bridge: mcast: Allow user space to specify MDB entry routing protocol

Add the 'MDBE_ATTR_RTPORT' attribute to allow user space to specify the
routing protocol of the MDB port group entry. Enforce a minimum value of
'RTPROT_STATIC' to prevent user space from using protocol values that
should only be set by the kernel (e.g., 'RTPROT_KERNEL'). Maintain
backward compatibility by defaulting to 'RTPROT_STATIC'.

The protocol is already visible to user space in RTM_NEWMDB responses
and notifications via the 'MDBA_MDB_EATTR_RTPROT' attribute.

The routing protocol allows a routing daemon to distinguish between
entries configured by it and those configured by the administrator. Once
MDB flush is supported, the protocol can be used as a criterion
according to which the flush is performed.

Examples:

 # bridge mdb add dev br0 port dummy10 grp 239.1.1.1 permanent proto kernel
 Error: integer out of range.

 # bridge mdb add dev br0 port dummy10 grp 239.1.1.1 permanent proto static

 # bridge mdb add dev br0 port dummy10 grp 239.1.1.1 src 192.0.2.1 permanent proto zebra

 # bridge mdb add dev br0 port dummy10 grp 239.1.1.2 permanent source_list 198.51.100.1,198.51.100.2 filter_mode include proto 250

 # bridge -d mdb show
 dev br0 port dummy10 grp 239.1.1.2 src 198.51.100.2 permanent filter_mode include proto 250
 dev br0 port dummy10 grp 239.1.1.2 src 198.51.100.1 permanent filter_mode include proto 250
 dev br0 port dummy10 grp 239.1.1.2 permanent filter_mode include source_list 198.51.100.2/0.00,198.51.100.1/0.00 proto 250
 dev br0 port dummy10 grp 239.1.1.1 src 192.0.2.1 permanent filter_mode include proto zebra
 dev br0 port dummy10 grp 239.1.1.1 permanent filter_mode exclude proto static

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: idosch

include/uapi/linux/if_bridge.h

@@ -725,6 +725,7 @@ enum {
 	MDBE_ATTR_SOURCE,
 	MDBE_ATTR_SRC_LIST,
 	MDBE_ATTR_GROUP_MODE,
+	MDBE_ATTR_RTPROT,
 	__MDBE_ATTR_MAX,
 };
 #define MDBE_ATTR_MAX (__MDBE_ATTR_MAX - 1)

net/bridge/br_mdb.c

@@ -682,6 +682,7 @@ static const struct nla_policy br_mdbe_attrs_pol[MDBE_ATTR_MAX + 1] = {
 	[MDBE_ATTR_GROUP_MODE] = NLA_POLICY_RANGE(NLA_U8, MCAST_EXCLUDE,
 						  MCAST_INCLUDE),
 	[MDBE_ATTR_SRC_LIST] = NLA_POLICY_NESTED(br_mdbe_src_list_pol),
+	[MDBE_ATTR_RTPROT] = NLA_POLICY_MIN(NLA_U8, RTPROT_STATIC),
 };
 
 static bool is_valid_mdb_entry(struct br_mdb_entry *entry,
@@ -823,7 +824,7 @@ static int br_mdb_add_group_sg(const struct br_mdb_config *cfg,
 	}
 
 	p = br_multicast_new_port_group(cfg->p, &cfg->group, *pp, flags, NULL,
-					MCAST_INCLUDE, RTPROT_STATIC);
+					MCAST_INCLUDE, cfg->rt_protocol);
 	if (unlikely(!p)) {
 		NL_SET_ERR_MSG_MOD(extack, "Couldn't allocate new (S, G) port group");
 		return -ENOMEM;
@@ -881,6 +882,7 @@ static int br_mdb_add_group_src_fwd(const struct br_mdb_config *cfg,
 	sg_cfg.group = sg_ip;
 	sg_cfg.src_entry = true;
 	sg_cfg.filter_mode = MCAST_INCLUDE;
+	sg_cfg.rt_protocol = cfg->rt_protocol;
 	return br_mdb_add_group_sg(&sg_cfg, sgmp, brmctx, flags, extack);
 }
 
@@ -982,7 +984,7 @@ static int br_mdb_add_group_star_g(const struct br_mdb_config *cfg,
 	}
 
 	p = br_multicast_new_port_group(cfg->p, &cfg->group, *pp, flags, NULL,
-					cfg->filter_mode, RTPROT_STATIC);
+					cfg->filter_mode, cfg->rt_protocol);
 	if (unlikely(!p)) {
 		NL_SET_ERR_MSG_MOD(extack, "Couldn't allocate new (*, G) port group");
 		return -ENOMEM;
@@ -1193,6 +1195,14 @@ static int br_mdb_config_attrs_init(struct nlattr *set_attrs,
 		return -EINVAL;
 	}
 
+	if (mdb_attrs[MDBE_ATTR_RTPROT]) {
+		if (!cfg->p) {
+			NL_SET_ERR_MSG_MOD(extack, "Protocol cannot be set for host groups");
+			return -EINVAL;
+		}
+		cfg->rt_protocol = nla_get_u8(mdb_attrs[MDBE_ATTR_RTPROT]);
+	}
+
 	return 0;
 }
 
@@ -1212,6 +1222,7 @@ static int br_mdb_config_init(struct net *net, const struct nlmsghdr *nlh,
 
 	memset(cfg, 0, sizeof(*cfg));
 	cfg->filter_mode = MCAST_EXCLUDE;
+	cfg->rt_protocol = RTPROT_STATIC;
 
 	bpm = nlmsg_data(nlh);
 	if (!bpm->ifindex) {

net/bridge/br_private.h

@@ -106,6 +106,7 @@ struct br_mdb_config {
 	u8				filter_mode;
 	struct br_mdb_src_entry		*src_entries;
 	int				num_src_entries;
+	u8				rt_protocol;
 };
 #endif