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author | melifaro <melifaro@FreeBSD.org> | 2015-09-16 14:26:28 +0000 |
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committer | melifaro <melifaro@FreeBSD.org> | 2015-09-16 14:26:28 +0000 |
commit | 493325342d2aeb9d06e09827e294b9407ec60e9b (patch) | |
tree | e04e3fcd4841d6aa1ce593fcc38aa9bb51b4cd33 /sys/netinet6/ip6_forward.c | |
parent | 1391356f66bee9ea2da2af8675144717f9efcfb3 (diff) | |
download | FreeBSD-src-493325342d2aeb9d06e09827e294b9407ec60e9b.zip FreeBSD-src-493325342d2aeb9d06e09827e294b9407ec60e9b.tar.gz |
Simplify the way of attaching IPv6 link-layer header.
Problem description:
How do we currently perform layer 2 resolution and header imposition:
For IPv4 we have the following chain:
ip_output() -> (ether|atm|whatever)_output() -> arpresolve()
Lookup is done in proper place (link-layer output routine) and it is possible
to provide cached lle data.
For IPv6 situation is more complex:
ip6_output() -> nd6_output() -> nd6_output_ifp() -> (whatever)_output() ->
nd6_storelladdr()
We have ip6_ouput() which calls nd6_output() instead of link output routine.
nd6_output() does the following:
* checks if lle exists, creates it if needed (similar to arpresolve())
* performes lle state transitions (similar to arpresolve())
* calls nd6_output_ifp() which pushes packets to link output routine along
with running SeND/MAC hooks regardless of lle state
(e.g. works as run-hooks placeholder).
After that, iface output routine like ether_output() calls nd6_storelladdr()
which performs lle lookup once again.
As a result, we perform lookup twice for each outgoing packet for most types
of interfaces. We also need to maintain runtime-checked table of 'nd6-free'
interfaces (see nd6_need_cache()).
Fix this behavior by eliminating first ND lookup. To be more specific:
* make all nd6_output() consumers use nd6_output_ifp() instead
* rename nd6_output[_slow]() to nd6_resolve_[slow]()
* convert nd6_resolve() and nd6_resolve_slow() to arpresolve() semantics,
e.g. copy L2 address to buffer instead of pushing packet towards lower
layers
* Make all nd6_storelladdr() users use nd6_resolve()
* eliminate nd6_storelladdr()
The resulting callchain is the following:
ip6_output() -> nd6_output_ifp() -> (whatever)_output() -> nd6_resolve()
Error handling:
Currently sending packet to non-existing la results in ip6_<output|forward>
-> nd6_output() -> nd6_output _lle() which returns 0.
In new scenario packet is propagated to <ether|whatever>_output() ->
nd6_resolve() which will return EWOULDBLOCK, and that result
will be converted to 0.
(And EWOULDBLOCK is actually used by IB/TOE code).
Sponsored by: Yandex LLC
Differential Revision: https://reviews.freebsd.org/D1469
Diffstat (limited to 'sys/netinet6/ip6_forward.c')
-rw-r--r-- | sys/netinet6/ip6_forward.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/sys/netinet6/ip6_forward.c b/sys/netinet6/ip6_forward.c index 83e58c1..9df8e4c 100644 --- a/sys/netinet6/ip6_forward.c +++ b/sys/netinet6/ip6_forward.c @@ -571,7 +571,7 @@ pass: goto bad; } - error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); + error = nd6_output_ifp(rt->rt_ifp, origifp, m, dst); if (error) { in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); IP6STAT_INC(ip6s_cantforward); |