gossipd: don't use pwrite, better error messaging on init.

Since we open with O_APPEND, any write() will append as we want it to.

But we want to distinguish a new store creation from a truncation due
to bad version.

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

gossipd/gossip_store.c

@@ -16,7 +16,6 @@ static u8 gossip_store_version = 0x01;
 
 struct gossip_store {
 	int fd;
-	off_t write_pos;
 	u8 version;
 };
 
@@ -29,22 +28,29 @@ struct gossip_store *gossip_store_new(const tal_t *ctx)
 {
 	struct gossip_store *gs = tal(ctx, struct gossip_store);
 	gs->fd = open(GOSSIP_STORE_FILENAME, O_RDWR|O_APPEND|O_CREAT, 0600);
-	gs->write_pos = lseek(gs->fd, 0, SEEK_END);
-
-	/* Try to read the version, write it if this is a new file, or truncate
-	 * if the version doesn't match */
-	if (pread(gs->fd, &gs->version, sizeof(gs->version), 0) != 1 ||
-	    gs->version != gossip_store_version) {
-		status_trace("Truncating gossip_store, either it was empty or "
-			     "the version was not supported.");
-		gs->version = gossip_store_version;
-		gs->write_pos = 1;
-		pwrite(gs->fd, &gossip_store_version, sizeof(gossip_store_version), 0);
-		ftruncate(gs->fd, gs->write_pos);
-	}
 
 	tal_add_destructor(gs, gossip_store_destroy);
 
+	/* Try to read the version, write it if this is a new file, or truncate
+	 * if the version doesn't match */
+	if (read(gs->fd, &gs->version, sizeof(gs->version))
+	    == sizeof(gs->version)) {
+		/* Version match?  All good */
+		if (gs->version == gossip_store_version)
+			return gs;
+
+		status_unusual("Gossip store version %u not %u: removing",
+			       gs->version, gossip_store_version);
+		if (ftruncate(gs->fd, 0) != 0)
+			status_failed(STATUS_FAIL_INTERNAL_ERROR,
+				      "Truncating store: %s", strerror(errno));
+	}
+	/* Empty file, write version byte */
+	gs->version = gossip_store_version;
+	if (write(gs->fd, &gs->version, sizeof(gs->version))
+	    != sizeof(gs->version))
+		status_failed(STATUS_FAIL_INTERNAL_ERROR,
+			      "Writing version to store: %s", strerror(errno));
 	return gs;
 }
 /**
@@ -59,11 +65,17 @@ static void gossip_store_append(struct gossip_store *gs, const u8 *msg)
 	u32 msglen = tal_len(msg);
 	beint32_t belen = cpu_to_be32(msglen);
 
-	if (pwrite(gs->fd, &belen, sizeof(belen), gs->write_pos) != sizeof(belen) ||
-	    pwrite(gs->fd, msg, msglen, gs->write_pos + sizeof(belen)) != msglen) {
+	/* Only give error message once. */
+	if (gs->fd == -1)
 		return;
-	} else
-		gs->write_pos += sizeof(belen) + msglen;
+
+	/* FORTIFY_SOURCE gets upset if we don't check return. */
+	if (write(gs->fd, &belen, sizeof(belen)) != sizeof(belen) ||
+	    write(gs->fd, msg, msglen) != msglen) {
+              status_broken("Failed writing to gossip store: %s",
+			    strerror(errno));
+	      gs->fd = -1;
+	}
 }
 
 void gossip_store_add_channel_announcement(struct gossip_store *gs, const u8 *gossip_msg, u64 satoshis)
@@ -107,6 +119,7 @@ void gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
 	/* We set/check version byte on creation */
 	off_t known_good = 1;
 	const char *bad;
+	size_t stats[] = {0, 0, 0, 0};
 
