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mike gerlach
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ethernet loopback with multiple/different IP addresses on the same device/board
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mike gerlach
02/17/2010 5:11 PM
post47614
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ethernet loopback with multiple/different IP addresses on the same device/board
I have a board that uses the MPC8347 cpu. This board has three separate
IP addresses on it; en0, en1, en2.
I am using en0 connected to my pc network for downloading files etc.
I am trying to create a functional loopback test for en1 and en2 where I
connect them via a cross-over cable.
I wrote two quick applications using UDP sockets to sendto and recvfrom
a command line address...
When I run them, everything appears to work fine (send: packet =
"123456", recv: packet = "123456").
The problem comes when I disconnect the loopback. The same messages
appear. It appears QNX knows the two IP addresses are on the same
machine and bypasses the external connection. I read up all about route
and ifconfig but must be missing something. Is this a limitation within
QNX, or do I have to configure something differently?
I am running io-net and it is setup with dhcp.clients. Also I ifconfig
each en# at boot up
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Andrew Boyd(deleted)
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RE: ethernet loopback with multiple/different IP addresses on the same device/board
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Andrew Boyd(deleted)
02/18/2010 9:05 AM
post47650
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RE: ethernet loopback with multiple/different IP addresses on the same device/board
I would just run two instances of io-net on en1
and en2 to avoid any confusion.
Probably too simple, though :)
--
aboyd
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Patrik Lahti
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Re: ethernet loopback with multiple/different IP addresses on the
same device/board
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Patrik Lahti
02/18/2010 10:06 AM
post47665
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Re: ethernet loopback with multiple/different IP addresses on the
same device/board
> The problem comes when I disconnect the loopback. The same messages
> appear. It appears QNX knows the two IP addresses are on the same
> machine and bypasses the external connection. I read up all about route
> and ifconfig but must be missing something. Is this a limitation within
> QNX, or do I have to configure something differently?
>
You're seeing expected behavior of any networking stack. Even in host
mode stacks, the packets sent to any locally assigned address will get
handled locally.
What you may want to do is run two separate networking stacks, like
Andrew suggested. Alternatively, I believe you can use socket options to
bind to an interface (SO_BINDTODEVICE) and bypass routing (SO_DONTROUTE)
when sending to force the packet out a particular interface. Or, yet
another alternative, you may also be able to set up some clever pf rules.
/P
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mike gerlach
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
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mike gerlach
02/18/2010 3:46 PM
post47701
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
I attempted to try a few of your suggestions... and I am awaiting a response from the SW guys on starting a 2nd instance
of io-net for the specific devices... But I'm not getting SO_BINDTODEVICE or SO_DONTROUTE to work. Here is some of the
code:
/*
struct addrinfo iface, *s_addrinfo_snd;
const char * iname3 = "en3";
memset(&iface, 0, sizeof iface);
iface.ai_family = AF_UNSPEC;
iface.ai_socktype = SOCK_DGRAM;
iface.ai_flags = AI_PASSIVE;
if(getaddrinfo("128.0.0.3", MYPORT, &iface, &s_addrinfo_snd) != 0)
printf("failed getaddrinfo: \n");
if(snd_sock_hndl = socket(s_addrinfo_snd->ai_family,
s_addrinfo_snd->ai_socktype,
s_addrinfo_snd->ai_protocol) == -1)
printf("failed to create sending socket\n");
if(setsockopt(snd_sock_hndl, SOL_SOCKET, SO_BINDTODEVICE,
iname3, sizeof(iname3)) == -1)
printf("setsockopt: can't bind to send device\n");
*/
BTW; if i do create a second instance of io-net... will the new iname3 become:
"/dev/io-net2/en3"
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Patrik Lahti
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Re: ethernet loopback with multiple/different IP addresses on the
same device/board
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Patrik Lahti
02/18/2010 3:57 PM
post47703
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Re: ethernet loopback with multiple/different IP addresses on the
same device/board
On 18/02/10 03:46 PM, mike gerlach wrote:
> But I'm not getting SO_BINDTODEVICE or SO_DONTROUTE to work.
What is it that isn't working?
> Here is some of the code:
>
I didn't see SO_DONTROUTE in your code, only SO_BINDTODEVICE, could that
be your problem?
> BTW; if i do create a second instance of io-net... will the new iname3 become:
> "/dev/io-net2/en3"
>
No, you should be able to use SOCK env var to direct the your socket
library calls to use the second stack instance. Please see the wiki.
