TS-4796 Change UnixNetHandler to always bubble up epoll errors to the VConnection

Before if the vcon wasn't read or write enabled errors would be swallowed. This leads to a variety of issues where the socket errors aren't dealt with immediately.

Author: jacksontj

iocore/net/P_UnixNetVConnection.h

@@ -498,6 +498,10 @@ UnixNetVConnection::set_action(Continuation *c)
 // declarations for local use (within the net module)
 
 void close_UnixNetVConnection(UnixNetVConnection *vc, EThread *t);
+
+int read_signal_error(NetHandler *nh, UnixNetVConnection *vc, int lerrno);
+int write_signal_error(NetHandler *nh, UnixNetVConnection *vc, int lerrno);
+
 void write_to_net(NetHandler *nh, UnixNetVConnection *vc, EThread *thread);
 void write_to_net_io(NetHandler *nh, UnixNetVConnection *vc, EThread *thread);
 

iocore/net/UnixNet.cc

@@ -465,6 +465,17 @@ NetHandler::mainNetEvent(int event, Event *e)
     epd = (EventIO *)get_ev_data(pd, x);
     if (epd->type == EVENTIO_READWRITE_VC) {
       vc = epd->data.vc;
+      int eventio_error_num = get_ev_events(pd, x) & EVENTIO_ERROR;
+      if (eventio_error_num != 0) {
+        // if the error was on the READ side, lets signal a read error
+        if (get_ev_events(pd, x) & EVENTIO_READ) {
+          read_signal_error(this, vc, eventio_error_num);
+        } else {  // otherwise it must be on the WRITE side, lets signal a write error
+          write_signal_error(this, vc, eventio_error_num);
+        }
+        // Since we just killed the VC-- there is no reason to run the rest of this look
+        continue;
+      }
       if (get_ev_events(pd, x) & (EVENTIO_READ | EVENTIO_ERROR)) {
         vc->read.triggered = 1;
         if (!read_ready_list.in(vc)) {

iocore/net/UnixNetVConnection.cc

@@ -231,14 +231,14 @@ write_signal_done(int event, NetHandler *nh, UnixNetVConnection *vc)
   }
 }
 
-static inline int
+int
 read_signal_error(NetHandler *nh, UnixNetVConnection *vc, int lerrno)
 {
   vc->lerrno = lerrno;
   return read_signal_done(VC_EVENT_ERROR, nh, vc);
 }
 
-static inline int
+int
 write_signal_error(NetHandler *nh, UnixNetVConnection *vc, int lerrno)
 {
   vc->lerrno = lerrno;