dev_disconnect: new option to stop using connection, but don't close.

This allows us to ensure a packet is read by the other end, but we
don't read anything else from them or write anything to them.

Using '+' is similar, but because it closes the connection, the peer
might notice before receiving the packet (such as if it does a write).

Signed-off-by: Rusty Russell <[email protected]>

common/crypto_sync.c

@@ -17,7 +17,7 @@
 void sync_crypto_write(struct per_peer_state *pps, const void *msg TAKES)
 {
 #if DEVELOPER
-	bool post_sabotage = false;
+	bool post_sabotage = false, post_close;
 	int type = fromwire_peektype(msg);
 #endif
 	u8 *enc;
@@ -28,18 +28,23 @@ void sync_crypto_write(struct per_peer_state *pps, const void *msg TAKES)
 #if DEVELOPER
 	switch (dev_disconnect(type)) {
 	case DEV_DISCONNECT_BEFORE:
-		dev_sabotage_fd(pps->peer_fd);
+		dev_sabotage_fd(pps->peer_fd, true);
 		peer_failed_connection_lost();
 	case DEV_DISCONNECT_DROPPKT:
 		enc = tal_free(enc); /* FALL THRU */
 	case DEV_DISCONNECT_AFTER:
 		post_sabotage = true;
+		post_close = true;
 		break;
 	case DEV_DISCONNECT_BLACKHOLE:
 		dev_blackhole_fd(pps->peer_fd);
 		break;
 	case DEV_DISCONNECT_NORMAL:
 		break;
+	case DEV_DISCONNECT_DISABLE_AFTER:
+		post_sabotage = true;
+		post_close = false;
+		break;
 	}
 #endif
 	if (!write_all(pps->peer_fd, enc, tal_count(enc)))
@@ -48,7 +53,7 @@ void sync_crypto_write(struct per_peer_state *pps, const void *msg TAKES)
 
 #if DEVELOPER
 	if (post_sabotage)
-		dev_sabotage_fd(pps->peer_fd);
+		dev_sabotage_fd(pps->peer_fd, post_close);
 #endif
 }
 

common/dev_disconnect.c

@@ -90,16 +90,13 @@ enum dev_disconnect dev_disconnect(int pkt_type)
 	return dev_disconnect_line[0];
 }
 
-void dev_sabotage_fd(int fd)
+void dev_sabotage_fd(int fd, bool close_fd)
 {
 	int fds[2];
 
 	if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds) != 0)
 		err(1, "dev_sabotage_fd: creating socketpair");
 
-	/* Close one. */
-	close(fds[0]);
-
 #if defined(TCP_NODELAY)
 	/* On Linux, at least, this flushes. */
 	int opt = TCP_NODELAY;
@@ -108,6 +105,14 @@ void dev_sabotage_fd(int fd)
 #else
 #error No TCP_NODELAY?
 #endif
+
+	/* Move fd out the way if we don't want to close it. */
+	if (!close_fd)
+		dup(fd);
+	else
+		/* Close other end of socket. */
+		close(fds[0]);
+
 	/* Move other over to the fd we want to sabotage. */
 	dup2(fds[1], fd);
 	close(fds[1]);

common/dev_disconnect.h

@@ -15,13 +15,15 @@ enum dev_disconnect {
 	DEV_DISCONNECT_DROPPKT = '@',
 	/* Swallow all writes from now on, and do no more reads. */
 	DEV_DISCONNECT_BLACKHOLE = '0',
+	/* Don't use connection after sending packet, but don't close. */
+	DEV_DISCONNECT_DISABLE_AFTER = 'x',
 };
 
 /* Force a close fd before or after a certain packet type */
 enum dev_disconnect dev_disconnect(int pkt_type);
 
 /* Make next write on fd fail as if they'd disconnected. */
-void dev_sabotage_fd(int fd);
+void dev_sabotage_fd(int fd, bool close_fd);
 
 /* No more data to arrive, what's written is swallowed. */
 void dev_blackhole_fd(int fd);

connectd/peer_exchange_initmsg.c

@@ -132,7 +132,14 @@ static struct io_plan *read_init(struct io_conn *conn, struct peer *peer)
 static struct io_plan *peer_write_postclose(struct io_conn *conn,
 					    struct peer *peer)
 {
-	dev_sabotage_fd(io_conn_fd(conn));
+	dev_sabotage_fd(io_conn_fd(conn), true);
+	return read_init(conn, peer);
+}
+
+static struct io_plan *peer_write_post_sabotage(struct io_conn *conn,
+						struct peer *peer)
+{
+	dev_sabotage_fd(io_conn_fd(conn), false);
 	return read_init(conn, peer);
 }
 #endif
@@ -197,7 +204,7 @@ struct io_plan *peer_exchange_initmsg(struct io_conn *conn,
 #if DEVELOPER
 	switch (dev_disconnect(WIRE_INIT)) {
 	case DEV_DISCONNECT_BEFORE:
-		dev_sabotage_fd(io_conn_fd(conn));
+		dev_sabotage_fd(io_conn_fd(conn), true);
 		break;
 	case DEV_DISCONNECT_DROPPKT:
 		peer->msg = tal_free(peer->msg); /* FALL THRU */
@@ -209,6 +216,9 @@ struct io_plan *peer_exchange_initmsg(struct io_conn *conn,
 		break;
 	case DEV_DISCONNECT_NORMAL:
 		break;
+	case DEV_DISCONNECT_DISABLE_AFTER:
+		next = peer_write_post_sabotage;
+		break;
 	}
 #endif /* DEVELOPER */
 

devtools/gossipwith.c

@@ -67,7 +67,7 @@ void status_fmt(enum log_level level,
 }
 
 #if DEVELOPER
-void dev_sabotage_fd(int fd)
+void dev_sabotage_fd(int fd, bool close_fd)
 {
 	abort();
 }