When iterating the table, we can't add new nodes to the hashmap because
we can't assure that we are not adding the new node before the iterator.
This also applies to rehashing - which might be triggered by both
isc_hashmap_add() and isc_hashmap_delete(), but not
isc_hashmap_iter_delcurrent_next().
When isc_hashmap_iter_delcurrent_next calls hashmap_delete_node
nodes from the front of the table could be added to the end of
the table resulting in them being returned twice. Detect when
this is happening and prevent those nodes being returned twice
buy reducing the effective size of the table by one each time
it happens.
Reusing TCP connections with dns_dispatch_gettcp() used linear linked
list to lookup existing outgoing TCP connections that could be reused.
Replace the linked list with per-loop cds_lfht hashtable to speedup the
lookups. We use cds_lfht because it allows non-unique node insertion
that we need to check for dispatches in different connection states.
Instead of high number of dispatches (4 * named_g_udpdisp)[1], make the
dispatches bound to threads and make dns_dispatchset_t create a dispatch
for each thread (event loop).
This required couple of other changes:
1. The dns_dispatch_createudp() must be called on loop, so the isc_tid()
is already initialized - changes to nsupdate and mdig were required.
2. The dns_requestmgr had only a single dispatch per v4 and v6. Instead
of using single dispatch, use dns_dispatchset_t for each protocol -
this is same as dns_resolver.
Looking up unique message ID in the dns_dispatch has been using custom
hash tables. Rewrite the custom hashtable to use cds_lfht API, removing
one extra lock in the cold-cache resolver hot path.
Refactor isc_hashmap to allow custom matching functions. This allows us
to have better tailored keys that don't require fixed uint8_t arrays,
but can be composed of more fields from the stored data structure.
The fixup commits' subject line has a prefix which has its own
length, so warning about the exceeding length is not accurate.
Given that the fixup commits can not be merged, because they
cause a danger failure, it's safe to ignore the length check
for them.
Test resolver-use-dns64 by simulating a connection to an IPv4-only
server through a NAT64.
This test uses EXTRAPORT1 rather than PORT for DNS traffic exchanged
between ns3 and ns4. Both servers also listen on PORT on their IPv4
addresses to support server startup testing in start.pl.
Add a configuration option, resolver-use-dns64, which when true
will cause named to map IPv4 address to IPv6 addresses using the
view's DNS64 mapping rules when making iterative queries.
Add support for incremental hashing to the isc_hash unit, both 32-bit
and 64-bit incremental hashing is now supported.
This is commit second in series adding incremental hashing to libisc.
When inserting items into hashtables (hashmaps), we might have a
fragmented key (as an example we might want to hash DNS name + class +
type). We either need to construct continuous key in the memory and
then hash it en bloc, or incremental hashing is required.
This incremental version of SipHash 2-4 algorithm is the first building
block.
As SipHash 2-4 is often used in the hot paths, I've turned the
implementation into header-only version in the process.
1. Replace the "high-performance" macros that were only used if
DNS_NAME_USEINLINE was defined before including <dns/name.h> with
inline header functions with assertion checks and thus use them
everywhere.
2. Replace the old struct initializers with C99 designated initializers
for better understanding what is happening in these macros.
This raises the log level of messages treated as FORMERR to NOTICE
when transfering in a zone. This also adds a missing log message
for TYPE0 and meta types received during a zone transfer.
7a78a85b moved the destruction of the validator from near the start
validated to the end. This reversed the order of dns_validator_destroy
and fetchctx_detach. Restore the order so that val->name remains
valid for the lifetime of the validator.
