Linux Ethernet Bridging - Apr 2022 - [Bridge] [PATCH v2 net-next 0/2] net: bridge: add support for host l2 mdb entries

This patch expands on the earlier work on layer-2 mdb entries by adding
support for host entries.  Due to the fact that host joined entries do
not have any flag field, we infer the permanent flag when reporting the
entries to userspace, which otherwise would be listed as 'temp'.

Before patch:

    ~# bridge mdb add dev br0 port br0 grp 01:00:00:c0:ff:ee permanent
    Error: bridge: Flags are not allowed for host groups.
    ~# bridge mdb add dev br0 port br0 grp 01:00:00:c0:ff:ee
    Error: bridge: Only permanent L2 entries allowed.

After patch:

    ~# bridge mdb add dev br0 port br0 grp 01:00:00:c0:ff:ee permanent
    ~# bridge mdb show
    dev br0 port br0 grp 01:00:00:c0:ff:ee permanent vid 1

Signed-off-by: Joachim Wiberg <troglobit at gmail.com>
---
 net/bridge/br_mdb.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index 4556d913955b..9ba5c5cc2f3d 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -257,8 +257,10 @@ static int __mdb_fill_info(struct sk_buff *skb,
 	else if (mp->addr.proto == htons(ETH_P_IPV6))
 		e.addr.u.ip6 = mp->addr.dst.ip6;
 #endif
-	else
+	else {
 		ether_addr_copy(e.addr.u.mac_addr, mp->addr.dst.mac_addr);
+		e.state = MDB_PG_FLAGS_PERMANENT;
+	}
 	e.addr.proto = mp->addr.proto;
 	nest_ent = nla_nest_start_noflag(skb,
 					 MDBA_MDB_ENTRY_INFO);
@@ -873,8 +875,8 @@ static int br_mdb_add_group(struct net_bridge *br, struct
net_bridge_port *port,
 		return -EINVAL;
 
 	/* host join errors which can happen before creating the group */
-	if (!port) {
-		/* don't allow any flags for host-joined groups */
+	if (!port && !br_group_is_l2(&group)) {
+		/* don't allow any flags for host-joined IP groups */
 		if (entry->state) {
 			NL_SET_ERR_MSG_MOD(extack, "Flags are not allowed for host
groups");
 			return -EINVAL;
-- 
2.25.1

On 23/02/2022 19:24, Joachim Wiberg wrote:
> This patch expands on the earlier work on layer-2 mdb entries by adding
> support for host entries.  Due to the fact that host joined entries do
> not have any flag field, we infer the permanent flag when reporting the
> entries to userspace, which otherwise would be listed as 'temp'.
> 
> Before patch:
> 
>     ~# bridge mdb add dev br0 port br0 grp 01:00:00:c0:ff:ee permanent
>     Error: bridge: Flags are not allowed for host groups.
>     ~# bridge mdb add dev br0 port br0 grp 01:00:00:c0:ff:ee
>     Error: bridge: Only permanent L2 entries allowed.
> 
> After patch:
> 
>     ~# bridge mdb add dev br0 port br0 grp 01:00:00:c0:ff:ee permanent
>     ~# bridge mdb show
>     dev br0 port br0 grp 01:00:00:c0:ff:ee permanent vid 1
> 
> Signed-off-by: Joachim Wiberg <troglobit at gmail.com>
> ---
>  net/bridge/br_mdb.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
It would be nice to add a selftest for L2 entries. You can send it as a
follow-up.
The patch looks good to me.

Acked-by: Nikolay Aleksandrov <razor at blackwall.org>

Fix to an obvious omissions for layer-2 host mdb entries, this v2 adds
the missing selftest and some minor style fixes.

Note: this patch revealed some worrying problems in how the bridge
      forwards unknown BUM traffic and also how unknown multicast is
      forwarded when a IP multicast router is known, which a another
      (RFC) patch series intend to address.  That series will build
      on this selftest, hence the name of the test.

 /Joachim

v2:
  - Add braces to other if/else clauses (Jakub)
  - Add selftest to verify add/del of mac/ipv4/ipv6 mdb entries (Jakub)

Joachim Wiberg (2):
  net: bridge: add support for host l2 mdb entries
  selftests: forwarding: new test, verify host mdb entries

 net/bridge/br_mdb.c                           |  12 +-
 .../testing/selftests/net/forwarding/Makefile |   1 +
 .../selftests/net/forwarding/bridge_mdb.sh    | 103 ++++++++++++++++++
 3 files changed, 111 insertions(+), 5 deletions(-)
 create mode 100755 tools/testing/selftests/net/forwarding/bridge_mdb.sh

-- 
2.25.1