net: sctp: dynamically enable or disable pf state

As we all know, the value of pf_retrans >= max_retrans_path can
disable pf state. The variables of pf_retrans and max_retrans_path
can be changed by the userspace application.

Sometimes the user expects to disable pf state while the 2
variables are changed to enable pf state. So it is necessary to
introduce a new variable to disable pf state.

According to the suggestions from Vlad Yasevich, extra1 and extra2
are removed. The initialization of pf_enable is added.

Acked-by: Vlad Yasevich <[e-mail]>
Signed-off-by: Zhu Yanjun <[e-mail]>
Acked-by: Marcelo Ricardo Leitner <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/networking/ip-sysctl.txt

···
 
 	Default: 0
 
+pf_enable - INTEGER
+	Enable or disable pf (pf is short for potentially failed) state. A value
+	of pf_retrans > path_max_retrans also disables pf state. That is, one of
+	both pf_enable and pf_retrans > path_max_retrans can disable pf state.
+	Since pf_retrans and path_max_retrans can be changed by userspace
+	application, sometimes user expects to disable pf state by the value of
+	pf_retrans > path_max_retrans, but occasionally the value of pf_retrans
+	or path_max_retrans is changed by the user application, this pf state is
+	enabled. As such, it is necessary to add this to dynamically enable
+	and disable pf state. See:
+	https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-failover for
+	details.
+
+	1: Enable pf.
+
+	0: Disable pf.
+
+	Default: 1
+
 addip_noauth_enable - BOOLEAN
 	Dynamic Address Reconfiguration (ADD-IP) requires the use of
 	authentication to protect the operations of adding or removing new
···
 	having to reduce path_max_retrans to a very low value.  See:
 	http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt
 	for details.  Note also that a value of pf_retrans > path_max_retrans
-	disables this feature
+	disables this feature. Since both pf_retrans and path_max_retrans can
+	be changed by userspace application, a variable pf_enable is used to
+	disable pf state.
 
 	Default: 0
 

include/net/netns/sctp.h

···
 	int pf_retrans;
 
 	/*
+	 * Disable Potentially-Failed feature, the feature is enabled by default
+	 * pf_enable	-  0  : disable pf
+	 *		- >0  : enable pf
+	 */
+	int pf_enable;
+
+	/*
 	 * Policy for preforming sctp/socket accounting
 	 * 0   - do socket level accounting, all assocs share sk_sndbuf
 	 * 1   - do sctp accounting, each asoc may use sk_sndbuf bytes

net/sctp/protocol.c

···
 	/* Max.Burst		    - 4 */
 	net->sctp.max_burst			= SCTP_DEFAULT_MAX_BURST;
 
+	/* Enable pf state by default */
+	net->sctp.pf_enable = 1;
+
 	/* Association.Max.Retrans  - 10 attempts
 	 * Path.Max.Retrans         - 5  attempts (per destination address)
 	 * Max.Init.Retransmits     - 8  attempts

net/sctp/sm_sideeffect.c

···
 					 struct sctp_transport *transport,
 					 int is_hb)
 {
+	struct net *net = sock_net(asoc->base.sk);
+
 	/* The check for association's overall error counter exceeding the
 	 * threshold is done in the state function.
 	 */
···
 	 * is SCTP_ACTIVE, then mark this transport as Partially Failed,
 	 * see SCTP Quick Failover Draft, section 5.1
 	 */
-	if ((transport->state == SCTP_ACTIVE) &&
+	if (net->sctp.pf_enable &&
+	   (transport->state == SCTP_ACTIVE) &&
 	   (asoc->pf_retrans < transport->pathmaxrxt) &&
 	   (transport->error_count > asoc->pf_retrans)) {
 

net/sctp/sysctl.c

···
 		.extra1		= &max_autoclose_min,
 		.extra2		= &max_autoclose_max,
 	},
+	{
+		.procname	= "pf_enable",
+		.data		= &init_net.sctp.pf_enable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
 
 	{ /* sentinel */ }
 };