[ovs-dev] IPv6 first/later fragments
blp at nicira.com
Wed Oct 26 15:36:55 PDT 2011
On Wed, Oct 26, 2011 at 03:34:10PM -0700, Jesse Gross wrote:
> On Wed, Oct 26, 2011 at 2:59 PM, Ben Pfaff <blp at nicira.com> wrote:
> > Navindra Yadav pointed out in a discussion over on an ONF issue tracker
> > that first/later fragment isn't as useful with IPv6: the TCP/UDP port
> > numbers aren't necessarily in the first fragment, because other
> > intermediate extension headers can follow the fragment header.
> > Any idea what we should do about this?
> This is always true, even for IPv4. You could have a fragment that is
> split very quickly after the IP header or simply a truncated packet.
I don't understand yet. An IP fragment is always at least 8 bytes long.
The TCP and UDP port numbers are in the first 8 bytes of the TCP and UDP
headers, respectively. So won't the first IP fragment of a complete TCP
or UDP packet always contain the TCP and UDP port numbers?
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