Instead of mixing the dns_resolver and dns_validator units directly with
the EDE code, split-out the dns_ede functionality into own separate
compilation unit and hide the implementation details behind abstraction.
Additionally, the EDE codes are directly copied into the ns_client
buffers by passing the EDE context to dns_resolver_createfetch().
This makes the dns_ede implementation simpler to use, although sligtly
more complicated on the inside.
Co-authored-by: Colin Vidal <colin@isc.org>
Co-authored-by: Ondřej Surý <ondrej@isc.org>
Extended DNS error 22 (No reachable authority) was previously detected
when `fctx_expired` fired. It turns out this function is used as a
"safety net" and the timeout detection should be caught earlier.
It was working though, because of another issue fixed by !9927. Since
this change, the recursive request timed out detection occurs before
`fctx_expired` so EDE 22 is not added to the response message anymore.
The fix of the problem is to add the EDE 22 code in two situations:
- When the dispatch code timed out (rctx_timedout) the resolver code
checks various properties to figure out if it needs to make another
fetch attempt. One of the paramters if the fetch expiration time. If
it expires, the whole recursion is canceled, so it now adds the EDE 22
code.
- If the fetch expiration time doesn't expires in the case above (and
other parameters allows it) a new fetch attempt is made (fctx_query).
But before the new request is actually made, the fetch expiration time
is re-checked. It might then has elapsed, and the whole recursion is
canceled. So it now also adds the EDE 22 code here as well.
Add support for EDE codes 1 (Unsupported DNSKEY Algorithm) and 2
(Unsupported DS Digest Type) which might occurs during DNSSEC
validation in case of unsupported DNSKEY algorithm or DS digest type.
Because DNSSEC internally kicks off various fetches, we need to copy
all encountered extended errors from fetch responses to the fetch
context. Upon an event, the errors from the fetch context are copied
to the client response.
When TCP is used, 'fctx_query()' adds one second to the rtt
(round-trip time) value, but there's a bug when the decision
about using TCP is made already after the calculation. Move the
block of the code which looks up the peers list to decide
whether to use TCP into a place that's before the rtt calculation
is performed. This commit doesn't add or remove any code, it just
moves the code and adds a comment block.
Currently, the fetch context will continue running even when the last
fetch (response) has been removed from the context, so named can process
and cache the answer. This can lead to a situation where the number of
outgoing recursing clients exceeds the the configured number for
recursive-clients.
Be more stringent about the recursive-clients limit and shutdown the
fetch context immediately after the last fetch has been canceled from
that particular fetch context.
The network manager layer has two different timers with their
own timeout values for TCP connections: connect timeout and read
timeout. Separate the connect and the read TCP timeouts in the
dispatch module too.
struct fetchctx does have a list of pending validators as well as a
pointer to the HEAD validator. Remove the validator pointer to avoid
confusion, as there is no perticular reasons to have it directly
accessible outside of the list.
Limit the number of records appended to ADDITIONAL section to the names
that have less than 14 records in the RDATA. This limits the number
of the lookups into the database(s) during single client query.
Also don't append any additional data to ANY queries. The answer to ANY
is already big enough.
Ensure the log prefixes passed to the dns_message_logpacketfrom()
function by its callers do not include the word "from" as the latter is
now emitted by the logfmtpacket() helper function.
Ensure the log prefixes passed to the dns_message_logpacketfromto()
function by its callers do not include the words "from" or "to" as those
are now emitted by the logfmtpacket() helper function.
Move dns_dispentry_getlocaladdress() calls around so that they are not
only invoked when dnstap support is compiled in. This function calls
isc_nmhandle_localaddr(), which may issue a system call, but only if the
ISC_SOCKET_DETAILS preprocessor macro is set at compile time.
Pass the value extracted by dns_dispentry_getlocaladdress() to
dns_message_logpacketfromto() so that it gets logged, adding useful
information to the relevant debug messages.
Since dns_message_logpacket() only takes a single socket address as a
parameter (and it is always the sending socket's address), rename it to
dns_message_logpacketfrom() so that its name better conveys its purpose
and so that the difference in purpose between this function and
dns_message_logpacketfromto() becomes more apparent.
Since dns_message_logfmtpacket() needs to be provided with both "from"
and "to" socket addresses, rename it to dns_message_logpacketfromto() so
that its name better conveys its purpose. Clean up the code comments
for that function.
Change the function prototype for dns_message_logfmtpacket() so that it
takes two isc_sockaddr_t parameters: one for the sending side and
another one for the receiving side. This enables debug messages to be
more precise.
Also adjust the function prototype for logfmtpacket() accordingly.
Unlike dns_message_logfmtpacket(), this function must not require both
'from' and 'to' parameters to be non-NULL as it is still going to be
used by dns_message_logpacket(), which only provides a single socket
address. Adjust its log format to handle both of these cases properly.
Adjust both dns_message_logfmtpacket() call sites accordingly, without
actually providing the second socket address yet. (This causes the
revised REQUIRE() assertion in dns_message_logfmtpacket() to fail; the
issue will be addressed in a separate commit.)
Both existing callers of the dns_message_logfmtpacket() function set the
argument passed as 'style' to &dns_master_style_comment. To simplify
these call sites, drop the 'style' parameter from the prototype for
dns_message_logfmtpacket() and use a fixed value of
&dns_master_style_comment in the function's body instead.
