Each time we get an incoming SYN to the RDS_TCP_PORT, the TCP
layer accepts the connection and then the rds_tcp_accept_one()
callback is invoked to process the incoming connection.
rds_tcp_accept_one() may reject the incoming syn for a number of
reasons, e.g., commit 1a0e100fb2c9 ("RDS: TCP: Force every connection
to be initiated by numerically smaller IP address"), or because
we are getting spammed by a malicious node that is triggering
a flood of connection attempts to RDS_TCP_PORT. If the incoming
syn is rejected, no data would have been sent on the TCP socket,
and we do not need to be in TIME_WAIT state, so we set linger on
the TCP socket before closing, thereby closing the socket efficiently
with a RST.
Signed-off-by: Sowmini Varadhan <sowmini.varad...@oracle.com>
Tested-by: Imanti Mendez <imanti.men...@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilim...@oracle.com>
---
net/rds/tcp_listen.c | 19 ++++++++++++++++++-
1 files changed, 18 insertions(+), 1 deletions(-)
diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c
index f9c6312..df291ac 100644
--- a/net/rds/tcp_listen.c
+++ b/net/rds/tcp_listen.c
@@ -112,6 +112,17 @@ struct rds_tcp_connection *rds_tcp_accept_one_path(struct
rds_connection *conn)
return NULL;
}
+static void rds_tcp_set_linger(struct socket *sock)
+{
+ struct linger no_linger = {
+ .l_onoff = 1,
+ .l_linger = 0,
+ };
+
+ kernel_setsockopt(sock, SOL_SOCKET, SO_LINGER,
+ (char *)&no_linger, sizeof(no_linger));
+}
+
int rds_tcp_accept_one(struct socket *sock)
{
struct socket *new_sock = NULL;
@@ -183,7 +194,13 @@ int rds_tcp_accept_one(struct socket *sock)
ret = 0;
goto out;
rst_nsk:
- /* reset the newly returned accept sock and bail */
+ /* reset the newly returned accept sock and bail.
+ * It is safe to set linger on new_sock because the RDS connection
+ * has not been brought up on new_sock, so no RDS-level data could
+ * be pending on it. By setting linger, we achieve the side-effect
+ * of avoiding TIME_WAIT state on new_sock.
+ */
+ rds_tcp_set_linger(new_sock);
kernel_sock_shutdown(new_sock, SHUT_RDWR);
ret = 0;
out:
--
1.7.1
