libhw: Allow zero-length TCP reads and writes

1 files changed, 6 insertions, 4 deletions

diff --git a/libhw/w5500.c b/libhw/w5500.c
index dfe169f..a8777db 100644
--- a/libhw/w5500.c
+++ b/libhw/w5500.c
@@ -589,8 +589,9 @@ static int w5500_tcplist_close(struct _w5500_socket *socket) {
 static ssize_t w5500_tcp_write(struct _w5500_socket *socket, void *buf, size_t count) {
 	debugf("tcp_conn.write(%zu)", count);
 	ASSERT_SELF(stream_conn, TCP);
-	assert(buf);
-	assert(count);
+	assert(count == 0 || buf);
+	if (count == 0)
+		return 0;
 
 	/* What we really want is to pause until we receive an ACK for
 	 * some data we just queued, so that we can line up some new
@@ -677,8 +678,9 @@ static void w5500_tcp_alarm_handler(void *_arg) {
 static ssize_t w5500_tcp_read(struct _w5500_socket *socket, void *buf, size_t count) {
 	debugf("tcp_conn.read()");
 	ASSERT_SELF(stream_conn, TCP);
-	assert(buf);
-	assert(count);
+	assert(count == 0 || buf);
+	if (count == 0)
+		return 0;
 
 	struct alarmclock_trigger trigger = {0};
 	if (socket->read_deadline_ns)