Linux Ethernet Bridging - Nov 2018 - [Bridge] [PATCH net-next v2 2/3] net: bridge: add no_linklocal_learn bool option

Hi,
This set adds a new bridge option which can control learning from
link-local packets, by default learning is on to be consistent and avoid
breaking users expectations. If the new no_linklocal_learn option is
enabled then the bridge will stop learning from link-local packets.

In order to save space for future boolean options, patch 01 adds a new
bool option API that uses a bitmask to control boolean options. The
bridge is by far the largest netlink attr user and we keep adding simple
boolean options which waste nl attr ids and space. We're not directly
mapping these to the in-kernel bridge flags because some might require
more complex configuration changes (e.g. if we were to add the per port
vlan stats now, it'd require multiple checks before changing value).
Any new bool option needs to be handled by both br_boolopt_toggle and get
in order to be able to retrieve its state later. All such options are
automatically exported via netlink. The behaviour of setting such
options is consistent with netlink option handling when a missing
option is being set (silently ignored), e.g. when a newer iproute2 is used
on older kernel. All supported options are exported via bm's optmask
when dumping the new attribute.

v2: address Andrew Lunn's comments, squash a minor change into patch 01,
    export all supported options via optmask when dumping, add patch 03,
    pass down extack so options can return meaningful errors, add
    WARN_ON on unsupported options (should not happen)

Thanks,
 Nik

Nikolay Aleksandrov (3):
  net: bridge: add support for user-controlled bool options
  net: bridge: add no_linklocal_learn bool option
  net: bridge: export supported boolopts

 include/uapi/linux/if_bridge.h | 21 ++++++++++
 include/uapi/linux/if_link.h   |  1 +
 net/bridge/br.c                | 76 ++++++++++++++++++++++++++++++++++
 net/bridge/br_input.c          |  4 +-
 net/bridge/br_netlink.c        | 17 +++++++-
 net/bridge/br_private.h        |  9 ++++
 net/bridge/br_sysfs_br.c       | 22 ++++++++++
 net/core/rtnetlink.c           |  2 +-
 8 files changed, 149 insertions(+), 3 deletions(-)

-- 
2.17.2

We have been adding many new bridge options, a big number of which are
boolean but still take up netlink attribute ids and waste space in the skb.
Recently we discussed learning from link-local packets[1] and decided
yet another new boolean option will be needed, thus introducing this API
to save some bridge nl space.
The API supports changing the value of multiple boolean options at once
via the br_boolopt_multi struct which has an optmask (which options to
set, bit per opt) and optval (options' new values). Future boolean
options will only be added to the br_boolopt_id enum and then will have
to be handled in br_boolopt_toggle/get. The API will automatically
add the ability to change and export them via netlink, sysfs can use the
single boolopt function versions to do the same. The behaviour with
failing/succeeding is the same as with normal netlink option changing.

If an option requires mapping to internal kernel flag or needs special
configuration to be enabled then it should be handled in
br_boolopt_toggle. It should also be able to retrieve an option's current
state via br_boolopt_get.

v2: WARN_ON() on unsupported option as that shouldn't be possible and
    also will help catch people who add new options without handling
    them for both set and get. Pass down extack so if an option desires
    it could set it on error and be more user-friendly.

