diff -Naurp squid-3.3.8.orig/src/ipc/TypedMsgHdr.cc squid-3.3.8/src/ipc/TypedMsgHdr.cc
--- squid-3.3.8.orig/src/ipc/TypedMsgHdr.cc	2013-07-13 15:25:14.000000000 +0200
+++ squid-3.3.8/src/ipc/TypedMsgHdr.cc	2015-04-20 14:28:32.971000390 +0200
@@ -167,10 +167,20 @@ Ipc::TypedMsgHdr::putRaw(const void *raw
     }
 }
 
+bool
+Ipc::TypedMsgHdr::hasFd() const
+{
+	struct cmsghdr *cmsg = CMSG_FIRSTHDR(this);
+	return cmsg &&
+	    cmsg->cmsg_level == SOL_SOCKET &&
+	    cmsg->cmsg_type == SCM_RIGHTS;
+}
+
 void
 Ipc::TypedMsgHdr::putFd(int fd)
 {
     Must(fd >= 0);
+    Must(!hasFd());
     allocControl();
 
     const int fdCount = 1;
@@ -183,12 +193,15 @@ Ipc::TypedMsgHdr::putFd(int fd)
     int *fdStore = reinterpret_cast<int*>(CMSG_DATA(cmsg));
     memcpy(fdStore, &fd, fdCount * sizeof(int));
     msg_controllen = cmsg->cmsg_len;
+
+    Must(hasFd());
 }
 
 int
 Ipc::TypedMsgHdr::getFd() const
 {
     Must(msg_control && msg_controllen);
+    Must(hasFd());
 
     struct cmsghdr *cmsg = CMSG_FIRSTHDR(this);
     Must(cmsg->cmsg_level == SOL_SOCKET);
diff -Naurp squid-3.3.8.orig/src/ipc/TypedMsgHdr.h squid-3.3.8/src/ipc/TypedMsgHdr.h
--- squid-3.3.8.orig/src/ipc/TypedMsgHdr.h	2013-07-13 15:25:14.000000000 +0200
+++ squid-3.3.8/src/ipc/TypedMsgHdr.h	2015-04-20 14:12:57.509303004 +0200
@@ -59,8 +59,8 @@ public:
 
     /* access to a "file" descriptor that can be passed between processes */
     void putFd(int aFd); ///< stores descriptor
-    int getFd() const; ///< returns descriptor
-
+    int getFd() const; ///< returns stored descriptor
+    bool hasFd() const; ///< whether the message has a descriptor stored
     /* raw, type-independent access for I/O */
     void prepForReading(); ///< reset and provide all buffers
     char *raw() { return reinterpret_cast<char*>(this); }
diff -Naurp squid-3.3.8.orig/src/snmp/Inquirer.cc squid-3.3.8/src/snmp/Inquirer.cc
--- squid-3.3.8.orig/src/snmp/Inquirer.cc	2013-07-13 15:25:14.000000000 +0200
+++ squid-3.3.8/src/snmp/Inquirer.cc	2015-04-20 14:15:12.324970907 +0200
@@ -28,6 +28,10 @@ Snmp::Inquirer::Inquirer(const Request&
     closer = asyncCall(49, 5, "Snmp::Inquirer::noteCommClosed",
                        CommCbMemFunT<Inquirer, CommCloseCbParams>(this, &Inquirer::noteCommClosed));
     comm_add_close_handler(conn->fd, closer);
+
+    // forget client FD to avoid sending it to strands that may forget to close
+    if (Request *snmpRequest = dynamic_cast<Request*>(request.getRaw()))
+	snmpRequest->fd = -1;
 }
 
 /// closes our copy of the client connection socket
diff -Naurp squid-3.3.8.orig/src/snmp/Request.cc squid-3.3.8/src/snmp/Request.cc
--- squid-3.3.8.orig/src/snmp/Request.cc	2013-07-13 15:25:14.000000000 +0200
+++ squid-3.3.8/src/snmp/Request.cc	2015-04-20 14:21:16.676074181 +0200
@@ -33,7 +33,8 @@ Snmp::Request::Request(const Ipc::TypedM
     session.unpack(msg);
     msg.getPod(address);
 
-    fd = msg.getFd();
+    // Requests from strands have FDs. Requests from Coordinator do not.
+    fd = msg.hasFd() ? msg.getFd() : -1;
 }
 
 void
@@ -46,7 +47,9 @@ Snmp::Request::pack(Ipc::TypedMsgHdr& ms
     session.pack(msg);
     msg.putPod(address);
 
-    msg.putFd(fd);
+    // Requests sent to Coordinator have FDs. Requests sent to strands do not.
+    if (fd >= 0)
+	msg.putFd(fd);
 }
 
 Ipc::Request::Pointer