This adds new "hold" timers : nx, refused, timeout, other. This timers
will be used to tell HAProxy to keep an erroneous response as valid for
the corresponding period. For now they're only configured, not enforced.
To avoid issues when porting code to some architecture, we need to know
the endianess the structures are currently used.
This patch simply had a short notice before those structures to report
endianess and ease contributor's job.
New DNS response parser function which turn the DNS response from a
network buffer into a DNS structure, much easier for later analysis
by upper layer.
Memory is pre-allocated at start-up in a chunk dedicated to DNS
response store.
New error code to report a wrong number of queries in a DNS response.
struct dns_query_item: describes a DNS query record
struct dns_answer_item: describes a DNS answer record
struct dns_response_packet: describes a DNS response packet
DNS_MIN_RECORD_SIZE: minimal size of a DNS record
DNS_MAX_QUERY_RECORDS: maximum number of query records we allow.
For now, we send one DNS query per request.
DNS_MAX_ANSWER_RECORDS: maximum number of records we may found in a
response
WIP dns: new MAX values
Current implementation of HAProxy's DNS resolution expect only 512 bytes
of data in the response.
Update DNS_MAX_UDP_MESSAGE to match this.
Backport: can be backported to 1.6
Alexander Lebedev reported that the response bit is set on SPARC when
DNS queries are sent. This has been tracked to the endianess issue, so
this patch makes the code portable.
Signed-off-by: Nenad Merdanovic <nmerdan@anine.io>
DNS requests (using the internal resolver) are corrupted since commit
e2f8497716 ("BUG/MINOR: dns: fix DNS header definition").
Fix it by defining the struct in network byte order, while complying
with RFC 2535, section 6.1.
First reported by Eduard Vopicka on discourse.
This must be backported to 1.6 (1.6.5 is affected).
Conforming to RFC 2535, section 6.1. This is not an important bug as
those fields don't seem to be set to something else than 0 and to be
checked on answers.
This options prioritize th choice of an ip address matching a network. This is
useful with clouds to prefer a local ip. In some cases, a cloud high
avalailibility service can be announced with many ip addresses on many
differents datacenters. The latency between datacenter is not negligible, so
this patch permitsto prefers a local datacenter. If none address matchs the
configured network, another address is selected.
DNS selection preferences are actually declared inline in the
struct server. There are copied from the server struct to the
dns_resolution struct for each resolution.
Next patchs adds new preferences options, and it is not a good
way to copy all the configuration information before each dns
resolution.
This patch extract the configuration preference from the struct
server and declares a new dedicated struct. Only a pointer to this
new striuict will be copied before each dns resolution.
Basically, it's ill-defined and shouldn't really be used going forward.
We can't guarantee that resolvers will do the 'legwork' for us and
actually resolve CNAMES when we request the ANY query-type. Case in point
(obfuscated, clearly):
PRODUCTION! ahayworth@secret-hostname.com:~$
dig @10.11.12.53 ANY api.somestartup.io
; <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> @10.11.12.53 ANY api.somestartup.io
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62454
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 0
;; QUESTION SECTION:
;api.somestartup.io. IN ANY
;; ANSWER SECTION:
api.somestartup.io. 20 IN CNAME api-somestartup-production.ap-southeast-2.elb.amazonaws.com.
;; AUTHORITY SECTION:
somestartup.io. 166687 IN NS ns-1254.awsdns-28.org.
somestartup.io. 166687 IN NS ns-1884.awsdns-43.co.uk.
somestartup.io. 166687 IN NS ns-440.awsdns-55.com.
somestartup.io. 166687 IN NS ns-577.awsdns-08.net.
;; Query time: 1 msec
;; SERVER: 10.11.12.53#53(10.11.12.53)
;; WHEN: Mon Oct 19 22:02:29 2015
;; MSG SIZE rcvd: 242
HAProxy can't handle that response correctly.
Rather than try to build in support for resolving CNAMEs presented
without an A record in an answer section (which may be a valid
improvement further on), this change just skips ANY record types
altogether. A and AAAA are much more well-defined and predictable.
Notably, this commit preserves the implicit "Prefer IPV6 behavior."
Furthermore, ANY query type by default is a bad idea: (from Robin on
HAProxy's ML):
Using ANY queries for this kind of stuff is considered by most people
to be a bad practice since besides all the things you named it can
lead to incomplete responses. Basically a resolver is allowed to just
return whatever it has in cache when it receives an ANY query instead
of actually doing an ANY query at the authoritative nameserver. Thus
if it only received queries for an A record before you do an ANY query
you will not get an AAAA record even if it is actually available since
the resolver doesn't have it in its cache. Even worse if before it
only got MX queries, you won't get either A or AAAA
Some DNS response may be valid from a protocol point of view but may not
contain any IP addresses.
This patch gives a new flag to the function dns_get_ip_from_response to
report such case.
It's up to the upper layer to decide what to do with this information.
Some DNS responses may be valid from a protocol point of view, but may
not contain any information considered as interested by the requester..
Purpose of the flag DNS_RESP_NO_EXPECTED_RECORD introduced by this patch is
to allow reporting such situation.
When this happens, a new DNS query is sent with a new query type.
For now, the function only expect A and AAAA query types which is enough
to cover current cases.
In a next future, it will be up to the caller to tell the function which
query types are expected.
This patch introduces a new internal response state about the analysis
of a DNS response received by a server.
It is dedicated to report to above layer that the response is
'truncated'.
This patch updates the dns_nameserver structure to integrate a counter
dedicated to 'truncated' response sent by servers.
Such response are important to track, since HAProxy is supposed to
replay its request.
Current DNS client code implementation doesn't take care of response
flags setup by the server.
This patch introduces a couple of bitmasks one can use to retrieve the
truncated flag and the reply code available in the 2-bytes flag field.
3 variables of the dns_resolution structure are set to 'time_t' type.
Since they are all set by 'now_ms' and used as 'ticks' in HAProxy's
internal, it is safer to set them to the same type than now_ms:
'unsigned int'.
Implementation of a DNS client in HAProxy to perform name resolution to
IP addresses.
It relies on the freshly created UDP client to perform the DNS
resolution. For now, all UDP socket calls are performed in the
DNS layer, but this might change later when the protocols are
extended to be more suited to datagram mode.
A new section called 'resolvers' is introduced thanks to this patch. It
is used to describe DNS servers IP address and also many parameters.
