From: Eric Dumazet <edumazet@google.com>
To: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>,
Kuniyuki Iwashima <kuniyu@google.com>,
Andrew Lunn <andrew+netdev@lunn.ch>,
netdev@vger.kernel.org, eric.dumazet@gmail.com,
Eric Dumazet <edumazet@google.com>
Subject: [PATCH v2 net-next 2/3] geneve: convert config to RCU-protected pointer
Date: Tue, 7 Jul 2026 14:53:29 +0000 [thread overview]
Message-ID: <20260707145331.3717941-3-edumazet@google.com> (raw)
In-Reply-To: <20260707145331.3717941-1-edumazet@google.com>
geneve_changelink() currently updates configuration by copying it over
the old one using memcpy() under RTNL, forcing data path pause via
geneve_quiesce() and synchronize_net() to avoid reading torn values.
Convert geneve->cfg to an RCU-protected pointer, allowing lockless
and safe reads under RCU read lock without synchronization overhead.
Key changes:
- Introduced geneve_config_alloc/free() helpers for lifecycle.
- geneve_configure() allocates config and publishes it via RCU.
- Setting dev->priv_destructor = geneve_free_dev handles config cleanup
if register_netdevice() fails or during netdev unregistration.
- geneve_changelink() performs RCU swap; old config is freed via call_rcu_hurry().
- Allocates new dst_cache during changelink to prevent pcpu sharing.
- Removed geneve_quiesce/unquiesce() and synchronize_net() from changelink.
- Added rcu_barrier() to module exit to wait for pending callbacks.
- Updated data path to use rcu_dereference().
- Updated geneve_fill_info() to use rtnl_dereference() for now.
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
drivers/net/geneve.c | 213 ++++++++++++++++++++++++-------------------
1 file changed, 118 insertions(+), 95 deletions(-)
diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index cab38e7de8715f5a1ee0869e1d6c7b7ea9c693c1..f14e019f3f3f4d861ebd9e5e81175b8149b9acc2 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -82,6 +82,7 @@ struct geneve_config {
u16 port_min;
u16 port_max;
+ struct rcu_head rcu;
/* Must be last --ends in a flexible-array member. */
struct ip_tunnel_info info;
};
@@ -100,7 +101,7 @@ struct geneve_dev {
#endif
struct list_head next; /* geneve's per namespace list */
struct gro_cells gro_cells;
- struct geneve_config cfg;
+ struct geneve_config __rcu *cfg;
};
struct geneve_sock {
@@ -182,8 +183,10 @@ static struct geneve_dev *geneve_lookup(struct geneve_sock *gs,
hash = geneve_net_vni_hash(vni);
vni_list_head = &gs->vni_list[hash];
hlist_for_each_entry_rcu(node, vni_list_head, hlist) {
- if (eq_tun_id_and_vni((u8 *)&node->geneve->cfg.info.key.tun_id, vni) &&
- addr == node->geneve->cfg.info.key.u.ipv4.dst)
+ const struct geneve_config *cfg = rcu_dereference(node->geneve->cfg);
+
+ if (eq_tun_id_and_vni((u8 *)&cfg->info.key.tun_id, vni) &&
+ addr == cfg->info.key.u.ipv4.dst)
return node->geneve;
}
return NULL;
@@ -201,8 +204,10 @@ static struct geneve_dev *geneve6_lookup(struct geneve_sock *gs,
hash = geneve_net_vni_hash(vni);
vni_list_head = &gs->vni_list[hash];
hlist_for_each_entry_rcu(node, vni_list_head, hlist) {
- if (eq_tun_id_and_vni((u8 *)&node->geneve->cfg.info.key.tun_id, vni) &&
- ipv6_addr_equal(&addr6, &node->geneve->cfg.info.key.u.ipv6.dst))
