Creating a VLAN in Netberg 710 P4 switch

The P4 switch has a “normal switch” mode that is using SONIC and comes with a P4 dataplane compiled and flashed, nothing to compile using Tofino or whatsoever.  This is useful when one of the switch is not used for an experiment and you want to simply wire machines virtually.

Creating a L2 bridge or a VLAN 

By default, the switch boots with all interface in Router mode. They have (random 10.0…) IPs. To use those interface as a switch, you must remove the IPs before adding them to a vlan or you will get the error “Ethernet0 is a router interface” 

$ show ip interfaces 

Interface    Master    IPv4 address/mask    Admin/Oper    BGP Neighbor    Neighbor IP 

———–  ——–  ——————-  ————  ————–  ————- 


Ethernet8              up/down       ARISTA03T2      10.0.0. 

Ethernet12             up/down       ARISTA04T2 


Remove all IPv4 IPs from the interface with, for instance… 

$ sudo config interface ip remove Ethernet0 

Then, disable IPv6 link-local addresses with : 

$ sudo config ipv6 disable link-local 

And for each interface : 

$ sudo config interface ipv6 disable use-link-local-only Ethernet0 

Then save the config and reboot as the IPv6 link local will stay 

$ sudo config save –y 

$ sudo reboot 

After a reboot, create the Vlan with : 

$ sudo config vlan add 10 

And add interfaces with : 

$ sudo config vlan member add -u 10 Ethernet0 

Personally, I saved and rebooted again afterward but it might have not be working beforehand due to an interface reset on the machines.

Looking for the right archive format with deduplication

I’m often copying my files to an external disk as a backup option. So far, nothing fancy.

However, I end up with many copies of more or less the same folders over time. And that takes a lot of space for nothing.

Incremental backups, that only add new files to an archive, might look as a solution for that, but over time the paths changes, the structure changes. So the deduplication would break.

One solution could be to format my disk with a system such as ZFS or BTRFS which have a deduplication built-in. However I can’t use my disk for quick operations/archiving on Windows, nor on Mac (easily at least).

So I want an archive format with:

  • Deduplication
  • Some compression (lot of source code files)

One might think, and I often came across that statement while searching on the web for a solution, that one shouldn’t worry about that as compression algorithm inheritely support deduplication. That is actually wrong, they’re not made to merge very large patterns. The following experiment shows it with file of random data (incompressible) :

-rwxrwxrwx 1 tbarbette tbarbette 10M Apr 17 21:09 binA
-rwxrwxrwx 1 tbarbette tbarbette 10M Apr 17 21:10 binACOPY
-rwxrwxrwx 1 tbarbette tbarbette 10M Apr 17 21:09 binB
-rwxrwxrwx 1 tbarbette tbarbette 256M Apr 17 21:19 binBIG
-rwxrwxrwx 1 tbarbette tbarbette 256M Apr 17 21:19 binBIGCOPY
-rwxrwxrwx 1 tbarbette tbarbette 10M Apr 17 21:09 binC

Here’s the size for a few formats :

tar.gz553M19.48star -cpazf [archive] [file]
tar.xz553M303star -cpaJf [archive] [file]
zpaq287M18.7szpaq add [archive] [file]
wim287M4.4s7zz a [archive].wim [file]
.7z543M37s7zz a [archive].7z [file]
.7z (512M dictionnary)287M140s7zz a [archive].7z -m0=LZMA2:d512m [file]
.7z (1513M dictionnary)287M114s7zz a [archive].7z -m0=LZMA2:d1513m [file]

zpaq is the clear winner considering it can also compress at the same time, however it’s not very widespread, and has no good GUI available. I’m wondering about recovery in case of problems.

wim has no compression, so it will need to be encapsulated in something else. The problem is then to add some files. I have to uncompress the inner wim format first. The idea being to save the same computer again and again, one of those archives is 200G, so it means adding a single file would take a huge time. While zpaq can add one quite fast.

7zip with a dictionary large enough to hold big duplicates would seem to be a good compromise.

Any input?

Extracting list of awarded badges on Moodle

A nice feature of Moodle is badges. Badges can be given to students as rewards for good actions, and incite them to do better and follow activities.

However, as often in Moodle, the functionalities are quite limited. One missing feature is the ability to give a badge to a list of user from an external system, e.g. using a CSV file. You can select students one by one in a list, which is cumbersome. As most as possible, for mass awarding you should try to use some “scripting” : for instance awarding badges when users finish an activity, with a certain grate.

The more problematic one I did not forsee was the inability to export badges. I wanted to give a small bonus points for students who won some badges. I thought of two leads : the moodle backups where I could extract the badges from the XML, and create a LTI activity to “steal” the badges.

The Moodle backups, even if you click on “Badges”, actually do not include badges in the backup… In 4 months this is the 4th bug I hit… After 3 confirmed bug that got no activity, I don’t even report them anymore… The Moodle community is rather slow, and internal resources are limited. The LTI 1.2 activities as far as I can tell do not have access to badges so that was a no-go as well.

