Are there any standard implementations of Mobile IP for Linux?
If I want to support mobile IP for a network, what all needs to be done?
If I have to write code from scratch, is it likely that a kernel module will suffice or I would have to make changes to the kernel code.
I just need a bit of headstart to know where to begin.
It appears likely to me that it can be done without requiring any kernel code at all, you can achieve it by having a userspace daemon create a tun interface (much like a VPN client would typically do) and then route or encapsulate packets in whatever way is required for mobile IP. The userspace daemon may have to modify the kernel's routing table but that's ok.
Examples of the tun interface users are openvpn and Qemu.
Related
I'm searching for help and an opinion-advice for a network project, in which I'm working lately. This requires a Linux machine to be a passive network appliance.
Network packets come in from one network interface and come out from another interface ( net--eth0-->Linux PC--eth1-->net) without making any modifications on data.
The application, which is going to run on the Linux system, will change only the order of the packets. It is going to be a "silly" network emulator application.
The first implementation was made with RAW sockets, where read() is called every time a packet arrives to user space and write() is called when an Ethernet packet should be sent down to the NIC.
I would like to know if there is a more practical and direct way than RAW sockets, bypassing Linux's network stack.
If what you want is to bypass the kernel, DPDK in Linux and NetMap in FreeBSD are options to do just that.
Indeed this can be done in dpdk in Linux. There are l3fw and l2fwd sample applications in the examples folder of the dpdk tree, which may inspire you. Also consider using vpp, a fd.io project hosted by Linux Foundation, which can use dpdk.
Rami Rosen
I'm trying to run some network program (like nginx) on RISC-V.
I'm not aware of network devices available on RISC-V, and I don't want to implement it myself, so I'm looking for the other way.
First I tried running simple program that send HTTP request to the given address. It resolves the IP address using gethostbyname and sends a HTTP request.
I successfully ran riscv-linux on spike simulator, and compiled the program and ran it. gethostbyname returns Unknown server error, and when I use IP address directly, connect returns Network is unreachable error.
I found that the front end server fesvr can handle system calls that is forwarded from the RISC-V processor, and thought maybe it will handle network related system calls. I also found fesvr-eth and thought maybe it is something related to handling network services, but according to this link it is just for connecting fesvr running on PC to the development board by ethernet. Also fesvr-eth has been removed from the latest git repo.
So now I want to look and risc-v linux and see how it actually handle network system calls like connect. I'm thinking maybe if the network operations are only done inside localhost, it can be handled properly without a network device. Or there can be easy way to extend fesvr to handle network services.
Summarizing the questions:
is there a way to run network applications in RISC-V, that I missed?
can network services be actually handled if the request is from within the same host, even if there is no network devices?
any other comments or references that can be helpful?
At the moment, neither spike nor riscv-qemu provide models for network interfaces. With both of these tools, you will be able to use the loopback device (127.0.0.1) for networking among processes. Loopback networking is implemented directly by the OS kernel.
For other architectures, qemu provides a large number of networking options. It should not be too difficult to modify riscv-qemu/hw/riscv/riscv_board.c to instantiate one of these virtual network interfaces into an emulated risc-v system.
I have tried using several commands as well as couple of examples using C/C++ but am still not able to find a flawless method that can differentiate between physical or virtual ethernet adapters. Physical means, on that available on your board or installed externally and virtual means created by virtualization apps such as VirtualBox/VMWare/Virtual PC or VPN etc.
Any pointers?
There is no flawless method. A virtual adapter can have any MAC address, including one that might have been assigned by a constructor to a physical device. And the other way around, given that one can change the MAC address of a physical adapter. You can only make an educated guess.
You might find it easier to detect if you are running virtualized at all, rather than look for specific information about the NICs. The virt-what(1) tool looks through aspects of the running system to guess if the system is virtualized or not. (The script isn't as smart as you think, but it does have a lot of small information gathering tools in one place.)
Someone intentionally trying to bypass a license check would probably not find it difficult to defeat this mechanism.
Maybe one can use mii-tool and check if it fails, which it does for virtual:
mii-tool vmbr2
SIOCGMIIPHY on 'vmbr2' failed: Operation not supported
mii-tool eno1
eno1: negotiated 1000baseT-FD flow-control, link ok
EDIT:
What is mii-tool: view, manipulate media-independent interface status
This utility checks or sets the status of a network interface's
Media Independent Interface (MII) unit. Most fast ethernet
adapters use an MII to autonegotiate link speed and duplex
setting.
https://www.man7.org/linux/man-pages/man8/mii-tool.8.html
I'm building a program that does network acceleration, and I need to know how to create a network interface on Linux that instead of directing data to an actual interface, directs information to my program, so that it can be accelerated. The idea is to make it a transparent system, so that programs just have to use the interface like a normal one, but the traffic will run faster.
You want the tun/tap device:
http://en.wikipedia.org/wiki/TUN/TAP
I'm unsure as to how exactly you hope to achieve this, or what the use-case is, but one other way of doing it is to use a NFQUEUE iptables target rule.
Then you can direct just some of the traffic to a userspace program which can optionally modify it or do anything it wants, really.
I need to store persistent reference to third party device on an arbitrary IP network where the IP address of the devices may be static or randomly assigned by DHCP. I don't control the devices on the network and I can't rely on DNS and other ad-hoc networking protocols existing or working with the devices.
So I have been instructed to investigate using hardware addresses and ARP. This will work but I don't want to duplicate code. The kernel must manage an ARP table. On Windows you can access it using GetIpNetTable etc.
I am hoping there is an API to answer these two questions:
How do I translate from IP to MAC address? (ARP)
How do I translate from MAC to IP address? (InARP)
If not then I may have to do it more manually:
How do I read the kernel's ARP table?
How do I add an entry if I have the determined a mapping myself?
/proc/net/arp
K
ARP tables tend to be fairly local and short-lived. If you examine the protocol, the real MAC addresses are generally only provided when the given IP address is in the local subnet.
Otherwise, the packet is forwarded to the local router, which is then responsible for forwarding it.
If you do "arp -g" on Windows or "arp -a" on UNIX, you'll see the table, but I don't think it will do you any good, due to the reasons mentioned above. That command and
That's really what DNS is for but, as you say, it may not be an option for you.
You may well have to write your own 'ARP' database at your application level.
As for ARP:
You could use system("/usr/bin/arp -option_of_choice"); and parse the output, but that's an ugly hack. -- Not my recommendation.
Take a look at /usr/include/linux/sockios.h -- At the SIOCGARP, SIOCDARP, and SIOCSARP details. Those are ioctls that you can perform to manage the ARP table on linux. Of course, you'll have to perform these ioctls on a socket fd.
Here's some examples: SIOCGARP examples
I'm sure you can find many other examples in several other languages as well. As I'm assuming that you're using C.
As for RARP:
A quote from the linux rarp manpage:
" This program is obsolete. From version 2.3, the Linux kernel no longer
contains RARP support. For a replacement RARP daemon, see ftp://ftp.demen-
tia.org/pub/net-tools"
So you'll have to install rarpd on the target system.