netdev - [PATCH net-next v3 3/6] rtnetlink: Lookup device in target netns when creating link

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Message-ID: <20241113125715.150201-4-shaw.leon@gmail.com>
Date: Wed, 13 Nov 2024 20:57:12 +0800
From: Xiao Liang <shaw.leon@...il.com>
To: netdev@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	Kuniyuki Iwashima <kuniyu@...zon.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Donald Hunter <donald.hunter@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Ido Schimmel <idosch@...dia.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Simon Horman <horms@...nel.org>,
	Shuah Khan <shuah@...nel.org>,
	Jiri Pirko <jiri@...nulli.us>,
	Hangbin Liu <liuhangbin@...il.com>,
	linux-rdma@...r.kernel.org,
	linux-can@...r.kernel.org,
	osmocom-net-gprs@...ts.osmocom.org,
	bpf@...r.kernel.org,
	linux-ppp@...r.kernel.org,
	wireguard@...ts.zx2c4.com,
	linux-wireless@...r.kernel.org,
	b.a.t.m.a.n@...ts.open-mesh.org,
	bridge@...ts.linux.dev,
	linux-wpan@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH net-next v3 3/6] rtnetlink: Lookup device in target netns when creating link

When creating link, lookup for existing device in target net namespace
instead of current one.
For example, two links created by:

  # ip link add dummy1 type dummy
  # ip link add netns ns1 dummy1 type dummy

should have no conflict since they are in different namespaces.

Signed-off-by: Xiao Liang <shaw.leon@...il.com>
---
 net/core/rtnetlink.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 327fa4957929..f573ace60234 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3846,20 +3846,26 @@ static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 {
 	struct nlattr ** const tb = tbs->tb;
 	struct net *net = sock_net(skb->sk);
+	struct net *device_net;
 	struct net_device *dev;
 	struct ifinfomsg *ifm;
 	bool link_specified;
 
+	/* When creating, lookup for existing device in target net namespace */
+	device_net = (nlh->nlmsg_flags & NLM_F_CREATE) &&
+		     (nlh->nlmsg_flags & NLM_F_EXCL) ?
+		     tgt_net : net;
+
 	ifm = nlmsg_data(nlh);
 	if (ifm->ifi_index > 0) {
 		link_specified = true;
-		dev = __dev_get_by_index(net, ifm->ifi_index);
+		dev = __dev_get_by_index(device_net, ifm->ifi_index);
 	} else if (ifm->ifi_index < 0) {
 		NL_SET_ERR_MSG(extack, "ifindex can't be negative");
 		return -EINVAL;
 	} else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME]) {
 		link_specified = true;
-		dev = rtnl_dev_get(net, tb);
+		dev = rtnl_dev_get(device_net, tb);
 	} else {
 		link_specified = false;
 		dev = NULL;
-- 
2.47.0