[1] https://www.spinics.net/lists/netdev/msg532698.html

Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
---
 include/uapi/linux/if_bridge.h | 18 +++++++++
 include/uapi/linux/if_link.h   |  1 +
 net/bridge/br.c                | 71 ++++++++++++++++++++++++++++++++++
 net/bridge/br_netlink.c        | 17 +++++++-
 net/bridge/br_private.h        |  8 ++++
 net/core/rtnetlink.c           |  2 +-
 6 files changed, 115 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index e41eda3c71f1..6dc02c03bdf8 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -292,4 +292,22 @@ struct br_mcast_stats {
 	__u64 mcast_bytes[BR_MCAST_DIR_SIZE];
 	__u64 mcast_packets[BR_MCAST_DIR_SIZE];
 };
+
+/* bridge boolean options
+ * IMPORTANT: if adding a new option do not forget to handle
+ *            it in br_boolopt_toggle/get and bridge sysfs
+ */
+enum br_boolopt_id {
+	BR_BOOLOPT_MAX
+};
+
+/* struct br_boolopt_multi - change multiple bridge boolean options
+ *
+ * @optval: new option values (bit per option)
+ * @optmask: options to change (bit per option)
+ */
+struct br_boolopt_multi {
+	__u32 optval;
+	__u32 optmask;
+};
 #endif /* _UAPI_LINUX_IF_BRIDGE_H */
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index f42c069d81db..d6533828123a 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -288,6 +288,7 @@ enum {
 	IFLA_BR_MCAST_IGMP_VERSION,
 	IFLA_BR_MCAST_MLD_VERSION,
 	IFLA_BR_VLAN_STATS_PER_PORT,
+	IFLA_BR_MULTI_BOOLOPT,
 	__IFLA_BR_MAX,
 };
 
diff --git a/net/bridge/br.c b/net/bridge/br.c
index 360ad66c21e9..c527160c1975 100644
--- a/net/bridge/br.c
+++ b/net/bridge/br.c
@@ -175,6 +175,77 @@ static struct notifier_block br_switchdev_notifier = {
 	.notifier_call = br_switchdev_event,
 };
 
+/* br_boolopt_toggle - change user-controlled boolean option
+ *
+ * @br: bridge device
+ * @opt: id of the option to change
+ * @on: new option value
+ * @extack: extack for error messages
+ *
+ * Changes the value of the respective boolean option to @on taking care of
+ * any internal option value mapping and configuration.
+ */
+int br_boolopt_toggle(struct net_bridge *br, enum br_boolopt_id opt, bool on,
+		      struct netlink_ext_ack *extack)
+{
+	switch (opt) {
+	default:
+		/* shouldn't be called with unsupported options */
+		WARN_ON(1);
+		break;
+	}
+
+	return 0;
+}
+
+int br_boolopt_get(const struct net_bridge *br, enum br_boolopt_id opt)
+{
+	switch (opt) {
+	default:
+		/* shouldn't be called with unsupported options */
+		WARN_ON(1);
+		break;
+	}
+
+	return 0;
+}
+
+int br_boolopt_multi_toggle(struct net_bridge *br,
+			    struct br_boolopt_multi *bm,
+			    struct netlink_ext_ack *extack)
+{
+	unsigned long bitmap = bm->optmask;
+	int err = 0;
+	int opt_id;
+
+	for_each_set_bit(opt_id, &bitmap, BR_BOOLOPT_MAX) {
+		bool on = !!(bm->optval & BIT(opt_id));
+
+		err = br_boolopt_toggle(br, opt_id, on, extack);
+		if (err) {
+			br_debug(br, "boolopt multi-toggle error: option: %d current: %d new:
%d error: %d\n",
+				 opt_id, br_boolopt_get(br, opt_id), on, err);
+			break;
+		}
+	}
+
+	return err;
+}
+
+void br_boolopt_multi_get(const struct net_bridge *br,
+			  struct br_boolopt_multi *bm)
+{
+	u32 optval = 0;
+	int opt_id;
+
+	for (opt_id = 0; opt_id < BR_BOOLOPT_MAX; opt_id++)
+		optval |= (br_boolopt_get(br, opt_id) << opt_id);
+
+	bm->optval = optval;
+	bm->optmask = 0;
+}
+
+/* private bridge options, controlled by the kernel */
 void br_opt_toggle(struct net_bridge *br, enum net_bridge_opts opt, bool on)
 {
 	bool cur = !!br_opt_get(br, opt);
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 3345f1984542..13cd50326af2 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -1035,6 +1035,8 @@ static const struct nla_policy br_policy[IFLA_BR_MAX + 1]
= {
 	[IFLA_BR_MCAST_IGMP_VERSION] = { .type = NLA_U8 },
 	[IFLA_BR_MCAST_MLD_VERSION] = { .type = NLA_U8 },
 	[IFLA_BR_VLAN_STATS_PER_PORT] = { .type = NLA_U8 },
+	[IFLA_BR_MULTI_BOOLOPT] = { .type = NLA_EXACT_LEN,
+				    .len = sizeof(struct br_boolopt_multi) },
 };
 
