net: tcp: Correctly determine when the TCP transmit window is full
In the stack both unacked_len and send_data_total track the amount
of data for retransmission. send_data_total actually accounts the
total bytes in the buffer, where unacked_len is used to control the
retransmission progress.
Using unacked_len is sometimes reset to 0, this can lead to more data
being allowd in the send_data buffer. In worse case this can cause
depletion of the net buffers, causing a stall and crash of the connection.
The value send_data_total actually accounts the total amount of data in
the send_data buffer, so it is the proper value to used in the
tcp_window_full function.
Signed-off-by: Sjors Hettinga <s.a.hettinga@gmail.com>
diff --git a/subsys/net/ip/tcp.c b/subsys/net/ip/tcp.c
index 8941ec5..0fd4450 100644
--- a/subsys/net/ip/tcp.c
+++ b/subsys/net/ip/tcp.c
@@ -978,7 +978,7 @@
static bool tcp_window_full(struct tcp *conn)
{
- bool window_full = !(conn->unacked_len < conn->send_win);
+ bool window_full = (conn->send_data_total >= conn->send_win);
NET_DBG("conn: %p window_full=%hu", conn, window_full);
