When the guest sends a TCP RST, or on certain error conditions, we want to
signal the abnormal termination of a TCP connection to the peer with an
RST as well. We attempt to do that by close()ing the socket.
That doesn't work: a close() will usually send a FIN, rather than an RST.
The standard method of forcing an RST on a socket is to set the SO_LINGER
socket option with a 0 timeout, then close().
Update the tcp_rst() path to do this, so it forces a socket side RST.
Update the handling of a guest side RST to use the same path (minus
sending a tap side RST) so that we properly propagate guest RSTs to the
peer.
Link: https://bugs.passt.top/show_bug.cgi?id=191
Signed-off-by: David Gibson
---
tcp.c | 37 +++++++++++++++++++++++++++++++++----
1 file changed, 33 insertions(+), 4 deletions(-)
diff --git a/tcp.c b/tcp.c
index 45dde5a0..9da37c2f 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1403,7 +1403,34 @@ static int tcp_send_flag(const struct ctx *c, struct tcp_tap_conn *conn,
}
/**
- * tcp_rst_do() - Reset a tap connection: send RST segment to tap, close socket
+ * tcp_sock_rst() - Close TCP connection forcing RST on socket side
+ * @c: Execution context
+ * @conn: Connection pointer
+ */
+static void tcp_sock_rst(const struct ctx *c, struct tcp_tap_conn *conn)
+{
+ const struct linger linger0 = {
+ .l_onoff = 1,
+ .l_linger = 0,
+ };
+
+ /* Force RST on socket to inform the peer
+ *
+ * We do this by setting SO_LINGER with 0 timeout, which means that
+ * close() will send an RST (unless the connection is already closed in
+ * both directions).
+ */
+ if (setsockopt(conn->sock, SOL_SOCKET,
+ SO_LINGER, &linger0, sizeof(linger0)) < 0) {
+ flow_dbg_perror(conn,
+ "SO_LINGER failed, may not send RST to peer");
+ }
+
+ conn_event(c, conn, CLOSED);
+}
+
+/**
+ * tcp_rst_do() - Reset a tap connection: send RST segment on both sides, close
* @c: Execution context
* @conn: Connection pointer
*/
@@ -1412,8 +1439,10 @@ void tcp_rst_do(const struct ctx *c, struct tcp_tap_conn *conn)
if (conn->events == CLOSED)
return;
+ /* Send RST on tap */
tcp_send_flag(c, conn, RST);
- conn_event(c, conn, CLOSED);
+
+ tcp_sock_rst(c, conn);
}
/**
@@ -1884,7 +1913,7 @@ static int tcp_data_from_tap(const struct ctx *c, struct tcp_tap_conn *conn,
return -1;
if (th->rst) {
- conn_event(c, conn, CLOSED);
+ tcp_sock_rst(c, conn);
return 1;
}
@@ -2248,7 +2277,7 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af,
flow_trace(conn, "packet length %zu from tap", l4len);
if (th->rst) {
- conn_event(c, conn, CLOSED);
+ tcp_sock_rst(c, conn);
return 1;
}
--
2.52.0