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rtnetlink: Introduce struct rtnl_nets and helpers.

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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@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20241108004823.29419-5-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
2024-11-07 16:48:17 -08:00
committed by Jakub Kicinski
parent 68297dbb96
commit cbaaa6326b
1 changed files with 67 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

70
net/core/rtnetlink.c
View File

@@ -258,8 +258,67 @@ 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
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;
};
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().
*/
static 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++;
}
static struct rtnl_link __rcu *__rcu *rtnl_msg_handlers[RTNL_FAMILY_MAX + 1];
static inline int rtm_msgindex(int msgtype)
@@ -3767,6 +3826,7 @@ 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;
@@ -3810,6 +3870,8 @@ 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;
@@ -3839,6 +3901,8 @@ 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]);
@@ -3849,6 +3913,8 @@ 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;
@@ -3858,9 +3924,7 @@ 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);