So the solution was to do some web scraping. After trying multiple chrome extensions (connecting to moodle through GET/POST request would be very complicated because of OAuth), I could finally do a correct extraction with this extension :

This extension supports following links, because there’s of course no web pages allowing to see all badges per students. You must “click” on the number of students for each badge, and then follow the pagination as there’s a limit of 50 students per pages.


Install the extension, go on the “Manage badges” pages on your Moodle course, and then press F12 to open chrome developer tools. Go to the new “Web Scraper” page and then “Create new sitemap” -> “Import sitemap”.

Here’s the “sitemap” defining how to follow links and scrape badge names, students that were awarded the badges, while supporting pagination.

{"_id":"moodle_badges","startUrl":[""],"selectors":[{"id":"Awards","multiple":true,"parentSelectors":["_root"],"selector":".awards a","type":"SelectorLink"},{"id":"Element","multiple":true,"parentSelectors":["Pages"],"selector":"tbody tr","type":"SelectorElement"},{"id":"Name","multiple":false,"parentSelectors":["Element"],"regex":"","selector":".cell.c0 a","type":"SelectorText"},{"id":"Pages","paginationType":"clickMore","parentSelectors":["Awards","Pages"],"selector":"nav:first-of-type li a[aria-label=\"Next\"].page-link","type":"SelectorPagination"},{"id":"BadgeName","multiple":false,"parentSelectors":["Awards"],"regex":"","selector":"h1","type":"SelectorText"}]}

Press Sitemap -> Scrape and voilà. After a while, you can download a CSV or an XLSX.

As a bonus, what I want is the number of badges per students, so here’s the formula to put on the student list where the Name and FirstName are separated columns:

=NB.SI(Badges!E:E;CONCAT([@Name];" ";[@FirstName]))

Tested on Moodle 3.9.

Leaving ownCloud for good

ownCloud was kind of abandonned after the fork to nextcloud. I wanted to stay true to my historic “own” cloud provider. But the lack of support for PHP 8.1 now that 7.X is EOL killed it for good.

Two messages for anyone that comes here through random search :

  • There is no way to migrate automatically to nextcloud anymore. Chances are you updated beyond ownCloud 10.5, and there’s no downgrade possible. So don’t try.
  • Long life nextCloud! I didn’t realise the many things I was missing with ownCloud… NextCloud has million more features. So leave ownCloud now and go to nextCloud.

A collection of Network Systems icons in SVG

You can use mine as you wish, I tried to find the original authors and the appropriate license whenever I could. Don’t hesitate to send me your own.

NAND SSD (inspired from, CC )
RAM Module ( inspired from CC)
CPU (absed on, CC)
DPI (unsure but I think it’s my own. Anyway it’s standard)
Fast (own)

GPU (own)
IPSEC (unsure)
Load Balancer (unsure)
Monitoring, monitor, measurements (unsure)

Mellanox NIC (not SVG, Mellanox)
100G NIC (inspired from the above, consider my own I guess)

Router (unsure, but this is quite sandard…)
VLAN (own)

Retina: Analyzing 100 GbE Traffic on Commodity Hardware

I’m pleased to announce Retina has been accepted to appear at SIGCOMM at the end of the month ! It is the result of a pleasant collaboration with Gerry Wan, Fengchen Gong and Zakir Durumeric from Stanford.

Retina enables high-speed network forensics by building a binary tailored to a specific experiment written in Rust. It provides convenient filtering capabilities to easily answer questions such as “Is the TLS SNI really random?” or “How many TLS handshake are destined to Netflix?”. Tested at up to 160Gbps with a commodity server on a Stanford traffic TAP, it supports 5-100x higher traffic rates than standard “bloatware” IDSes.

paper ; github ; the video will follow after SIGCOMM

New position: Assistant Professor at UCLouvain

I’m delighted to announce I’ll start as assistant professor on the 1st of September in the INGI department of the ICTEAM, EPL faculty at UCLouvain. Right where I am currently conducting my post-doc.

I’ll continue my research on high-speed networking and programmable networks (including Smart NICs) while taking care of multiple lectures. Stay tuned for exciting news !

MPTCP on Windows with WSL2


It is possible to use MPTCP, but WSL2 uses a virtual interface that prevents advertising multiple paths. There might be a solution using multiple forwarded ports but I haven’t been able to use it yet.