 static int br_changelink(struct net_device *brdev, struct nlattr *tb[],
@@ -1296,6 +1298,15 @@ static int br_changelink(struct net_device *brdev, struct
nlattr *tb[],
 	}
 #endif
 
+	if (data[IFLA_BR_MULTI_BOOLOPT]) {
+		struct br_boolopt_multi *bm;
+
+		bm = nla_data(data[IFLA_BR_MULTI_BOOLOPT]);
+		err = br_boolopt_multi_toggle(br, bm, extack);
+		if (err)
+			return err;
+	}
+
 	return 0;
 }
 
@@ -1374,6 +1385,7 @@ static size_t br_get_size(const struct net_device *brdev)
 	       nla_total_size(sizeof(u8)) +     /* IFLA_BR_NF_CALL_IP6TABLES */
 	       nla_total_size(sizeof(u8)) +     /* IFLA_BR_NF_CALL_ARPTABLES */
 #endif
+	       nla_total_size(sizeof(struct br_boolopt_multi)) + /*
IFLA_BR_MULTI_BOOLOPT */
 	       0;
 }
 
@@ -1387,6 +1399,7 @@ static int br_fill_info(struct sk_buff *skb, const struct
net_device *brdev)
 	u32 stp_enabled = br->stp_enabled;
 	u16 priority = (br->bridge_id.prio[0] << 8) |
br->bridge_id.prio[1];
 	u8 vlan_enabled = br_vlan_enabled(br->dev);
+	struct br_boolopt_multi bm;
 	u64 clockval;
 
 	clockval = br_timer_value(&br->hello_timer);
@@ -1403,6 +1416,7 @@ static int br_fill_info(struct sk_buff *skb, const struct
net_device *brdev)
 	if (nla_put_u64_64bit(skb, IFLA_BR_GC_TIMER, clockval, IFLA_BR_PAD))
 		return -EMSGSIZE;
 
+	br_boolopt_multi_get(br, &bm);
 	if (nla_put_u32(skb, IFLA_BR_FORWARD_DELAY, forward_delay) ||
 	    nla_put_u32(skb, IFLA_BR_HELLO_TIME, hello_time) ||
 	    nla_put_u32(skb, IFLA_BR_MAX_AGE, age_time) ||
@@ -1420,7 +1434,8 @@ static int br_fill_info(struct sk_buff *skb, const struct
net_device *brdev)
 	    nla_put_u8(skb, IFLA_BR_TOPOLOGY_CHANGE, br->topology_change) ||
 	    nla_put_u8(skb, IFLA_BR_TOPOLOGY_CHANGE_DETECTED,
 		       br->topology_change_detected) ||
-	    nla_put(skb, IFLA_BR_GROUP_ADDR, ETH_ALEN, br->group_addr))
+	    nla_put(skb, IFLA_BR_GROUP_ADDR, ETH_ALEN, br->group_addr) ||
+	    nla_put(skb, IFLA_BR_MULTI_BOOLOPT, sizeof(bm), &bm))
 		return -EMSGSIZE;
 
 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index bc2653738fc3..6d4c208fbf08 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -507,6 +507,14 @@ static inline int br_opt_get(const struct net_bridge *br,
 	return test_bit(opt, &br->options);
 }
 
