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Message-ID: <20241105020514.41963-2-kuniyu@amazon.com>
Date: Mon, 4 Nov 2024 18:05:07 -0800
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>, Simon Horman <horms@...nel.org>
CC: Andrew Lunn <andrew+netdev@...n.ch>, Marc Kleine-Budde
<mkl@...gutronix.de>, Vincent Mailhol <mailhol.vincent@...adoo.fr>, "Daniel
Borkmann" <daniel@...earbox.net>, Nikolay Aleksandrov <razor@...ckwall.org>,
Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
<kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v1 net-next 1/8] rtnetlink: Introduce struct rtnl_nets and helpers.
rtnl_newlink() needs to hold 3 per-netns RTNL: 2 for a new device
and 1 for its peer.
We will add rtnl_nets_lock() later, which performs the nested locking
based on struct rtnl_nets, which has an array of struct net pointers.
rtnl_nets_add() adds a net pointer to the array and sorts it so that
rtnl_nets_lock() can simply acquire per-netns RTNL from array[0] to [2].
Before calling rtnl_nets_add(), get_net() must be called for the net,
and rtnl_nets_destroy() will call put_net() for each.
Let's apply the helpers to rtnl_newlink().
When CONFIG_DEBUG_NET_SMALL_RTNL is disabled, we do not call
rtnl_net_lock() thus do not care about the array order, so
rtnl_net_cmp_locks() returns -1 so that the loop in rtnl_nets_add()
can be optimised to NOP.
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
include/net/rtnetlink.h | 10 +++++++
net/core/rtnetlink.c | 63 +++++++++++++++++++++++++++++++++++++++--
2 files changed, 70 insertions(+), 3 deletions(-)
diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index b260c0cc9671..814364367dd7 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -68,6 +68,16 @@ static inline int rtnl_msg_family(const struct nlmsghdr *nlh)
return AF_UNSPEC;
}
+struct rtnl_nets {
+ /* ->newlink() needs to freeze 3 netns at most;
+ * 2 for the new device, 1 for its peer.
+ */
+ struct net *net[3];
+ unsigned char len;
+};
+
+void rtnl_nets_add(struct rtnl_nets *rtnl_nets, struct net *net);
+
/**
* struct rtnl_link_ops - rtnetlink link operations
*
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 3b33810d92a8..f98706ad390a 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -258,8 +258,60 @@ bool lockdep_rtnl_net_is_held(struct net *net)
return lockdep_rtnl_is_held() && lockdep_is_held(&net->rtnl_mutex);
}
EXPORT_SYMBOL(lockdep_rtnl_net_is_held);
+#else
+static int rtnl_net_cmp_locks(const struct net *net_a, const struct net *net_b)
+{
+ /* No need to swap */
+ return -1;
+}
#endif
+static void rtnl_nets_init(struct rtnl_nets *rtnl_nets)
+{
+ memset(rtnl_nets, 0, sizeof(*rtnl_nets));
+}
+
+static void rtnl_nets_destroy(struct rtnl_nets *rtnl_nets)
+{
+ int i;
+
+ for (i = 0; i < rtnl_nets->len; i++) {
+ put_net(rtnl_nets->net[i]);
+ rtnl_nets->net[i] = NULL;
+ }
+
+ rtnl_nets->len = 0;
+}
+
+/**
+ * rtnl_nets_add - Add netns to be locked before ->newlink().
+ *
+ * @rtnl_nets: rtnl_nets pointer passed to ->get_peer_net().
+ * @net: netns pointer with an extra refcnt held.
+ *
+ * The extra refcnt is released in rtnl_nets_destroy().
+ */
+void rtnl_nets_add(struct rtnl_nets *rtnl_nets, struct net *net)
+{
+ int i;
+
+ DEBUG_NET_WARN_ON_ONCE(rtnl_nets->len == ARRAY_SIZE(rtnl_nets->net));
+
+ for (i = 0; i < rtnl_nets->len; i++) {
+ switch (rtnl_net_cmp_locks(rtnl_nets->net[i], net)) {
+ case 0:
+ put_net(net);
+ return;
+ case 1:
+ swap(rtnl_nets->net[i], net);
+ }
+ }
+
+ rtnl_nets->net[i] = net;
+ rtnl_nets->len++;
+}
+EXPORT_SYMBOL(rtnl_nets_add);
+
static struct rtnl_link __rcu *__rcu *rtnl_msg_handlers[RTNL_FAMILY_MAX + 1];
static inline int rtm_msgindex(int msgtype)
@@ -3796,6 +3848,7 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
struct net *tgt_net, *link_net = NULL;
struct rtnl_link_ops *ops = NULL;
struct rtnl_newlink_tbs *tbs;
+ struct rtnl_nets rtnl_nets;
int ops_srcu_index;
int ret;
@@ -3839,6 +3892,8 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
#endif
}
+ rtnl_nets_init(&rtnl_nets);
+
if (ops) {
if (ops->maxtype > RTNL_MAX_TYPE) {
ret = -EINVAL;
@@ -3868,6 +3923,8 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
goto put_ops;
}
+ rtnl_nets_add(&rtnl_nets, tgt_net);
+
if (tb[IFLA_LINK_NETNSID]) {
int id = nla_get_s32(tb[IFLA_LINK_NETNSID]);
@@ -3878,6 +3935,8 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
goto put_net;
}
+ rtnl_nets_add(&rtnl_nets, link_net);
+
if (!netlink_ns_capable(skb, link_net->user_ns, CAP_NET_ADMIN)) {
ret = -EPERM;
goto put_net;
@@ -3887,9 +3946,7 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
ret = __rtnl_newlink(skb, nlh, ops, tgt_net, link_net, tbs, data, extack);
put_net:
- if (link_net)
- put_net(link_net);
- put_net(tgt_net);
+ rtnl_nets_destroy(&rtnl_nets);
put_ops:
if (ops)
rtnl_link_ops_put(ops, ops_srcu_index);
--
2.39.5 (Apple Git-154)
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