+ const struct geneve_config *cfg = rcu_dereference(node->geneve->cfg);
+
+ if (eq_tun_id_and_vni((u8 *)&cfg->info.key.tun_id, vni) &&
+ ipv6_addr_equal(&addr6, &cfg->info.key.u.ipv6.dst))
return node->geneve;
}
return NULL;
@@ -386,11 +391,6 @@ static int geneve_init(struct net_device *dev)
if (err)
return err;
- err = dst_cache_init(&geneve->cfg.info.dst_cache, GFP_KERNEL);
- if (err) {
- gro_cells_destroy(&geneve->gro_cells);
- return err;
- }
netdev_lockdep_set_classes(dev);
return 0;
}
@@ -399,7 +399,6 @@ static void geneve_uninit(struct net_device *dev)
{
struct geneve_dev *geneve = netdev_priv(dev);
- dst_cache_destroy(&geneve->cfg.info.dst_cache);
gro_cells_destroy(&geneve->gro_cells);
}
@@ -650,6 +649,7 @@ static int geneve_post_decap_hint(const struct sock *sk, struct sk_buff *skb,
/* Callback from net/ipv4/udp.c to receive packets */
static int geneve_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
{
+ const struct geneve_config *cfg;
struct genevehdr *geneveh;
struct geneve_dev *geneve;
struct geneve_sock *gs;
@@ -675,8 +675,9 @@ static int geneve_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
inner_proto = geneveh->proto_type;
- if (unlikely((!geneve->cfg.inner_proto_inherit &&
- inner_proto != htons(ETH_P_TEB)))) {
+ cfg = rcu_dereference(geneve->cfg);
+ if (unlikely(!cfg || (!cfg->inner_proto_inherit &&
+ inner_proto != htons(ETH_P_TEB)))) {
dev_dstats_rx_dropped(geneve->dev);
goto drop;
}
@@ -1141,10 +1142,11 @@ static int geneve_sock_add(struct geneve_dev *geneve,
static int geneve_open(struct net_device *dev)
{
struct geneve_dev *geneve = netdev_priv(dev);
- const struct geneve_config *cfg = &geneve->cfg;
+ const struct geneve_config *cfg;
bool ipv4, ipv6, dualstack;
int ret = 0;
+ cfg = rtnl_dereference(geneve->cfg);
dualstack = cfg->dualstack;
ipv6 = cfg->info.mode & IP_TUNNEL_INFO_IPV6 || dualstack;
ipv4 = !ipv6 || dualstack;
@@ -1552,20 +1554,21 @@ static netdev_tx_t geneve_xmit(struct sk_buff *skb, struct net_device *dev)
const struct geneve_config *cfg;
int err;
- cfg = &geneve->cfg;
+ rcu_read_lock();
+ cfg = rcu_dereference(geneve->cfg);
if (cfg->collect_md) {
info = skb_tunnel_info(skb);
if (unlikely(!info || !(info->mode & IP_TUNNEL_INFO_TX))) {
netdev_dbg(dev, "no tunnel metadata\n");
dev_kfree_skb(skb);
dev_dstats_tx_dropped(dev);
+ rcu_read_unlock();
return NETDEV_TX_OK;
}
} else {
info = &cfg->info;
}
- rcu_read_lock();
#if IS_ENABLED(CONFIG_IPV6)
if (info->mode & IP_TUNNEL_INFO_IPV6)
err = geneve6_xmit_skb(skb, dev, geneve, cfg, info);
@@ -1604,9 +1607,13 @@ static int geneve_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb)
{
struct ip_tunnel_info *info = skb_tunnel_info(skb);
struct geneve_dev *geneve = netdev_priv(dev);
- const struct geneve_config *cfg = &geneve->cfg;
+ const struct geneve_config *cfg;
__be16 sport;
+ cfg = rcu_dereference(geneve->cfg);
+ if (unlikely(!cfg))
+ return -ENODEV;
+
if (ip_tunnel_info_af(info) == AF_INET) {
struct rtable *rt;
struct geneve_sock *gs4 = rcu_dereference(geneve->sock4);
@@ -1721,7 +1728,50 @@ static void geneve_offload_rx_ports(struct net_device *dev, bool push)
}
}
+static struct geneve_config *geneve_config_alloc(const struct geneve_config *src)
+{
