Remove bpf_ktime from simplebridge and use custom thread

This commit removes the bpf_ktime() helper from the Simplebridge
used to remove old entries from the filtering database.
This helper introduces a performance degradation that could be removed
by using a custom thread that updates a percpu map with the timestamp
at the same way it is done in the Iptables service.

Signed-off-by: Sebastiano Miano <mianosebastiano@gmail.com>

src/services/pcn-simplebridge/src/FdbEntry.cpp

@@ -28,7 +28,7 @@ FdbEntry::FdbEntry(Fdb &parent, const FdbEntryJsonObject &conf): parent_(parent)
   logger()->info("Creating FdbEntry instance");
 }
 
-FdbEntry::FdbEntry(Fdb &parent, const std::string &address, uint64_t entry_age, uint32_t out_port) :
+FdbEntry::FdbEntry(Fdb &parent, const std::string &address, uint32_t entry_age, uint32_t out_port) :
 parent_(parent), address_(address), entry_age_(entry_age), port_no_(out_port)
 {
   auto port = parent.parent_.get_port(port_no_);
@@ -74,12 +74,10 @@ void FdbEntry::create(Fdb &parent, const std::string &address, const FdbEntryJso
 
   struct timespec now_timespec;
   clock_gettime(CLOCK_MONOTONIC, &now_timespec);
-  const uint64_t SEC2NANOSEC = 1000000000ULL;
-  uint64_t now = now_timespec.tv_sec*SEC2NANOSEC + now_timespec.tv_nsec;
 
   uint64_t key = utils::mac_string_to_be_uint(address);
   fwd_entry value {
-    .timestamp = now,
+    .timestamp = (uint32_t) now_timespec.tv_sec,
     .port = port_index,
   };
 
@@ -97,22 +95,21 @@ std::shared_ptr<FdbEntry> FdbEntry::constructFromMap(Fdb &parent, const std::str
                                                      const fwd_entry &value) {
   struct timespec now_timespec;
   clock_gettime(CLOCK_MONOTONIC, &now_timespec);
-  const uint64_t SEC2NANOSEC = 1000000000ULL;
-  uint64_t now = now_timespec.tv_sec*SEC2NANOSEC + now_timespec.tv_nsec;
+  uint32_t now = now_timespec.tv_sec;
 
   uint64_t key = utils::mac_string_to_be_uint(address);
-  uint64_t timestamp = value.timestamp;
+  uint32_t timestamp = value.timestamp;
 
   //Here I'm going to check if the entry in the filtering database is too old.\
   //In this case, I'll not show the entry
-  if ((now - timestamp) > parent.getAgingTime()*SEC2NANOSEC) {
+  if ((now - timestamp) > parent.getAgingTime()) {
     parent.logger()->debug("Ignoring old entry: now {0}, last_seen: {1}",
-      now/SEC2NANOSEC, timestamp/SEC2NANOSEC);
+      now, timestamp);
     auto fwdtable =  parent.parent_.get_hash_table<uint64_t, fwd_entry>("fwdtable");
     fwdtable.remove(key);
     return nullptr;
   }
-  uint64_t entry_age = (now - timestamp)/SEC2NANOSEC;
+  uint32_t entry_age = now - timestamp;
   uint32_t port_no = value.port;
   return std::make_shared<FdbEntry>(parent, address, entry_age, port_no);
 }

src/services/pcn-simplebridge/src/FdbEntry.h

@@ -27,7 +27,7 @@ class Fdb;
 
 /* definitions copied from datapath */
 struct fwd_entry {
-  uint64_t timestamp;
+  uint32_t timestamp;
   uint32_t port;
 } __attribute__((packed));
 
@@ -36,7 +36,7 @@ using namespace io::swagger::server::model;
 class FdbEntry : public FdbEntryInterface {
 public:
   FdbEntry(Fdb &parent, const FdbEntryJsonObject &conf);
-  FdbEntry(Fdb &parent, const std::string &address, uint64_t entry_age, uint32_t out_port);
+  FdbEntry(Fdb &parent, const std::string &address, uint32_t entry_age, uint32_t out_port);
   virtual ~FdbEntry();
 
   static void create(Fdb &parent, const std::string &address, const FdbEntryJsonObject &conf);
@@ -77,7 +77,7 @@ class FdbEntry : public FdbEntryInterface {
 
   std::string address_;
   std::string port_name_;
-  uint64_t entry_age_;
+  uint32_t entry_age_;
   uint32_t port_no_;
 };
 

src/services/pcn-simplebridge/src/Simplebridge.cpp

@@ -23,23 +23,57 @@
 
 #include <tins/ethernetII.h>
 #include <tins/tins.h>
+#include <thread>
 
 using namespace Tins;
 
