I think this is a greping problem rather than a networking one:
My computer uses to have multiple ppp connections running at the same time, sometimes 0, sometimes 1, 2... etc.
For example, before connecting:
$ ifconfig | grep "ppp"
ppp0 Link encap:Point-to-Point Protocol
ppp1 Link encap:Point-to-Point Protocol
And, after connecting a new one:
$ ifconfig | grep "ppp"
ppp0 Link encap:Point-to-Point Protocol
ppp1 Link encap:Point-to-Point Protocol
ppp2 Link encap:Point-to-Point Protocol
How could I programmatically guess the ppp device (ppp2 in this example) just created?
EDIT-1: This could be another possible before connecting case:
$ ifconfig | grep "ppp"
$
(No ppp devices active)
EDIT-2: This could be another possible before connecting case:
$ ifconfig | grep "ppp"
ppp0 Link encap:Point-to-Point Protocol
ppp2 Link encap:Point-to-Point Protocol
A "hole" at ppp1: it does not exist, so the new ppp status after connecting will be:
$ ifconfig | grep "ppp"
ppp0 Link encap:Point-to-Point Protocol
ppp1 Link encap:Point-to-Point Protocol
ppp2 Link encap:Point-to-Point Protocol
I think the ppp devices behave that way.
Related
How can I check the GUI network setting is set DHCP or Static with command line? for the active and connected interface in Ubuntu 18.04
I want one line command like grep give me static/dhcp or true/false
Can use ip command to check interface you're interested in.
E.g. to check the interface eth0:
if ip -6 addr show eth0 | grep -q dynamic; then
echo "Uses DHCP addressing"
else
echo "Uses static addressing"
fi
-6 option is for checking IPv6 interface. You can use -4 for IPv4.
nmcli -f ipv4.method con show
If the output is auto, then it is DHCP.
If the output is manual, then it is static.
or
cat /etc/network/interfaces
DHCP enabled
auto eth0
iface eth0 inet dhcp
I've my eth0connection and I've a ppp0 connection.
keeping alive my ppp0 connection, can I test eth0 connection?
like checking
ping <ip> <eth0 connection>
Have you tried the following (Copying from different question that uses your issue unix.stackexchange)?:
If you look at ping manual man ping, you can read:
-I interface address
Set source address to specified interface address. Argument may be numeric IP
address or name of device.
So try, e.g.:
ping -I eth0 google.com
I heard that there are types of ip addresses like primary address etc. and tried to get the ip address using the below command
ifconfig | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1'
and got the result as below
192.168.122.1
192.168.168.1
172.16.142.1
192.168.1.102
so from the above can someone answer which my primary address is?
There is no such things as "primary address" or "primary device". You have multiple ip addresses related to multiple networt devices.
You could find out what devices allows you to access to the internet and finds its local ip.
To do that, issue the command route. It will output something like
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 192.168.0.254 0.0.0.0 UG 0 0 0 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
Now all you need is to use the device on the line default and use it in this command:
ifconfig <DEVICENAME> | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*'
When a machine has different IP addresses, it is impossible to define the primary IP from a network only point of view. But a machine normaly has a name that can be obtained by the command uname -n, or by the POSIX function uname. Once you have that name, you can find the IP address corresponding to it by the getent command or the gethostbyname function: what is called the primary IP address is the first address returned.
So here you could use:
getent hosts $(uname -n) | head -1 | cut -f 1 -w
Primary address depends on your usage, there is nothing as such at the network level. If you use one IP to access your server usually, you may call it primary and the network devices won't know the difference.
I have a Linux (3.14.36) embedded board acting as a WiFi AP.
The WiFi chipset doesn't support monitoring mode.
My laptop(the client) is connected to this board by WiFi
The WiFi AP is acting as a network bridge to another computer, and doesn't provide an IP adress to the client (the WiFi AP only has the MAC address of the client)
I want to monitor the signal strengh of the connection WiFi AP <-> Client and be able to trigger a "refresh" of the signal strengh value.
Doing : iw dev wlan0 station dump gives me :
Station xx:xx:xx:xx:xx:xx (on wlan0)
inactive time: 123820 ms // <-- The problem
rx bytes: 10291
rx packets: 60
...
signal: -65 dBm // What I want to refresh
...
