100 lines
3.0 KiB
Diff
100 lines
3.0 KiB
Diff
From a742a423b3c8fd345c4af50dd5f06b95af6c75bf Mon Sep 17 00:00:00 2001
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From: David Gibson <david@gibson.dropbear.id.au>
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Date: Tue, 27 Jan 2026 19:39:52 +1100
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Subject: [PATCH 12/18] tcp: Properly propagate tap-side RST to socket side
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When the guest sends a TCP RST, or on certain error conditions, we want to
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signal the abnormal termination of a TCP connection to the peer with an
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RST as well. We attempt to do that by close()ing the socket.
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That doesn't work: a close() will usually send a FIN, rather than an RST.
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The standard method of forcing an RST on a socket is to set the SO_LINGER
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socket option with a 0 timeout, then close().
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Update the tcp_rst() path to do this, so it forces a socket side RST.
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Update the handling of a guest side RST to use the same path (minus
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sending a tap side RST) so that we properly propagate guest RSTs to the
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peer.
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Link: https://bugs.passt.top/show_bug.cgi?id=191
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Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
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(cherry picked from commit cce94e92fb3d2a90730c125f2bad32c9ed51da3f)
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---
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tcp.c | 37 +++++++++++++++++++++++++++++++++----
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1 file changed, 33 insertions(+), 4 deletions(-)
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diff --git a/tcp.c b/tcp.c
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index 146d460..602e810 100644
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--- a/tcp.c
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+++ b/tcp.c
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@@ -1417,7 +1417,34 @@ static int tcp_send_flag(const struct ctx *c, struct tcp_tap_conn *conn,
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}
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/**
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- * tcp_rst_do() - Reset a tap connection: send RST segment to tap, close socket
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+ * tcp_sock_rst() - Close TCP connection forcing RST on socket side
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+ * @c: Execution context
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+ * @conn: Connection pointer
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+ */
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+static void tcp_sock_rst(const struct ctx *c, struct tcp_tap_conn *conn)
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+{
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+ const struct linger linger0 = {
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+ .l_onoff = 1,
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+ .l_linger = 0,
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+ };
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+
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+ /* Force RST on socket to inform the peer
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+ *
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+ * We do this by setting SO_LINGER with 0 timeout, which means that
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+ * close() will send an RST (unless the connection is already closed in
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+ * both directions).
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+ */
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+ if (setsockopt(conn->sock, SOL_SOCKET,
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+ SO_LINGER, &linger0, sizeof(linger0)) < 0) {
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+ flow_dbg_perror(conn,
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+ "SO_LINGER failed, may not send RST to peer");
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+ }
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+
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+ conn_event(c, conn, CLOSED);
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+}
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+
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+/**
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+ * tcp_rst_do() - Reset a tap connection: send RST segment on both sides, close
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* @c: Execution context
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* @conn: Connection pointer
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*/
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@@ -1426,8 +1453,10 @@ void tcp_rst_do(const struct ctx *c, struct tcp_tap_conn *conn)
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if (conn->events == CLOSED)
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return;
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+ /* Send RST on tap */
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tcp_send_flag(c, conn, RST);
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- conn_event(c, conn, CLOSED);
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+
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+ tcp_sock_rst(c, conn);
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}
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/**
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@@ -1898,7 +1927,7 @@ static int tcp_data_from_tap(const struct ctx *c, struct tcp_tap_conn *conn,
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return -1;
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if (th->rst) {
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- conn_event(c, conn, CLOSED);
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+ tcp_sock_rst(c, conn);
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return 1;
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}
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@@ -2262,7 +2291,7 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af,
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flow_trace(conn, "packet length %zu from tap", l4len);
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if (th->rst) {
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- conn_event(c, conn, CLOSED);
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+ tcp_sock_rst(c, conn);
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return 1;
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}
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--
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2.47.1
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