Vivodi Full LLU και Packet Filtering ?

Χθες προσπαθούσα να βοηθήσω κάποιον στο IRC να βάλει gentoo (δεν χρειάζονται σχόλια 😛 ). Είχε διαβάσει το gentoo handbook φτάσει στο σημείο που πρέπει να κατεβάσει το stage3 tarball (Παράγραφος 5a του handbook). Αρχίζει να κατεβάζει όλο χαρά το stage3 tarball από το mirror του ntua ( και ξαφνικά κολλάει στο 72%. Το ξαναβάζει…τα ίδια. Δοκιμάζει με ftp αντί http….τα ίδια. Του δείχνω το wget -c ώστε να κάνει resume…τίποτα…δεν γινόταν resume. Του λέω ότι εγώ στο σπίτι μου το κατεβάζω κανονικά (Vivodi με γραμμή ΟΤΕ)…και του δίνω το mirror του uoi. Αρχίζει το download από την αρχή, στο 72% πάλι κόψιμο. Δοκιμάζει να κατεβάσει το αρχείο από windows ώστε να το περάσει μετά με usb flash στο gentoo, πάλι κόλλημα στο 72%. Δοκιμάζει mirror από την Γερμανία, τα ίδια…ενώ εγώ να το κατεβάζω κανονικότατα σε 2-3 διαφορετικές dsl. Του λέω δεν γίνεται…κάποιο δικτυακό πρόβλημα έχεις. Του ζητάω να μου ανοίξει ssh πάνω στο PC που θα γινόταν το install, δοκιμάζω και εγώ να το κατεβάσω…τίποτα…ούτε με links ούτε με wget, πάντα κόλλημα στο 72%. H κάρτα δικύου έπαιζε κανονικά…collisions, errors όλα μηδενικά.

Λέω…δεν γίνεται, το modem σου πρέπει να έχει πρόβλημα, κάποιο time-out γίνεται…δεν βγάζω άκρη. Τον ρωτάω αν έχει 2ο adsl modem, μου απαντάει θετικά και το αλλάζει κατευθείαν. Αρχίζει πάλι το download, στο 72% πάλι τα ίδια. Η κατάσταση ήταν πλέον για κλάμματα.
Τον ρωτάω τη σύνδεση έχει και μου απαντάει Vivodi Full LLU στην Πάτρα. Τον ρωτάω έπειτα αν έχει κανένα άλλο φίλο/γνωστό με full LLU στην Πάτρα και μου απαντάει θετικά. Βάζει το γνωστό του να κατεβάσει το ίδιο αρχείο…και ναι…κολλάει στο 72% !!!! Παράλληλα ο γνωστός του αυτός του αναφέρει πως ακούγεται πως η Vivodi έχει στήσει filtering σε κάποια σημεία του δικτύου της…
Η τελευταία ελπίδα ήταν να πειράξω το mirror του uoi ώστε να απαντάει και σε https ώστε τα πακέτα να είναι encrypted και να μην μπορούν να τα πιάσουν τα οποιαδήποτε φίλτρα. Δοκιμάζει να το κατεβάσει με https…και όντως δούλεψε! Πέρασε το 72% και ολοκληρώθηκε χωρίς κανένα πρόβλημα…

Το συμπέρασμα είναι πως σίγουρα το dslam της Vivodi στην Πάτρα είναι προβληματικό. Πολύ πιθανό η Vivodi να εφαρμόζει κάποιο packet filtering, και το συγκεκριμένο αρχείο στο “72%” να κάνει trigger ένα από τα filtra της vivodi και να γίνεται corrupt ύστερα. Εγώ δεν μπορώ να το εξηγήσω διαφορετικά. Αν κάποιος μπορεί και έχει μια άλλη εξήγηση…ευχαρίστως να την ακούσουμε…Αν επίσης κάποιος με full LLU από Vivodi έχει λίγο χρόνο ας δοκιμάσει να κατεβάσει το αρχείο:

και να μας πει αν κολλάει στο 72%. Αν ναι ας πει και σε ποια πόλη/περιοχή μένει…μήπως και βγει κάποια άκρη…

Εννοείται πως σήμερα όταν ο άνθρωπος αυτός πήρε τηλέφωνο στην Vivodi να ρωτήσει πως και γιατί…δεν είχαν να του πουν τίποτα. Ποιος όμως θα τον αποζημιώσει για τις 4-5 και παραπάνω ώρες που έχασε και κόντεψαν να τον φέρουν σε κατάσταση υστερίας ?

