netdev - [PATCH net-next] Add support for PIO p flag

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Message-ID: <20240726010629.111077-1-prohr@google.com>
Date: Thu, 25 Jul 2024 18:06:29 -0700
From: Patrick Rohr <prohr@...gle.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: Linux Network Development Mailing List <netdev@...r.kernel.org>, Patrick Rohr <prohr@...gle.com>, 
	"Maciej Żenczykowski" <maze@...gle.com>, Lorenzo Colitti <lorenzo@...gle.com>, 
	David Lamparter <equinox@...nsourcerouting.org>
Subject: [PATCH net-next] Add support for PIO p flag

draft-ietf-6man-pio-pflag is adding a new flag to the Prefix Information
Option to signal the pd-per-device addressing mechanism.

When accept_pio_pflag is enabled, the presence of the p-flag will cause
an a flag in the same PIO to be ignored.

An automated test has been added in Android (r.android.com/3195335) to
go along with this change.

Cc: Maciej Żenczykowski <maze@...gle.com>
Cc: Lorenzo Colitti <lorenzo@...gle.com>
Cc: David Lamparter <equinox@...nsourcerouting.org>
Signed-off-by: Patrick Rohr <prohr@...gle.com>
---
 Documentation/networking/ip-sysctl.rst | 11 +++++++++++
 include/linux/ipv6.h                   |  1 +
 include/net/addrconf.h                 |  8 ++++++--
 net/ipv6/addrconf.c                    | 15 ++++++++++++++-
 4 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 3616389c8c2d..322a0329b366 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -2362,6 +2362,17 @@ ra_honor_pio_life - BOOLEAN
 
 	Default: 0 (disabled)
 
+accept_pio_pflag - BOOLEAN
+	Used to indicate userspace support for a DHCPv6-PD client.
+	If enabled, the presence of the PIO p flag indicates to the
+	kernel to ignore the autoconf flag.
+
+	- If disabled, the P flag is ignored.
+	- If enabled, disables SLAAC to obtain new addresses from
+	  prefixes with the P flag set.
+
+	Default: 0 (disabled)
+
 accept_ra_rt_info_min_plen - INTEGER
 	Minimum prefix length of Route Information in RA.
 
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 383a0ea2ab91..396b87d76b55 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -89,6 +89,7 @@ struct ipv6_devconf {
 	__u8		ioam6_enabled;
 	__u8		ndisc_evict_nocarrier;
 	__u8		ra_honor_pio_life;
+	__u8		accept_pio_pflag;
 
 	struct ctl_table_header *sysctl_header;
 };
diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 62a407db1bf5..59496aa23012 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -38,9 +38,13 @@ struct prefix_info {
 #if defined(__BIG_ENDIAN_BITFIELD)
 			__u8	onlink : 1,
 			 	autoconf : 1,
-				reserved : 6;
+			 	routeraddr : 1,
+				pdpreferred : 1,
+				reserved : 4;
 #elif defined(__LITTLE_ENDIAN_BITFIELD)
-			__u8	reserved : 6,
+			__u8	reserved : 4,
+				pdpreferred : 1,
+			 	routeraddr : 1,
 				autoconf : 1,
 				onlink : 1;
 #else
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 55a0fd589fc8..3e27725a12fc 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -239,6 +239,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
 	.ioam6_id_wide		= IOAM6_DEFAULT_IF_ID_WIDE,
 	.ndisc_evict_nocarrier	= 1,
 	.ra_honor_pio_life	= 0,
+	.accept_pio_pflag	= 0,
 };
 
 static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
@@ -302,6 +303,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
 	.ioam6_id_wide		= IOAM6_DEFAULT_IF_ID_WIDE,
 	.ndisc_evict_nocarrier	= 1,
 	.ra_honor_pio_life	= 0,
+	.accept_pio_pflag	= 0,
 };
 
 /* Check if link is ready: is it up and is a valid qdisc available */
@@ -2762,6 +2764,7 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len, bool sllao)
 	u32 addr_flags = 0;
 	struct inet6_dev *in6_dev;
 	struct net *net = dev_net(dev);
+	bool ignore_autoconf_flag = false;
 
 	pinfo = (struct prefix_info *) opt;
 
@@ -2864,7 +2867,8 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len, bool sllao)
 
 	/* Try to figure out our local address for this prefix */
 
-	if (pinfo->autoconf && in6_dev->cnf.autoconf) {
+	ignore_autoconf_flag = READ_ONCE(in6_dev->cnf.accept_pio_pflag) && pinfo->pdpreferred;
+	if (pinfo->autoconf && in6_dev->cnf.autoconf && !ignore_autoconf_flag) {
 		struct in6_addr addr;
 		bool tokenized = false, dev_addr_generated = false;
 
@@ -6926,6 +6930,15 @@ static const struct ctl_table addrconf_sysctl[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_ONE,
 	},
+	{
+		.procname	= "accept_pio_pflag",
+		.data		= &ipv6_devconf.accept_pio_pflag,
+		.maxlen		= sizeof(u8),
+		.mode		= 0644,
+		.proc_handler	= proc_dou8vec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
 #ifdef CONFIG_IPV6_ROUTER_PREF
 	{
 		.procname	= "accept_ra_rtr_pref",
-- 
2.46.0.rc1.232.g9752f9e123-goog