+int br_boolopt_toggle(struct net_bridge *br, enum br_boolopt_id opt, bool on,
+		      struct netlink_ext_ack *extack);
+int br_boolopt_get(const struct net_bridge *br, enum br_boolopt_id opt);
+int br_boolopt_multi_toggle(struct net_bridge *br,
+			    struct br_boolopt_multi *bm,
+			    struct netlink_ext_ack *extack);
+void br_boolopt_multi_get(const struct net_bridge *br,
+			  struct br_boolopt_multi *bm);
 void br_opt_toggle(struct net_bridge *br, enum net_bridge_opts opt, bool on);
 
 /* br_device.c */
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 86f2d9cbdae3..a498bb41c9aa 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -59,7 +59,7 @@
 #include <net/rtnetlink.h>
 #include <net/net_namespace.h>
 
-#define RTNL_MAX_TYPE		49
+#define RTNL_MAX_TYPE		50
 #define RTNL_SLAVE_MAX_TYPE	36
 
 struct rtnl_link {
-- 
2.17.2

Use the new boolopt API to add an option which disables learning from
link-local packets. The default is kept as before and learning is
enabled. This is a simple map from a boolopt bit to a bridge private
flag that is tested before learning.

v2: pass NULL for extack via sysfs

Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
---
 include/uapi/linux/if_bridge.h |  3 +++
 net/bridge/br.c                |  5 +++++
 net/bridge/br_input.c          |  4 +++-
 net/bridge/br_private.h        |  1 +
 net/bridge/br_sysfs_br.c       | 22 ++++++++++++++++++++++
 5 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index 6dc02c03bdf8..773e476a8e54 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -294,10 +294,13 @@ struct br_mcast_stats {
 };
 
 /* bridge boolean options
+ * BR_BOOLOPT_NO_LL_LEARN - disable learning from link-local packets
+ *
  * IMPORTANT: if adding a new option do not forget to handle
  *            it in br_boolopt_toggle/get and bridge sysfs
  */
 enum br_boolopt_id {
+	BR_BOOLOPT_NO_LL_LEARN,
 	BR_BOOLOPT_MAX
 };
 
diff --git a/net/bridge/br.c b/net/bridge/br.c
index c527160c1975..b4a51a053586 100644
--- a/net/bridge/br.c
+++ b/net/bridge/br.c
@@ -189,6 +189,9 @@ int br_boolopt_toggle(struct net_bridge *br, enum
br_boolopt_id opt, bool on,
 		      struct netlink_ext_ack *extack)
 {
 	switch (opt) {
+	case BR_BOOLOPT_NO_LL_LEARN:
+		br_opt_toggle(br, BROPT_NO_LL_LEARN, on);
+		break;
 	default:
 		/* shouldn't be called with unsupported options */
 		WARN_ON(1);
@@ -201,6 +204,8 @@ int br_boolopt_toggle(struct net_bridge *br, enum
br_boolopt_id opt, bool on,
 int br_boolopt_get(const struct net_bridge *br, enum br_boolopt_id opt)
 {
 	switch (opt) {
+	case BR_BOOLOPT_NO_LL_LEARN:
+		return br_opt_get(br, BROPT_NO_LL_LEARN);
 	default:
 		/* shouldn't be called with unsupported options */
 		WARN_ON(1);
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 3ddca11f44c2..5ea7e56119c1 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -188,7 +188,9 @@ static void __br_handle_local_finish(struct sk_buff *skb)
 	u16 vid = 0;
 
 	/* check if vlan is allowed, to avoid spoofing */
-	if (p->flags & BR_LEARNING && br_should_learn(p, skb,
&vid))
+	if ((p->flags & BR_LEARNING) &&
+	    !br_opt_get(p->br, BROPT_NO_LL_LEARN) &&
+	    br_should_learn(p, skb, &vid))
 		br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
 }
 
