If the peer shrinks the window to zero, we'll skip storing the new
window, as a convenient way to cause window probes (which exceed any
zero-sized window, strictly speaking) if we don't get window updates
in a while.
As we do so, though, we need to ensure we don't try to queue more data
from the socket right after we process this window update, as the
entire point of a zero-window advertisement is to keep us from sending
more data.
Signed-off-by: Stefano Brivio
Reviewed-by: David Gibson
---
tcp.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/tcp.c b/tcp.c
index fccea35..051550d 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1260,8 +1260,10 @@ static void tcp_get_tap_ws(struct tcp_tap_conn *conn,
* @c: Execution context
* @conn: Connection pointer
* @wnd: Window value, host order, unscaled
+ *
+ * Return: false on zero window (not stored to wnd_from_tap), true otherwise
*/
-static void tcp_tap_window_update(const struct ctx *c,
+static bool tcp_tap_window_update(const struct ctx *c,
struct tcp_tap_conn *conn, unsigned wnd)
{
wnd = MIN(MAX_WINDOW, wnd << conn->ws_from_tap);
@@ -1274,13 +1276,14 @@ static void tcp_tap_window_update(const struct ctx *c,
*/
if (!wnd && SEQ_LT(conn->seq_ack_from_tap, conn->seq_to_tap)) {
tcp_rewind_seq(c, conn);
- return;
+ return false;
}
conn->wnd_from_tap = MIN(wnd >> conn->ws_from_tap, USHRT_MAX);
/* FIXME: reflect the tap-side receiver's window back to the sock-side
* sender by adjusting SO_RCVBUF? */
+ return true;
}
/**
@@ -2075,9 +2078,8 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af,
if (!th->ack)
goto reset;
- tcp_tap_window_update(c, conn, ntohs(th->window));
-
- tcp_data_from_sock(c, conn);
+ if (tcp_tap_window_update(c, conn, ntohs(th->window)))
+ tcp_data_from_sock(c, conn);
if (p->count - idx == 1)
return 1;
@@ -2087,8 +2089,8 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af,
if (conn->events & TAP_FIN_RCVD) {
tcp_sock_consume(conn, ntohl(th->ack_seq));
tcp_update_seqack_from_tap(c, conn, ntohl(th->ack_seq));
- tcp_tap_window_update(c, conn, ntohs(th->window));
- tcp_data_from_sock(c, conn);
+ if (tcp_tap_window_update(c, conn, ntohs(th->window)))
+ tcp_data_from_sock(c, conn);
if (conn->seq_ack_from_tap == conn->seq_to_tap) {
if (th->ack && conn->events & TAP_FIN_SENT)
--
2.43.0