Thoughts on the evolution of Operating Systems

Linux is a multiuser operating system “designed to be secure by design”. Each user has it’s own home directory and can only execute applications that the Administrator (root) of the system has allowed him to. That means that users that want to run priviledged applications must either have root’s permission to do so or are asked for a password to escalate their priviledges. So every linux user not only knows the difference of a simple user and the “root of all evil”, but is well aware of where/when to use passwords, what are file permissions and so on and so on. A linux user has (or had, until recently) given up pretty graphics in favor of a more stable, more secure and more “free” operating system.

Windows is a (multiuser?) operating system with emphasis on usability. Since the first windows versions, the users of windows got used to being able to do almost everything without ever being asked for another password than the one at the login screen. Sometimes there wasn’t even such a login screen. A windows user is used to doing administrative tasks with his every day account. Most windows users don’t even know about file permissions and how to use them on their system. That makes life both easier and riskier.

Until broadband came to our lives at the very end of the 20th century, when Windows 98 and ME ruled the IT universe, windows users had very little to fear. While they only exchanged files with their friends on floppies and cdroms, and their computers were not 24/7 online, remote exploits, internet worms and trojans were unknown words to them. A decent antivirus was the only thing required. Windows 98/ME did not even have “services” running on them by default (apart from shared folders). During that time Microsoft only had to worry about making their users’ OS easier and more beautiful. And they were pretty successful in that.
Their server (NT) version though had tons of problems. It was very incompatible with a lot of software and was easily attacked by internet worms. The number of service packs for NT reached a ridiculous number, and still Microsoft couldn’t handle all the problems. Their enhanced server edition, Windows 2000 was a lot better than NT, but the security weaknesses remained. What made Windows NT and Windows 2000 so insecure was that they were supposed to be 24/7 online. The bad guys attacked WinNT and Win2K because they could then use them for their own purposes. A hacked win98 box behind a dialup was useless compared to an always online windows server. While more and more windows 2000 servers were getting online and worms hammered them, more and more people started bitching Microsoft about it. Microsoft tried to fix problems those problems with numerous service packs, but that wasn’t enough.
Then came Windows XP, the first Microsoft OS for users that had various services enabled by default. At the same time more and more people started having broadband at their homes. Now the bad guys had something new and more powerful to fiddle, and it wasn’t long until the first remotely exploitable problems appeared. The bad guys created worms and trojans that attacked WinXP, the OS of millions users. Users’ machines are millions more than server machines, and they were all probable targets/victims for those worms. If a remotely exploitable vulnerability was somehow found for Win98, the impact would be a lot smaller because the number of online PCs was a lot smaller back then . Every remotely exploitable hole found for XP drove users crazy. XP was not designed to be secure, it was to designed to be a _lot_ more beautiful than 98/ME. It was designed with multimedia, games, office work, etc in mind. People started asking for more than an antivirus for their PCs and a new word came to every windows user life, “Firewall”. Then came service pack 1, then service pack 2…and problems still existed and will exist even if a service pack 3 is launched sometime in the future. One of the basic problems with Microsoft XP is that it doesn’t help users understand how and when to use the Administrator account. Most users create a user with Administrator privileges during XP’s installation process and then run their machines with that admin account. This is _plain_ wrong. Every windows XP user feels that he can do everything he wants with his PC without ever being asked for a single password. So when something infects their PC and runs with their user’s privileges, it actually runs as the administrator of the machine. This leads to total destruction.

Vista is said to have a different approach to security though. It has supposedly been built from scratch with security in mind. Users are now ‘just users’ and their default account does not have administrative privileges. So every time they want to do an administrative task dozens of warnings appear before them. That supposedly ensures that nothing can run with administrative privilege unless the user explicitly wants it to be that way. Someone I know who used Vista told me that Vista makes you think that it’s for more advanced users than XP was. All these notifications that pop up asking you for permission to do this and that, makes you feel a bit uncomfortable. New users of computers, that first stumble upon Vista will feel much more uncomfortable with that OS than they would feel if their first OS was XP. And that’s bad for a “Windows OS”, every version until Vista was easier to use than the previous one, apart from Vista…which is harder.
Microsoft with Vista acts as parent who has spoiled their children for a veeeery long time, giving them free chocolates and candies even though they knew that by doing this they hurt their children’s health, and are now trying to put them on a diet. And this just can’t be done. Windows have spoiled users for more than 10-15 years and it’s too late to start telling people, “Hey mind your security!”. “Your account is now on a diet, no more candies for you”.

