gossmap: routine gossmap_disable_mmap() to force read() calls.

And use this if we spot corruption in gossipd.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Author: rustyrussell

common/gossmap.c

@@ -784,12 +784,9 @@ static bool load_gossip_store(struct gossmap *map, bool must_be_clean)
 	map->local_announces = NULL;
 	map->local_updates = NULL;
 
-	/* gossipd uses pwritev(), which is not consistent with mmap on OpenBSD! */
-#ifndef __OpenBSD__
 	/* If this fails, we fall back to read */
 	map->mmap = mmap(NULL, map->map_size, PROT_READ, MAP_SHARED, map->fd, 0);
 	if (map->mmap == MAP_FAILED)
-#endif /* __OpenBSD__ */
 		map->mmap = NULL;
 
 	/* We only support major version 0 */
@@ -1224,12 +1221,12 @@ bool gossmap_refresh(struct gossmap *map)
 	if (map->mmap)
 		munmap(map->mmap, map->map_size);
 	map->map_size = len;
-	/* gossipd uses pwritev(), which is not consistent with mmap on OpenBSD! */
-#ifndef __OpenBSD__
-	map->mmap = mmap(NULL, map->map_size, PROT_READ, MAP_SHARED, map->fd, 0);
-	if (map->mmap == MAP_FAILED)
-#endif /* __OpenBSD__ */
-		map->mmap = NULL;
+
+	if (map->mmap) {
+		map->mmap = mmap(NULL, map->map_size, PROT_READ, MAP_SHARED, map->fd, 0);
+		if (map->mmap == MAP_FAILED)
+			map->mmap = NULL;
+	}
 
 	map_catchup(map, false, &changed);
 	return changed;
@@ -1862,6 +1859,18 @@ int gossmap_fd(const struct gossmap *map)
 	return map->fd;
 }
 
+bool gossmap_has_mmap(const struct gossmap *map)
+{
+	return map->mmap != NULL;
+}
+
+void gossmap_disable_mmap(struct gossmap *map)
+{
+	if (map->mmap)
+		munmap(map->mmap, map->map_size);
+	map->mmap = NULL;
+}
+
 const u8 *gossmap_fetch_tail(const tal_t *ctx, const struct gossmap *map)
 {
 	size_t len;

common/gossmap.h

@@ -70,6 +70,10 @@ struct gossmap *gossmap_load_(const tal_t *ctx,
 					    ...),
 			      void *cb_arg);
 
+/* Disable mmap.  Noop if already disabled. */
+void gossmap_disable_mmap(struct gossmap *map);
+bool gossmap_has_mmap(const struct gossmap *map);
+
 /* Call this before using to ensure it's up-to-date.  Returns true if something
  * was updated. Note: this can scramble node and chan indexes! */
 bool gossmap_refresh(struct gossmap *map);

gossipd/gossmap_manage.c

@@ -1419,10 +1419,12 @@ struct gossmap *gossmap_manage_get_gossmap(struct gossmap_manage *gm)
 	written_len = gossip_store_len_written(gm->gs);
 
 	if (map_size != written_len) {
-		status_broken("gossmap size %"PRIu64" != written size %"PRIu64,
-			      map_size, written_len);
-		/* Push harder! */
-		gossip_store_fsync(gm->gs);
+		status_broken("gossmap size %"PRIu64" != written size %"PRIu64
+			      ": %s mmap!",
+			      map_size, written_len,
+			      gossmap_has_mmap(gm->raw_gossmap)
+			      ? "disabling": "ALREADY DISABLED");
+		gossmap_disable_mmap(gm->raw_gossmap);
 		gossmap_refresh(gm->raw_gossmap);
 
 		/* Sanity check that we see everything we wrote. */
@@ -1443,12 +1445,22 @@ struct gossmap *gossmap_manage_get_gossmap(struct gossmap_manage *gm)
 		remainder_fd = fetch_tail_fd(tmpctx,
 					     gossmap_fd(gm->raw_gossmap),
 					     map_used, map_size);
-		status_failed(STATUS_FAIL_INTERNAL_ERROR,
-			      "Gossmap failed to process entire gossip_store: "
+		status_broken("Gossmap failed to process entire gossip_store, %s mmap: "
 			      "at %"PRIu64" of %"PRIu64" remaining_mmap=%s remaining_fd=%s",
+			      gossmap_has_mmap(gm->raw_gossmap)
+			      ? "disabling": "ALREADY DISABLED",
 			      map_used, map_size,
 			      tal_hex(tmpctx, remainder_mmap),
 			      tal_hex(tmpctx, remainder_fd));
+		gossmap_disable_mmap(gm->raw_gossmap);
+		gossmap_refresh(gm->raw_gossmap);
+
+		map_used = gossmap_lengths(gm->raw_gossmap, &map_size);
+		if (map_size != map_used) {
+			status_failed(STATUS_FAIL_INTERNAL_ERROR,
+				      "Gossmap map_used %"PRIu64" of %"PRIu64" with %"PRIu64" written",
+				      map_used, map_size, written_len);
+		}
 	}
 
 	return gm->raw_gossmap;