[PATCH net-next 3/3] rds: tcp: Set linger when rejecting an incoming conn in rds_tcp_accept_one
flat view
STALE3412d
REVIEWED: 2 (0M)
From: Sowmini Varadhan <hidden>
Date: 2017-06-15 18:31:34
Subsystem:
networking [general], rds - reliable datagram sockets, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Allison Henderson, Linus Torvalds
2 review trailers.
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 <redacted>
Tested-by: Imanti Mendez <redacted>
Acked-by: Santosh Shilimkar <redacted>
---
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