Commit Graph

21 Commits

Author SHA1 Message Date
Roman Arutyunyan
c8c44f7478 Resolver: per-request DNS server balancer.
Previously, a global server balancer was used to assign the next DNS server to
send a query to.  That could lead to a non-uniform distribution of servers per
request.  A request could be assigned to the same dead server several times in a
row and wait longer for a valid server or even time out without being processed.

Now each query is sent to all servers sequentially in a circle until a
response is received or timeout expires.  Initial server for each request is
still globally balanced.
2016-01-28 15:28:20 +03:00
Roman Arutyunyan
1945fff7bf Resolver: renamed UDP-specific structures, fields and variables.
They will be used for TCP connections as well.
2016-01-28 15:28:20 +03:00
Roman Arutyunyan
52d3601155 Resolver: removed unused field from ngx_resolver_ctx_t. 2016-01-28 15:28:19 +03:00
Roman Arutyunyan
a3d42258d9 Resolver: fixed use-after-free memory accesses with CNAME.
When several requests were waiting for a response, then after getting
a CNAME response only the last request's context had the name updated.
Contexts of other requests had the wrong name.  This name was used by
ngx_resolve_name_done() to find the node to remove the request context
from.  When the name was wrong, the request could not be properly
cancelled, its context was freed but stayed linked to the node's waiting
list.  This happened e.g. when the first request was aborted or timed
out before the resolving completed.  When it completed, this triggered
a use-after-free memory access by calling ctx->handler of already freed
request context.  The bug manifests itself by
"could not cancel <name> resolving" alerts in error_log.

When a request was responded with a CNAME, the request context kept
the pointer to the original node's rn->u.cname.  If the original node
expired before the resolving timed out or completed with an error,
this would trigger a use-after-free memory access via ctx->name in
ctx->handler().

The fix is to keep ctx->name unmodified.  The name from context
is no longer used by ngx_resolve_name_done().  Instead, we now keep
the pointer to resolver node to which this request is linked.
Keeping the original name intact also improves logging.
2016-01-26 16:46:59 +03:00
Ruslan Ermilov
4b581a7c21 Resolver: fixed crashes in timeout handler.
If one or more requests were waiting for a response, then after
getting a CNAME response, the timeout event on the first request
remained active, pointing to the wrong node with an empty
rn->waiting list, and that could cause either null pointer
dereference or use-after-free memory access if this timeout
expired.

If several requests were waiting for a response, and the first
request terminated (e.g., due to client closing a connection),
other requests were left without a timeout and could potentially
wait indefinitely.

This is fixed by introducing per-request independent timeouts.
This change also reverts 954867a2f0a6 and 5004210e8c78.
2016-01-26 16:46:31 +03:00
Ruslan Ermilov
ef563debf1 Resolver: fixed debug event logging.
In 954867a2f0a6, we switched to using resolver node as the timer event data.
This broke debug event logging.

Replaced now unused ngx_resolver_ctx_t.ident with ngx_resolver_node_t.ident
so that ngx_event_ident() extracts something sensible when accessing
ngx_resolver_node_t as ngx_connection_t.
2014-11-20 15:24:42 +03:00
Ruslan Ermilov
e0caf51711 The "ipv6=" boolean parameter of the "resolver" directive.
When set to "off", only IPv4 addresses will be resolved,
and no AAAA queries are ever sent.
2013-12-09 10:53:30 +04:00
Ruslan Ermilov
769eded732 Resolver: implemented IPv6 name to address resolving. 2013-12-09 10:53:28 +04:00
Ruslan Ermilov
809bee30b7 Resolver: implemented IPv6 address to name resolving. 2013-12-06 14:30:28 +04:00
Ruslan Ermilov
3aeefbcaea Changed resolver API to use ngx_addr_t. 2013-12-06 14:30:27 +04:00
Maxim Konovalov
f8d59e33f3 Copyright updated. 2012-01-18 15:07:43 +00:00
Igor Sysoev
620718102b Support of several servers in the "resolver" directive.
Patch by Kirill A. Korinskiy.
2011-10-24 16:09:05 +00:00
Igor Sysoev
089b2fd31e add context to a resolver log 2010-01-11 11:01:02 +00:00
Igor Sysoev
0c189c5159 rename ngx_peer_addr_t to ngx_addr_t 2009-11-02 15:14:17 +00:00
Igor Sysoev
a8372d8a84 limit CNAME recursion 2008-04-12 07:29:20 +00:00
Igor Sysoev
19540cd83e take into account DNAME 2008-04-10 17:12:21 +00:00
Igor Sysoev
dfd5511f7a use cf->cycle->new_log because at merge stage cf->pool->log is old log 2008-03-04 10:42:05 +00:00
Igor Sysoev
4491daef30 cleanup resolver 2008-02-28 20:38:34 +00:00
Igor Sysoev
8ee01f5cb8 static ngx_resolver_calloc() 2008-02-28 15:34:53 +00:00
Igor Sysoev
6b2fce430b allow to use IP addresses without defined resolver 2007-12-03 10:05:19 +00:00
Igor Sysoev
cb4d53861c resolver 2007-11-23 17:13:26 +00:00