[tcp] Discard all TCP connections on shutdown

Allow detection of genuine memory leaks by ensuring that all TCP
connections are freed on shutdown.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/tcp.c

 #include <ipxe/timer.h>
 #include <ipxe/iobuf.h>
 #include <ipxe/malloc.h>
+#include <ipxe/init.h>
 #include <ipxe/retry.h>
 #include <ipxe/refcnt.h>
 #include <ipxe/xfer.h>
 
 		/* Remove from list and drop reference */
 		stop_timer ( &tcp->timer );
+		stop_timer ( &tcp->wait );
 		list_del ( &tcp->list );
 		ref_put ( &tcp->refcnt );
 		DBGC ( tcp, "TCP %p connection deleted\n", tcp );
 	.discard = tcp_discard,
 };
 
+/**
+ * Shut down all TCP connections
+ *
+ */
+static void tcp_shutdown ( int booting __unused ) {
+	struct tcp_connection *tcp;
+
+	while ( ( tcp = list_first_entry ( &tcp_conns, struct tcp_connection,
+					   list ) ) != NULL ) {
+		tcp->tcp_state = TCP_CLOSED;
+		tcp_dump_state ( tcp );
+		tcp_close ( tcp, -ECANCELED );
+	}
+}
+
+/** TCP shutdown function */
+struct startup_fn tcp_startup_fn __startup_fn ( STARTUP_EARLY ) = {
+	.shutdown = tcp_shutdown,
+};
+
 /***************************************************************************
  *
  * Data transfer interface