+ struct geneve_config *cfg;
+ int err;
+
+ cfg = kmemdup(src, sizeof(*src), GFP_KERNEL);
+ if (!cfg)
+ return ERR_PTR(-ENOMEM);
+
+ cfg->info.dst_cache.cache = NULL;
+ err = dst_cache_init(&cfg->info.dst_cache, GFP_KERNEL);
+ if (err) {
+ kfree(cfg);
+ return ERR_PTR(err);
+ }
+
+ return cfg;
+}
+
+static void geneve_config_free(struct geneve_config *cfg)
+{
+ if (cfg) {
+ dst_cache_destroy(&cfg->info.dst_cache);
+ kfree(cfg);
+ }
+}
+
+static void geneve_config_free_rcu(struct rcu_head *head)
+{
+ struct geneve_config *cfg = container_of(head, struct geneve_config, rcu);
+
+ geneve_config_free(cfg);
+}
+
/* Initialize the device structure. */
+static void geneve_free_dev(struct net_device *dev)
+{
+ struct geneve_dev *geneve = netdev_priv(dev);
+ struct geneve_config *cfg = rcu_dereference_protected(geneve->cfg, 1);
+
+ geneve_config_free(cfg);
+ RCU_INIT_POINTER(geneve->cfg, NULL);
+}
+
static void geneve_setup(struct net_device *dev)
{
ether_setup(dev);
@@ -1729,6 +1779,7 @@ static void geneve_setup(struct net_device *dev)
dev->netdev_ops = &geneve_netdev_ops;
dev->ethtool_ops = &geneve_ethtool_ops;
dev->needs_free_netdev = true;
+ dev->priv_destructor = geneve_free_dev;
SET_NETDEV_DEVTYPE(dev, &geneve_type);
@@ -1890,15 +1941,17 @@ static struct geneve_dev *geneve_find_dev(struct geneve_net *gn,
*tun_on_same_port = false;
*tun_collect_md = false;
list_for_each_entry(geneve, &gn->geneve_list, next) {
- if (info->key.tp_dst == geneve->cfg.info.key.tp_dst &&
- (cfg->dualstack || geneve->cfg.dualstack ||
- geneve_saddr_conflict(info, &geneve->cfg.info))) {
- *tun_collect_md |= geneve->cfg.collect_md;
+ const struct geneve_config *gcfg = rtnl_dereference(geneve->cfg);
+
+ if (info->key.tp_dst == gcfg->info.key.tp_dst &&
+ (cfg->dualstack || gcfg->dualstack ||
+ geneve_saddr_conflict(info, &gcfg->info))) {
+ *tun_collect_md |= gcfg->collect_md;
*tun_on_same_port = true;
}
- if (info->key.tun_id == geneve->cfg.info.key.tun_id &&
- info->key.tp_dst == geneve->cfg.info.key.tp_dst &&
- !memcmp(&info->key.u, &geneve->cfg.info.key.u, sizeof(info->key.u)))
+ if (info->key.tun_id == gcfg->info.key.tun_id &&
+ info->key.tp_dst == gcfg->info.key.tp_dst &&
+ !memcmp(&info->key.u, &gcfg->info.key.u, sizeof(info->key.u)))
t = geneve;
}
return t;
@@ -1934,6 +1987,7 @@ static int geneve_configure(struct net *net, struct net_device *dev,
struct geneve_dev *t, *geneve = netdev_priv(dev);
const struct ip_tunnel_info *info = &cfg->info;
bool tun_collect_md, tun_on_same_port;
+ struct geneve_config *new_cfg;
int err, encap_len;
if (cfg->collect_md && !is_tnl_info_zero(info)) {
@@ -1974,10 +2028,13 @@ static int geneve_configure(struct net *net, struct net_device *dev,
}
}
- dst_cache_reset(&geneve->cfg.info.dst_cache);
- memcpy(&geneve->cfg, cfg, sizeof(*cfg));
+ new_cfg = geneve_config_alloc(cfg);
+ if (IS_ERR(new_cfg))
+ return PTR_ERR(new_cfg);
+
+ rcu_assign_pointer(geneve->cfg, new_cfg);
- if (geneve->cfg.inner_proto_inherit) {
+ if (cfg->inner_proto_inherit) {
dev->header_ops = NULL;
dev->type = ARPHRD_NONE;
dev->hard_header_len = 0;
@@ -2335,81 +2392,45 @@ static int geneve_newlink(struct net_device *dev,
return 0;
}
-/* Quiesces the geneve device data path for both TX and RX.
- *
- * On transmit geneve checks for non-NULL geneve_sock before it proceeds.
- * So, if we set that socket to NULL under RCU and wait for synchronize_net()
- * to complete for the existing set of in-flight packets to be transmitted,
- * then we would have quiesced the transmit data path. All the future packets
- * will get dropped until we unquiesce the data path.
- *
- * On receive geneve dereference the geneve_sock stashed in the socket. So,
- * if we set that to NULL under RCU and wait for synchronize_net() to
- * complete, then we would have quiesced the receive data path.
+/* Update the device configuration under RTNL.
+ * We use RCU swap to update the configuration atomically, so the data path
+ * (both TX and RX) can continue running without interruption or packet loss.
*/
-static void geneve_quiesce(struct geneve_dev *geneve, struct geneve_sock **gs4,
- struct geneve_sock **gs6)
-{
- *gs4 = rtnl_dereference(geneve->sock4);
- rcu_assign_pointer(geneve->sock4, NULL);
- if (*gs4)
- rcu_assign_sk_user_data((*gs4)->sk, NULL);
-#if IS_ENABLED(CONFIG_IPV6)
- *gs6 = rtnl_dereference(geneve->sock6);
- rcu_assign_pointer(geneve->sock6, NULL);
- if (*gs6)
- rcu_assign_sk_user_data((*gs6)->sk, NULL);
-#else
- *gs6 = NULL;
-#endif
- synchronize_net();
-}
-
-/* Resumes the geneve device data path for both TX and RX. */
-static void geneve_unquiesce(struct geneve_dev *geneve, struct geneve_sock *gs4,
- struct geneve_sock __maybe_unused *gs6)
-{
- rcu_assign_pointer(geneve->sock4, gs4);
- if (gs4)
- rcu_assign_sk_user_data(gs4->sk, gs4);
-#if IS_ENABLED(CONFIG_IPV6)
- rcu_assign_pointer(geneve->sock6, gs6);
- if (gs6)
- rcu_assign_sk_user_data(gs6->sk, gs6);
-#endif
-}
-
static int geneve_changelink(struct net_device *dev, struct nlattr *tb[],
struct nlattr *data[],
struct netlink_ext_ack *extack)
{
struct geneve_dev *geneve = netdev_priv(dev);
- struct geneve_sock *gs4, *gs6;
- struct geneve_config cfg;
+ struct geneve_config *old_cfg = rtnl_dereference(geneve->cfg);
+ struct geneve_config *cfg;
int err;
/* If the geneve device is configured for metadata (or externally
* controlled, for example, OVS), then nothing can be changed.
*/
- if (geneve->cfg.collect_md)
+ if (old_cfg->collect_md)
return -EOPNOTSUPP;
/* Start with the existing info. */
- memcpy(&cfg, &geneve->cfg, sizeof(cfg));
- err = geneve_nl2info(tb, data, extack, &cfg, true);
+ cfg = geneve_config_alloc(old_cfg);
+ if (IS_ERR(cfg))
+ return PTR_ERR(cfg);
+
+ err = geneve_nl2info(tb, data, extack, cfg, true);
if (err)
- return err;
+ goto err_free_cfg;
- if (!geneve_dst_addr_equal(&geneve->cfg.info, &cfg.info)) {
- dst_cache_reset(&cfg.info.dst_cache);
- geneve_link_config(dev, &cfg.info, tb);
- }
+ if (!geneve_dst_addr_equal(&old_cfg->info, &cfg->info))
+ geneve_link_config(dev, &cfg->info, tb);
- geneve_quiesce(geneve, &gs4, &gs6);
- memcpy(&geneve->cfg, &cfg, sizeof(cfg));
- geneve_unquiesce(geneve, gs4, gs6);
+ rcu_assign_pointer(geneve->cfg, cfg);
+ call_rcu_hurry(&old_cfg->rcu, geneve_config_free_rcu);
