Linux Networking

This is a story about six months of work that didn’t ship, and what I’m still figuring out about why. The surface story is technical: I implemented RFC 8362 Extended LSA support for FRR’s ospf6d. The code works. The tests pass. It wasn’t accepted upstream. The deeper story is about what happens when…

In 2014 I wrote about the state of Linux network configuration, lamenting the proliferation of netlink libraries and how most projects hadn’t progressed past shell scripting and iproute2. I concluded that “there is a need for a good netlink library for one of the popular scripting languages.” A deca…

In my previous post, we hit a wall with the kernel’s multicast forwarding logic. The core issue was the RPF (Reverse Path Forwarding) check failure for sources on unroutable networks. While digging deeper into this, I found it’s a well-documented challenge in multicast literature, often called the “…

Many consumer and industrial devices—from home security cameras to the HDMI-over-IP extenders I investigated in a previous post—are designed as simple appliances. They often have hard-coded, unroutable IP addresses (e.g., 192.168.1.100) and expect to live on a simple, isolated network. This becomes …

Thanks to rapido, it’s become much simpler to test Linux device drivers for real PCIe devices in VMs. The advantages of this approach are: the host is protected from memory corruption errors caused by buggy kernel drivers the PCI peripheral can be physically installed in a multi-use machine, reduci…

On a good day, my day job involves building networking tools in python. Too many python networking tools look like shell scripts, spawning subprocesses for basic tools like ‘ping’ or ‘ip’ - often resulting in a fragile mess due to poor, or inconsistent error handling. I was quite excited to find icm…

New hardware for BufferUpr has arrived! I’m working on adding Wifi capability into the product and with new hardware comes new challenges. Challenge: Find a simple way to list all the network interfaces in the system, including the PCIe slot and MAC address for each. Solution: find /sys/devices/pci0…

I received some encouraging comments on G+ from Jesper Dangaard Brouer about my previous post on DSCP, Linux and VLAN priorities. Those comments and the work linked to (here) points to a few long-standing (but minor) issues with the way DSCP priorities are handled in Linux. Some DSCP values, like E…

I recently discovered a flaw in the VLAN implementation I did at work. It seemed that the normal TCP traffic had the correct VLAN priorities applied, but audio streaming UDP traffic did not. This was due to DSCP being applied to the streaming audio and the fact that the VLAN device’s egress-qos-map …

This concerns the proliferation of netlink libraries and a lack of direction and documentation. Background: I’ve configured a router with netem (see Bandwidth Throttling with NetEM Network Emulation and the tc-netem man page) to test Tieline devices under various delay and loss network conditions. I…