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Feature/limit tcp reassembly #662

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merged 3 commits into from
Apr 17, 2023
Merged

Feature/limit tcp reassembly #662

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e9034f3
Add limit to tcp reassembly to avoid memory growth
Apr 13, 2023
37f999e
Add unit test
Apr 13, 2023
404c056
rename pcap tcp reassembly config
Apr 17, 2023
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2 changes: 2 additions & 0 deletions RFCs/2021-04-16-76-collection-policies.md
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,8 @@ visor:
input_type: pcap
filter:
bpf: "port 53"
config:
tcp_packet_reassembly_cache_limit: 100000
# stream handlers to attach to this input stream
# these decide exactly which data to summarize and expose for collection
handlers:
Expand Down
33 changes: 33 additions & 0 deletions src/handlers/dns/v2/tests/test_dns_layer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -126,6 +126,39 @@ TEST_CASE("Parse DNS TCP IPv4 tests", "[pcap][ipv4][tcp][dns]")
CHECK(j["unknown"]["top_qname2_xacts"][0]["estimate"] == 210);
}

TEST_CASE("Parse DNS TCP tests with limit", "[pcap][ipv4][tcp][dns]")
{
PcapInputStream stream{"pcap-test"};
stream.config_set("pcap_file", "tests/fixtures/dns_ipv4_tcp.pcap");
stream.config_set("bpf", "");
stream.config_set<uint64_t>("tcp_packet_reassembly_cache_limit", 10);

visor::Config c;
auto stream_proxy = stream.add_event_proxy(c);
c.config_set<uint64_t>("num_periods", 1);
DnsStreamHandler dns_handler{"dns-test", stream_proxy, &c};

dns_handler.start();
stream.start();
dns_handler.stop();
stream.stop();

auto counters = dns_handler.metrics()->bucket(0)->counters(TransactionDirection::unknown);
auto event_data = dns_handler.metrics()->bucket(0)->event_data_locked();
json j;
dns_handler.metrics()->bucket(0)->to_json(j);

CHECK(event_data.num_events->value() == 140);
CHECK(counters.TCP.value() == 70);
CHECK(counters.IPv4.value() == 70);
CHECK(counters.IPv6.value() == 0);
CHECK(counters.xacts.value() == 70);
CHECK(counters.timeout.value() == 0);
CHECK(counters.orphan.value() == 0);
CHECK(j["unknown"]["top_qname2_xacts"][0]["name"] == ".test.com");
CHECK(j["unknown"]["top_qname2_xacts"][0]["estimate"] == 70);
}

TEST_CASE("Parse DNS UDP IPv6 tests", "[pcap][ipv6][udp][dns]")
{

Expand Down
27 changes: 21 additions & 6 deletions src/inputs/pcap/PcapInputStream.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,7 @@ static void _pcap_stats_update(pcpp::IPcapDevice::PcapStats &stats, void *cookie

PcapInputStream::PcapInputStream(const std::string &name)
: visor::InputStream(name)
, _lru_list(std::make_unique<LRUList<uint32_t, timeval>>(DEFAULT_LRULIST_SIZE))
, _pcapDevice(nullptr)
, _tcp_reassembly(_tcp_message_ready_cb,
this,
Expand All @@ -93,6 +94,10 @@ void PcapInputStream::start()

validate_configs(_config_defs);

if (config_exists("tcp_packet_reassembly_cache_limit")) {
auto limit = config_get<uint64_t>("tcp_packet_reassembly_cache_limit");
_lru_list = std::make_unique<LRUList<uint32_t, timeval>>(limit);
}
if (config_exists("pcap_file")) {
// read from pcap file. this is a special case from a command line utility
if (!config_exists("bpf")) {
Expand Down Expand Up @@ -252,7 +257,9 @@ void PcapInputStream::tcp_message_ready(int8_t side, const pcpp::TcpStreamData &
for (auto &proxy : _event_proxies) {
dynamic_cast<PcapInputEventProxy *>(proxy.get())->tcp_message_ready_cb(side, tcpData, _packet_dir_cache);
}
_lru_list.put(tcpData.getConnectionData().flowKey, tcpData.getConnectionData().endTime);
if (_lru_list->put(tcpData.getConnectionData().flowKey, tcpData.getConnectionData().endTime, &_deleted_data)){
_lru_overflow.push_back(_deleted_data.first);
}
}

