Make 'rtt_exponential_decay' relative to an interface

babeld.c

@@ -58,10 +58,6 @@ struct timeval now;
 unsigned char myid[8];
 int debug = 0;
 
-/* A higher value means we forget old RTT samples faster. Must be
-   between 1 and 256, inclusive. */
-unsigned int rtt_exponential_decay = 42;
-
 int link_detect = 0;
 int all_wireless = 0;
 int default_wireless_hello_interval = -1;

babeld.h

@@ -90,7 +90,6 @@ extern int do_daemonise;
 extern const char *logfile, *pidfile, *state_file;
 extern int link_detect;
 extern int all_wireless;
-extern unsigned int rtt_exponential_decay;
 
 extern unsigned char myid[8];
 

interface.h

@@ -91,6 +91,9 @@ struct interface {
     unsigned short hello_seqno;
     unsigned hello_interval;
     unsigned update_interval;
+    /* A higher value means we forget old RTT samples faster. Must be
+       between 1 and 256, inclusive. */
+    unsigned int rtt_exponential_decay;
     /* Parameters for computing the cost associated to RTT. */
     unsigned int rtt_min;
     unsigned int rtt_max;

message.c

@@ -611,14 +611,16 @@ parse_packet(const unsigned char *from, struct interface *ifp,
         debugf("RTT to %s on %s sample result: %d us.\n",
                format_address(from), ifp->name, rtt);
 
-        if (valid_rtt(neigh))
+        if (valid_rtt(neigh)) {
             /* Running exponential average. */
-            neigh->rtt = (rtt_exponential_decay * MAX(rtt, 0)
-                          + (256 - rtt_exponential_decay) * neigh->rtt) / 256;
-        else
+            neigh->rtt = (ifp->rtt_exponential_decay * MAX(rtt, 0)
+                          + (256 - ifp->rtt_exponential_decay) * neigh->rtt);
+            neigh->rtt /= 256;
+        } else {
             /* We prefer to be conservative with new neighbours
                (higher RTT) */
             neigh->rtt = MAX(2*rtt, 0);
+        }
         neigh->rtt_time = now;
     }
     return;