Make route->channels carry an explicit length.

This allows 0 to appear within a channel list, which is consistent with
draft-chroboczek-babel-diversity-routing-01.

babeld.c

@@ -1059,23 +1059,19 @@ dump_route(FILE *out, struct babel_route *route)
         NULL : route->nexthop;
     char channels[100];
 
-    if(route->channels[0] == 0)
+    if(route->channels_len == 0) {
         channels[0] = '\0';
-    else {
+    } else {
         int k, j = 0;
         snprintf(channels, 100, " chan (");
         j = strlen(channels);
-        for(k = 0; k < DIVERSITY_HOPS; k++) {
-            if(route->channels[k] == 0)
-                break;
+        for(k = 0; k < route->channels_len; k++) {
             if(k > 0)
                 channels[j++] = ',';
             snprintf(channels + j, 100 - j, "%u", (unsigned)route->channels[k]);
             j = strlen(channels);
         }
         snprintf(channels + j, 100 - j, ")");
-        if(k == 0)
-            channels[0] = '\0';
     }
 
     fprintf(out, "%s from %s metric %d (%d) refmetric %d id %s "

message.c

@@ -57,6 +57,8 @@ struct timeval unicast_flush_timeout = {0, 0};
 static const unsigned char v4prefix[16] =
     {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF, 0, 0, 0, 0 };
 
+#define MAX_CHANNEL_HOPS 20
+
 /* Parse a network prefix, encoded in the somewhat baroque compressed
    representation used by Babel.  Return the number of bytes parsed. */
 static int
@@ -122,21 +124,22 @@ network_prefix(int ae, int plen, unsigned int omitted,
 static void
 parse_update_subtlv(struct interface *ifp, int metric,
                     const unsigned char *a, int alen,
-                    unsigned char *channels)
+                    unsigned char *channels, int *channels_len_return)
 {
     int type, len, i = 0;
+    int channels_len;
 
-    if((ifp->flags & IF_FARAWAY)) {
-        channels[0] = 0;
+    /* This will be overwritten if there's a DIVERSITY_HOPS sub-TLV. */
+    if(*channels_len_return < 1 || (ifp->flags & IF_FARAWAY)) {
+        channels_len = 0;
     } else {
-        /* This will be overwritten if there's a DIVERSITY_HOPS sub-TLV. */
         if(metric < 256) {
             /* Assume non-interfering (wired) link. */
-            channels[0] = 0;
+            channels_len = 0;
         } else {
             /* Assume interfering. */
             channels[0] = IF_CHANNEL_INTERFERING;
-            channels[1] = 0;
+            channels_len = 1;
         }
     }
 
@@ -160,27 +163,15 @@ parse_update_subtlv(struct interface *ifp, int metric,
         if(type == SUBTLV_PADN) {
             /* Nothing. */
         } else if(type == SUBTLV_DIVERSITY) {
-            if(!(ifp->flags & IF_FARAWAY)) {
-                if(len > DIVERSITY_HOPS) {
-                    fprintf(stderr,
-                            "Received overlong channel information (%d > %d).\n",
-                            len, DIVERSITY_HOPS);
-                    len = DIVERSITY_HOPS;
-                }
-                if(memchr(a + i + 2, 0, len) != NULL) {
-                    /* 0 is reserved. */
-                    fprintf(stderr, "Channel information contains 0!");
-                    return;
-                }
-                memset(channels, 0, DIVERSITY_HOPS);
-                memcpy(channels, a + i + 2, len);
-            }
+            memcpy(channels, a + i + 2, MIN(len, *channels_len_return));
+            channels_len = MIN(len, *channels_len_return);
         } else {
             debugf("Received unknown update sub-TLV %d.\n", type);
         }
 
         i += len + 2;
     }
+    *channels_len_return = channels_len;
 }
 
 static int
@@ -277,13 +268,6 @@ network_address(int ae, const unsigned char *a, unsigned int len,
     return network_prefix(ae, -1, 0, a, NULL, len, a_r);
 }
 