 Simplebridge::Simplebridge(const std::string name, const SimplebridgeJsonObject &conf, CubeType type)
-                             : Cube(name, {generate_code()}, {}, type, conf.getPolycubeLoglevel()) {
+                             : Cube(name, {generate_code()}, {}, type, conf.getPolycubeLoglevel()),
+                             quit_thread_(false) {
   logger()->set_pattern("[%Y-%m-%d %H:%M:%S.%e] [Simplebridge] [%n] [%l] %v");
   logger()->info("Creating Simplebridge instance");
 
   addFdb(conf.getFdb());
   addPortsList(conf.getPorts());
+
+  timestamp_update_thread_ = std::thread(&Simplebridge::updateTimestampTimer, this);
 }
 
 Simplebridge::~Simplebridge() {
   // we are destroying this service, prepare for it.
+  quitAndJoin();
   Cube::dismount();
 }
 
+void Simplebridge::quitAndJoin() {
+  quit_thread_ = true;
+  timestamp_update_thread_.join();
+}
+
+void Simplebridge::updateTimestampTimer() {
+  do {
+    sleep(1);
+    updateTimestamp();
+  } while (!quit_thread_);
+}
+
+/*
+ * This method is in charge of updating the timestamp table
+ * that is used in the dataplane to avoid calling the bpf_ktime helper
+ * that introduces a non-negligible overhead to the eBPF program.
+ */
+void Simplebridge::updateTimestamp() {
+  try {
+    // get timestamp from system
+    struct timespec now_timespec;
+    clock_gettime(CLOCK_MONOTONIC, &now_timespec);
+    auto timestamp_table = get_array_table<uint32_t>("timestamp");
+    timestamp_table.set(0, now_timespec.tv_sec);
+  } catch (...) {
+    logger()->error("Error while updating the timestamp table");
+  }
+}
+
 void Simplebridge::update(const SimplebridgeJsonObject &conf) {
   //This method updates all the object/parameter in Simplebridge object specified in the conf JsonObject.
   //You can modify this implementation.
@@ -141,4 +175,3 @@ void Simplebridge::reloadCodeWithAgingtime(uint32_t aging_time) {
 
 
 
-

src/services/pcn-simplebridge/src/Simplebridge.h

@@ -25,6 +25,7 @@
 #include "polycube/services/utils.h"
 
 #include <spdlog/spdlog.h>
+#include <thread>
 
 #include "Fdb.h"
 #include "Ports.h"
@@ -96,6 +97,13 @@ class Simplebridge : public polycube::service::Cube<Ports>, public SimplebridgeI
   std::unordered_map<std::string, Ports> ports_;
   std::shared_ptr<Fdb> fdb_ = nullptr;
 
+  void updateTimestamp();
+  void updateTimestampTimer();
+  void quitAndJoin();
+
+  std::thread timestamp_update_thread_;
+  std::atomic<bool> quit_thread_;
+
   void flood_packet(Port &port, PacketInMetadata &md, const std::vector<uint8_t> &packet);
   std::mutex ports_mutex_;
 };

src/services/pcn-simplebridge/src/Simplebridge_dp.c

@@ -32,18 +32,28 @@
 #define REASON_FLOODING 0x01
 
 struct fwd_entry {
-  u64 timestamp;
+  u32 timestamp;
   u32 port;
-} __attribute__((packed));
+} __attribute__((packed, aligned(8)));
 
 BPF_TABLE("hash", __be64, struct fwd_entry, fwdtable, 1024);
+BPF_TABLE("array", int, uint32_t, timestamp, 1);
 
 struct eth_hdr {
   __be64   dst:48;
   __be64   src:48;
   __be16   proto;
 } __attribute__((packed));
 
+static __always_inline u32 time_get_sec() {
+  int key = 0;
+  u32 *ts = timestamp.lookup(&key);
+  if (ts)
+    return *ts;
+
+  return 0;
+}
+
 static __always_inline
 int handle_rx(struct CTXTYPE *ctx, struct pkt_metadata *md) {
   void *data = (void *)(long)ctx->data;
@@ -60,7 +70,7 @@ int handle_rx(struct CTXTYPE *ctx, struct pkt_metadata *md) {
 
   // LEARNING PHASE
   __be64 src_key = eth->src;
-  u64 now = bpf_ktime_get_ns();
+  u32 now = time_get_sec();
 
   struct fwd_entry e; // used to update the entry in the fdb
 
@@ -84,15 +94,7 @@ int handle_rx(struct CTXTYPE *ctx, struct pkt_metadata *md) {
   u64 timestamp = entry->timestamp;
 
   // Check if the entry is still valid (not too old)
-  // Warning: the bpf_ktime_get_ns() used before is not monotonic and it may return
-  //  a value that is older than a previously returned value. So, we have to add
-  //  the very strange check 'now < timestamp' to handle this special case
-  if (now < timestamp) {
-    pcn_log(ctx, LOG_TRACE, "Entry is valid (but 'now < timestamp'). FORWARDING");
-    goto FORWARD;
-  }
-
-  if ((now - timestamp) > FDB_TIMEOUT*1000000000ULL) {
+  if ((now - timestamp) > FDB_TIMEOUT) {
     pcn_log(ctx, LOG_TRACE, "Entry is too old. FLOODING");
     fwdtable.delete(&dst_mac);
     goto DO_FLOODING;