2008-10-29 05:26:30     IP stack issue (Multicast packets)

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2008-10-29 05:26:30     IP stack issue (Multicast packets)

Tinku Jose (INDIA)

Message: 64325   

 

Hi,

 

release: 2007R1

 

While testing one of the aspects of IP stack we have observed the following. The sequence followed is as follows.

 

1. set the ethernet interface ip address to 127.x.y.z and bring it up (using ifconfig)

 

2. bring down the interface

 

3. set the ethernet interface ip to a valid IP

 

4. Do a multicast transmit (multicast join and transmit)

 

Observation

 

for the multicast transmit the source address is going as 0.0.0.0 instead of the valid ip which is set in step 3. The unicast packets are transmitted properly.

 

Is this a know issue,

 

I am aware of the fact that the 127.x.y.z is not a valid ip for an ethernet interface, but why is it having this side effect after setting the proper IP address.

 

Thanks in advance.

 

best regards

 

tinku

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2008-10-29 05:41:48     Re: IP stack issue (Multicast packets)

Mike Frysinger (UNITED STATES)

Message: 64328   

 

please post small test cases that can be compiled & run on a Blackfin board

 

also, fully describe your hardware setup

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2008-10-29 12:22:03     Re: IP stack issue (Multicast packets)

Tinku Jose (INDIA)

Message: 64365   

 

Hi Mike,

 

Please find the files are details of test

 

1) multi_simple_test.c -> simple multicast application which will send 10 multicast packets to multicast address 239.255.255.250 (compiled using the bfin-linux-uclibc-gcc).

 

2) command_seq.txt -> sequence of command used (once the executable is transfered to the system)

 

3) 2007R1.cap -> packet capture (using libpcap) while executing the application. kernel used uImage-bf533-ezkit-2007R1-RC3 which is downloaded from the website

 

4) 2008R1.5.cap -> packet capture (using libpcap) while executing the application. kernel used uImage-bf533-ezkit-2008R1.5-RC3 which is downloaded from the website

 

In both the captures you can see that the second set of 10 packets (seq num 11 - 20 in 2007R1.cap and seq num 15 - 24 in 2008R1.5.cap) are going with source ip as 0.0.0.0. (the first set is going without any issues)

 

the second set of capture is done after making the ipaddress of the system to 127.2.3.4 and then immediately changing the ipaddress back to 192.168.0.124

 

the observation is, i am seeing this issue only when i set the ipaddress to 127.x.y.z and it is not giving this issue with any other ip address.

 

Please do let me know if you require additional details.

 

thanks and best regards

 

tinku

 

multi_simple_test.c

command_seq.txt

2008R1.5.cap

2007R1.cap

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2008-10-29 12:25:38     Re: IP stack issue (Multicast packets)

Tinku Jose (INDIA)

Message: 64366   

 

Missed to mention the Hardware setup.

 

Using the BF533EzKit with Lan extender

 

PC and board connected over ethernet (through hub or cross cable)

 

IP address of the PC 192.168.0.1

 

IP address of the board 192.168.0.124

 

 

 

please do let me know if additional info is required on the setup.

 

best regards

 

tinku

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2008-10-29 13:43:03     Re: IP stack issue (Multicast packets)

Mike Frysinger (UNITED STATES)

Message: 64370   

 

do you get different behavior if you add the proper multicast routes first ?

 

http://andrew.triumf.ca/pub/linux/multicast-FAQ

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2008-10-29 13:48:39     Re: IP stack issue (Multicast packets)

Tinku Jose (INDIA)

Message: 64372   

 

Hi Mike,

 

I guess in the standard binary provided the kernel mulitcast option is not enabled and hence in these the multicast route cannot be added in the binary (it was giving error).

 

But i've tried in our kernel (on a different board) with the multicast route and still we see this issue. (in our system since gateway is not mandatory for having the multicast packet transmit we need to have the multicast route)

 

best regards

 

tinku

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