dev_disconnect: support multiple disconnects in the same daemon.

We currently assume the daemon gives up; gossipd won't, and we want to
test it there too.

This reveals a bug (returning io_close() is bad if the call is to
duplex()), and breaks a test which now continues after dropping a
packet..

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

common/cryptomsg.c

@@ -346,7 +346,8 @@ struct io_plan *peer_write_message(struct io_conn *conn,
 
 	switch (dev_disconnect(type)) {
 	case DEV_DISCONNECT_BEFORE:
-		return io_close(conn);
+		dev_sabotage_fd(io_conn_fd(conn));
+		break;
 	case DEV_DISCONNECT_DROPPKT:
 		pcs->out = NULL; /* FALL THRU */
 	case DEV_DISCONNECT_AFTER:

common/dev_disconnect.c

@@ -19,15 +19,16 @@ static bool dev_disconnect_nocommit;
 
 bool dev_suppress_commit;
 
-void dev_disconnect_init(int fd)
+static void next_dev_disconnect(void)
 {
 	int r;
 	char *asterisk;
 
-	r = read(fd, dev_disconnect_line, sizeof(dev_disconnect_line)-1);
+	r = read(dev_disconnect_fd,
+		 dev_disconnect_line, sizeof(dev_disconnect_line)-1);
 	if (r < 0)
 		err(1, "Reading dev_disconnect file");
-	lseek(fd, -r, SEEK_CUR);
+	lseek(dev_disconnect_fd, -r, SEEK_CUR);
 
 	/* Get first line */
 	dev_disconnect_line[r] = '\n';
@@ -49,22 +50,29 @@ void dev_disconnect_init(int fd)
 		*asterisk = '\0';
 	} else
 		dev_disconnect_count = 1;
+}
 
+void dev_disconnect_init(int fd)
+{
 	/* So we can move forward if we do use the line. */
 	dev_disconnect_fd = fd;
 }
 
 enum dev_disconnect dev_disconnect(int pkt_type)
 {
+	if (dev_disconnect_fd == -1)
+		return DEV_DISCONNECT_NORMAL;
+
+	if (!dev_disconnect_count)
+		next_dev_disconnect();
+
 	if (!streq(wire_type_name(pkt_type), dev_disconnect_line+1))
 		return DEV_DISCONNECT_NORMAL;
 
-	if (dev_disconnect_count != 1) {
-		dev_disconnect_count--;
+	if (--dev_disconnect_count != 0) {
 		return DEV_DISCONNECT_NORMAL;
 	}
 
-	assert(dev_disconnect_fd != -1);
 	lseek(dev_disconnect_fd, dev_disconnect_len+1, SEEK_CUR);
 
 	status_trace("dev_disconnect: %s%s", dev_disconnect_line,

tests/test_lightningd.py

@@ -1354,9 +1354,12 @@ class LightningDTests(BaseLightningDTests):
         assert l2.rpc.listinvoice('testpayment2')[0]['complete'] == True
 
     def test_reconnect_receiver_fulfill(self):
-        disconnects = ['-WIRE_UPDATE_FULFILL_HTLC',
-                       '@WIRE_UPDATE_FULFILL_HTLC',
+        # Ordering matters: after +WIRE_UPDATE_FULFILL_HTLC, channeld
+        # will continue and try to send WIRE_COMMITMENT_SIGNED: if
+        # that's the next failure, it will do two in one run.
+        disconnects = ['@WIRE_UPDATE_FULFILL_HTLC',
                        '+WIRE_UPDATE_FULFILL_HTLC',
+                       '-WIRE_UPDATE_FULFILL_HTLC',
                        '-WIRE_COMMITMENT_SIGNED',
                        '@WIRE_COMMITMENT_SIGNED',
                        '+WIRE_COMMITMENT_SIGNED',