I understood that the signal strengh is updated every time there is a network activity. (So, in the example above, it has been refreshed 123s ago).
How can I force a refresh of this value ? (By forcing the AP to send "something" to the client for example) Knowing that the board/WiFi driver/WiFi device doesn't support tools such as iwconfig
For anyone finding this thread now:
I had this issue and my solution was to ping the device before doing the iw dump, e.g.
Get the list of of connected MAC addresses:
iw dev wlan0 station dump | grep 'signal' | awk '{print $2}'
Then get the IP address from these MAC addresses (alternatively you could use arp):
ip neigh | grep 'ma:ca:dd:re:ss:ss' | awk '{print $1}'
Then ping each of those:
ping -c 1 'IP.address'
Then get the refreshed signal for that MAC address
iw dev wlan0 station get 'ma:ca:dd:re:ss:ss' | grep 'signal' | awk '{print $2}'
I wrapped all this up in a Python script and it seemed to give reliable data.
I'll give it a try:
You're embedded so I guess you have busybox. You have no IP but you may then use arping (if this applet is not configured in your busybox build, change the config) to send something small and useless that may wake up the thing. What IP to use for your ARP requests? Well it seems you can use a "dummy" IP.
I'm running this on a PC but I do have busybox with its arping, and I use a wired interface, but here is the concept:
jbm#sumo:~/sandbox/iw$ sudo busybox arping -w 1 -U -I eth0 0.0.0.0
ARPING to 0.0.0.0 from 192.168.1.66 via eth0
Sent 2 probe(s) (2 broadcast(s))
Received 0 reply (0 request(s), 0 broadcast(s))
The useful thing is that though the "dummy" IP, I can check with tcpdump that the arp requests do actually go on the wire (or in the air in your case):
jbm#sumo:~$ sudo tcpdump -i eth0 -v arp
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
10:42:20.111100 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 0.0.0.0 (Broadcast) tell sumo, length 28
10:42:21.111206 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 0.0.0.0 (Broadcast) tell sumo, length 28
^C
2 packets captured
2 packets received by filter
0 packets dropped by kernel
So sending ARP request on your wireless interface may be enough to "wake up" your connection and refresh your RSSI.
EDIT:
See the interesting uses and properties of IP 0.0.0.0 here:
https://en.wikipedia.org/wiki/0.0.0.0
EDIT 2:
Re-thinking about it, I realized there will be a problem if your wireless interface does not have an IP itself. Which, if I'm not mistaking, may not necessarily be case in your bridging configuration. In such case, arping will not have a source address to build its request packets (nor will know how to listen for responses), and will fail.
But you can create your own "mini-unidirectional arping", using an AF_PACKET socket and build your own ARP request packet with a dummy/random source IP address. It will be unidirectional because the response to your forged ARP request, if any, would go to to the random source IP which may and preferably should not exist. But it the principle of just awaking your wireless connection by sending "something", that may do the trick.
For inspiration on how to code this "mini-unidirectional arping", have a look at busybox implementation from its udhcpc/udhcpd (it's simpler than the full-blown arping busybox applet):
https://git.busybox.net/busybox/tree/networking/udhcp/arpping.c#n38
The from_ip parameter is what you want to forge. You can use your actual MAC as from_mac, just for the sake of dignity :-) You don't even have to wait for a response (starting line 89), so that would be something like 50 lines of C code + a little main if you want to add a few options to it.
I'm writing a testing tool that requires known traffic to be captured from a NIC (using libpcap), then fed into the application we are trying to test.
What I'm attempting to set-up is a web server (in this case, lighttpd) and a client (curl) running on the same machine, on an isolated test network. A script will drive the entire setup, and the goal is to be able to specify a number of clients as well as a set of files for each client to download from the web server.
My initial approach was to simply use the loopback (lo) interface... run the web server on 127.0.0.1, have the clients fetch their files from http://127.0.0.1, and run my libpcap-based tool on the lo interface. This works ok, apart from the fact that the loopback interface doesn't emulate a real Ethernet interface. The main problem with that is that packets are all inconsistent sizes... 32kbytes and bigger, and somewhat random... it's also not possible to lower the MTU on lo (well, you can, but it has no effect!).
