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

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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 1a0e100fb2 ("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>
This commit is contained in:
Sowmini Varadhan 2017-06-15 11:28:55 -07:00 committed by David S. Miller
parent 00354de577
commit 10beea7d74
1 changed files with 18 additions and 1 deletions
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19
net/rds/tcp_listen.c
View File

@ -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: