[PATCH net-next 2/2] geneve: make geneve_fill_info() RTNL independent

[Eric Dumazet <edumazet@google.com>]

Now that geneve->cfg is an RCU-protected pointer, we can update
geneve_fill_info() to read the configuration under RCU read lock
instead of relying on RTNL.

Also add const qualifiers to the dereferenced pointers where appropriate.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 drivers/net/geneve.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index c777c1a1fa930d74768a659e16380d719f12a6b2..7197f90eeb0f3a381fac5be4a96d6570ca4fccb1 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -2483,17 +2483,28 @@ static size_t geneve_get_size(const struct net_device *dev)
 
 static int geneve_fill_info(struct sk_buff *skb, const struct net_device *dev)
 {
-	struct geneve_dev *geneve = netdev_priv(dev);
-	struct geneve_config *cfg = rtnl_dereference(geneve->cfg);
-	struct ip_tunnel_info *info = &cfg->info;
-	bool ttl_inherit = cfg->ttl_inherit;
-	bool metadata = cfg->collect_md;
-	struct ifla_geneve_port_range ports = {
-		.low	= htons(cfg->port_min),
-		.high	= htons(cfg->port_max),
-	};
+	const struct geneve_dev *geneve = netdev_priv(dev);
+	struct ifla_geneve_port_range ports;
+	const struct geneve_config *cfg;
+	const struct ip_tunnel_info *info;
+	bool ttl_inherit;
+	bool metadata;
 	__u8 tmp_vni[3];
 	__u32 vni;
+	int err = 0;
+
+	rcu_read_lock();
+	cfg = rcu_dereference(geneve->cfg);
+	if (!cfg) {
+		err = -ENODEV;
+		goto out;
+	}
+
+	info = &cfg->info;
+	ttl_inherit = cfg->ttl_inherit;
+	metadata = cfg->collect_md;
+	ports.low = htons(cfg->port_min);
+	ports.high = htons(cfg->port_max);
 
 	tunnel_id_to_vni(info->key.tun_id, tmp_vni);
 	vni = (tmp_vni[0] << 16) | (tmp_vni[1] << 8) | tmp_vni[2];
@@ -2573,10 +2584,13 @@ static int geneve_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	    nla_put_flag(skb, IFLA_GENEVE_GRO_HINT))
 		goto nla_put_failure;
 
-	return 0;
+out:
+	rcu_read_unlock();
+	return err;
 
 nla_put_failure:
-	return -EMSGSIZE;
+	err = -EMSGSIZE;
+	goto out;
 }
 
 static struct rtnl_link_ops geneve_link_ops __read_mostly = {
-- 
2.55.0.rc0.799.gd6f94ed593-goog