rx_arping handle sigchld (#691)

* rx_arping pclose gave -1 due to sigchld being ignored, fixed with sig handler doing a wait

RELEASE.txt

@@ -30,6 +30,7 @@ This document describes the differences between v7.x.x and v7.0.0
 
 - moench being made compatible with jungfrau 2.0 boards (jungfrau structure, away from ctb)
 - eiger febl and feb in versions
+- fixed rx_arping error
 - fix hdf5 compilation (detspec fields)
 
 

slsReceiverSoftware/src/Arping.cpp

@@ -7,6 +7,7 @@
 #include <signal.h>
 #include <thread>
 #include <unistd.h>
+#include<sys/wait.h>
 
 namespace sls {
 
@@ -16,6 +17,10 @@ namespace sls {
 #define gettid() syscall(SYS_gettid)
 #endif
 
+void func(int signum) {
+    wait(NULL);
+}
+
 Arping::Arping() {}
 
 Arping::~Arping() {
@@ -44,10 +49,11 @@ pid_t Arping::GetProcessId() const { return childPid; }
 bool Arping::IsRunning() const { return runningFlag; }
 
 void Arping::StartProcess() {
-    TestCommands();
-
     // to prevent zombies from child processes being killed
-    signal(SIGCHLD, SIG_IGN);
+    signal(SIGCHLD, func);
+
+    // test once to throw exception if arping failed
+    TestForErrors();
 
     // Needs to be a fork and udp socket deleted after Listening threads
     // done running to prevent udp socket cannot bind because of popen
@@ -90,7 +96,7 @@ void Arping::ProcessExecution() {
     }
 }
 
-void Arping::TestCommands() {
+void Arping::TestForErrors() {
     // atleast one interface must be set up
     if (commands[0].empty()) {
         throw RuntimeError(
@@ -116,7 +122,7 @@ std::string Arping::ExecuteCommands() {
         FILE *sysFile = popen(cmd.c_str(), "r");
         if (sysFile == NULL) {
             std::ostringstream os;
-            os << "Could not Arping [" << cmd << " ] : Popen fail";
+            os << "Could not Arping (" << cmd << " ) : Popen fail (" << strerror(errno) << ')';
             return os.str();
         }
 
@@ -128,7 +134,7 @@ std::string Arping::ExecuteCommands() {
         // check exit status of command
         if (pclose(sysFile)) {
             std::ostringstream os;
-            os << "Could not arping[" << cmd << "] : " << output;
+            os << "Could not arping (" << cmd << ") : " <<  strerror(errno);
             return os.str();
         } else {
             LOG(logDEBUG) << output;

slsReceiverSoftware/src/Arping.h

@@ -28,7 +28,7 @@ class Arping {
     void StopProcess();
 
   private:
-    void TestCommands();
+    void TestForErrors();
     std::string ExecuteCommands();
     void ProcessExecution();