-static int
-channels_len(unsigned char *channels)
-{
-    unsigned char *p = memchr(channels, 0, DIVERSITY_HOPS);
-    return p ? (p - channels) : DIVERSITY_HOPS;
-}
-
 void
 parse_packet(const unsigned char *from, struct interface *ifp,
              const unsigned char *packet, int packetlen)
@@ -461,7 +445,8 @@ parse_packet(const unsigned char *from, struct interface *ifp,
         } else if(type == MESSAGE_UPDATE) {
             unsigned char prefix[16], *nh;
             unsigned char plen;
-            unsigned char channels[DIVERSITY_HOPS];
+            unsigned char channels[MAX_CHANNEL_HOPS];
+            int channels_len = MAX_CHANNEL_HOPS;
             unsigned short interval, seqno, metric;
             int rc, parsed_len;
             if(len < 10) {
@@ -541,10 +526,10 @@ parse_packet(const unsigned char *from, struct interface *ifp,
             }
 
             parse_update_subtlv(ifp, metric, message + 2 + parsed_len,
-                                len - parsed_len, channels);
+                                len - parsed_len, channels, &channels_len);
             update_route(router_id, prefix, plen, zeroes, 0, seqno,
                          metric, interval, neigh, nh,
-                         channels, channels_len(channels));
+                         channels, channels_len);
         } else if(type == MESSAGE_REQUEST) {
             unsigned char prefix[16], plen;
             int rc;
@@ -590,7 +575,8 @@ parse_packet(const unsigned char *from, struct interface *ifp,
         } else if(type == MESSAGE_UPDATE_SRC_SPECIFIC) {
             unsigned char prefix[16], src_prefix[16], *nh;
             unsigned char ae, plen, src_plen, omitted;
-            unsigned char channels[DIVERSITY_HOPS];
+            unsigned char channels[MAX_CHANNEL_HOPS];
+            int channels_len = MAX_CHANNEL_HOPS;
             unsigned short interval, seqno, metric;
             const unsigned char *src_prefix_beginning = NULL;
             int rc, parsed_len = 0;
@@ -654,11 +640,10 @@ parse_packet(const unsigned char *from, struct interface *ifp,
             }
 
             parse_update_subtlv(ifp, metric, message + 2 + parsed_len,
-                                len - parsed_len, channels);
-
+                                len - parsed_len, channels, &channels_len);
             update_route(router_id, prefix, plen, src_prefix, src_plen,
                          seqno, metric, interval, neigh, nh,
-                         channels, channels_len(channels));
+                         channels, channels_len);
         } else if(type == MESSAGE_REQUEST_SRC_SPECIFIC) {
             unsigned char prefix[16], plen, ae, src_prefix[16], src_plen;
             int rc, parsed = 5;
@@ -1361,7 +1346,7 @@ flushupdates(struct interface *ifp)
                 last_src_prefix = xroute->src_prefix;
                 last_src_plen = xroute->src_plen;
             } else if(route) {
-                unsigned char channels[DIVERSITY_HOPS];
+                unsigned char channels[MAX_CHANNEL_HOPS];
                 int chlen;
                 struct interface *route_ifp = route->neigh->ifp;
                 unsigned short metric;
@@ -1384,7 +1369,9 @@ flushupdates(struct interface *ifp)
                     continue;
 
                 if(route_ifp->channel == IF_CHANNEL_NONINTERFERING) {
-                    memcpy(channels, route->channels, DIVERSITY_HOPS);
+                    memcpy(channels, route->channels,
+                           MIN(route->channels_len, MAX_CHANNEL_HOPS));
+                    chlen = MIN(route->channels_len, MAX_CHANNEL_HOPS);
                 } else {
                     if(route_ifp->channel == IF_CHANNEL_UNKNOWN)
                         channels[0] = IF_CHANNEL_INTERFERING;
@@ -1393,10 +1380,11 @@ flushupdates(struct interface *ifp)
                                route_ifp->channel <= 255);
                         channels[0] = route_ifp->channel;
                     }
-                    memcpy(channels + 1, route->channels, DIVERSITY_HOPS - 1);
+                    memcpy(channels + 1, route->channels,
+                           MIN(route->channels_len, MAX_CHANNEL_HOPS - 1));
+                    chlen = 1 + MIN(route->channels_len, MAX_CHANNEL_HOPS - 1);
                 }
 
