bridge: add new BR_NEIGH_SUPPRESS port flag to suppress arp and nd flood

This patch adds a new bridge port flag BR_NEIGH_SUPPRESS to
suppress arp and nd flood on bridge ports. It implements
rfc7432, section 10.
https://tools.ietf.org/html/rfc7432#section-10
for ethernet VPN deployments. It is similar to the existing
BR_PROXYARP* flags but has a few semantic differences to conform
to EVPN standard. Unlike the existing flags, this new flag suppresses
flood of all neigh discovery packets (arp and nd) to tunnel ports.
Supports both vlan filtering and non-vlan filtering bridges.

In case of EVPN, it is mainly used to avoid flooding
of arp and nd packets to tunnel ports like vxlan.

This patch adds netlink and sysfs support to set this bridge port
flag.
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/if_bridge.h

@@ -49,6 +49,7 @@ struct br_ip_list {
 #define BR_MULTICAST_TO_UNICAST	BIT(12)
 #define BR_VLAN_TUNNEL		BIT(13)
 #define BR_BCAST_FLOOD		BIT(14)
+#define BR_NEIGH_SUPPRESS	BIT(15)
 
 #define BR_DEFAULT_AGEING_TIME	(300 * HZ)
 

include/uapi/linux/if_link.h

@@ -327,6 +327,7 @@ enum {
 	IFLA_BRPORT_VLAN_TUNNEL,
 	IFLA_BRPORT_BCAST_FLOOD,
 	IFLA_BRPORT_GROUP_FWD_MASK,
+	IFLA_BRPORT_NEIGH_SUPPRESS,
 	__IFLA_BRPORT_MAX
 };
 #define IFLA_BRPORT_MAX (__IFLA_BRPORT_MAX - 1)

net/bridge/Makefile

@@ -7,7 +7,7 @@ obj-$(CONFIG_BRIDGE) += bridge.o
 bridge-y	:= br.o br_device.o br_fdb.o br_forward.o br_if.o br_input.o \
 			br_ioctl.o br_stp.o br_stp_bpdu.o \
 			br_stp_if.o br_stp_timer.o br_netlink.o \
-			br_netlink_tunnel.o
+			br_netlink_tunnel.o br_arp_nd_proxy.o
 
 bridge-$(CONFIG_SYSFS) += br_sysfs_if.o br_sysfs_br.o
 

net/bridge/br_arp_nd_proxy.c

+/*
+ *  Handle bridge arp/nd proxy/suppress
+ *
+ *  Copyright (C) 2017 Cumulus Networks
+ *  Copyright (c) 2017 Roopa Prabhu <roopa@cumulusnetworks.com>
+ *
+ *  Authors:
+ *	Roopa Prabhu <roopa@cumulusnetworks.com>
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include "br_private.h"
+
+void br_recalculate_neigh_suppress_enabled(struct net_bridge *br)
+{
+	struct net_bridge_port *p;
+	bool neigh_suppress = false;
+
+	list_for_each_entry(p, &br->port_list, list) {
+		if (p->flags & BR_NEIGH_SUPPRESS) {
+			neigh_suppress = true;
+			break;
+		}
+	}
+
+	br->neigh_suppress_enabled = neigh_suppress;
+}

net/bridge/br_forward.c

@@ -204,7 +204,7 @@ void br_flood(struct net_bridge *br, struct sk_buff *skb,
 		/* Do not flood to ports that enable proxy ARP */
 		if (p->flags & BR_PROXYARP)
 			continue;
-		if ((p->flags & BR_PROXYARP_WIFI) &&
+		if ((p->flags & (BR_PROXYARP_WIFI | BR_NEIGH_SUPPRESS)) &&
 		    BR_INPUT_SKB_CB(skb)->proxyarp_replied)
 			continue;
 

net/bridge/br_if.c

@@ -310,6 +310,8 @@ void br_dev_delete(struct net_device *dev, struct list_head *head)
 		del_nbp(p);
 	}
 
