Commit 10beea7d authored Jun 15, 2017 by Sowmini Varadhan Committed by David S. Miller Jun 16, 2017

rds: tcp: Set linger when rejecting an incoming conn in rds_tcp_accept_one



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 1a0e100f ("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.varadhan@oracle.com>
Tested-by: Imanti Mendez <imanti.mendez@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 00354de5

net/rds/tcp_listen.c

+18 −1

Original line number	Diff line number	Diff line
		@@ -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: