About the netmask (Was:Wireshark-commits: [Wireshark-commits] rev 33461: /trunk/gtk/ /trunk/gtk/: capture_dlg.c)

[Jaap Keuter <jaap.keuter () xs4all nl>]

> From: guy@xxxxxxxxxxxxx
> Date: Wed, 07 Jul 2010 01:55:39 GMT
>
> http://anonsvn.wireshark.org/viewvc/viewvc.cgi?view=rev&revision=33461
>
> User: guy
> Date: 2010/07/06 06:55 PM
>
> Log:
>  I added PCAP_NETMASK_UNKNOWN in libpcap 1.1.0; it's not present in
>  1.0.0.  You're supposed to just use 0 in releases prior to 1.1.0 - in
>  1.1.0 and later, a netmask of PCAP_NETMASK_UNKNOWN will cause errors if
>  you try to use "ip broadcast" (as you need the netmask to check for
>  local broadcasts), but, prior to that, the netmask value is blindly used
>  even if the filter will always fail.


Guy, first of all thanks for fixing this.

When working on this parameter I was wondering what was happening here.

What if I have an interface with:
1. untagged 192.168.16.0/24
2. tagged 10.0.0.0/28
and have a filter 'ip broadcast or vlan and ip broadcast'.

Or even worse, what if I have an interface with:
1. tagged 192.168.16.0/24
2. tagged 10.0.0.0/28
and have a filter 'vlan and ip broadcast'.

If I understand it correctly either case will only partially match when setting 
up the netmask parameter to either /24 or /28.

Thanks,
Jaap

PS: Holland, Holland!!! ;)
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