I also tried running it on my real interface (eth0), but since it's an internal web client talking to an internal web server, traffic never leaves the interface, so libpcap never sees it.
So then I turned to tun/tap. I used socat to bind two tun interfaces together with a tcp connection, so in effect, i had:
10.0.1.1/24 <-> tun0 <-socat-> tcp connection <-socat-> tun1 <-> 10.0.2.1/24
This seems like a really neat solution... tun/tap devices emulate real Ethernet devices, so i can run my web server on tun0 (10.0.1.1) and my capture tool on tun0, and bind my clients to tun1 (10.0.2.1)... I can even use tc to apply shaping rules to this traffic and create a virtual WAN inside my linux box... but it just doesn't work...
Here are the socat commands I used:
$ socat -d TCP-LISTEN:11443,reuseaddr TUN:10.0.1.1/24,up &
$ socat TCP:127.0.0.1:11443 TUN:10.0.2.1/24,up &
Which produces 2 tun interfaces (tun0 and tun1), with their respective IP addresses.
If I run ping -I tun1 10.0.1.1, there is no response, but when i tcpdump -n -i tun0, i see the ICMP echo requests making it to the other side, just no sign of the response coming back.
# tcpdump -i tun0 -n
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on tun0, link-type RAW (Raw IP), capture size 65535 bytes
16:49:16.772718 IP 10.0.2.1 > 10.0.1.1: ICMP echo request, id 4062, seq 5, length 64
<--- insert sound of crickets here (chirp, chirp)
So am I missing something obvious or is this the wrong approach? Is there something else i can try (e.g. 2 physical interfaces, eth0 and eth1???).
The easiest way is just to use 2 machines, but I want all of this self-contained, so it can all be scripted and automated on a single machine, without and other dependencies...
UPDATE:
There is no need for the 2 socats to be connected with a tcp connection, it's possible (and preferable for me) to do this:
socat TUN:10.0.1.1/24,up TUN:10.0.2.1/24,up &
The same problem still exists though...
OK, so I found a solution using Linux network namespaces (netns). There is a helpful article about how to use it here: http://code.google.com/p/coreemu/wiki/Namespaces
This is what I did for my setup....
First, download and install CORE: http://cs.itd.nrl.navy.mil/work/core/index.php
Next, run this script:
#!/bin/sh
core-cleanup.sh > /dev/null 2>&1
ip link set vbridge down > /dev/null 2>&1
brctl delbr vbridge > /dev/null 2>&1
# create a server node namespace container - node 0
vnoded -c /tmp/n0.ctl -l /tmp/n0.log -p /tmp/n0.pid > /dev/null
# create a virtual Ethernet (veth) pair, installing one end into node 0
ip link add name veth0 type veth peer name n0.0
ip link set n0.0 netns `cat /tmp/n0.pid`
vcmd -c /tmp/n0.ctl -- ip link set n0.0 name eth0
vcmd -c /tmp/n0.ctl -- ifconfig eth0 10.0.0.1/24 up
# start web server on node 0
vcmd -I -c /tmp/n0.ctl -- lighttpd -f /etc/lighttpd/lighttpd.conf
# create client node namespace container - node 1
vnoded -c /tmp/n1.ctl -l /tmp/n1.log -p /tmp/n1.pid > /dev/null
# create a virtual Ethernet (veth) pair, installing one end into node 1
ip link add name veth1 type veth peer name n1.0
ip link set n1.0 netns `cat /tmp/n1.pid`
vcmd -c /tmp/n1.ctl -- ip link set n1.0 name eth0
vcmd -c /tmp/n1.ctl -- ifconfig eth0 10.0.0.2/24 up
# bridge together nodes using the other end of each veth pair
brctl addbr vbridge
brctl setfd vbridge 0
brctl addif vbridge veth0
brctl addif vbridge veth1
ip link set veth0 up
ip link set veth1 up
ip link set vbridge up
This basically sets up 2 virtual/isolated/name-spaced networks on your Linux host, in this case, node 0 and node 1. A web server is started on node 0.
All you need to do now is run curl on node 1:
vcmd -c /tmp/n1.ctl -- curl --output /dev/null http://10.0.0.1
And monitor the traffic with tcpdump:
tcpdump -s 1514 -i veth0 -n
This seems to work quite well... still experimenting, but looks like it will solve my problem.