dns_sd: treat linked lists properly when removing things

When we were deleting nodes from the linked list, we accessed the
"next", from the node that we just cut out (and free()'ed).

Fix by keeping track of the previous node, which is used for the "next"
when we cut it out.

Signed-off-by: Robin Getz <[email protected]>

Author: rgetz

dns_sd.c

@@ -215,7 +215,7 @@ void port_knock_discovery_data(struct dns_sd_discovery_data **ddata)
 
 void remove_dup_discovery_data(struct dns_sd_discovery_data **ddata)
 {
-	struct dns_sd_discovery_data *d, *ndata, *mdata;
+	struct dns_sd_discovery_data *d, *ndata, *mdata, *prev;
 	int i, j;
 
 	d = *ddata;
@@ -227,15 +227,26 @@ void remove_dup_discovery_data(struct dns_sd_discovery_data **ddata)
 		return;
 
 	iio_mutex_lock(d->lock);
+	/* since we are removing nodes in the linked list, we keep track of the
+	 * previous "good" node, so we always can link from the last to the next
+	 */
 	for (i = 0, ndata = d; ndata->next != NULL; ndata = ndata->next) {
+		prev = ndata;
 		for (j = i + 1, mdata = ndata->next; mdata->next != NULL; mdata = mdata->next) {
 			if (!strcmp(mdata->hostname, ndata->hostname) &&
 					!strcmp(mdata->addr_str, ndata->addr_str) &&
 					mdata->port == ndata->port){
-				IIO_DEBUG("Removing duplicate in list: '%s'\n",
-						ndata->hostname);
+				IIO_DEBUG("Removing duplicate in list: %i '%s' '%s' port:%hu\n",
+						j, ndata->hostname, ndata->addr_str,
+						ndata->port);
 				dnssd_remove_node(&d, j);
+				/* back up one, so the mdata->next will point to the
+				 * next one to be tested.
+				 */
+				mdata = prev;
+				continue;
 			}
+			prev = mdata;
 			j++;
 		}
 		i++;