return 0;
+
+err_free_cfg:
+ geneve_config_free(cfg);
+ return err;
}
static void geneve_dellink(struct net_device *dev, struct list_head *head)
@@ -2444,12 +2465,13 @@ 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 ip_tunnel_info *info = &geneve->cfg.info;
- bool ttl_inherit = geneve->cfg.ttl_inherit;
- bool metadata = geneve->cfg.collect_md;
+ 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(geneve->cfg.port_min),
- .high = htons(geneve->cfg.port_max),
+ .low = htons(cfg->port_min),
+ .high = htons(cfg->port_max),
};
__u8 tmp_vni[3];
__u32 vni;
@@ -2480,17 +2502,17 @@ static int geneve_fill_info(struct sk_buff *skb, const struct net_device *dev)
#endif
}
- if (!geneve->cfg.dualstack) {
+ if (!cfg->dualstack) {
if (ip_tunnel_info_af(info) == AF_INET) {
if ((info->key.u.ipv4.src ||
- geneve->cfg.collect_md) &&
+ metadata) &&
nla_put_in_addr(skb, IFLA_GENEVE_LOCAL,
info->key.u.ipv4.src))
goto nla_put_failure;
#if IS_ENABLED(CONFIG_IPV6)
} else {
if ((!ipv6_addr_any(&info->key.u.ipv6.src) ||
- geneve->cfg.collect_md) &&
+ metadata) &&
nla_put_in6_addr(skb, IFLA_GENEVE_LOCAL6,
&info->key.u.ipv6.src))
goto nla_put_failure;
@@ -2503,7 +2525,7 @@ static int geneve_fill_info(struct sk_buff *skb, const struct net_device *dev)
nla_put_be32(skb, IFLA_GENEVE_LABEL, info->key.label))
goto nla_put_failure;
- if (nla_put_u8(skb, IFLA_GENEVE_DF, geneve->cfg.df))
+ if (nla_put_u8(skb, IFLA_GENEVE_DF, cfg->df))
goto nla_put_failure;
if (nla_put_be16(skb, IFLA_GENEVE_PORT, info->key.tp_dst))
@@ -2514,21 +2536,21 @@ static int geneve_fill_info(struct sk_buff *skb, const struct net_device *dev)
#if IS_ENABLED(CONFIG_IPV6)
if (nla_put_u8(skb, IFLA_GENEVE_UDP_ZERO_CSUM6_RX,
- !geneve->cfg.use_udp6_rx_checksums))
+ !cfg->use_udp6_rx_checksums))
goto nla_put_failure;
#endif
if (nla_put_u8(skb, IFLA_GENEVE_TTL_INHERIT, ttl_inherit))
goto nla_put_failure;
- if (geneve->cfg.inner_proto_inherit &&
+ if (cfg->inner_proto_inherit &&
nla_put_flag(skb, IFLA_GENEVE_INNER_PROTO_INHERIT))
goto nla_put_failure;
if (nla_put(skb, IFLA_GENEVE_PORT_RANGE, sizeof(ports), &ports))
goto nla_put_failure;
- if (geneve->cfg.gro_hint &&
+ if (cfg->gro_hint &&
nla_put_flag(skb, IFLA_GENEVE_GRO_HINT))
goto nla_put_failure;
@@ -2683,6 +2705,7 @@ static void __exit geneve_cleanup_module(void)
rtnl_link_unregister(&geneve_link_ops);
unregister_netdevice_notifier(&geneve_notifier_block);
unregister_pernet_subsys(&geneve_net_ops);
+ rcu_barrier();
}
module_exit(geneve_cleanup_module);
--
2.55.0.795.g602f6c329a-goog
next prev parent reply other threads:[~2026-07-07 14:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-07 14:53 [PATCH v2 net-next 0/3] geneve: make geneve_fill_info() RTNL-less Eric Dumazet
2026-07-07 14:53 ` [PATCH v2 net-next 1/3] geneve: pass geneve_config pointer to helper functions Eric Dumazet
2026-07-07 14:53 ` Eric Dumazet [this message]
2026-07-07 14:53 ` [PATCH v2 net-next 3/3] geneve: make geneve_fill_info() RTNL independent Eric Dumazet
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