-                chlen = channels_len(channels);
                 really_send_update(ifp, route->src->id,
                                    route->src->prefix, route->src->plen,
                                    route->src->src_prefix, route->src->src_plen,

route.c

@@ -242,6 +242,13 @@ insert_route(struct babel_route *route)
     return route;
 }
 
+static void
+destroy_route(struct babel_route *route)
+{
+    free(route->channels);
+    free(route);
+}
+
 void
 flush_route(struct babel_route *route)
 {
@@ -267,7 +274,7 @@ flush_route(struct babel_route *route)
     if(route == routes[i]) {
         routes[i] = route->next;
         route->next = NULL;
-        free(route);
+        destroy_route(route);
 
         if(routes[i] == NULL) {
             if(i < route_slots - 1)
@@ -288,7 +295,7 @@ flush_route(struct babel_route *route)
             r = r->next;
         r->next = route->next;
         route->next = NULL;
-        free(route);
+        destroy_route(route);
     }
 
     if(lost)
@@ -620,10 +627,9 @@ route_interferes(struct babel_route *route, struct interface *ifp)
             return 1;
         if(diversity_kind == DIVERSITY_CHANNEL) {
             int i;
-            for(i = 0; i < DIVERSITY_HOPS; i++) {
-                if(route->channels[i] == 0)
-                    break;
-                if(channels_interfere(ifp->channel, route->channels[i]))
+            for(i = 0; i < route->channels_len; i++) {
+                if(route->channels[i] != 0 &&
+                   channels_interfere(ifp->channel, route->channels[i]))
                     return 1;
             }
         }
@@ -910,10 +916,24 @@ update_route(const unsigned char *id,
             route->time = now.tv_sec;
         route->seqno = seqno;
 
-        memset(&route->channels, 0, sizeof(route->channels));
-        if(channels_len > 0)
-            memcpy(&route->channels, channels,
-                   MIN(channels_len, DIVERSITY_HOPS));
+        if(channels_len == 0) {
+            free(route->channels);
+            route->channels_len = 0;
+        } else {
+            if(channels_len != route->channels_len) {
+                unsigned char *new_channels =
+                    realloc(route->channels, channels_len);
+                if(new_channels == NULL) {
+                    perror("malloc(channels)");
+                    /* Truncate the data. */
+                    channels_len = MIN(channels_len, route->channels_len);
+                } else {
+                    route->channels = new_channels;
+                }
+            }
+            memcpy(route->channels, channels, channels_len);
+            route->channels_len = channels_len;
+        }
 
         change_route_metric(route,
                             refmetric, neighbour_cost(neigh), add_metric);
@@ -956,14 +976,19 @@ update_route(const unsigned char *id,
         route->hold_time = hold_time;
         route->smoothed_metric = MAX(route_metric(route), INFINITY / 2);
         route->smoothed_metric_time = now.tv_sec;
-        if(channels_len > 0)
-            memcpy(&route->channels, channels,
-                   MIN(channels_len, DIVERSITY_HOPS));
+        if(channels_len > 0) {
+            route->channels = malloc(channels_len);
+            if(route->channels == NULL) {
+                perror("malloc(channels)");
+            } else {
+                memcpy(route->channels, channels, channels_len);
+            }
+        }
         route->next = NULL;
         new_route = insert_route(route);
         if(new_route == NULL) {
             fprintf(stderr, "Couldn't insert route.\n");
-            free(route);
+            destroy_route(route);
             return NULL;
         }
         local_notify_route(route, LOCAL_ADD);

route.h

@@ -25,8 +25,6 @@ THE SOFTWARE.
 #define DIVERSITY_CHANNEL_1 2
 #define DIVERSITY_CHANNEL 3
 
-#define DIVERSITY_HOPS 8
-
 struct babel_route {
     struct source *src;
     unsigned short refmetric;
@@ -40,7 +38,8 @@ struct babel_route {
     unsigned short smoothed_metric; /* for route selection */
     time_t smoothed_metric_time;
     short installed;
-    unsigned char channels[DIVERSITY_HOPS];
+    short channels_len;
+    unsigned char *channels;
     struct babel_route *next;
 };