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

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 <redacted>
---
 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,

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

On 3/10/21 11:49 AM, Subash Abhinov Kasiviswanathan wrote:

this seems to duplicate accept_ra_pinfo

On 2021-03-10 12:28, David Ahern wrote:

On 3/10/21 11:49 AM, Subash Abhinov Kasiviswanathan wrote:

quoted

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 
[off-list ref]
---
 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.

this seems to duplicate accept_ra_pinfo

Thanks David. We will try out that entry instead and check.

On 2021-03-10 14:33, subashab@codeaurora.org wrote:

On 2021-03-10 12:28, David Ahern wrote:

quoted

On 3/10/21 11:49 AM, Subash Abhinov Kasiviswanathan wrote:

quoted

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 
[off-list ref]
---
 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.

this seems to duplicate accept_ra_pinfo

Thanks David. We will try out that entry instead and check.

We are seeing that the interface itself doesn't get the address assigned
via RA when setting accept_ra_pinfo = 0.

We would like to have the interface address assigned via SLAAC
here while the route management would be handled via the userspace 
daemon.
In that case, we do not want the kernel installed route to be present
(behavior controlled via this proc entry).

On 3/11/21 7:22 PM, subashab@codeaurora.org wrote:

We are seeing that the interface itself doesn't get the address assigned
via RA when setting accept_ra_pinfo = 0.

We would like to have the interface address assigned via SLAAC
here while the route management would be handled via the userspace daemon.
In that case, we do not want the kernel installed route to be present
(behavior controlled via this proc entry).

sysctl's are not free and in this case you want to add a second one to
pick and choose which data in the message you want the kernel to act on.

Why can't the userspace daemon remove the route and add the one it
prefers? Or add another route with a metric that makes it the preferred
route making the kernel one effectively moot?

sysctl's are not free and in this case you want to add a second one to
pick and choose which data in the message you want the kernel to act 
on.

Why can't the userspace daemon remove the route and add the one it
prefers? Or add another route with a metric that makes it the preferred
route making the kernel one effectively moot?

As I recall, kernel was adding back the prefix based route when it is
deleted by userspace. I'll check this again to confirm the behavior
and also try installing the routes with lower metric.