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net: tcp: Avoid deadlock in updating the TCP receive window

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The function tcp_data_get tries to update the TCP receive window using
net_context_update_recv_wnd. This function graps the context lock while
the tcp_data_get is called from a situation where it already has tcp lock
is already. Transmission actions do first grab the the context lock and
try to grab the tcp lock afterwards. The combination of both can cause a
deadlock.

By taking the shortcut to directly update the tcp receive window without
going through the net context, the context lock is not required avoiding a
possible deadlock situation.

Signed-off-by: Sjors Hettinga <s.a.hettinga@gmail.com>
This commit is contained in:
Sjors Hettinga 2022-05-23 09:59:08 +02:00 • committed by Carles Cufí
commit d74bd3d7d1
1 changed files with 25 additions and 11 deletions
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36
subsys/net/ip/tcp.c
View file

@ -692,6 +692,29 @@ end:
return result;
}
/**
* @brief Update TCP receive window
*
* @param conn TCP network connection
* @param delta Receive window delta
*
* @return 0 on success, -EINVAL
* if the receive window delta is out of bounds
*/
static int tcp_update_recv_wnd(struct tcp *conn, int32_t delta)
{
int32_t new_win;
new_win = conn->recv_win + delta;
if (new_win < 0 || new_win > UINT16_MAX) {
return -EINVAL;
}
conn->recv_win = new_win;
return 0;
}
static size_t tcp_check_pending_data(struct tcp *conn, struct net_pkt *pkt,
size_t len)
{
@ -747,7 +770,7 @@ static int tcp_data_get(struct tcp *conn, struct net_pkt *pkt, size_t *len)
net_pkt_skip(up, net_pkt_get_len(up) - *len);
net_context_update_recv_wnd(conn->context, -*len);
tcp_update_recv_wnd(conn, -*len);
/* Do not pass data to application with TCP conn
* locked as there could be an issue when the app tries
@ -2250,21 +2273,12 @@ int net_tcp_listen(struct net_context *context)
int net_tcp_update_recv_wnd(struct net_context *context, int32_t delta)
{
int32_t new_win;
if (!context->tcp) {
NET_ERR("context->tcp == NULL");
return -EPROTOTYPE;
}
new_win = ((struct tcp *)context->tcp)->recv_win + delta;
if (new_win < 0 || new_win > UINT16_MAX) {
return -EINVAL;
}
((struct tcp *)context->tcp)->recv_win = new_win;
return 0;
return tcp_update_recv_wnd((struct tcp *)context->tcp, delta);
}
/* net_context queues the outgoing data for the TCP connection */