When Vista starts spreading among users (maybe in 1 year from now?), users themselves will eventually understand more and more about security concepts. They will start to understand why it is so important that the administrative account is something completely different than theirs and why they should only “touch” it occasionally. Vista might be a lot more beautiful as an OS but it will be a lot more difficult for users to “manage”. Nag screens will be all over the place. Passwords might be frequently asked to change something fundamental for the system.

Where does this lead ? Users will get more and more acquainted with the whole administrator’s rights idea and Linux will not look so much like an alien OS to them. The transition from Windows to Linux for users will get easier and easier as linux becomes (slowly and painfully) more good looking and windows becomes (slowly and painfully) more secure.

Every OS has a different beginning and a different approach on evolution, but they tend to meet at some place in the future. They have just taken different roads to reach their goal. Windows prefers user-friendliness over security and stability and linux prefers it the other way around.

Traffic shaping TorrentFlux

*Update on peers supporting encryption at the end of the post*

TorrentFlux is a great program/interface to download your torrents remotely on a linux machine. It is based on php and it uses a modified bittornado client to download the torrents.

The problem: The bittornado client is able to put specific limits on a per torrent basis. That means that you can put a 100kb/sec download and 50kb/sec upload limit per torrent through torrentflux’s web interface. If you have 20 torrents though, this easily becomes 20*50=1Mb/sec upload “limit”. There are cases that you don’t want this to happen and you want both a per torrent limit (eg 50kb/sec) and a global limit (eg 300kb/sec).

The solution: My solution is based on iptables, layer7 filter and tc (iproute2). I am using layer7 filter to pick out the bittorrent packets, iptables to mark those packets with specific values and tc to shape those marked packets into categories. Beware that the method I am using works mostly on the “uploading” part (outgoing traffic). It is not that hard to make it work for the incoming traffic as well, but it is my personal view that downloading with a few Mb/sec is not as harmfull as uploading with a few Mb/sec. I usually have my downloads seeded over many weeks…so it’s good for my ratio to have the torrent downloaded as fast as possible and then seed it endlessly. I usually like to seed until i get a ratio over 1000% per torrent (that means 10 times as much uploaded traffic than downloaded). The following example configs are created for use on a 100mbit line and keeping in mind that outgoing torrent traffic should not exceed 2-2.5Mbits (~250-300kb/sec).

The procedure:
0) Before you begin make sure you have the kernel sources on /usr/src/linux.

1) Then, you need to patch your kernel for layer7 filtering and enable marking. On gentoo linux you only need to:
#emerge -avt net-misc/l7-filter net-misc/l7-protocols
and then configure your kernel for marking.

Here’s how my netfilter configuration looks like:


# Core Netfilter Configuration

# IP: Netfilter Configuration
# CONFIG_IP_NF_RAW is not set

You can clearly see layer7 being enabled as a module: CONFIG_IP_NF_MATCH_LAYER7=m
Rebuild your kernel and install the proper modules. If you need to reboot your machine to apply the new kernel do it now.

2) Now it’s time to install iptables and iproute2 if you don’t have them already. On gentoo linux:

#echo "net-firewall/iptables extensions l7filter" >> /etc/portage/package.use
#emerge -avt net-firewall/iptables sys-apps/iproute2

3) Now it’s the iptables marking time. I am going to show you (some of) the output of my iptables-save command. Change it to fit your neeeds:

# Generated by iptables-save v1.3.5 on Fri Jan 12 20:50:52 2007
:PREROUTING ACCEPT [1102387:193393325]
:INPUT ACCEPT [1102372:193390208]
:OUTPUT ACCEPT [2100485:2922693566]
:POSTROUTING ACCEPT [2100483:2922690566]
-A PREROUTING -s IP.OF.MACHINE -p tcp -m multiport --sports 22,80 -j MARK --set-mark 1001
-A PREROUTING -d IP.OF.MACHINE -p tcp -m multiport --dports 22,80 -j MARK --set-mark 1001
-A PREROUTING -m layer7 --l7proto ssh -j MARK --set-mark 1001
#-A PREROUTING -m layer7 --l7proto bittorrent -j MARK --set-mark 11090
-A PREROUTING -m mark --mark 1001 -j RETURN
-A POSTROUTING -s IP.OF.MACHINE -p tcp -m multiport --sports 22,80 -j MARK --set-mark 1001
-A POSTROUTING -d IP.OF.MACHINE -p tcp -m multiport --dports 22,80 -j MARK --set-mark 1001
-A POSTROUTING -m mark --mark 1001 -j RETURN
-A POSTROUTING -m connmark --mark 0x0 -j MARK --set-mark 11030
-A POSTROUTING -m layer7 --l7proto dns -j MARK --set-mark 11010
-A POSTROUTING -m layer7 --l7proto ssh -j MARK --set-mark 11010
-A POSTROUTING -p tcp -m tcp --tcp-flags SYN,RST,ACK SYN -j MARK --set-mark 11010
-A POSTROUTING -p icmp -j MARK --set-mark 11010
-A POSTROUTING -m layer7 --l7proto bittorrent -j MARK --set-mark 11090
# Completed on Fri Jan 12 20:50:52 2007
# Generated by iptables-save v1.3.5 on Fri Jan 12 20:50:52 2007
:OUTPUT ACCEPT [111:6662]
# Completed on Fri Jan 12 20:50:52 2007
# Generated by iptables-save v1.3.5 on Fri Jan 12 20:50:52 2007
:INPUT ACCEPT [266369:32040284]
:OUTPUT ACCEPT [479227:676859047]
# Completed on Fri Jan 12 20:50:52 2007

You need to change IP.OF.MACHINE with the IP of your linux box.

4) And now the traffic shaping part:

# Main Link
# High Priority
# Normal
# Downloads
# del old
tc qdisc del dev $DEV root 2> /dev/null > /dev/null
# add root
tc qdisc add dev $DEV root handle 100: htb default 1
tc class add dev $DEV parent 100: classid 100:1 htb rate ${LINK}kbit
tc qdisc add dev $DEV parent 100:1 handle 1: htb
tc class add dev $DEV parent 1: classid 1:1 htb rate ${SHAPEDLINK}kbit
# some more rules
tc class add dev $DEV parent 100: classid 100:1 htb rate ${LINK}kbit
tc qdisc add dev $DEV parent 100:1 sfq perturb 10
tc filter add dev $DEV parent 100:0 protocol ip prio 1 handle 1001 fw flowid 100:1
tc class add dev $DEV parent 1:1 classid 1:10 htb rate ${SHAPEDLINK}kbit ceil ${SHAPEDLINK}kbit prio 5
tc qdisc add dev $DEV parent 1:10 sfq perturb 10
# High priority
tc class add dev $DEV parent 1:10 classid 1:1010 htb rate ${HIGHPRIO}kbit ceil ${HIGHPRIO_MAX}kbit prio 0
tc qdisc add dev $DEV parent 1:1010 sfq perturb 10
tc filter add dev $DEV parent 1:0 protocol ip prio 0 handle 11010 fw flowid 1:1010
# normal
tc class add dev $DEV parent 1:10 classid 1:1030 htb rate ${NORMAL}kbit ceil ${NORMAL_MAX}kbit prio 5
tc qdisc add dev $DEV parent 1:1030 sfq perturb 10
tc filter add dev $DEV parent 1:0 protocol ip prio 5 handle 11030 fw flowid 1:1030
# bittorent
tc class add dev $DEV parent 1:10 classid 1:1090 htb rate ${TOR}kbit ceil ${TOR_MAX}kbit prio 10
tc qdisc add dev $DEV parent 1:1090 sfq perturb 10
tc filter add dev $DEV parent 1:0 protocol ip prio 10 handle 11090 fw flowid 1:1090

The rules are pretty straightforward…so I am not going to fully explain them. The basic concept is that you create a “shaped” partition of your bandwith and you add classes (high priority, normal , bittorrent) there. The trick is that you can skip anything you don’t want shaped by marking it with iptables 1001 mark.

