Implement ip6_tryforward()

[ae]

Summary

This patch adds ip6_tryforward() - a fast run to completion forwarding implementation for IPv6.

[ae]

Fix copy/paste problem with missed code lines.

[ae]

Fix ifnet pointer in dtrace probe

[ae]

Include netinet/in_kdtrace.h

[olivier]

There is a problem somewhere because I didn't see any difference :-(
Ministat output of Packet-per-second forwarded on an small atom-4cores with gigabit Intel NIC:

x 12-head r308878
+ 12-head r308878 with D8527
+--------------------------------------------------------------------------+
|+        +          xx             x       x         x +     +           +|
|                     |_____________A_____________|                        |
|       |________________________________A______________M________________| |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5        858189        866458        861860      861749.5     3530.3342
+   5      853023.5        871471        866940      863030.7     8312.3947
No difference proven at 95.0% confidence

Output of "pmcstat -S instructions -T -w1" WITHOUT the patch (with traffic limited to 200Kpps):

PMC: [INSTR_RETIRED_ANY] Samples: 16538 (100.0%) , 0 unresolved

%SAMP IMAGE      FUNCTION             CALLERS
  4.9 kernel     in6_setscope         ip6_forward:3.3 ip6_input:1.6
  4.9 kernel     bounce_bus_dmamap_lo bus_dmamap_load_mbuf_sg
  4.4 kernel     ip6_forward          ip6_input
  4.0 kernel     igb_mq_start_locked  igb_mq_start
  3.7 libc.so.7  bsearch              0x64bc
  3.6 kernel     igb_rxeof            igb_msix_que
  3.6 kernel     uma_zfree_arg        m_freem:2.6 mb_free_ext:1.0
  3.1 kernel     uma_zalloc_arg       m_getjcl:1.2 m_copym:1.0 m_prepend:0.9
  3.0 kernel     ip6_input            netisr_dispatch_src
  3.0 kernel     rn_match             rtalloc1_fib
  2.6 kernel     ether_output         ip6_forward
  2.5 kernel     bzero                m_pkthdr_init:1.6 nd6_resolve:0.5
  2.5 kernel     m_copym              ip6_forward
  2.0 kernel     __rw_rlock           nd6_resolve:1.1 rtalloc1_fib:0.9

Output of "pmcstat -S instructions -T -w1" WITHT D8527 patch (with traffic still limited to 200Kpps):

PMC: [INSTR_RETIRED_ANY] Samples: 10678 (100.0%) , 0 unresolved

%SAMP IMAGE      FUNCTION             CALLERS
  6.1 kernel     igb_mq_start_locked  igb_mq_start
  6.0 kernel     igb_rxeof            igb_msix_que
  4.5 kernel     rn_match             fib6_lookup_nh_basic
  4.2 kernel     bounce_bus_dmamap_lo bus_dmamap_load_mbuf_sg
  4.2 kernel     ether_output         ip6_tryforward
  3.7 libc.so.7  bsearch              0x64bc
  3.6 kernel     bzero                fib6_lookup_nh_basic:1.3 m_pkthdr_init:0.8 nd6_resolve:0.8 ip6_tryforward:0.7
  3.2 kernel     __rw_rlock           fib6_lookup_nh_basic:1.7 nd6_resolve:1.5
  2.9 kernel     ip6_tryforward       ip6_input
  2.6 kernel     fib6_lookup_nh_basic ip6_findroute
  2.5 kernel     ip6_input            netisr_dispatch_src
  2.2 kernel     _rw_runlock_cookie   fib6_lookup_nh_basic:1.2 nd6_resolve:1.1
  2.2 kernel     bus_dmamap_load_mbuf igb_mq_start_locked:1.2 igb_refresh_mbufs:1.1
  2.2 kernel     igb_mq_start         ether_output
  2.2 kernel     netisr_dispatch_src  ether_input:1.4 ether_demux:0.8
  2.0 kernel     ether_nh_input       netisr_dispatch_src

[ae]

Add workaround to correctly handle LLA as gateway address.

[olivier]

I'm working on fixing my bench scripts (was not so easy to add IPv6) and re-run the bench using this last patch revision, on a bigger server (Xeon_E5-2650 with 8Cores, same Chelsio T540 NIC).
Then I will re-run them on the other platforms too.
Meanwhile the results are… impressive: From 2.4Mpps to 4.1Mpps :-)

x head r309424.inet6.pps
+ head r309424 with D8527.inet6.pps
+--------------------------------------------------------------------------+
|      x                                   +                              +|
|x     xx                                  + +                            +|
|  |__AM_|                                                                 |
|                                      |_____M__________A_______________|  |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5       2208236     2497598.5     2472890.5     2427075.3     122943.06
+   5     4043284.5       5424029       4127901     4615409.7     731887.23
Difference at 95.0% confidence
        2.18833e+06 +/- 765352
        90.1634% +/- 32.6463%
        (Student's t, pooled s = 524773)

[olivier]

I've re-run the fixed bench script on 8core ATOM.
Same excellent improvement with this patch on this platform:

x r309424 inet6.pps
+ r309424 with D8527 inet6.pps
+--------------------------------------------------------------------------+
|     x                                                                 + +|
|x xx x                                                                 +++|
| |_A_|                                                                    |
|                                                                       |A||
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5       1048371     1178036.5     1118136.5     1123344.5     54959.786
+   5       2969705     3028344.5       3003420     2999605.6     24042.596
Difference at 95.0% confidence
        1.87626e+06 +/- 61864.7
        167.025% +/- 13.6524%

[bz]

This is multiple independent changes. The "rcvif" statistics changes are all non-functional noise to my understanding and should be factored out and committed separately. It'll help to review the functional changes a lot easier.

There's an #ifdef in there which clearly will not compile.

sys/netinet6/ip6_fastfwd.c

142

That won't compile, will it?

sys/netinet6/ip6_input.c

594

All these "rcvif" changes could be factored out into a separate change and committed as non-functional change irrelevant to this work, please?

732

Put the V_ip6_forwarding check first please?

[ae]

sys/netinet6/ip6_fastfwd.c

142

Why not? It just adds additional check when IPSTEALTH is enabled.
When we work in "stealth" mode the following hlim check will be ignored.

sys/netinet6/ip6_input.c

594

Ok, I'll resubmit the patch a bit later.

732

Yes of course. Also we have to do the same for both ipv4.

[bz]

sys/netinet6/ip6_fastfwd.c

142

Oh I see. Sorry, wasn't obvious reading it on the web. Ignore me on this one :)

sys/netinet6/ip6_input.c

594

Great. Thanks!

[ae]

Remove statistic counters changes.

[ae]

So, if there is no objection, I will commit this patch tomorrow.

[bz]

I've not read in detail through the ip6_fastfwd.c code but I am fine with the other changes.