svn commit: r280971 - in head: contrib/ipfilter/tools share/man/man4 sys/contrib/ipfilter/netinet sys/netinet sys/netipsec sys/netpfil/pf

[Robert Watson]

On Thu, 2 Apr 2015, Hans Petter Selasky wrote:

>>> Does somebody here know what happens in these two cases:
>>> 
>>> If we are transmitting using TSO, will the network adapter increment the 
>>> IP ID field somehow? What happens if an outgoing IP packet resulting from 
>>> a TSO packet get fragmented by a router?
>> 
>> Quite possibly -- this is presumably specified by the NIC vendor, but it 
>> would be good to do a bit of a survey and see what happens in practice.
>> 
>>> In ip_fragment() when we create fragments we should increment the ip_id 
>>> value for each fragment?
>
> I'm asking because the code in FreeBSD, since the beginning probably, just 
> copies the IP header, and use the same IP ID for all the fragments ! This 
> just hit my mind after some recent work in this area.

I honestly cannot believe you are proposing that.

Please go read about how IP fragmentation works.  Having an identical IP ID in 
ip_fragment() is the point of the function!

Robert