In my iptables example above, I mark as 1001 the outgoing ssh and http traffic. This way I can shape the seeding of my torrents using TorrentFlux but I can download via http without any traffic shaping the torrents to my PC at home. I can also ssh to the machine without any latency caused by the shaping because the sshd port (22) is marked with 1001.

The only problem I faced with those scripts was that sometimes the layer7 filter for bittorrent let’s some torrent traffic pass by. My solution to that was to change NORMAL_MAX=$SHAPEDLINK to NORMAL_MAX=2048 for example. Then, even “normal traffic” was shaped. Remember that anything I didn’t want shaped, was marked as 1001 on the iptables script…so the machine was still very responsive even after shaping the “normal traffic”.

To check how your scripts are doing in terms of shaping you can download this excellent perl script: tc-viewer. Click here for a screenshot: tc-viewer htb screenshot

The above example configs are very very generic. If you have a server that serves many other duties apart from ssh, http and bittorrent, then this script might not work out of the box for you.

It looks like the problem I had with layer7 bittorrent filter missing packets was not actually a layer7’s “problem”, but rather a new feature of the latest version of bittornado. I was using bittornado version 0.3.18 (experimental) which is the first bittornado version that comes with Message_Stream_Encryption. What this means: whenever bittornado finds another peer with encryption capabilities, it encrypts all traffic between you and the other peer, so the layer7 filter cannot understand that these flows are torrent traffic anymore, and categorizes them as “normal” traffic. That’s why I needed to “shape” normal traffic as well.
There are three ways to cope with encrypted bittorrent traffic. The first one is the one I described above without even knowing about it (shaping normal traffic). The second way is to go back to a version without encryption (0.3.17), which I think is a _really_ bad idea. Encryption came to help us hide our traffic from ISP filters, and is a step we can all take to protect ourselves. The third way is to mark the port range that torrentflux uses (check the admin panel of torrentflux for it) as torrent traffic by our iptables script. If the port range is high enough it can be almost certain that no other service will use those ports, so no priority traffic will be mis-matched as “torrent traffic”. If, for example, you have defined your port range to be from port 61000 to port 63000, then inject a command like:
-A POSTROUTING -p tcp --sport 61000:63000 -j MARK --set-mark 11090
just below the
-A POSTROUTING -m layer7 --l7proto bittorrent -j MARK --set-mark 11090
command of the iptables script above.

Enjoy shaped encrypted bittorent uploads! Keep seeding…

Random stuff

I’ve made a few changes to the sidebar of my blog, I’ve added Recent Tracks listing and a Meebome widget. The meebome widget is a very nice flash application that let’s you chat with visitors of your site while being online on meebo. I was introduced to meebo sometime ago by thatha. It is an “Instant Messaging Portal”, you create an account and then you can log in to your msn, icq, yahoo, aim, jabber and gtalk account. I use it whenever I am away from my pc, since I find it a lot more “comfortable” to log in to the networks I am interested through meebo than through Portable Gaim that I keep on my usb flash drive.

btw…Gaim is so broken these days…Looks like noone is interested to fix the aging problems it has. No nat-to-nat transfers, random crashes even on normal filetransfers. Even the developer(s) suggest that you use the beta version to log in to msn. How dumb is this ? What are they waiting for ? Since even the developer promotes the beta in favor to the “stable”..shouldn’t the beta be named as “stable” now ? Noone is still using Gaim 1.5.0 …all the latest gnome based distros use 2.0-betaX…

I’ve steadily become more and more unsupportive of OLPC. There are many reasons to this. First of all I think that it made by western people believing that they know what is better for africans or asians. That’s plain wrong. In my view the OLPC is something that western rich kids will enjoy far more than poor africans or asians. It’s a “western toy” for “western rich kids”. Then comes the “open-ness” of the whole project. In the beggining everything looked very promising, then came the closed source drivers and firmwares. I don’t care for whatever reasons Marvell doesn’t open source the wifi driver, but if someone touts for a “complete open source project”, then e v e r y t h i n g must be open source. Not whatever we like. Oh, and then came the added sd card slot in order for the OLPC to be able to run a version of windows. That’s open source too right ? More bashing of the OLPC on beranger.