ctl: add command to change the cost multiplier of a neighbour

To be pushed upstream.
Co-authored-by: Julien Muchembled <jm@nexedi.com>

ctl.c

@@ -72,6 +72,70 @@ ctl_resize_buffer(struct ctl_buffer *buffer, size_t n)
     return 0;
 }
 
+static int
+ctl_set_cost_multiplier(struct ctl_buffer *buffer, void *packet, size_t length)
+{
+    struct {
+        uint8_t address[16];
+        uint32_t ifindex;
+        uint16_t cost_multiplier;
+    } __attribute__((packed)) *request = packet;
+    unsigned ifindex = ntohl(request->ifindex);
+    struct neighbour *neigh;
+    struct {
+        uint16_t type;
+        uint32_t length;
+        uint8_t unknown:1;
+        uint8_t changed:1;
+    } __attribute__((packed)) *response;
+
+    size_t end = buffer->end + sizeof *response;
+    if(ctl_resize_buffer(buffer, end))
+        return -1;
+    response = (void *)(buffer->data + buffer->end);
+
+    response->type = htons(CTL_MSG_SET_COST_MULTIPLIER);
+    response->length = htonl(sizeof *response - 6);
+    response->unknown = 1;
+    response->changed = 0;
+
+    FOR_ALL_NEIGHBOURS(neigh)
+        if(neigh->ifp->ifindex == ifindex &&
+           !memcmp(request->address, neigh->address, sizeof request->address)) {
+            struct babel_route *route;
+            struct route_stream *routes;
+            unsigned short cost_multiplier;
+            cost_multiplier = ntohs(request->cost_multiplier);
+            response->unknown = 0;
+            response->changed = neigh->cost_multiplier != cost_multiplier;
+            if(!cost_multiplier && response->changed) {
+                routes = route_stream(1);
+                if(!routes)
+                    return -1;
+                while((route = route_stream_next(routes)))
+                    if(route->neigh == neigh) {
+                        response->changed = 0;
+                        break;
+                    }
+                route_stream_done(routes);
+            }
+            if(response->changed) {
+                routes = route_stream(0);
+                if(!routes)
+                    return -1;
+                neigh->cost_multiplier = cost_multiplier;
+                while((route = route_stream_next(routes)))
+                    if(route->neigh == neigh)
+                        update_route_metric(route);
+                route_stream_done(routes);
+            }
+            break;
+        }
+
+    buffer->end = end;
+    return 0;
+}
+
 static int
 ctl_dump_interface(struct ctl_buffer *buffer, struct interface *ifp)
 {
@@ -101,6 +165,7 @@ ctl_dump_neighbour(struct ctl_buffer *buffer, struct neighbour *neigh)
     neigh_dump->rttcost = htonl(neighbour_rttcost(neigh));
     neigh_dump->channel = htonl(neigh->ifp->channel);
     neigh_dump->if_up = htons(if_up(neigh->ifp));
+    neigh_dump->cost_multiplier = htons(neigh->cost_multiplier);
     buffer->end = end;
     return 0;
 }
@@ -247,6 +312,9 @@ ctl_work(struct ctl *ctl)
             case CTL_MSG_DUMP:
                 ret = ctl_dump(&ctl->buffer_out, p, length);
                 break;
+            case CTL_MSG_SET_COST_MULTIPLIER:
+                ret = ctl_set_cost_multiplier(&ctl->buffer_out, p, length);
+                break;
             }
         else if(length < CTL_MAX_SIZE)
             return;

ctl.h

@@ -28,6 +28,7 @@ THE SOFTWARE.
 #define CTL_VERSION 1
 
 #define CTL_MSG_DUMP       1
+#define CTL_MSG_SET_COST_MULTIPLIER   2
 
 #define CTL_DUMP_NONE      0
 #define CTL_DUMP_INSTALLED 1
@@ -50,6 +51,7 @@ struct ctl_dump_neighbour {
     uint16_t rttcost;
     int32_t channel;
     uint16_t if_up;
+    uint16_t cost_multiplier;
 } __attribute__((packed));
 
 

neighbour.c

@@ -103,6 +103,7 @@ find_neighbour(const unsigned char *address, struct interface *ifp)
     neigh->rtt = 0;
     neigh->rtt_time = zero;
     neigh->ifp = ifp;
+    neigh->cost_multiplier = 256;
     neigh->next = neighs;
     neighs = neigh;
     local_notify_neighbour(neigh, LOCAL_ADD);
@@ -358,6 +359,10 @@ neighbour_cost(struct neighbour *neigh)
 
     cost += neighbour_rttcost(neigh);
 
+    if(!neigh->cost_multiplier)
+        return INFINITY;
+    cost = cost * neigh->cost_multiplier >> 8 ?: 1;
+
     return MIN(cost, INFINITY);
 }
 

neighbour.h

@@ -39,6 +39,7 @@ struct neighbour {
     unsigned int rtt;
     struct timeval rtt_time;
     struct interface *ifp;
+    unsigned short cost_multiplier;
 };
 
 extern struct neighbour *neighs;