Reuse NF Instance IDs (#92)

Reuse instance IDs of old NFs that have terminated. Reusing will only
happen when the next instance id counter hits the set MAX_NFS limit.
Allows to infinitely run NFs and makes MAX_NFS a value of concurrent
running NFs instead.

Commit log:

* Reuse NF instance IDs

* Minor cleanup

onvm/onvm_mgr/main.c

@@ -257,11 +257,9 @@ main(int argc, char *argv[]) {
         unsigned i;
 
         /* initialise the system */
-
-        /* Reserve ID 0 for internal manager things */
-        next_instance_id = 1;
         if (init(argc, argv) < 0)
                 return -1;
+
         RTE_LOG(INFO, APP, "Finished Process Init.\n");
 
         /* clear statistics */

onvm/onvm_mgr/onvm_mgr.h

@@ -79,9 +79,4 @@
 #define TO_PORT 0
 #define TO_NF 1
 
-/***************************Shared global variables***************************/
-
-/* ID to be assigned to the next NF that starts */
-extern uint16_t next_instance_id;
-
 #endif  // _ONVM_MGR_H_

onvm/onvm_mgr/onvm_nf.c

@@ -50,7 +50,9 @@
 #include "onvm_mgr.h"
 #include "onvm_stats.h"
 
-uint16_t next_instance_id = 0;
+/* ID 0 is reserved */
+uint16_t next_instance_id = 1;
+uint16_t starting_instance_id = 1;
 
 /************************Internal functions prototypes************************/
 
@@ -89,16 +91,35 @@ onvm_nf_stop(struct onvm_nf_info *nf_info);
 uint16_t
 onvm_nf_next_instance_id(void) {
         struct onvm_nf *nf;
-        uint16_t instance_id = MAX_NFS;
+        uint16_t instance_id;
 
+        if (num_nfs >= MAX_NFS)
+                return MAX_NFS;
+
+        /* Do a first pass for NF IDs bigger than current next_instance_id */
         while (next_instance_id < MAX_NFS) {
                 instance_id = next_instance_id++;
+                /* Check if this id is occupied by another NF */
                 nf = &nfs[instance_id];
                 if (!onvm_nf_is_valid(nf))
-                        break;
+                        return instance_id;
+        }
+
+        /* Reset to starting position */
+        next_instance_id = starting_instance_id;
+
+        /* Do a second pass for other NF IDs */
+        while (next_instance_id < MAX_NFS) {
+                instance_id = next_instance_id++;
+                /* Check if this id is occupied by another NF */
+                nf = &nfs[instance_id];
+                if (!onvm_nf_is_valid(nf))
+                        return instance_id;
         }
 
-        return instance_id;
+        /* This should never happen, means our num_nfs counter is wrong */
+        RTE_LOG(ERR, APP, "Tried to allocated a next instance ID but num_nfs is corrupted\n");
+        return MAX_NFS;
 }
 
 void

onvm/onvm_mgr/onvm_nf.h

@@ -52,8 +52,6 @@
 
 #include "onvm_threading.h"
 
-extern uint16_t next_instance_id;
-
 /********************************Interfaces***********************************/
 
 /*

onvm/onvm_nflib/onvm_common.h

@@ -51,7 +51,7 @@
 #include "onvm_msg_common.h"
 
 #define ONVM_MAX_CHAIN_LENGTH 4  // the maximum chain length
-#define MAX_NFS 128              // total number of NFs allowed
+#define MAX_NFS 128              // total number of concurrent NFs allowed (-1 because ID 0 is reserved)
 #define MAX_SERVICES 32          // total number of unique services allowed
 #define MAX_NFS_PER_SERVICE 32   // max number of NFs per service.