Ethereal-users: Re: [Ethereal-users] how to dissect packets in mobile ipv6?

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From: "Huang Qian" <huangq@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 6 Aug 2002 13:19:38 +0800
----- Original Message -----
From: "Guy Harris" <gharris@xxxxxxxxx>
To: "Huang Qian" <huangq@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: <ethereal-users@xxxxxxxxxxxx>
Sent: Monday, August 05, 2002 3:26 PM
Subject: Re: [Ethereal-users] how to dissect packets in mobile ipv6?
>
> No, libpcap does not.  The only place where libpcap knows anything at
> all about network addresses is in capture filters, and a capture filter
> is converted to "machine code" for the BPF interpreter when it's
> compiled, and the numerical values of those addresses are wired into the
> machine code - they do not change over time.
>
> So if you use a capture filter that specifies the host name or the IPv6
> address of the mobile node at the time that you start capturing, so that
> only packets to or from the address that host name resolves to, or the
> specified IPv6 address, are captured, it will *NOT* capture packets to
> or from the mobile node if its IP address changes.
>

libpcap only use the IP address in the filter? I found Function " int
pcap_lookupnet ( char *device, bpf_u_int32 *netp, bpf_u_int32 *maskp, char
*errbuf)" includes the use of  "localnet and mask", so for what they are
used? whether their setting will influence the libpcap work?
capture online or read from a captured file, the two fields work the same
way?