Allow all RTT parameters to be configured

Note that this commit effectively disables the computation of a cost
from the RTT, since 'max-rtt-penalty' defaults to 0.

babeld.man

@@ -329,6 +329,35 @@ This defines the interval between full routing table dumps sent on this
 interface; since Babel uses triggered updates and doesn't count to
 infinity, this can be set to a fairly large value, unless significant
 packet loss is expected.  The default is four times the hello interval.
+.TP
+.BI rtt\-exponential\-decay " decay"
+This specifies the decay factor for the exponential moving average of
+RTT samples, in units of 1/256.  Must be between 1 and 256, inclusive.
+Higher values discard old samples faster.  The default is
+.BR 42 .
+.TP
+.BI rtt\-min " rtt"
+This specifies the minimum RTT, in milliseconds, starting from which
+we increase the cost to a neighbour. The additional cost is linear in
+(rtt -
+.BR rtt\-min ).
+The default is
+.B 10
+ms.
+.TP
+.BI rtt\-max " rtt"
+This specifies the maximum RTT, in milliseconds, above which we don't
+increase the cost to a neighbour. The default is
+.B 120
+ms.
+.TP
+.BI max\-rtt\-penalty " cost"
+This specifies the maximum cost added to a neighbour because of RTT,
+i.e. when the RTT is higher or equal than
+.BR rtt\-max .
+The default is
+.BR 0 ,
+which effectively disables the use of a RTT-based cost.
 .SS Filtering rules
 A filtering rule is defined by a single line with the following format:
 .IP

configuration.c

@@ -464,6 +464,30 @@ parse_anonymous_ifconf(int c, gnc_t gnc, void *closure,
             if((if_conf->channel < 1 || if_conf->channel > 255) &&
                if_conf->channel != IF_CHANNEL_NONINTERFERING)
                 goto error;
+        } else if(strcmp(token, "rtt-exponential-decay") == 0) {
+            int decay;
+            c = getint(c, &decay, gnc, closure);
+            if(c < -1 || decay <= 0 || decay > 256)
+                goto error;
+            if_conf->rtt_exponential_decay = decay;
+        } else if(strcmp(token, "rtt-min") == 0) {
+            int rtt;
+            c = getthousands(c, &rtt, gnc, closure);
+            if(c < -1 || rtt <= 0)
+                goto error;
+            if_conf->rtt_min = rtt;
+        } else if(strcmp(token, "rtt-max") == 0) {
+            int rtt;
+            c = getthousands(c, &rtt, gnc, closure);
+            if(c < -1 || rtt <= 0)
+                goto error;
+            if_conf->rtt_max = rtt;
+        } else if(strcmp(token, "max-rtt-penalty") == 0) {
+            int cost;
+            c = getint(c, &cost, gnc, closure);
+            if(c < -1 || cost <= 0 || cost > 0xFFFF)
+                goto error;
+            if_conf->max_rtt_penalty = cost;
         } else {
             goto error;
         }
@@ -544,6 +568,10 @@ merge_ifconf(struct interface_conf *dest,
     MERGE(lq);
     MERGE(faraway);
     MERGE(channel);
+    MERGE(rtt_exponential_decay);
+    MERGE(rtt_min);
+    MERGE(rtt_max);
+    MERGE(max_rtt_penalty);
 
 #undef MERGE
 }

interface.c

@@ -79,9 +79,6 @@ add_interface(char *ifname, struct interface_conf *if_conf)
     ifp->bucket_time = now.tv_sec;
     ifp->bucket = BUCKET_TOKENS_MAX;
     ifp->hello_seqno = (random() & 0xFFFF);
-    ifp->rtt_min = 10000;
-    ifp->rtt_max = 120000;
-    ifp->max_rtt_penalty = 150;
 
     if(interfaces == NULL)
         interfaces = ifp;
@@ -308,6 +305,25 @@ interface_up(struct interface *ifp, int up)
             IF_CONF(ifp, update_interval) :
            ifp->hello_interval * 4;
 
+        ifp->rtt_exponential_decay =
+            IF_CONF(ifp, rtt_exponential_decay) > 0 ?
+            IF_CONF(ifp, rtt_exponential_decay) : 42;
+
+        ifp->rtt_min =
+            IF_CONF(ifp, rtt_min) > 0 ?
+            IF_CONF(ifp, rtt_min) : 10000;
+        ifp->rtt_max =
+            IF_CONF(ifp, rtt_max) > 0 ?
+            IF_CONF(ifp, rtt_max) : 120000;
+        if(ifp->rtt_max <= ifp->rtt_min) {
+            fprintf(stderr,
+                    "Uh, rtt-max is less than or equal to rtt-min (%d <= %d). "
+                    "Setting it to %d.\n", ifp->rtt_max, ifp->rtt_min,
+                    ifp->rtt_min + 10000);
+            ifp->rtt_max = ifp->rtt_min + 10000;
+        }
+        ifp->max_rtt_penalty = IF_CONF(ifp, max_rtt_penalty);
+
         if(ifp->ll)
             free(ifp->ll);
         ifp->numll = 0;

interface.h

@@ -37,6 +37,10 @@ struct interface_conf {
     char lq;
     char faraway;
     int channel;
+    unsigned int rtt_exponential_decay;
+    unsigned int rtt_min;
+    unsigned int rtt_max;
+    unsigned int max_rtt_penalty;
     struct interface_conf *next;
 };