This patch introduce the "dns_stream_nameserver" to use DNS over
TCP on strict nameservers. For the upper layer it is analog to
the api used with udp nameservers except that the user que switch
the name server in "stream" mode at the init using "dns_stream_init".
The fallback from UDP to TCP is not handled and this is not the
purpose of this feature. This is done to choose the transport layer
during the initialization.
Currently there is a hardcoded limit of 4 pipelined transactions
per TCP connections. A batch of idle connections is expired every 5s.
This code is designed to support a maximum DNS message size on TCP: 64k.
Note: this code won't perform retry on unanswered queries this
should be handled by the upper layer
This patch splits current dns.c into two files:
The first dns.c contains code related to DNS message exchange over UDP
and in future other TCP. We try to remove depencies to resolving
to make it usable by other stuff as DNS load balancing.
The new resolvers.c inherit of the code specific to the actual
resolvers.
Note:
It was really difficult to obtain a clean diff dur to the amount
of moved code.
Note2:
Counters and stuff related to stats is not cleany separated because
currently counters for both layers are merged and hard to separate
for now.
This patch splits recv and send functions in two layers. the
lowest is responsible of DNS message transactions over
the network. Doing this we could use DNS message layer
for something else than resolving. Load balancing for instance.
This patch also re-works the way to init a nameserver and
introduce the new struct dns_dgram_server to prepare the arrival
of dns_stream_server and the support of DNS over TCP.
The way to retry a send failure of a request because of EAGAIN
was re-worked. Previously there was no control and all "pending"
queries were re-played each time it reaches a EAGAIN. This
patch introduce a ring to stack messages in case of sent
failure. This patch is emptied if poller shows that the
socket is ready again to push messages.
Some types are specific to resolver code and a renamed using
the 'resolv' prefix instead 'dns'.
-struct dns_query_item {
+struct resolv_query_item {
-struct dns_answer_item {
+struct resolv_answer_item {
-struct dns_response_packet {
+struct resolv_response {
This patch adds the attribute packed on struct dns_question
because it is directly memcpy to network building a response.
This patch also removes the commented line:
// struct list options; /* list of option records */
because it is also used directly using memcpy to build a request
and must not contain host data.
Resolv callbacks are also updated to rely on counters and not on
nameservers.
"show stat domain dns" will now show the parent id (i.e. resolvers
section name).
A few structures were slightly rearranged in order to plug some holes
left around the locks. Sizes ranging from 8 to 32 bytes could be saved
depending on the structures. No performance difference was noticed (none
was expected there), though memory usage might be slightly reduced in
some rare cases.
Use the new stats module API to integrate the dns counters in the
standard stats. This is done in order to avoid code duplication, keep
the code related to cli out of dns and use the full possibility of the
stats function, allowing to print dns stats in csv or json format.
A SRV record keeps a reference on the corresponding additional record, if
any. But this additional record is also inserted in a separate linked-list into
the dns response. The problems arise when obsolete additional records are
released. The additional records list is purged but the SRV records always
reference these objects, leading to an undefined behavior. Worst, this happens
very quickly because additional records are never renewed. Thus, once received,
an additional record will always expire.
Now, the addtional record are only associated to a SRV record or simply
ignored. And the last version is always used.
This patch helps to fix the issue #841. It must be backported to 2.2.
The set of files proto_udp.{c,h} were misleadingly named, as they do not
provide anything related to the UDP protocol but to datagram handling
instead, since currently all UDP processing is hard-coded where it's used
(dns, logs). They are to UDP what connection.{c,h} are to proto_tcp. This
was causing confusion about how to insert UDP socket management code,
so let's rename them right now to dgram.{c,h} which more accurately
matches what's inside since every function and type is already prefixed
with "dgram_".
There are list definitions everywhere in the code, let's drop the need
for including list-t.h to declare them. The rest of the list manipulation
is huge however and not needed everywhere so using the list walking macros
still requires to include list.h.
This patch fixes all the leftovers from the include cleanup campaign. There
were not that many (~400 entries in ~150 files) but it was definitely worth
doing it as it revealed a few duplicates.
The type file is becoming a mess, half of it is for the proxy protocol,
another good part describes conn_streams and mux ops, it would deserve
being split again. At least it was reordered so that elements are easier
to find, with the PP-stuff left at the end. The MAX_SEND_FD macro was moved
to compat.h as it's said to be the value for Linux.
The TASK_IS_TASKLET() macro was moved to the proto file instead of the
type one. The proto part was a bit reordered to remove a number of ugly
forward declaration of static inline functions. About a tens of C and H
files had their dependency dropped since they were not using anything
from task.h.
global.h was one of the messiest files, it has accumulated tons of
implicit dependencies and declares many globals that make almost all
other file include it. It managed to silence a dependency loop between
server.h and proxy.h by being well placed to pre-define the required
structs, forcing struct proxy and struct server to be forward-declared
in a significant number of files.
It was split in to, one which is the global struct definition and the
few macros and flags, and the rest containing the functions prototypes.
The UNIX_MAX_PATH definition was moved to compat.h.
