I am testing a custom FPGA NIC and I need to send management information (such as header info for matching) and traffic data to it using a traffic generator from within the user space.
The driver built for the FPGA is a modified version of IXGBE with DMA support for management, and also supports DPDK for kernel bypass to achieve high throughput.
I am trying to understand how the various software (driver, userspace application, etc) should be stacked/connected to each-other so I can achieve the objective of reading and writing to PCIe on the NIC using set of scripts from user space?
I have also been looking at this project
https://github.com/CospanDesign/python-pci
which is useful however based on Xilinx XDMA.
Would appreciate any help, pointers on this.
Sorry, the question is too broad. For such a broad question there is a generic answer: have a look at Inter Process Communication:
https://en.wikipedia.org/wiki/Inter-process_communication
There are variety of methods, like Unix sockets, shared memory, netlink etc, to communicate between user space processes. As well as a variety of methods to communicate between user space and kernel space.
Just pick the best for you and try to do something. If it fails, come again on SO and ask ;)
Related
I would like to know if it is possible for a Ruby program to possess multiple IP addresses? I am trying to download a lot of data from a site, but it is very slow with only 1 connection at a time.
I intend to multi-thread my program with each thread using its own IP address, but I do not know if it is possible in the first place, any help or hints would be greatly appreciated.
It is definitely possible for a machine or a program to have multiple IP addresses. You can even have multiple network adapters, and tie each of them to different physical connections.
However, it can get really hairy to maintain. The challenge for that is partly in the code, partly in the system maintenance, and partly in the networking required to make that happen.
A better approach that you can take is to design your program so that it can run distributed. As such, you can have several copies of it synchronized and doing the work in parallel. You can then scale it horizontally (build more copies) as required, and over different machines and connections if required.
EDIT: You mentioned that you cannot scale horizontally, and that you prefer to use multiple connections from the same machine.
It's very likely that for this you'll have to go a little bit lower in the network stack, developing yourself the connection through sockets in order to use specific network interfaces.
Check out an introduction to Ruby sockets.
Also, check out these related questions:
How does a socket know which network interface controller to use?
Binding to networking interfaces in ruby
Ruby: Binding a listening socket to a specific interface
Can I make ruby send network traffic over a specific iface?
I am trying to understand the working of wireless in linux. I started with wpa_supplicant, hostapd applications with the help of their documentation and source code.Understood the flow and basic functionalities of :
wpa_supplicant,nl80211(driver interface)
libnl library(socket communication between user space and kernel using netlink protocol)
cfg80211(kernel interface used for communicating with the driver from userspace with the help of nl80211 implementation in user space),mac80211(software media access control layer)
driver(loadable driver ex:ath6kl - atheros driver).
I understood the above software flow and in my exploration I came to know that for providing freedom for developers MAC layer is implemented in software(popular implementation mac80211).
Is this true in all the cases ? If so what are pros and cons of softMAC and hardMAC ? Do cfg80211 interface in kernel directly communicates with the driver ? who and how communication with mac80211 happens ?
Thanks in advance.
The term 'SoftMAC' refers to a wireless network interface device (WNIC) which does not implement the MAC layer in hardware, rather it expects the drivers to implement the MAC layer.
'HardMAC' (also called 'FullMAC') describes a WNIC which implements the MAC layer in hardware.
The advantages of SoftMAC are:
Potentially lower hardware costs
Possibility to upgrade to newer standards by updating the driver only
Possibility to correct faults in the MAC implementation by updating the driver only
An additional advantage (in the Linux kernel at least) is that many different drivers for different types of WNIC can all share the same MAC implementation, provided by the kernel itself.
Despite the advantages, not all WNICs use SoftMAC. The main advantages of HardMAC is that since the MAC functions are implemented in hardware, they contribute less CPU load.
mac80211 is the framework within the Linux kernel for implementing SoftMAC drivers. It implements the cfg80211 callbacks which would otherwise have to be implemented by the driver itself, and also implements the MAC layer functions. As such it goes between cfg80211 and the SoftMAC drivers.
HardMAC drivers have to implement the cfg80211 interfaces fully themselves.
Also to add :-
Hardmac drivers helps in better as compared to SoftMAC, power save and quick connection/disconnection recovery due to MLME implemented in HW. Better power save is because HW/FW need not to wake up host on disconnection and still can connect and recover .
I have implemented a small program which uses Net-SNMP to get network related information. It uses asynchronous mode to query multiple hosts.
Since Net-SNMPv3 does not support multi-threading, is it beneficial to shift to SNMP++?
I have a lot of hosts or routers in the network where I need to monitor the traps and general network information of ~2000 routers.
Will using SNMP++ be much faster that Net-SNMP as it uses multi-threading?
I guess you are implementing in C++ and maybe need to, but I you can use snmp4j it has the possibility to use multi-threading. Even if you have to wrap the code to using Java.
Are at the same issue, where 1-2000 units need both SNMP Get / Walks and due to slow units, there needs to be multiple threads fetching data in parallel.
I am new in Linux and i want to know the internals of drivers and how it is interacting with hardware, so my question is that How the application is interacting with hardware means when the core part will come in picture and what it will do?
When the controller of that driver will come and how it will handle the request generated by the application.
And what is Firmware and when it comes into picture in Linux?
For eg: if i am using usb device like
$ cat /dev/usb0.1
then which is the core of usb(usb_storage.c) and
which is the controller(usb_hub.c)
and how they are related to each other.
Thanks in advance..
Basically linux kernel driver provide interface such as device file node then application can use standard read()/write()/ioctl() to pass parameter to operate hardware. Provide interface in /proc or /sys can be facilities to do that too. Detail implementation how to handle request depends on respective hardware spec.
I realise this is a somewhat open ended question...
In the context of low latency applications I've heard references to by-passing the TCP-IP stack.
What does this really mean and assuming you have two processes on a network that need to exchange messages what are the various options (and associated trade-offs) for doing so?
Typically the first steps are using a TCP offload engine, ToE, or a user-space TCP/IP stack such as OpenOnload.
Completely skipping TCP/IP means usually looking at InfiniBand and using RDMA verbs or even implementing custom protocols above raw Ethernet.
Generally you have latency due to using anything in the kernel and so user-space mechanisms are ideal, and then the TCP/IP stack is an overhead itself consider all of the layers and the complexity that in can be arranged: IP families, sub-networking, VLANs, IPSEC, etc.
This is not a direct answer to your question but i thought it might give you another view on this topic.
Before trying to bypass TCP-IP stack I would suggest researching proven real-time communication middleware.
One good solution for real-time communication is Data Distribution Service from OMG (Object Management Group)
DDS offers 12 or so quality attributes and has bindings for various languages.
It has LATENCY_BUDGET ,TRANSPORT_PRIORITY and many other quality of service attributes that makes data distribution very easy and fast.
Check out an implementation of DDS standard by PrismTech. It is called OpenSplice and
works well at LAN scale.
Depends on the nature of your protocol really.
If by low-latency applications you mean electronic trading systems, than they normally use IP or UDP multi-cast for market data, such as Pragmatic General Multicast. Mostly because there is one sender and many receivers of the data, so that using TCP would require sending copies of the data to each recipient individually requiring more bandwidth and increasing the latency.
Trading connections traditionally use TCP with application-level heartbeats because the connection needs to be reliable and connection loss must be detected promptly.