On 04/02/15 20:46, Robert Watson wrote:
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!
Hi,
rwatson: You're right, the more fragment flag gets set there, I
overlooked that bit. Sorry.
glebius: Given that you admit there is a small chance of an IP ID
collision in the previous e-mails exchanged in this thread, why don't we
have checks for that in ip_reass() when receiving fragmented IP packets?
For example when ip->ip_off == 0 we know the TCP and/or UDP port numbers
for TCP and UDP payloads and can check if a new fragment is starting
before the previous one is completed. Then we would know if a collision
has happened and could discard that packet. Not ideal, but better than
data corruption.
--HPS
_______________________________________________
svn-src-all@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
