[PATCH v1 net-next 3/8] rtnetlink: Add peer_type in struct rtnl_link_ops.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

For veth, vxcan, and netkit, we need to prefetch the peer device's
netns in rtnl_newlink() for per-netns RTNL.

All of the three get the netns in the same way peer netlink attr tb:

  1. Call rtnl_nla_parse_ifinfomsg()
  2. Call ops->validate() (vxcan doesn't have)
  3. Call rtnl_link_get_net_tb()

Let's add a new field peer_type to struct rtnl_link_ops and fetch
netns in peer attrbutes to add it to rtnl_nets in rtnl_newlink().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/net/rtnetlink.h |  2 ++
 net/core/rtnetlink.c    | 39 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index b9ed44b2d056..c3548da95ffa 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -85,6 +85,7 @@ void rtnl_nets_add(struct rtnl_nets *rtnl_nets, struct net *net);
  *	@srcu: Used internally
  *	@kind: Identifier
  *	@netns_refund: Physical device, move to init_net on netns exit
+ *	@peer_type: Peer device specific netlink attribute number (e.g. VETH_INFO_PEER)
  *	@maxtype: Highest device specific netlink attribute number
  *	@policy: Netlink policy for device specific attribute validation
  *	@validate: Optional validation function for netlink/changelink parameters
@@ -126,6 +127,7 @@ struct rtnl_link_ops {
 	void			(*setup)(struct net_device *dev);
 
 	bool			netns_refund;
+	const unsigned char	peer_type;
 	unsigned int		maxtype;
 	const struct nla_policy	*policy;
 	int			(*validate)(struct nlattr *tb[],
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 1bc8afcefc1e..48bd9e062550 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3798,6 +3798,37 @@ static int rtnl_newlink_create(struct sk_buff *skb, struct ifinfomsg *ifm,
 	goto out;
 }
 
+static int rtnl_add_peer_net(struct rtnl_nets *rtnl_nets,
+			     const struct rtnl_link_ops *ops,
+			     struct nlattr *data[],
+			     struct netlink_ext_ack *extack)
+{
+	struct nlattr *tb[IFLA_MAX + 1];
+	struct net *net;
+	int err;
+
+	if (!data || !data[ops->peer_type])
+		return 0;
+
+	err = rtnl_nla_parse_ifinfomsg(tb, data[ops->peer_type], extack);
+	if (err < 0)
+		return err;
+
+	if (ops->validate) {
+		err = ops->validate(tb, NULL, extack);
+		if (err < 0)
+			return err;
+	}
+
+	net = rtnl_link_get_net_tb(tb);
+	if (IS_ERR(net))
+		return PTR_ERR(net);
+	if (net)
+		rtnl_nets_add(rtnl_nets, net);
+
+	return 0;
+}
+
 static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			  const struct rtnl_link_ops *ops,
 			  struct net *tgt_net, struct net *link_net,
@@ -3926,12 +3957,18 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			if (ret < 0)
 				goto put_ops;
 		}
+
+		if (ops->peer_type) {
+			ret = rtnl_add_peer_net(&rtnl_nets, ops, data, extack);
+			if (ret < 0)
+				goto put_ops;
+		}
 	}
 
 	tgt_net = rtnl_link_get_net_capable(skb, sock_net(skb->sk), tb, CAP_NET_ADMIN);
 	if (IS_ERR(tgt_net)) {
 		ret = PTR_ERR(tgt_net);
-		goto put_ops;
+		goto put_net;
 	}
 
 	rtnl_nets_add(&rtnl_nets, tgt_net);
-- 
2.39.5 (Apple Git-154)