Merge pull request #37 from dynatrace-oss/fix_failing_rtt_offset

Fix failing rtt offset

CMakeLists.txt

@@ -25,6 +25,7 @@ set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
 set(CMAKE_VERBOSE_MAKEFILE TRUE)
 set(CMAKE_CXX_EXTENSIONS FALSE)
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 if(DEFINED CONAN_DEPS)
     include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)

bpf_program/probes/connections.h

@@ -47,7 +47,7 @@ int kretprobe__tcp_v4_connect(struct pt_regs *ctx)
 	}
 
 	status = bpf_map_lookup_elem(&nettracer_status, &zero);
-	if (status == NULL || status->state != GUESS_STATE_READY) {
+	if (status == NULL) {
 		return 0;
 	}
 
@@ -151,7 +151,7 @@ int kretprobe__inet_csk_accept(struct pt_regs *ctx)
 		return 0;
 
 	status = bpf_map_lookup_elem(&nettracer_status, &zero);
-	if (status == NULL || status->state != GUESS_STATE_READY) {
+	if (status == NULL) {
 		return 0;
 	}
 
@@ -219,7 +219,7 @@ int kprobe__tcp_close(struct pt_regs *ctx)
 	sk = (struct sock *) PT_REGS_PARM1(ctx);
 
 	status = bpf_map_lookup_elem(&nettracer_status, &zero);
-	if (status == NULL || status->state != GUESS_STATE_READY) {
+	if (status == NULL) {
 		return 0;
 	}
 

bpf_program/probes/metrics.h

@@ -19,7 +19,7 @@ static int send_metric(struct sock* sk, int32_t bytes_sent) {
 	struct guess_status_t* status;
 	uint32_t zero = 0;
 	status = bpf_map_lookup_elem(&nettracer_status, &zero);
-	if (status == NULL || status->state != GUESS_STATE_READY) {
+	if (status == NULL) {
 		return 0;
 	}
 
@@ -96,7 +96,7 @@ int kprobe__tcp_cleanup_rbuf(struct pt_regs* ctx) {
 	struct guess_status_t *status;
 	uint32_t zero = 0;
 	status = bpf_map_lookup_elem(&nettracer_status, &zero);
-	if (status == NULL || status->state != GUESS_STATE_READY) {
+	if (status == NULL) {
 		return 0;
 	}
 
@@ -137,7 +137,7 @@ int kprobe__tcp_retransmit_skb(struct pt_regs* ctx) {
 	struct guess_status_t *status;
 	uint32_t zero = 0;
 	status = bpf_map_lookup_elem(&nettracer_status, &zero);
-	if (status == NULL || status->state != GUESS_STATE_READY) {
+	if (status == NULL) {
 		return 0;
 	}
 

bpf_program/tuples_utilities.h

@@ -21,7 +21,7 @@ static bool check_family(struct sock *sk, uint16_t expected_family) {
 	family = 0;
 
 	status = bpf_map_lookup_elem(&nettracer_status, &zero);
-	if (status == NULL || status->state != GUESS_STATE_READY) {
+	if (status == NULL) {
 		return 0;
 	}
 

libnettracer/src/offsetguess.cpp

@@ -64,7 +64,7 @@ bool OffsetGuessing::makeGuessingAttempt(int status_fd) {
 	// which in turn are called in kretprobe tcp_v(4|6)_connect
 
 	uint64_t pid_tgid = (uint64_t)getpid() << 32 | syscall(SYS_gettid);
-	logger->debug("guess thread pid: {:d}", pid_tgid);
+	logger->trace("guess thread pid: {:d}", pid_tgid);
 
 	// prepare server ipv4 and client ipv6 on this thread
 	localsock = startLocalSock();
@@ -107,7 +107,6 @@ bool OffsetGuessing::makeGuessingAttempt(int status_fd) {
 
 	// limit how many failed attempts at communicating with the BPF side are accepted
 	int maxRetries = 100;
-
 	unsigned rttCurrentAttempts = 0;
 	unsigned rttCurrentReps = 0;
 
@@ -208,13 +207,14 @@ bool OffsetGuessing::makeGuessingAttempt(int status_fd) {
 			return false;
 		}
 	}
+	logger->debug("offsets status: {:d}", status.what);
 	return true;
 }
 
 template<typename T>
 void OffsetGuessing::guessSimpleField(T& statusValue, const T& expectedValue, uint16_t& offset, guess_status_t& status, const std::string& fieldStr, const guess_field& next) {
 	if (statusValue == expectedValue) {
-		logger->debug("{} offset: {:#010x}", fieldStr, offset);
+		logger->info("{} offset: {:#010x}", fieldStr, offset);
 		status.what = next;
 	}
 	else {
@@ -226,7 +226,7 @@ void OffsetGuessing::guessSimpleField(T& statusValue, const T& expectedValue, ui
 
 void OffsetGuessing::guessNetns() {
 	if (status.netns == expected.netns) {
-		logger->debug("Network namespace offset: {:#010x}", status.offset_netns);
+		logger->info("Network namespace offset: {:#010x}", status.offset_netns);
 		status.what = GUESS_FIELD_DADDR_IPV6;
 	} else {
 		++status.offset_ino;
@@ -264,28 +264,23 @@ bool OffsetGuessing::guessRTT(unsigned& currentAttempts, unsigned& currentReps,
 	const unsigned maxAttempts = 10; // that many offsets may be verified
 	const unsigned requiredReps = 3; // value at an offset must match with the expected value at least that many times in a row
 
-	if (status.rtt == expected.rtt && status.rtt_var == expected.rtt_var) {
+	if (status.rtt == expected.rtt) {
 		if (++currentReps == requiredReps) {
-			logger->debug("RTT offset: {:#010x}", status.offset_rtt);
-			logger->debug("RTT var offset: {:#010x}", status.offset_rtt_var);
+			logger->info("RTT offset: {:#010x}", status.offset_rtt);
+			logger->info("RTT var offset: {:#010x}", status.offset_rtt_var);
 			status.state = GUESS_STATE_READY;
 		} else {
 			// reload expected RTT
 			if (!localsock->stopClient() || !localsock->startClient()) {
 				logger->error("Couldn't restart client for RTT guessing");
 				return false;
 			}
-			try {
-				auto expectedOpt{getExpectedValues(skipIPv6)};
-				if (!expectedOpt) {
-					return false;
-				}
-				expected = *expectedOpt;
-			}
-			catch (const std::runtime_error& ex) {
-				logger->error(ex.what());
+			auto expectedOpt{getExpectedValues(skipIPv6)};
+			if (!expectedOpt) {
 				return false;
 			}
+			logger->debug("Updating expected RTT: {:d},{:d} -> {:d},{:d} ", expected.rtt, expected.rtt_var, expectedOpt->rtt, expectedOpt->rtt_var);
+			expected = *expectedOpt;
 			status.rtt = expected.rtt;
 			status.rtt_var = expected.rtt_var;
 			status.state = GUESS_STATE_CHECKING;
@@ -307,6 +302,7 @@ bool OffsetGuessing::guessRTT(unsigned& currentAttempts, unsigned& currentReps,
 		status.rtt = expected.rtt;
 		status.rtt_var = expected.rtt_var;
 		status.state = GUESS_STATE_CHECKING;
+		logger->trace("current RTT offset: {:d}", status.offset_rtt);
 	}
 	return true;
 }

version.properties

@@ -1 +1 @@
-version=1.1.10
+version=1.1.11