Simulate Packet API

Summary: Exposing simulator generic packet processing via API.

Reviewed By: frankfeir, tagrawal03

Differential Revision: D68521022

fbshipit-source-id: aca506c6b4c4eece63781ad2f86c22f699200f9c

katran/lib/KatranLb.cpp

@@ -2265,6 +2265,23 @@ std::unordered_map<uint32_t, std::string> KatranLb::getHealthcheckersDst() {
   return hcs;
 }
 
+std::string KatranLb::simulatePacket(const std::string& inPacket) {
+  std::string result;
+  if (!progsLoaded_) {
+    LOG(ERROR) << "bpf programs are not loaded";
+    return result;
+  }
+  auto inBuf = folly::IOBuf::copyBuffer(inPacket);
+  auto sim = KatranSimulator(getKatranProgFd());
+  auto outBuf = sim.runSimulation(std::move(inBuf));
+  if (!outBuf) {
+    LOG(ERROR) << "simulator failed to run simulation";
+    return result;
+  }
+  result = outBuf->moveToFbString().toStdString();
+  return result;
+}
+
 const std::string KatranLb::getRealForFlow(const KatranFlow& flow) {
   if (!progsLoaded_) {
     LOG(ERROR) << "bpf programs are not loaded";

katran/lib/KatranLb.h

@@ -732,6 +732,18 @@ class KatranLb {
    */
   KatranBpfMapStats getBpfMapStats(const std::string& map);
 
+  /*
+   * @param inPacket binary data of the packet, including Ethernet header and up
+   * @return binary data of the packet after it was processed by Katran
+   *
+   * Processes given packet thru Katran BPF and returns the resulting packet.
+   * Note that while the packet is not going thru actual networking stack, it
+   * is processed by the same BPF program and affects it's state (like maps,
+   * stats, etc).
+
+   */
+  std::string simulatePacket(const std::string& inPacket);
+
   /**
    * @param KatranFlow 5 tuple which describes a flow
    * @return string address of the real.

katran/lib/KatranSimulator.cpp

@@ -215,6 +215,18 @@ KatranSimulator::~KatranSimulator() {}
 
 std::unique_ptr<folly::IOBuf> KatranSimulator::runSimulation(
     std::unique_ptr<folly::IOBuf> pckt) {
+  if (!pckt) {
+    LOG(ERROR) << "packet is empty";
+    return nullptr;
+  }
+  if (pckt->isChained()) {
+    LOG(ERROR) << "Chained buffers are not supported";
+    return nullptr;
+  }
+  if (pckt->length() > kMaxXdpPcktSize) {
+    LOG(ERROR) << "packet is too big";
+    return nullptr;
+  }
   auto rpckt = folly::IOBuf::create(kMaxXdpPcktSize);
   if (!rpckt) {
     LOG(ERROR) << "not able to allocate memory for resulting packet";
@@ -226,7 +238,7 @@ std::unique_ptr<folly::IOBuf> KatranSimulator::runSimulation(
       progFd_,
       kTestRepeatCount,
       pckt->writableData(),
-      pckt->computeChainDataLength(),
+      pckt->length(),
       rpckt->writableData(),
       &output_pckt_size,
       &prog_ret_val);

katran/lib/KatranSimulator.h

@@ -59,12 +59,13 @@ class KatranSimulator final {
    */
   const std::string getRealForFlow(const KatranFlow& flow);
 
- private:
   // runSimulation takes packet (in iobuf represenation) and
   // run it through katran bpf program. It returns a modified pckt, if the
   // result was XDP_TX or nullptr otherwise.
   std::unique_ptr<folly::IOBuf> runSimulation(
       std::unique_ptr<folly::IOBuf> pckt);
+
+ private:
   int progFd_;
 };
 } // namespace katran