IT Politics, Network, Technology

Open fibre

3 Comments

One of the big telecom operators in Sweden, Telia, has started to offer “fibre to the house”- called “Öppen Fiber” in Swedish – and I’ve signed up for it. They’re investing 5 billion SEK into building fibre infrastructure and I happen to live in an area which is among the first ones in Sweden that gets the chance to participate. What’s in this blog post is information as I’ve received and understood it. I will of course follow-up in the future and tell how it all turns out in reality.

Copper is a Dead End

fiber cableI have my own house. My thinking is that copper-based technologies such as the up-to-24mbit-but-really-12mbit ADSL (I have some 700 meters or so to the nearest station) I have now has reached something of an end of the road. I had 3 mbit/sec ADSL almost ten years ago: obviously not a lot of improvement is happening in this area. We need to look elsewhere in order to up our connection speeds. I think getting a proper fibre connection to the house will be a good thing for years to come. I don’t expect wireless/radio techniques to be able to compete properly, at least not within the next coming years.

Open

This is an “open fibre” in the sense that Telia will install and own the physical fibre and installation but they will not run any services on top of it. I will then buy my internet services, TV and telephone services (should I decide that TV and phone over the fibre is desirable) from the selection of service companies that decide to join in and compete for my money.

Installation

They’re promising delivery “before the end of the year”. I won’t even get an estimated installation date until around mid August. If an existing tube doesn’t exist for the copper or electricity that they can use to push the fibre through, they will dig. From the road outside my house to my building, across whatever land that exists there. They need to dig roughly 40 cm deep. The fibre is terminated inside the house (a maximum of 5 meter inside the building) in a small “media converter” box which basically converts from fibre to a RJ45 network plug. It is the size of a regular small switch or so. It is claimed to be possible to get a different “box” that provide a direct fibre plug of some sorts for the people who may already have fibre installed in their houses. I currently have a burglar alarm in my house that uses the current phone connection which I’ll need to get either just dumped completely or converted over to use a telephone-over-fibre concept. I don’t plan on paying for or using any copper-based service once the fibre gets here. (There’s however no way to use the Swedish tax deduction “rot-avdrag”.)

Price

dlink DIR 635There’s no monthly fee for the fibre, I only pay a one-time installation fee of 16700 SEK (roughly 1800 Euros) to get it. I then of course will have to pay for the services if I want to actually use the installation but until I do there are no fees involved. This price is actually fixed and the same for all the houses in my area that got this deal. At August 15th the deal ends and they’ll increase the installation price to 26700 SEK. Given the amount of work they have to put in for each new customer, I don’t really consider this price to be steep. A lot of money, sure, but also quite a lot of value.

Speeds to expect

The physical speed between my house and the other end (some kind of fibre termination station somewhere) will be exactly 1000mbit/sec and no more “up to” phrasing or similar in the contract. Of course, that’s just the physical speed that is used and with this equipment the network cannot be any faster than 1000 mbit. There will then be ISPs that offer an internet connection, and they may very well offer lower speeds and even varying different speeds at different tariffs. Right now, other fibre installations done by Telia seem to get offered up to 100/100 mbit connections. As this is then not a physical maximum, it should allow for future increasing without much problems. The 1000 mbit/sec speed over the fibre is a limitation in the actual installed hardware (not the fibre) so in the future Telia can indeed replace the media converters in both ends and bump the speed up significantly should they want to and feel that there’s business in doing so. My current D-Link wifi router only has 100 mbit WAN support so clearly I’ll have to replace that if I go beyond.

IPv6

Seriously, I believe I may be closer to actually get a real IPv6 offer using this than with ADSL here in Sweden. I haven’t really investigated this for real though.

Update

December 16th: I got a mail from Telia today that informed me that the installation in my area has been delayed so it won’t happen until Q2 2012! 🙁

Network

IRC use is declining

I discovered IRC around 1993.

Back then, before EFnet split in two, the IRC channel I frequented was #amiga and we were a small bunch of people from all over the globe who got to know each other pretty good. In the 90s I participated in one of my first open source projects and we created the IRC bot we named Dancer. Dancer was a really talented “defence bot” back in the days of the “wild west” of IRC when channel take overs, flood attacks and nick collisions were widespread and frequently occurring. Dancer helped us keep things calm. Later on, I was part of the team that created and setup the new IRC network called amiganet.

I’ve been using IRC on and off since those days in the early 1990s and still today I hang out on 5-6 channels on freenode every day.

