Re: PROBLEM: Interface address change netlink socket problem.(Patch

[Vividh Siddha <vividh@ipinfusion.com>]

Thats true but we are working around a problem which exists in the Linux 
stack. Ideally when we set only a interface address, the netmask should 
remain the same as it was before. Also the default netmasks based on 
classes might not be what is set. If we set netmask as /23, then:

ifconfig eth0 10.10.10.50

will cause the netmask to be /8. The end result of all of these is correct but the intermediate messages can cause problems in higher layer protocols.

vividh

jamal wrote:

>Moved to netdev where it belongs. Vividh in the future please post
>to netdev or at least cross-post to it ... because the kernel list
>FAQ says so.
>
>In your posting you say:
>  
>
>>Imagine a interface eth0 with address 10.10.10.10, netmask 0xffffff00
>>and broadcast 10.10.10.255.
>>
>>For eg: if the following command is issued:
>>ifconfig eth0 10.10.10.50 netmask 0xffffff00 broadcast 10.10.10.255
>>
>>The kernel sends the following three sets of messages on the netlink
>>socket:
>>
>>Interface address delete: (with address 10.10.10.10)
>>Interface address add   : (with address 10.10.10.50)
>>
>>Interface address delete: (with address 10.10.10.50)
>>Interface address add   : (with address 10.10.10.50)
>>
>>Interface address delete: (with address 10.10.10.50)
>>Interface address add   : (with address 10.10.10.50)
>>
>>Ideally as only the interface address is changed only one address
>>delete/add should be sent.
>>    
>>
>
>State is not maintained in user space. You change that IP address,
>it actually gets deleted then a new one added. The bcast and netmask
>changeto defaults  as a result; you then change the netmask and
>broadcast with each requiring a call from user space. If you modify your
>netlink program to print both net and broadcast address you should see
>this. BTW, you MUST check for these.
>
>Example try just:
>ifconfig eth0 10.10.10.50
>
>and after you change it try:
>ifconfig eth0 10.10.10.50 netmask 0xffffff00
>
>and then
>ifconfig eth0 10.10.10.50 netmask 0xffffff00 broadcast 10.10.10.255
>
>cheers,
>jamal
>
>
>  
>