...as I'm going to need a third occurrence of this in the next change.
This introduces a small functional change in tcp_data_from_tap(): the
sequence was previously rewound to the highest ACK number we found in
the current packet batch, and not to the current value of
seq_ack_from_tap.
The two might differ in case tcp_sock_consume() failed, because in
that case we're ignoring that ACK altogether. But if we're ignoring
it, it looks more correct to me to start retransmitting from an
earlier sequence anyway.
Signed-off-by: Stefano Brivio
Reviewed-by: David Gibson
---
tcp.c | 47 ++++++++++++++++++++++++++++++++---------------
1 file changed, 32 insertions(+), 15 deletions(-)
diff --git a/tcp.c b/tcp.c
index 7c1f237..1402ca2 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1097,6 +1097,26 @@ static void tcp_update_seqack_from_tap(const struct ctx *c,
}
}
+/**
+ * tcp_rewind_seq() - Rewind sequence to tap and socket offset to current ACK
+ * @c: Execution context
+ * @conn: Connection pointer
+ *
+ * Return: 0 on success, -1 on failure, with connection reset
+ */
+static int tcp_rewind_seq(const struct ctx *c, struct tcp_tap_conn *conn)
+{
+ conn->seq_to_tap = conn->seq_ack_from_tap;
+ conn->events &= ~TAP_FIN_SENT;
+
+ if (tcp_set_peek_offset(conn, 0)) {
+ tcp_rst(c, conn);
+ return -1;
+ }
+
+ return 0;
+}
+
/**
* tcp_prepare_flags() - Prepare header for flags-only segment (no payload)
* @c: Execution context
@@ -1757,13 +1777,11 @@ static int tcp_data_from_tap(const struct ctx *c, struct tcp_tap_conn *conn,
if (retr) {
flow_trace(conn,
"fast re-transmit, ACK: %u, previous sequence: %u",
- max_ack_seq, conn->seq_to_tap);
- conn->seq_to_tap = max_ack_seq;
- conn->events &= ~TAP_FIN_SENT;
- if (tcp_set_peek_offset(conn, 0)) {
- tcp_rst(c, conn);
+ conn->seq_ack_from_tap, conn->seq_to_tap);
+
+ if (tcp_rewind_seq(c, conn))
return -1;
- }
+
tcp_data_from_sock(c, conn);
}
@@ -2285,17 +2303,16 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref)
tcp_rst(c, conn);
} else {
flow_dbg(conn, "ACK timeout, retry");
- conn->retrans++;
- conn->seq_to_tap = conn->seq_ack_from_tap;
- conn->events &= ~TAP_FIN_SENT;
+
if (!conn->wnd_from_tap)
conn->wnd_from_tap = 1; /* Zero-window probe */
- if (tcp_set_peek_offset(conn, 0)) {
- tcp_rst(c, conn);
- } else {
- tcp_data_from_sock(c, conn);
- tcp_timer_ctl(c, conn);
- }
+
+ conn->retrans++;
+ if (tcp_rewind_seq(c, conn))
+ return;
+
+ tcp_data_from_sock(c, conn);
+ tcp_timer_ctl(c, conn);
}
} else {
struct itimerspec new = { { 0 }, { ACT_TIMEOUT, 0 } };
--
2.43.0