/P
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mike gerlach
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
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mike gerlach
02/18/2010 4:33 PM
post47708
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
sorry, i only posted a few lines of code. Both setsockopt return -1
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Patrik Lahti
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Re: ethernet loopback with multiple/different IP addresses on the
same device/board
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Patrik Lahti
02/18/2010 4:54 PM
post47713
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Re: ethernet loopback with multiple/different IP addresses on the
same device/board
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mike gerlach
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
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mike gerlach
03/01/2010 4:40 PM
post48567
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
OK. I changed my process around since I had no luck with the direct loopback method... I probably should re-start this
post under SW discussion... but here it goes anyway since you know the history.
Instead of doing a direct loopback, I run each interface (en1, en2, en3) into a hub. The hub goes into a test PC.
option 1: *** prefer this method so I can communicate to each device directly
- have 3 seperate IP addresses on the test PC named 128.1.0.100, 128.2.0.100, and 128.3.0.100
- configure the devices as
ifconfig en1 128.1.0.1
ifconfig en2 128.2.0.1
ifconfig en3 128.3.0.1
option 2:
- have 1 address on the test PC named 128.1.0.100
- configure the devices as
ifconfig en1 128.1.0.1
ifconfig en2 128.1.0.2
ifconfig en3 128.1.0.3
and setsockopt SO_BINDTODEVICE within my test program to ensure each device is actually sending the data.
Either way, I have an echo server running on the test pc configured to a specific port. My test program creates the
socket, connects to the echo server, sends some data, and reads/verifies the incomming data is valid (from the correct
device).
Everything works with one problem that I believe has to do with the route table, but I don't know how to set it up
Here is the problem:
After setting the ifconfig commands I can not ping to 128.X.0.100. When I do, it just sits there. ***As it sits there***
, if I ping from windows to the specific device, both start to work (i.e. ping works to/from). If I ping from windows to
all the devices all will work and my test program will work. So it seems something is not updating the routing tables
and the ping forces the system to learn it. Since this is a test program, I don't want the test PC (echo server) to
start the process, I want it to just sit there and echo back once the devices start the test. Is this something with
the routing?
attached is the route tables before/after. Please ignore en0 and lo0 for now. Eventually en0 will also be hooked up to
the hub and echo server.
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mike gerlach
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
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mike gerlach
03/01/2010 4:43 PM
post48569
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
OK. I changed my process around since I had no luck with the direct
loopback method... I probably should re-start this post under SW
discussion... but here it goes anyway since you know the history.
Instead of doing a direct loopback, I run each interface (en1, en2, en3)
into a hub. The hub goes into a test PC.
option 1: *** prefer this method so I can communicate to each device directly
- have 3 seperate IP addresses on the test PC named 128.1.0.100, 128.2.0.100, and 128.3.0.100
- configure the devices as
ifconfig en1 128.1.0.1
ifconfig en2 128.2.0.1
ifconfig en3 128.3.0.1
option 2:
- have 1 address on the test PC named 128.1.0.100
- configure the devices as
ifconfig en1 128.1.0.1
ifconfig en2 128.1.0.2
ifconfig en3 128.1.0.3
and setsockopt SO_BINDTODEVICE within my test program to
ensure each device is actually sending the data.
Either way, I have an echo server running on the test pc configured
to a specific port. My test program creates the socket, connects to
the echo server, sends some data, and reads/verifies the incomming
data is valid (from the correct device).
Everything works with one problem that I believe has to do with the
route table, but I don't know how to set it up
Here is the problem:
After setting the ifconfig commands I can not ping to 128.X.0.100.
When I do, it just sits there. ***As it sits there***, if I ping from windows
to the specific device, both start to work (i.e. ping works to/from). If I
ping from windows to all the devices all will work and my test program
will work. So it seems something is not updating the routing tables and
the ping forces the system to learn it. Since this is a test program, I
don't want the test PC (echo server) to start the process, I want it to
just sit there and echo back once the devices start the test. Is this
something with the routing?
attached is the route tables before/after. Please ignore en0 and lo0 for
now. Eventually en0 will also be hooked up to the hub and echo server.
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Vineet Garg
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
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Vineet Garg
07/02/2010 7:54 AM
post58321
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Re: ethernet loopback with multiple/different IP addresses on the same device/board
Hi
Looks like some issue with ARP resolution.
You can try putting sniffer/wireshark on each interface of test PC and see if your device sends ARP request when you
ping. You can run your experiment and capture the entire thing on wireshark.
Analysis of that might be able to help you.
VG
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