From: Stephen Hemminger <stephen@networkplumber.org>
Date: Mon, 29 Apr 2013 18:50:15 -0700
Subject: [PATCH] VyOS: Add linkstate IP device attribute

Backport of earlier Vyatta patch.

(cherry picked from commit 7c5a851086686be14ae937c80d6cee34814dbefc)

Refreshed against Linux 6.18.x:
  * include/uapi/linux/ipv6.h gained DEVCONF_FORCE_FORWARDING; insert
    DEVCONF_LINK_FILTER after it so the new sentinel keeps a stable value.
  * include/linux/ipv6.h grew ra_honor_pio_life / ra_honor_pio_pflag
    members before sysctl_header.
  * net/ipv6/addrconf.c::ipv6_store_devconf() now uses READ_ONCE() and
    publishes DEVCONF_FORCE_FORWARDING; use READ_ONCE() for link_filter
    and append after force_forwarding.
  * net/ipv6/route.c context shifted; rt6_link_filter() unchanged.
---
 Documentation/networking/ip-sysctl.rst | 11 +++++++++++
 include/linux/inetdevice.h             |  1 +
 include/linux/ipv6.h                   |  1 +
 include/uapi/linux/ip.h                |  1 +
 include/uapi/linux/ipv6.h              |  1 +
 net/ipv4/devinet.c                     |  1 +
 net/ipv6/addrconf.c                    |  8 ++++++++
 net/ipv6/route.c                       | 10 ++++++++++
 8 files changed, 34 insertions(+)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -2042,6 +2042,17 @@ src_valid_mark - BOOLEAN
 
 	Default value is 0.
 
+link_filter - INTEGER
+	0 - Allow packets to be received for the address on this interface
+	    even if interface is disabled or no carrier.
+	1 - Ignore packets received if interface associated with the incoming
+	    address is down.
+	2 - Ignore packets received if interface associated with the incoming
+	    address is down or has no carrier.
+
+	Default value is 0. Note that some distributions enable it
+	in startup scripts.
+
 arp_filter - BOOLEAN
 	- 1 - Allows you to have multiple network interfaces on the same
 	  subnet, and have the ARPs for each interface be answered
diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -139,6 +139,7 @@ static inline void ipv4_devconf_setall(struct in_device *in_dev)
 #define IN_DEV_ARP_NOTIFY(in_dev)	IN_DEV_MAXCONF((in_dev), ARP_NOTIFY)
 #define IN_DEV_ARP_EVICT_NOCARRIER(in_dev) IN_DEV_ANDCONF((in_dev), \
 							  ARP_EVICT_NOCARRIER)
+#define IN_DEV_LINKFILTER(in_dev)	IN_DEV_MAXCONF((in_dev), LINKFILTER)
 
 struct in_ifaddr {
 	struct hlist_node	addr_lst;
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -91,6 +91,7 @@ struct ipv6_devconf {
 	__u8		ndisc_evict_nocarrier;
 	__u8		ra_honor_pio_life;
 	__u8		ra_honor_pio_pflag;
+	__s32		link_filter;
 
 	struct ctl_table_header *sysctl_header;
 };
diff --git a/include/uapi/linux/ip.h b/include/uapi/linux/ip.h
--- a/include/uapi/linux/ip.h
+++ b/include/uapi/linux/ip.h
@@ -189,6 +189,7 @@ enum
 	IPV4_DEVCONF_DROP_GRATUITOUS_ARP,
 	IPV4_DEVCONF_BC_FORWARDING,
 	IPV4_DEVCONF_ARP_EVICT_NOCARRIER,
+	IPV4_DEVCONF_LINKFILTER,
 	__IPV4_DEVCONF_MAX
 };
 
diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -200,6 +200,7 @@ enum {
 	DEVCONF_ACCEPT_UNTRACKED_NA,
 	DEVCONF_ACCEPT_RA_MIN_LFT,
 	DEVCONF_FORCE_FORWARDING,
+	DEVCONF_LINK_FILTER,
 	DEVCONF_MAX
 };
 
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2652,6 +2652,7 @@ static struct devinet_sysctl_table {
 					      "route_localnet"),
 		DEVINET_SYSCTL_FLUSHING_ENTRY(DROP_UNICAST_IN_L2_MULTICAST,
 					      "drop_unicast_in_l2_multicast"),
+		DEVINET_SYSCTL_RW_ENTRY(LINKFILTER, "link_filter"),
 	},
 };
 
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5716,6 +5716,7 @@ static void ipv6_store_devconf(const struct ipv6_devconf *cnf,
 		READ_ONCE(cnf->accept_untracked_na);
 	array[DEVCONF_ACCEPT_RA_MIN_LFT] = READ_ONCE(cnf->accept_ra_min_lft);
 	array[DEVCONF_FORCE_FORWARDING] = READ_ONCE(cnf->force_forwarding);
+	array[DEVCONF_LINK_FILTER] = READ_ONCE(cnf->link_filter);
 }
 
 static inline size_t inet6_ifla6_size(void)
@@ -7251,6 +7252,13 @@ static const struct ctl_table addrconf_sysctl[] = {
 		.extra1		= (void *)SYSCTL_ZERO,
 		.extra2		= (void *)SYSCTL_ONE,
 	},
+	{
+		.procname	= "link_filter",
+		.data		= &ipv6_devconf.link_filter,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
 	{
 		.procname	= "ioam6_id",
 		.data		= &ipv6_devconf.ioam6_id,
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -714,6 +714,14 @@ static inline void rt6_probe(struct fib6_nh *fib6_nh)
 }
 #endif
 
+static inline int rt6_link_filter(const struct fib6_nh *nh)
+{
+	const struct net_device *dev = nh->fib_nh_dev;
+	int linkf = __in6_dev_get(dev)->cnf.link_filter;
+	return (linkf && !netif_running(dev))
+		|| (linkf > 1 && !netif_carrier_ok(dev));
+}
+
 /*
  * Default Router Selection (RFC 2461 6.3.6)
  */
@@ -755,6 +763,8 @@ static int rt6_score_route(const struct fib6_nh *nh, u32 fib6_flags, int oif,
 
 	if (!m && (strict & RT6_LOOKUP_F_IFACE))
 		return RT6_NUD_FAIL_HARD;
+	if (rt6_link_filter(nh))
+		return -1;
 #ifdef CONFIG_IPV6_ROUTER_PREF
 	m |= IPV6_DECODE_PREF(IPV6_EXTRACT_PREF(fib6_flags)) << 2;
 #endif
-- 
2.39.5