Intel 82599 hardware filtering questions

Hi,

I have a powerful Dual Xeon server with Intel 82599-based network
card, 4 ports of which is fed by 40Gb/s of data in peak time. Of
course, not all packets are interesting and I've trying to use
hardware filtering.

Use case: filter out all UDP (over IPv4)

I've trying to use

a) 5-tuple filters as described in datasheet (7.1.2.5) via the FTQF,
SDPQF, L34TIMIR, DAQF, and SAQF registers
(patching ixgbe driver, because vanilla drivers does not provide
interface for custom FTQF filters programming) - I don't find an
explicit description how to drop packet with this filter type and
configure Rx Queue field of L34TIMIR = 127
b) Flow Director Filters
using ethtool -K ntuple on & ethtool -N flow-type udp4 action -1

The results was very similar for both filter types.
In both cases I've inspected the ethtool -S output and
/proc/net/pf_ring/*eth* files.
After applied filtering (any of above) the number of rx_missed_errors
become 0, but rx_no_dma_resources become non-zero. Number of lost
packets in pf_ring stat is 0.

Questions:
1. Why FTQF custom filters configuration is not available in 'vanilla'
ixgbe driver?
2. Is it correct to use Rx Queue = 127 to drop the packets with FTQF?
3. Why rx_no_dma_resources increased proportional of processed
packets? Is this indicates of any drops of interesting packets?
4. Is it expected to get similar results? (I thought 5-tuple filters
is simpler and more productive, but less flexible).

Please excuse me if I post the questions in a wrong mailing list -
correct mailing list address is appreciated.

Thanks for your attention.
Max