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 6d4c208fbf08..d29f837cd7a2 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -328,6 +328,7 @@ enum net_bridge_opts {
 	BROPT_NEIGH_SUPPRESS_ENABLED,
 	BROPT_MTU_SET_BY_USER,
 	BROPT_VLAN_STATS_PER_PORT,
+	BROPT_NO_LL_LEARN,
 };
 
 struct net_bridge {
diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
index 60182bef6341..6a378a7e16ea 100644
--- a/net/bridge/br_sysfs_br.c
+++ b/net/bridge/br_sysfs_br.c
@@ -328,6 +328,27 @@ static ssize_t flush_store(struct device *d,
 }
 static DEVICE_ATTR_WO(flush);
 
+static ssize_t no_linklocal_learn_show(struct device *d,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct net_bridge *br = to_bridge(d);
+	return sprintf(buf, "%d\n", br_boolopt_get(br,
BR_BOOLOPT_NO_LL_LEARN));
+}
+
+static int set_no_linklocal_learn(struct net_bridge *br, unsigned long val)
+{
+	return br_boolopt_toggle(br, BR_BOOLOPT_NO_LL_LEARN, !!val, NULL);
+}
+
+static ssize_t no_linklocal_learn_store(struct device *d,
+					struct device_attribute *attr,
+					const char *buf, size_t len)
+{
+	return store_bridge_parm(d, buf, len, set_no_linklocal_learn);
+}
+static DEVICE_ATTR_RW(no_linklocal_learn);
+
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 static ssize_t multicast_router_show(struct device *d,
 				     struct device_attribute *attr, char *buf)
@@ -841,6 +862,7 @@ static struct attribute *bridge_attrs[] = {
 	&dev_attr_gc_timer.attr,
 	&dev_attr_group_addr.attr,
 	&dev_attr_flush.attr,
+	&dev_attr_no_linklocal_learn.attr,
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 	&dev_attr_multicast_router.attr,
 	&dev_attr_multicast_snooping.attr,
-- 
2.17.2

Now that we have at least one bool option, we can export all of the
supported bool options via optmask when dumping them.

v2: new patch

Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
---
 net/bridge/br.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bridge/br.c b/net/bridge/br.c
index b4a51a053586..4e7cd993ce94 100644
--- a/net/bridge/br.c
+++ b/net/bridge/br.c
@@ -247,7 +247,7 @@ void br_boolopt_multi_get(const struct net_bridge *br,
 		optval |= (br_boolopt_get(br, opt_id) << opt_id);
 
 	bm->optval = optval;
-	bm->optmask = 0;
+	bm->optmask = GENMASK((BR_BOOLOPT_MAX - 1), 0);
 }
 
 /* private bridge options, controlled by the kernel */
-- 
2.17.2

From: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
Date: Sat, 24 Nov 2018 04:34:19 +0200
> This set adds a new bridge option which can control learning from
> link-local packets, by default learning is on to be consistent and avoid
> breaking users expectations. If the new no_linklocal_learn option is
> enabled then the bridge will stop learning from link-local packets.
> 
> In order to save space for future boolean options, patch 01 adds a new
> bool option API that uses a bitmask to control boolean options. The
> bridge is by far the largest netlink attr user and we keep adding simple
> boolean options which waste nl attr ids and space. We're not directly
> mapping these to the in-kernel bridge flags because some might require
> more complex configuration changes (e.g. if we were to add the per port
> vlan stats now, it'd require multiple checks before changing value).
> Any new bool option needs to be handled by both br_boolopt_toggle and get
> in order to be able to retrieve its state later. All such options are
> automatically exported via netlink. The behaviour of setting such
> options is consistent with netlink option handling when a missing
> option is being set (silently ignored), e.g. when a newer iproute2 is used
> on older kernel. All supported options are exported via bm's optmask
> when dumping the new attribute.
> 
> v2: address Andrew Lunn's comments, squash a minor change into patch
01,
>     export all supported options via optmask when dumping, add patch 03,
>     pass down extack so options can return meaningful errors, add
>     WARN_ON on unsupported options (should not happen)
Series applied, thanks Nikolay.