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It's properly aligned and can hold any supported sockaddr.
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It is implied for "x" and "X".
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It hints the amount of time a response could be considered
as valid.
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Use the original query name in error and debug messages when
processing PTR responses.
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The previous code only parsed the first answer, without checking its
type, and required a compressed RR name.
The new code checks the RR type, supports responses with multiple
answers, and doesn't require the RR name to be compressed.
This has a side effect in limited support of CNAME. If a response
includes both CNAME and PTR RRs, like when recursion is enabled on
the server, PTR RR is handled.
Full CNAME support in PTR response is not implemented in this change.
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Renamed argument in ngx_resolver_process_a() for consistency.
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Found by Coverity (CID 1351175).
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Resend DNS query over TCP once UDP response came truncated.
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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.
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They will be used for TCP connections as well.
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Previously, the recursion was only limited for cached responses.
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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.
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No functional changes.
This is needed by the following change.
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When several requests were waiting for a response, then after getting
a CNAME response only the last request was properly processed, while
others were left waiting.
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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.
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This is specifically useful on graceful shutdown.
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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.
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In 954867a2f0a6, we switched to using resolver node as the
timer event data, so make sure we do not free resolver node
memory until the corresponding timer is deleted.
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It's mostly dead code. And the idea of thread support for this task has
been deprecated.
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If a "resolver_timeout" occurs, only the first waiting request
was notified. Other requests may hang forever.
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DNS request resend on malformed responses was broken in 98876ce2a7fd (1.5.8).
Reported by Pramod Korathota.
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If initial attempt to connect() the UDP socket failed, e.g.
due to network unreachable, no further attempts were made.
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When set to "off", only IPv4 addresses will be resolved,
and no AAAA queries are ever sent.
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Verify that class of RR is "IN".
Verify that RR data length is non-zero.
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Verify that class of RR is "IN".
Verify that RR data length is exactly four octets.
Correctly shift to the next RR if RR type is unknown.
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Stricten response header checks: ensure that reserved bits are zeroes,
and that the opcode is "standard query".
Fixed the "zero-length domain name in DNS response" condition.
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Renamed ngx_resolver_query_t to ngx_resolver_hdr_t as it describes
the header that is common to DNS queries and answers.
Replaced the magic number 12 by the size of the header structure.
The other changes are self-explanatory.
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Several warnings silenced, notably (ngx_socket_t) -1 is now checked
on socket operations instead of -1, as ngx_socket_t is unsigned on win32
and gcc complains on comparison.
With this patch, it's now possible to compile nginx using mingw gcc,
with options we normally compile on win32.
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This ensures balancing when working with dynamically resolved upstream
servers with multiple addresses.
Based on patch by Anton Jouline.
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Found by Coverity.
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resolved address was used. Now all addresses will be used.
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