 	lseek(gs->fd, known_good, SEEK_SET);
 	while (read(gs->fd, &belen, sizeof(belen)) == sizeof(belen)) {
@@ -127,18 +140,21 @@ void gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
 				bad = "Bad channel_announcement";
 				goto truncate;
 			}
+			stats[0]++;
 		} else if (fromwire_gossip_store_channel_update(msg, msg,
 								&gossip_msg)) {
 			if (!routing_add_channel_update(rstate, gossip_msg)) {
 				bad = "Bad channel_update";
 				goto truncate;
 			}
+			stats[1]++;
 		} else if (fromwire_gossip_store_node_announcement(msg, msg,
 								   &gossip_msg)) {
 			if (!routing_add_node_announcement(rstate, gossip_msg)) {
 				bad = "Bad node_announcement";
 				goto truncate;
 			}
+			stats[2]++;
 		} else if (fromwire_gossip_store_channel_delete(msg, &scid)) {
 			struct chan *c = get_channel(rstate, &scid);
 			if (!c) {
@@ -146,6 +162,7 @@ void gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
 				goto truncate;
 			}
 			tal_free(c);
+			stats[3]++;
 		} else {
 			bad = "Unknown message";
 			goto truncate;
@@ -153,6 +170,9 @@ void gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
 		known_good += sizeof(belen) + msglen;
 		tal_free(msg);
 	}
+	status_trace("gossip_store: Read %zu/%zu/%zu/%zu cannounce/cupdate/nannounce/cdelete from store in %"PRIu64" bytes",
+		     stats[0], stats[1], stats[2], stats[3],
+		     (u64)known_good);
 	return;
 
 truncate:

gossipd/test/run-bench-find_route.c

@@ -86,6 +86,9 @@ u8 fromwire_u8(const u8 **cursor UNNEEDED, size_t *max UNNEEDED)
 /* Generated stub for fromwire_wireaddr */
 bool fromwire_wireaddr(const u8 **cursor UNNEEDED, size_t *max UNNEEDED, struct wireaddr *addr UNNEEDED)
 { fprintf(stderr, "fromwire_wireaddr called!\n"); abort(); }
+/* Generated stub for gossip_wire_type_name */
+const char *gossip_wire_type_name(int e UNNEEDED)
+{ fprintf(stderr, "gossip_wire_type_name called!\n"); abort(); }
 /* Generated stub for onion_type_name */
 const char *onion_type_name(int e UNNEEDED)
 { fprintf(stderr, "onion_type_name called!\n"); abort(); }

gossipd/test/run-find_route-specific.c

@@ -50,6 +50,9 @@ u8 fromwire_u8(const u8 **cursor UNNEEDED, size_t *max UNNEEDED)
 /* Generated stub for fromwire_wireaddr */
 bool fromwire_wireaddr(const u8 **cursor UNNEEDED, size_t *max UNNEEDED, struct wireaddr *addr UNNEEDED)
 { fprintf(stderr, "fromwire_wireaddr called!\n"); abort(); }
+/* Generated stub for gossip_wire_type_name */
+const char *gossip_wire_type_name(int e UNNEEDED)
+{ fprintf(stderr, "gossip_wire_type_name called!\n"); abort(); }
 /* Generated stub for onion_type_name */
 const char *onion_type_name(int e UNNEEDED)
 { fprintf(stderr, "onion_type_name called!\n"); abort(); }

gossipd/test/run-find_route.c

@@ -48,6 +48,9 @@ u8 fromwire_u8(const u8 **cursor UNNEEDED, size_t *max UNNEEDED)
 /* Generated stub for fromwire_wireaddr */
 bool fromwire_wireaddr(const u8 **cursor UNNEEDED, size_t *max UNNEEDED, struct wireaddr *addr UNNEEDED)
 { fprintf(stderr, "fromwire_wireaddr called!\n"); abort(); }
+/* Generated stub for gossip_wire_type_name */
+const char *gossip_wire_type_name(int e UNNEEDED)
+{ fprintf(stderr, "gossip_wire_type_name called!\n"); abort(); }
 /* Generated stub for onion_type_name */
 const char *onion_type_name(int e UNNEEDED)
 { fprintf(stderr, "onion_type_name called!\n"); abort(); }