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Refactor DNS script's state management to improve performance.

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The amount of timers involved in DNS::PendingMessage tables'
expiration attributes have a significant performance hit.  Instead the
script now relies solely on maximum thresholds for pending message
quantities to limit amount of accumulated state.  There's a new option,
"DNS::max_pending_query_ids", to limit the number outstanding messages
across all DNS query IDs ("DNS::max_pending_msgs" still limits number
of outstanding messages for a *given* query ID).
This commit is contained in:
Jon Siwek 2014-02-13 14:55:45 -06:00
parent f45bd84f4c
commit 3c95d1d695
2 changed files with 33 additions and 36 deletions
Download patch file Download diff file Expand all files Collapse all files

60
scripts/base/protocols/dns/main.bro
View file

@ -109,16 +109,6 @@ export {
## DNS message query/transaction ID.
type PendingMessages: table[count] of Queue::Queue;
## Called when a pending DNS query has not been matched with a reply (or
## vice versa) in a sufficent amount of time.
##
## pending: table of pending messages, indexed by transaction ID.
##
## id: the index of he element being expired.
##
## Returns: amount of time to delay expiration of the element.
global expire_pending_msg: function(pending: PendingMessages, id: count): interval;
## The amount of time that DNS queries or replies for a given
## query/transaction ID are allowed to be queued while waiting for
## a matching reply or query.
@ -131,16 +121,21 @@ export {
## response is ongoing).
const max_pending_msgs = 50 &redef;
## Give up trying to match pending DNS queries or replies across all
## query/transaction IDs once there is at least one unmatched query or
## reply across this number of different query IDs.
const max_pending_query_ids = 50 &redef;
## A record type which tracks the status of DNS queries for a given
## :bro:type:`connection`.
type State: record {
## Indexed by query id, returns Info record corresponding to
## queries that haven't been matched with a response yet.
pending_queries: PendingMessages &read_expire=pending_msg_expiry_interval &expire_func=expire_pending_msg;
pending_queries: PendingMessages;
## Indexed by query id, returns Info record corresponding to
## replies that haven't been matched with a query yet.
pending_replies: PendingMessages &read_expire=pending_msg_expiry_interval &expire_func=expire_pending_msg;
pending_replies: PendingMessages;
};
}
@ -176,8 +171,12 @@ function log_unmatched_msgs_queue(q: Queue::Queue)
Queue::get_vector(q, infos);
for ( i in infos )
{
event flow_weird("dns_unmatched_msg",
infos[i]$id$orig_h, infos[i]$id$resp_h);
Log::write(DNS::LOG, infos[i]);
}
}
function log_unmatched_msgs(msgs: PendingMessages)
{
@ -191,16 +190,28 @@ function log_unmatched_msgs(msgs: PendingMessages)
function enqueue_new_msg(msgs: PendingMessages, id: count, msg: Info)
{
if ( id !in msgs )
msgs[id] = Queue::init();
else if ( Queue::len(msgs[id]) > max_pending_msgs )
{
local info: Info = Queue::peek(msgs[id]);
event flow_weird("dns_unmatched_msg_quantity", info$id$orig_h,
info$id$resp_h);
if ( |msgs| > max_pending_query_ids )
{
event flow_weird("dns_unmatched_query_id_quantity",
msg$id$orig_h, msg$id$resp_h);
# Throw away all unmatched on assumption they'll never be matched.
log_unmatched_msgs(msgs);
}
msgs[id] = Queue::init();
}
else
{
if ( Queue::len(msgs[id]) > max_pending_msgs )
{
event flow_weird("dns_unmatched_msg_quantity",
msg$id$orig_h, msg$id$resp_h);
log_unmatched_msgs_queue(msgs[id]);
# Throw away all unmatched on assumption they'll never be matched.
msgs[id] = Queue::init();
}
}
Queue::put(msgs[id], msg);
}
@ -447,18 +458,3 @@ event connection_state_remove(c: connection) &priority=-5
log_unmatched_msgs(c$dns_state$pending_queries);
log_unmatched_msgs(c$dns_state$pending_replies);
}
function expire_pending_msg(pending: PendingMessages, id: count): interval
{
local infos: vector of Info;
Queue::get_vector(pending[id], infos);
for ( i in infos )
{
Log::write(DNS::LOG, infos[i]);
event flow_weird("dns_unmatched_msg", infos[i]$id$orig_h,
infos[i]$id$resp_h);
}
return 0sec;
}

5
testing/btest/Baseline/scripts.base.protocols.dns.duplicate-reponses/weird.log
View file

@ -3,9 +3,10 @@
#empty_field (empty)
#unset_field -
#path weird
#open 2013-08-26-19-36-33
#open 2014-02-13-20-36-35
#fields ts uid id.orig_h id.orig_p id.resp_h id.resp_p name addl notice peer
#types time string addr port addr port string string bool string
1363716396.798286 CXWv6p3arKYeMETxOg 55.247.223.174 27285 222.195.43.124 53 DNS_RR_unknown_type - F bro
1363716396.798374 CXWv6p3arKYeMETxOg 55.247.223.174 27285 222.195.43.124 53 dns_unmatched_reply - F bro
#close 2013-08-26-19-36-33
1363716396.798374 - - - - - dns_unmatched_msg - F bro
#close 2014-02-13-20-36-35