dev_disconnect: add '<' to close after an incoming msg.

I'd been resisting this, but some tests really do want "hang up after
*receiving* this", and it's more reliable than getting the peer to
"hang up afer *sending* this" which seems not always work.

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

common/dev_disconnect.c

@@ -59,6 +59,7 @@ enum dev_disconnect_out dev_disconnect_out(const struct node_id *id, int pkt_typ
 		next_dev_disconnect();
 
 	if (!dev_disconnect_line[0]
+	    || dev_disconnect_line[0] == DEV_DISCONNECT_IN_AFTER_RECV
 	    || !streq(peer_wire_name(pkt_type), dev_disconnect_line+1))
 		return DEV_DISCONNECT_OUT_NORMAL;
 
@@ -76,6 +77,32 @@ enum dev_disconnect_out dev_disconnect_out(const struct node_id *id, int pkt_typ
 	return dev_disconnect_line[0];
 }
 
+enum dev_disconnect_in dev_disconnect_in(const struct node_id *id, int pkt_type)
+{
+	if (dev_disconnect_fd == -1)
+		return DEV_DISCONNECT_IN_NORMAL;
+
+	if (!dev_disconnect_count)
+		next_dev_disconnect();
+
+	if (dev_disconnect_line[0] != DEV_DISCONNECT_IN_AFTER_RECV
+	    || !streq(peer_wire_name(pkt_type), dev_disconnect_line+1))
+		return DEV_DISCONNECT_IN_NORMAL;
+
+	if (--dev_disconnect_count != 0) {
+		return DEV_DISCONNECT_IN_NORMAL;
+	}
+
+	if (lseek(dev_disconnect_fd, dev_disconnect_len+1, SEEK_CUR) < 0) {
+		err(1, "lseek failure");
+	}
+
+	status_peer_debug(id, "dev_disconnect: %s (%s)",
+			  dev_disconnect_line,
+			  peer_wire_name(pkt_type));
+	return dev_disconnect_line[0];
+}
+
 void dev_sabotage_fd(int fd, bool close_fd)
 {
 	int fds[2];

common/dev_disconnect.h

@@ -23,6 +23,16 @@ enum dev_disconnect_out {
 /* Force a close fd before or after a certain packet type */
 enum dev_disconnect_out dev_disconnect_out(const struct node_id *id, int pkt_type);
 
+enum dev_disconnect_in {
+	/* Do nothing. */
+	DEV_DISCONNECT_IN_NORMAL = '=',
+	/* Close connection after receiving packet. */
+	DEV_DISCONNECT_IN_AFTER_RECV = '<',
+};
+
+/* Force a close fd after receiving a certain packet type */
+enum dev_disconnect_in dev_disconnect_in(const struct node_id *id, int pkt_type);
+
 /* Make next write on fd fail as if they'd disconnected. */
 void dev_sabotage_fd(int fd, bool close_fd);