void PcapInputStream::tcp_connection_start(const pcpp::ConnectionData &connectionData)
Expand All @@ -261,7 +268,9 @@ void PcapInputStream::tcp_connection_start(const pcpp::ConnectionData &connectio
for (auto &proxy : _event_proxies) {
dynamic_cast<PcapInputEventProxy *>(proxy.get())->tcp_connection_start_cb(connectionData, _packet_dir_cache);
}
_lru_list.put(connectionData.flowKey, connectionData.startTime);
if (_lru_list->put(connectionData.flowKey, connectionData.startTime, &_deleted_data)) {
_lru_overflow.push_back(_deleted_data.first);
}
}

void PcapInputStream::tcp_connection_end(const pcpp::ConnectionData &connectionData, pcpp::TcpReassembly::ConnectionEndReason reason)
Expand All @@ -270,7 +279,7 @@ void PcapInputStream::tcp_connection_end(const pcpp::ConnectionData &connectionD
for (auto &proxy : _event_proxies) {
static_cast<PcapInputEventProxy *>(proxy.get())->tcp_connection_end_cb(connectionData, reason);
}
_lru_list.eraseElement(connectionData.flowKey);
_lru_list->eraseElement(connectionData.flowKey);
}

void PcapInputStream::process_pcap_stats(const pcpp::IPcapDevice::PcapStats &stats)
Expand Down Expand Up @@ -438,15 +447,21 @@ void PcapInputStream::process_raw_packet(pcpp::RawPacket *rawPacket)
}

for (uint8_t counter = 0; counter < MAX_TCP_CLEANUPS; counter++) {
if (_lru_list.getSize() == 0) {
if (_lru_list->getSize() == 0) {
break;
}
auto connection = _lru_list.getLRUElement();
auto connection = _lru_list->getLRUElement();
if (timestamp.tv_sec < connection.second.tv_sec + TCP_TIMEOUT) {
break;
}
_tcp_reassembly.closeConnection(connection.first);
_lru_list.eraseElement(connection.first);
_lru_list->eraseElement(connection.first);
}
if (_lru_overflow.size() > 0) {
for (const auto &fKey : _lru_overflow) {
_tcp_reassembly.closeConnection(fKey);
}
_lru_overflow.clear();
}
} else {
// unsupported layer3 protocol
Expand Down
8 changes: 6 additions & 2 deletions src/inputs/pcap/PcapInputStream.h
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Original file line number Diff line number Diff line change
Expand Up @@ -96,9 +96,12 @@ class PcapInputStream : public visor::InputStream
private:
static constexpr uint8_t TCP_TIMEOUT = 30;
static constexpr uint8_t MAX_TCP_CLEANUPS = 100;
static constexpr size_t DEFAULT_LRULIST_SIZE = TCP_TIMEOUT * 10000;

static const PcapSource DefaultPcapSource = PcapSource::libpcap;
LRUList<uint32_t, timeval> _lru_list;
std::unique_ptr<LRUList<uint32_t, timeval>> _lru_list;
std::pair<uint32_t, timeval> _deleted_data;
std::vector<uint32_t> _lru_overflow;
lib::utils::IPv4subnetList _hostIPv4;
lib::utils::IPv6subnetList _hostIPv6;
PacketDirection _packet_dir_cache{PacketDirection::unknown};
Expand Down Expand Up @@ -127,7 +130,8 @@ class PcapInputStream : public visor::InputStream
"debug",
"host_spec",
"pcap_file",
"pcap_source"};
"pcap_source",
"tcp_packet_reassembly_cache_limit"};

protected:
void _open_pcap(const std::string &fileName, const std::string &bpfFilter);
Expand Down