Currently, we're not advertising link-netnsid for bridge ports, so the
"bridge link" command will not correctly interpret the value of the
IFLA_LINK attribute.

With this setup (ip link output):
    9: bridge0: <BROADCAST,MULTICAST> mtu 1500 ...
    10: veth0@if10: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master bridge0 ...
    11: veth1@if9: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master bridge0 ...

we'll get:
    10: veth0: <BROADCAST,MULTICAST> mtu 1500 master bridge0 ...
    11: veth1@bridge0: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 master ...

instead of:
    10: veth0@if10: <BROADCAST,MULTICAST> mtu 1500 master bridge0 ...
    11: veth1@if9: <BROADCAST,MULTICAST> mtu 1500 master bridge0 ...

br_fill_ifinfo can be called without RTNL (from
br_forward_delay_timer_expired), so we need to change get_link_net
callbacks to use rcu_dereference_rtnl instead of rtnl_dereference.

Signed-off-by: Sabrina Dubroca <s...@queasysnail.net>
---
 drivers/net/can/vxcan.c | 2 +-
 drivers/net/veth.c      | 2 +-
 include/net/rtnetlink.h | 4 ++++
 net/bridge/br_netlink.c | 2 ++
 net/core/rtnetlink.c    | 8 +++++---
 5 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/net/can/vxcan.c b/drivers/net/can/vxcan.c
index d6ba9426be4d..870109d38b28 100644
--- a/drivers/net/can/vxcan.c
+++ b/drivers/net/can/vxcan.c
@@ -276,7 +276,7 @@ static const struct nla_policy vxcan_policy[VXCAN_INFO_MAX 
+ 1] = {
 static struct net *vxcan_get_link_net(const struct net_device *dev)
 {
        struct vxcan_priv *priv = netdev_priv(dev);
-       struct net_device *peer = rtnl_dereference(priv->peer);
+       struct net_device *peer = rcu_dereference_rtnl(priv->peer);
 
        return peer ? dev_net(peer) : dev_net(dev);
 }
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index a475f48d43c4..5f814620d97e 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -1433,7 +1433,7 @@ static const struct nla_policy veth_policy[VETH_INFO_MAX 
+ 1] = {
 static struct net *veth_get_link_net(const struct net_device *dev)
 {
        struct veth_priv *priv = netdev_priv(dev);
-       struct net_device *peer = rtnl_dereference(priv->peer);
+       struct net_device *peer = rcu_dereference_rtnl(priv->peer);
 
        return peer ? dev_net(peer) : dev_net(dev);
 }
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index e2091bb2b3a8..c37cb3d98c7c 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -168,6 +168,10 @@ int rtnl_nla_parse_ifla(struct nlattr **tb, const struct 
nlattr *head, int len,
                        struct netlink_ext_ack *exterr);
 struct net *rtnl_get_net_ns_capable(struct sock *sk, int netnsid);
 
+int rtnl_fill_link_netnsid(struct sk_buff *skb,
+                          const struct net_device *dev,
+                          struct net *src_net, gfp_t gfp);
+
 #define MODULE_ALIAS_RTNL_LINK(kind) MODULE_ALIAS("rtnl-link-" kind)
 
 #endif
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 6af5d62ddf7b..81ea4e89edba 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -164,6 +164,7 @@ static inline size_t br_nlmsg_size(struct net_device *dev, 
u32 filter_mask)
                + nla_total_size(4) /* IFLA_MASTER */
                + nla_total_size(4) /* IFLA_MTU */
                + nla_total_size(4) /* IFLA_LINK */
+               + nla_total_size(4) /* IFLA_LINK_NETNSID */
                + nla_total_size(1) /* IFLA_OPERSTATE */
                + nla_total_size(br_port_info_size()) /* IFLA_PROTINFO */
                + nla_total_size(br_get_link_af_size_filtered(dev,
@@ -410,6 +411,7 @@ static int br_fill_ifinfo(struct sk_buff *skb,
            nla_put_u8(skb, IFLA_OPERSTATE, operstate) ||
            (dev->addr_len &&
             nla_put(skb, IFLA_ADDRESS, dev->addr_len, dev->dev_addr)) ||
+           rtnl_fill_link_netnsid(skb, dev, dev_net(br->dev), GFP_ATOMIC) ||
            (dev->netdev_ops && dev->netdev_ops->ndo_get_iflink &&
             nla_put_u32(skb, IFLA_LINK, dev_get_iflink(dev))))
                goto nla_put_failure;
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 3d8051158890..26ce9fafc379 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1568,9 +1568,9 @@ static noinline_for_stack int nla_put_ifalias(struct 
sk_buff *skb,
        return ret > 0 ? nla_put_string(skb, IFLA_IFALIAS, buf) : 0;
 }
 
-static int rtnl_fill_link_netnsid(struct sk_buff *skb,
-                                 const struct net_device *dev,
-                                 struct net *src_net, gfp_t gfp)
+int rtnl_fill_link_netnsid(struct sk_buff *skb,
+                          const struct net_device *dev,
+                          struct net *src_net, gfp_t gfp)
 {
        if (dev->rtnl_link_ops && dev->rtnl_link_ops->get_link_net) {
                struct net *link_net = dev->rtnl_link_ops->get_link_net(dev);
@@ -1585,6 +1585,7 @@ static int rtnl_fill_link_netnsid(struct sk_buff *skb,
 
        return 0;
 }
+EXPORT_SYMBOL_GPL(rtnl_fill_link_netnsid);
 
 static int rtnl_fill_link_af(struct sk_buff *skb,
                             const struct net_device *dev,
@@ -4625,6 +4626,7 @@ int ndo_dflt_bridge_getlink(struct sk_buff *skb, u32 pid, 
u32 seq,
             nla_put_u32(skb, IFLA_MASTER, br_dev->ifindex)) ||
            (dev->addr_len &&
             nla_put(skb, IFLA_ADDRESS, dev->addr_len, dev->dev_addr)) ||
+           rtnl_fill_link_netnsid(skb, dev, dev_net(br_dev), GFP_ATOMIC) ||
            (dev->netdev_ops && dev->netdev_ops->ndo_get_iflink &&
             nla_put_u32(skb, IFLA_LINK, dev_get_iflink(dev))))
                goto nla_put_failure;
-- 
2.28.0

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