comm: ignore SIGPIPE

This prevents client and server from being sent a SIGPIPE (and
terminating) when the other side unexpectedly closes the connection.
It's way easier to handle this condition when checking the write()
return value, than to do anything smart in a SIGPIPE handler.  More
details:
<http://stackoverflow.com/questions/108183/how-to-prevent-sigpipes-or-handle-them-properly>

Change-Id: I1da5bf5ef79c8b7b00ede976e96ed4f1c560049d

src/core/comm/SocketComm.cc

@@ -1,10 +1,18 @@
 #include <string>
 #include <errno.h>
+#include <signal.h>
 
 #include "SocketComm.hpp"
 
 namespace fail {
 
+void SocketComm::init()
+{
+	// It's usually much easier to handle the error on write(), than to do
+	// anything intelligent in a SIGPIPE handler.
+	signal(SIGPIPE, SIG_IGN);
+}
+
 bool SocketComm::sendMsg(int sockfd, google::protobuf::Message& msg)
 {
 #ifdef USE_SIZE_PREFIX

src/core/comm/SocketComm.hpp

@@ -21,6 +21,10 @@ namespace fail {
 
 class SocketComm {
 public:
+	/**
+	 * This allows us to ignore SIGPIPE.
+	 */
+	static void init();
 	/**
 	 * Send Protobuf-generated message
 	 * @param sockfd open socket descriptor to write to