Install Ubuntu in WSL2 (simply look for Ubuntu in the Microsoft Store)

Optional: Allow Windows to keep both Wifi and Ethernet open

Windows will automatically turn off wifi when Ethernet is plugged in. If you want to try MPTCP over Wifi + Ethernet (or 4G through USB, all the same) you must disable this behavior :

1. Open Registry Editor.

2. Go to HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\WcmSvc\Local.

3. Create/change the fMinimizeConnections registry DWORD to 0.

4. Close Registry Editor and reboot.

Step 1 : Install an MPTCP-compatible Kernel (easier than it sounds!)

sudo apt install build-essential flex bison libssl-dev libelf-dev pahole
git clone
cd WSL2-Linux-Kernel
cp Microsoft/config-wsl .config

Edit .config and change “#CONFIG_MPTCP is not set” by CONFIG_MPTCP=y

make -j4
cp arch/x86/boot/vmlinux.bin /mnt/c/vmlinux

Then shut down WSL in a CMD window:

wsl --shutdown

And to boot in your new kernel add a file in C:\Users\$USER\.wslconfig


Step 2 : Install mptcpd

This is to get the “mptcpize” command to run a legacy TCP application with mptcp

sudo apt install mptcpd

Step 3 : Try it out !

sudo apt install iperf
sudo tcpdump -i  lo -w capture.pcap
mptcpize run iperf -s
mptcpize run iperf -c -b 1k -l 1

Then open capture.pcap with wireshark and you should see MPTCP instead of TCP 🙂

Step 3 : SSH and failover


Packet Order Matters won the NSDI’22 community award !

Data centers increasingly deploy commodity servers with high-speed network interfaces to enable low-latency communication. However, achieving low latency at high data rates crucially depends on how the incoming traffic interacts with the system’s caches. When packets that need to be processed in the same way are consecutive, i.e., exhibit high temporal and spatial locality, caches deliver great benefits.

In this paper, we systematically study the impact of temporal and spatial traffic locality on the performance of commodity servers equipped with high-speed network interfaces. Our results show that (i) the performance of a variety of widely deployed applications degrade substantially with even the slightest lack of traffic locality, and (ii) a traffic trace from our organization reveals poor traffic locality as networking protocols, drivers, and the underlying switching/routing fabric spread packets out in time (reducing locality).

To address these issues, we built Reframer, a software solution that deliberately delays packets and reorders them to increase traffic locality. Despite introducing μs-scale delays of some packets, we show that Reframer increases the throughput of a network service chain by up to 84% and reduces the flow completion time of a web server by 11% while improving its throughput by 20%.

Links : paper ; usenix

VOO in bridge mode with IPv6 (optional: and prefix delegation!)

Despite old threads that can be seen on VOO’s forum, VOO do not seem to use SLAAC in bridge mode (anymore?), but DHCPv6. Also VOO only gives a /64 prefix so you can’t do internal subnets 🙁

Important: my outgoing (WAN) interface directly connected to the VOO modem in bridge mode is enx000ec6ec03b3 . My internal LAN interface is br0 (it’s a bridge between my actual eth0 LAN interface and a WiFi access point using hostapd, but that’s for another day).

This tutorial assumes Ubuntu 18.04:

sudo apt install wide-dhcpv6-client

sudo vi /etc/wide-dhcpv6/dhcp6c.conf

interface enx000ec6ec03b3 {
  send ia-na 1;
  send ia-pd 1;
  request domain-name-servers;
  request domain-name;
  script "/etc/wide-dhcpv6/dhcp6c-script";

# Only for prefix delegation
id-assoc pd 1 {
  prefix-interface br0 { #internal facing interface (LAN)
    sla-id 0; # subnet. Combined with ia-pd to configure the subnet for this interface.
    ifid 1; #IP address "postfix". if not set it will use EUI-64 address of the interface. Combined with SLA-ID'd prefix to create full IP address of interface.
    sla-len 0; # Number of prefix bits assigned. Sadly this is 0 with voo... 

  id-assoc na 1 {
  # id-assoc for eth1

sudo vi /etc/default/wide-dhcpv6-client


sudo service wide-dhcpv6-client restart

At this point you should get an IPv6 address:

enx000ec6ec03b3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 109.89.XXX  netmask  broadcast 109.89.XXXX
        inet6 2a02:2788:XXXXXXXXX:8458  prefixlen 128  scopeid 0x0<global>
        inet6 fe80::20e:c6ff:feec:3b3  prefixlen 64  scopeid 0x20<link>
        ether 00:0e:c6:ec:03:b3  txqueuelen 1000  (Ethernet)
        RX packets 1358557038  bytes 1701875645905 (1.7 TB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 648168501  bytes 176987273193 (176.9 GB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Enable prefix delegation

Actually enable the prefix delegation with radvd:

sudo apt-get install radvd

sudo vi /etc/radvd.conf

interface br0 # LAN interface
  AdvManagedFlag off; # no DHCPv6 server here.
  AdvOtherConfigFlag off; # not even for options.
  AdvSendAdvert on;
  AdvDefaultPreference high;
  AdvLinkMTU 1280;
  prefix ::/64 #pick one non-link-local prefix assigned to the interface and start advertising it
    AdvOnLink on;
    AdvAutonomous on;

sudo service radvd restart

Some configuration is taken and adapted from