+	br_recalculate_neigh_suppress_enabled(br);
+
 	br_fdb_delete_by_port(br, NULL, 0, 1);
 
 	cancel_delayed_work_sync(&br->gc_work);
@@ -660,4 +662,7 @@ void br_port_flags_change(struct net_bridge_port *p, unsigned long mask)
 
 	if (mask & BR_AUTO_MASK)
 		nbp_update_port_count(br);
+
+	if (mask & BR_NEIGH_SUPPRESS)
+		br_recalculate_neigh_suppress_enabled(br);
 }

net/bridge/br_netlink.c

@@ -138,6 +138,7 @@ static inline size_t br_port_info_size(void)
 		+ nla_total_size(1)	/* IFLA_BRPORT_PROXYARP */
 		+ nla_total_size(1)	/* IFLA_BRPORT_PROXYARP_WIFI */
 		+ nla_total_size(1)	/* IFLA_BRPORT_VLAN_TUNNEL */
+		+ nla_total_size(1)	/* IFLA_BRPORT_NEIGH_SUPPRESS */
 		+ nla_total_size(sizeof(struct ifla_bridge_id))	/* IFLA_BRPORT_ROOT_ID */
 		+ nla_total_size(sizeof(struct ifla_bridge_id))	/* IFLA_BRPORT_BRIDGE_ID */
 		+ nla_total_size(sizeof(u16))	/* IFLA_BRPORT_DESIGNATED_PORT */
@@ -210,7 +211,9 @@ static int br_port_fill_attrs(struct sk_buff *skb,
 	    nla_put_u8(skb, IFLA_BRPORT_CONFIG_PENDING, p->config_pending) ||
 	    nla_put_u8(skb, IFLA_BRPORT_VLAN_TUNNEL, !!(p->flags &
 							BR_VLAN_TUNNEL)) ||
-	    nla_put_u16(skb, IFLA_BRPORT_GROUP_FWD_MASK, p->group_fwd_mask))
+	    nla_put_u16(skb, IFLA_BRPORT_GROUP_FWD_MASK, p->group_fwd_mask) ||
+	    nla_put_u8(skb, IFLA_BRPORT_NEIGH_SUPPRESS,
+		       !!(p->flags & BR_NEIGH_SUPPRESS)))
 		return -EMSGSIZE;
 
 	timerval = br_timer_value(&p->message_age_timer);
@@ -785,6 +788,11 @@ static int br_setport(struct net_bridge_port *p, struct nlattr *tb[])
 		p->group_fwd_mask = fwd_mask;
 	}
 
+	err = br_set_port_flag(p, tb, IFLA_BRPORT_NEIGH_SUPPRESS,
+			       BR_NEIGH_SUPPRESS);
+	if (err)
+		return err;
+
 	br_port_flags_change(p, old_flags ^ p->flags);
 	return 0;
 }

net/bridge/br_private.h

@@ -404,6 +404,7 @@ struct net_bridge {
 #ifdef CONFIG_NET_SWITCHDEV
 	int offload_fwd_mark;
 #endif
+	bool				neigh_suppress_enabled;
 };
 
 struct br_input_skb_cb {
@@ -1139,4 +1140,5 @@ static inline void br_switchdev_frame_unmark(struct sk_buff *skb)
 }
 #endif /* CONFIG_NET_SWITCHDEV */
 
+void br_recalculate_neigh_suppress_enabled(struct net_bridge *br);
 #endif

net/bridge/br_sysfs_if.c

@@ -191,6 +191,7 @@ BRPORT_ATTR_FLAG(proxyarp, BR_PROXYARP);
 BRPORT_ATTR_FLAG(proxyarp_wifi, BR_PROXYARP_WIFI);
 BRPORT_ATTR_FLAG(multicast_flood, BR_MCAST_FLOOD);
 BRPORT_ATTR_FLAG(broadcast_flood, BR_BCAST_FLOOD);
+BRPORT_ATTR_FLAG(neigh_suppress, BR_NEIGH_SUPPRESS);
 
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 static ssize_t show_multicast_router(struct net_bridge_port *p, char *buf)
@@ -241,6 +242,7 @@ static const struct brport_attribute *brport_attrs[] = {
 	&brport_attr_multicast_flood,
 	&brport_attr_broadcast_flood,
 	&brport_attr_group_fwd_mask,
+	&brport_attr_neigh_suppress,
 	NULL
 };