add EPICS_CA_MCAST_TTL

may be necessary/helpful for mcast search/beacon usage
across sub-nets.

configure/CONFIG_ENV

@@ -38,6 +38,7 @@ EPICS_CA_MAX_ARRAY_BYTES=16384
 EPICS_CA_AUTO_MAX_ARRAY_BYTES=NO
 EPICS_CA_BEACON_PERIOD=15.0
 EPICS_CA_MAX_SEARCH_PERIOD=300.0
+EPICS_CA_MCAST_TTL=1
 EPICS_CAS_BEACON_PERIOD=
 EPICS_CAS_BEACON_PORT=
 EPICS_CAS_AUTO_BEACON_ADDR_LIST=""

documentation/RELEASE_NOTES.html

@@ -21,6 +21,11 @@
 
 -->
 
+<h3>Add EPICS_CA_MCAST_TTL</h3>
+
+<p>Add option EPICS_CA_MCAST_TTL to set the Time To Live (TTL) of any IP multi-cast
+CA search or beacon packets sent.</p>
+
 <h3>EPICS_CA_MAX_ARRAY_BYTES is optional</h3>
 
 <p>

src/ca/client/udpiiu.cpp

@@ -191,6 +191,22 @@ udpiiu::udpiiu (
     }
 #endif
 
+#ifdef IP_MULTICAST_TTL
+    {
+        int ttl;
+        long val;
+        if(envGetLongConfigParam(&EPICS_CA_MCAST_TTL, &val))
+            val =1;
+        ttl = val;
+        if ( setsockopt(this->sock, IPPROTO_IP, IP_MULTICAST_TTL, (char*)&ttl, sizeof(ttl))) {
+            char sockErrBuf[64];
+            epicsSocketConvertErrnoToString (
+                sockErrBuf, sizeof ( sockErrBuf ) );
+            errlogPrintf("CAC: failed to set mcast ttl %d\n", ttl);
+        }
+    }
+#endif
+
     int boolValue = true;
     int status = setsockopt ( this->sock, SOL_SOCKET, SO_BROADCAST, 
                 (char *) &boolValue, sizeof ( boolValue ) );

src/ioc/rsrv/caservertask.c

@@ -320,6 +320,22 @@ void rsrv_build_addr_lists(void)
             }
         }
 #endif
+
+#ifdef IP_MULTICAST_TTL
+    {
+        int ttl;
+        long val;
+        if(envGetLongConfigParam(&EPICS_CA_MCAST_TTL, &val))
+            val =1;
+        ttl = val;
+        if ( setsockopt(beaconSocket, IPPROTO_IP, IP_MULTICAST_TTL, (char*)&ttl, sizeof(ttl))) {
+            char sockErrBuf[64];
+            epicsSocketConvertErrnoToString (
+                sockErrBuf, sizeof ( sockErrBuf ) );
+            errlogPrintf("rsrv: failed to set mcast ttl %d\n", ttl);
+        }
+    }
+#endif
     }
 
     /* populate the interface address list (default is empty) */

src/libCom/env/envDefs.h

@@ -51,6 +51,7 @@ epicsShareExtern const ENV_PARAM EPICS_CA_MAX_ARRAY_BYTES;
 epicsShareExtern const ENV_PARAM EPICS_CA_AUTO_MAX_ARRAY_BYTES;
 epicsShareExtern const ENV_PARAM EPICS_CA_MAX_SEARCH_PERIOD;
 epicsShareExtern const ENV_PARAM EPICS_CA_NAME_SERVERS;
+epicsShareExtern const ENV_PARAM EPICS_CA_MCAST_TTL;
 epicsShareExtern const ENV_PARAM EPICS_CAS_INTF_ADDR_LIST;
 epicsShareExtern const ENV_PARAM EPICS_CAS_IGNORE_ADDR_LIST;
 epicsShareExtern const ENV_PARAM EPICS_CAS_AUTO_BEACON_ADDR_LIST;