Subject: [PATCH net-next] net: ipv6: addrconf: Add accept_ra_prefix_route.

From: Subash Abhinov Kasiviswanathan <[email-masked]>
Date: Wed, 10 Mar 2021 11:49:53 -0700

Added new procfs flag to toggle the automatic addition of prefix
routes on a per device basis. The new flag is accept_ra_prefix_route.

A value of 0 for the flag maybe used in some forwarding scenarios
when a userspace daemon is managing the routing.
Manual deletion of the kernel installed route was not sufficient as
kernel was adding back the route.

Defaults to 1 as to not break existing behavior.

Signed-off-by: Subash Abhinov Kasiviswanathan <[email-masked]>
---
 Documentation/networking/ip-sysctl.rst | 10 ++++++++++
 include/linux/ipv6.h                   |  1 +
 include/uapi/linux/ipv6.h              |  1 +
 net/ipv6/addrconf.c                    | 16 +++++++++++++---
 4 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index c7952ac..9f0d92d 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -2022,6 +2022,16 @@ accept_ra_mtu - BOOLEAN
 		- enabled if accept_ra is enabled.
 		- disabled if accept_ra is disabled.
 
+accept_ra_prefix_route - BOOLEAN
+	Apply the prefix route based on the RA. If disabled, kernel
+	does not install the route. This can be used if a userspace
+	daemon is managing the routing.
+
+	Functional default:
+
+		- enabled if accept_ra_prefix_route is enabled
+		- disabled if accept_ra_prefix_route is disabled
+
 accept_redirects - BOOLEAN
 	Accept Redirects.
 
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 70b2ad3..ae81f7d 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -76,6 +76,7 @@ struct ipv6_devconf {
 	__s32		disable_policy;
 	__s32           ndisc_tclass;
 	__s32		rpl_seg_enabled;
+	__s32		accept_ra_prefix_route;
 
 	struct ctl_table_header *sysctl_header;
 };
diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index 70603775..194b272 100644
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -190,6 +190,7 @@ enum {
 	DEVCONF_NDISC_TCLASS,
 	DEVCONF_RPL_SEG_ENABLED,
 	DEVCONF_RA_DEFRTR_METRIC,
+	DEVCONF_ACCEPT_RA_PREFIX_ROUTE,
 	DEVCONF_MAX
 };
 
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index f2337fb..5ddef05 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -237,6 +237,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
 	.addr_gen_mode		= IN6_ADDR_GEN_MODE_EUI64,
 	.disable_policy		= 0,
 	.rpl_seg_enabled	= 0,
+	.accept_ra_prefix_route = 1,
 };
 
 static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
@@ -293,6 +294,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
 	.addr_gen_mode		= IN6_ADDR_GEN_MODE_EUI64,
 	.disable_policy		= 0,
 	.rpl_seg_enabled	= 0,
+	.accept_ra_prefix_route = 1,
 };
 
 /* Check if link is ready: is it up and is a valid qdisc available */
@@ -2750,9 +2752,10 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len, bool sllao)
 				flags |= RTF_EXPIRES;
 				expires = jiffies_to_clock_t(rt_expires);
 			}
-			addrconf_prefix_route(&pinfo->prefix, pinfo->prefix_len,
-					      0, dev, expires, flags,
-					      GFP_ATOMIC);
+			if (dev->ip6_ptr->cnf.accept_ra_prefix_route) {
+				addrconf_prefix_route(&pinfo->prefix, pinfo->prefix_len,
+						      0, dev, expires, flags, GFP_ATOMIC);
+			}
 		}
 		fib6_info_release(rt);
 	}
@@ -6859,6 +6862,13 @@ static const struct ctl_table addrconf_sysctl[] = {
 	{
 		.procname	= "seg6_enabled",
 		.data		= &ipv6_devconf.seg6_enabled,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec,
+	},
+	{
+		.procname	= "accept_ra_prefix_route",
+		.data		= &ipv6_devconf.accept_ra_prefix_route,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
-- 
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