IRC was launched to the world already 1988, almost 23 years ago. I’ve been trying to document the basic history of IRC and when I updated that page the other day with some usage numbers for freenode, I decided to have a look around the net to see if there are any general numbers for IRC usage at large, and I found out that usage is decreasing all over and has been doing so for years. Without research, I figure IRC users are either old farts like myself or at least very tech oriented and geeky. Younger, newer and less techy people use other means of communication.

IRC never “took off” among the general public. In general, I find that general people prefer various IM systems (something that I’ve never understood or adopted myself) and most “ordinary”humans I know don’t even know what IRC is. Possibly, the fact that the IRC protocol never got very good (there’s only that original spec from ’93), that there’s a million completely separated IRC networks with no cross-network messages or that all IRC networks still today suffer from netsplits and other artifacts due deficiencies in how the IRC servers are talking to each other.

5-6 years ago the four most popular networks were all over 100,000 users regularly. Quakenet were well over 200,000. Last year, only Quakenet reached over 100,000. It seems basically all of  them have roughly half the numbers they had 2004.

Graphs from irc.netsplit.de:

2004

IRC usage 2004

2010

IRC usage 2010

Network, Windows

localhost hack on Windows

There's no place like 127.0.0.1

Readers of my blog and friends in general know that I’m not really a Windows guy. I never use it and I never develop things explicitly for windows – but I do my best in making sure my portable code also builds and runs on windows. This blog post is about a new detail that I’ve just learned and that I think I could help shed the light on, to help my fellow hackers. The other day I was contacted by a user of libcurl because he was using it on Windows and he noticed that when wanting to transfer data from the loopback device (where he had a service of his own), and he accessed it using “localhost” in the URL passed to libcurl, he would spot a DNS request for the address of that host name while when he used regular windows tools he would not see that! After some mails back and forth, the details got clear:

Windows has a default /etc/hosts version (conveniently instead put at “c:\WINDOWS\system32\drivers\etc\hosts”) and that default  /etc/hosts alternative used to have an entry for “localhost” in it that would point to 127.0.0.1.

When Windows 7 was released, Microsoft had removed the localhost entry from the /etc/hosts file. Reading sources on the net, it might be related to them supporting IPv6 for real but it’s not at all clear what the connection between those two actions would be.

getaddrinfo() in Windows has since then, and it is unclear exactly at which point in time it started to do this, been made to know about the specific string “localhost” and is documented to always return “all loopback addresses on the local computer”.

So, a custom resolver such as c-ares that doesn’t use Windows’ functions to resolve names but does it all by itself, that has been made to look in the /etc/host file etc now suddenly no longer finds “localhost” in a local file but ends up asking the DNS server for info about it… A case that is far from ideal. Most servers won’t have an entry for it and others might simply provide the wrong address.

I think we’ll have to give in and provide this hack in c-ares as well, just the way Windows itself does.

Oh, and as a bonus there’s even an additional hack mentioned in the getaddrinfo docs: On Windows Server 2003 and later if the pNodeName parameter points to a string equal to “..localmachine”, all registered addresses on the local computer are returned.

Electronics, Network

NASed and RAID1ed

Synology DS211jI finally got my act together and bought myself a Synology DS211j NAS  with two 2TB drives. I’ll use it as a shared network disk at home and I intend to backup to it – as I also have a home office it’ll feel better to be able to also backup company related data somewhat more safely. My previous backup was only copying data from one HDD to another within the same physical machine.

To make it slightly more resistant to disk and hardware errors I’ve configured the disks to do RAID1 (all data is stored on both disks simultaneously).

The GPLv2 license was provided printed on paper in the package.

Linux, Network

Add latency to localhost

15 Comments

Pádraig Brady taught me a great trick in a comment to a previous blog post and it was so neat I feel a need to highlight it further as it also makes it easier for me to find it again later!

To simulate a far away server, add RTT time to the localhost device. For example if we add 100 milliseconds (which then makes 200ms ping time to localhost):

$ tc qdisc add dev lo root handle 1:0 netem delay 100msec
Restore it back to normal again with:
$ tc qdisc del dev lo root
tc qdisc add dev lo root handle 1:0 netem delay 100msec

Restore it back to normal again with:

tc qdisc del dev lo root

In addition, add a random packet loss. 500ms latency with 2.5% packet loss:

tc qdisc add dev lo root handle 1:0 netem delay 250msec loss 2.5%