The dnssec-must-be-secure feature was added in the early days of BIND 9
and DNSSEC and it makes sense only as a debugging feature. There are no
reasons to keep this feature in the production code anymore.
Remove the feature to simplify the code.
While implementing the global limit 'max-query-count', initially I
thought adding the variable to the resolver structure. But the limit
is per client request so it was moved to the view structure (and
counter in ns_query structure). However, I forgot to remove the
variable from the resolver structure again. This commit fixes that.
Add another option to configure how many outgoing queries per
client request is allowed. The existing 'max-recursion-queries' is
per restart, this one is a global limit.
Add support for Extended DNS Errors (EDE) error 22: No reachable
authority. This occurs when after a timeout delay when the resolver is
trying to query an authority server.
The lame-ttl processing was overriden to be disabled in the config,
but the code related to the lame-ttl was still kept in the resolver
code. More importantly, the DNS_RESOLVER_BADCACHETTL() macro would
cause the entries in the resolver badcache to be always cached for at
least 30 seconds even if the lame-ttl would be set to 0.
Remove the dns_badcache code from the dns_resolver unit, so we save some
processing time and memory in the resolver code.
Instead of cleaning the dns_badcache opportunistically, add per-loop
LRU, so each thread-loop can clean the expired entries. This also
allows removal of the atomic operations as the badcache entries are now
immutable, instead of updating the badcache entry in place, the old
entry is now deleted from the hashtable and the LRU list, and the new
entry is inserted in the LRU.
QPDB is now a default implementation for both cache and zone. Remove
the venerable RBTDB database implementation, so we can fast-track the
changes to the database without having to implement the design changes
to both QPDB and RBTDB and this allows us to be more aggressive when
refactoring the database design.
Dispatch needs to know the transport that is being used over the
TCP connection to correctly allow for it to be reused. Add a
transport parameter to dns_dispatch_createtcp and dns_dispatch_gettcp
and use it when selecting a TCP socket for reuse.
Static-stub address and addresses from other sources where being
mixed together resulting in static-stub queries going to addresses
not specified in the configuration or alternatively static-stub
addresses being used instead of the real addresses.
The 'all_spilled' local variable in resolver.c:fctx_getaddresses()
is 'true' by default, and only becomes false when there is at least
one successfully found NS address. However, when a 'forward only;'
configuration is used, the code jumps over the part where it looks
for NS addresses and doesn't reset the 'all_spilled' to false, which
results in incorretly increased 'serverquota' statistics variable,
and also in invalid return error code from the function. The result
code error didn't make any differences, because all codes other than
'ISC_R_SUCCESS' or 'DNS_R_WAIT' were treated in the same way, and
the result code was never logged anywhere.
Set the default value of 'all_spilled' to 'false', and only make it
'true' before actually starting to look up NS addresses.
fctx->state should be read with the lock held.
1559 /*
1560 * Caller must be holding the fctx lock.
1561 */
CID 468796: (#1 of 1): Data race condition (MISSING_LOCK)
1. missing_lock: Accessing fctx->state without holding lock fetchctx.lock.
Elsewhere, fetchctx.state is written to with fetchctx.lock held 2 out of 2 times.
1562 REQUIRE(fctx->state == fetchstate_done);
1563
1564 FCTXTRACE("sendevents");
1565
1566 LOCK(&fctx->lock);
1567
Give prefetches a free pass through the quota so that the cache
entries for popular zones could be updated successfully even if the
quota for is already reached.
Give prefetches a free pass through the quota so that the cache entry
for a popular zone could be updated successfully even if the quota for
it is already reached.
Remove the complicated mechanism that could be (in theory) used by
external libraries to register new categories and modules with
statically defined lists in <isc/log.h>. This is similar to what we
have done for <isc/result.h> result codes. All the libraries are now
internal to BIND 9, so we don't need to provide a mechanism to register
extra categories and modules.
The fcount_incr() was not increasing counter->count when force was set
to true, but fcount_decr() would try to decrease the counter leading to
underflow and assertion failure. Swap the order of the arguments in the
condition, so the !force is evaluated after incrementing the .count.
there were cases in resolver.c when queries for NS records were
started without passing a pointer to the parent fetch's query counter;
as a result, the max-recursion-queries quota for those queries started
counting from zero, instead of sharing the limit for the parent fetch,
making the quota ineffective in some cases.
when searching the cache for a node so that we can delete an
rdataset, it is not necessary to set the 'create' flag. if the
node doesn't exist yet, we then we won't be able to delete
anything from it anyway.
when a priming query is complete, it's currently logged at
level ISC_LOG_DEBUG(1), regardless of success or failure. we
are now raising it to ISC_LOG_NOTICE in the case of failure.
The fcount_incr() was incorrectly skipping the accounting for the
fetches-per-zone if the force argument was set to true. We want to skip
the accounting only when the fetches-per-zone is completely disabled,
but for individual names we need to do the accounting even if we are
forcing the result to be success.
There are use cases for which shorter timeout values make sense.
For example if there is a load balancer which sets RD=1 and
forwards queries to a BIND resolver which is then configured to
talk to backend servers which are not visible in the public NS set.
WIth a shorter timeout value the frontend can give back SERVFAIL
early when backends are not available and the ultimate client will
not penalize the BIND-frontend for non-response.
