[PATCH net-next v1 1/5] rtnetlink: add rtnl_get_net_ns_capable()

[Christian Brauner <christian@brauner.io>]

get_target_net() will be used in follow-up patches in ipv{4,6} codepaths to
retrieve network namespaces based on network namespace identifiers. So
remove the static declaration and export in the rtnetlink header. Also,
rename it to rtnl_get_net_ns_capable() to make it obvious what this
function is doing.

Signed-off-by: Christian Brauner <christian@brauner.io>
---
v0->v1:
- export rtnl_get_net_ns_capable().
  Kbuild reported a build failure when ipv6 is built as a module. This was
  caused by rtnl_get_net_ns_capable() not being exported. Fix this by
  exporting it.
---
 include/net/rtnetlink.h |  1 +
 net/core/rtnetlink.c    | 17 +++++++++++++----
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index 0bbaa5488423..cf26e5aacac4 100644
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -165,6 +165,7 @@ int rtnl_configure_link(struct net_device *dev, const struct ifinfomsg *ifm);
 
 int rtnl_nla_parse_ifla(struct nlattr **tb, const struct nlattr *head, int len,
 			struct netlink_ext_ack *exterr);
+struct net *rtnl_get_net_ns_capable(struct sock *sk, int netnsid);
 
 #define MODULE_ALIAS_RTNL_LINK(kind) MODULE_ALIAS("rtnl-link-" kind)
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 24431e578310..30645d9a9801 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1841,7 +1841,15 @@ static bool link_dump_filtered(struct net_device *dev,
 	return false;
 }
 
-static struct net *get_target_net(struct sock *sk, int netnsid)
+/**
+ * rtnl_get_net_ns_capable - Get netns if sufficiently privileged.
+ * @sk: netlink socket
+ * @netnsid: network namespace identifier
+ *
+ * Returns the network namespace identified by netnsid on success or an error
+ * pointer on failure.
+ */
+struct net *rtnl_get_net_ns_capable(struct sock *sk, int netnsid)
 {
 	struct net *net;
 
@@ -1858,6 +1866,7 @@ static struct net *get_target_net(struct sock *sk, int netnsid)
 	}
 	return net;
 }
+EXPORT_SYMBOL_GPL(rtnl_get_net_ns_capable);
 
 static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
 {
@@ -1893,7 +1902,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
 			ifla_policy, NULL) >= 0) {
 		if (tb[IFLA_IF_NETNSID]) {
 			netnsid = nla_get_s32(tb[IFLA_IF_NETNSID]);
-			tgt_net = get_target_net(skb->sk, netnsid);
+			tgt_net = rtnl_get_net_ns_capable(skb->sk, netnsid);
 			if (IS_ERR(tgt_net)) {
 				tgt_net = net;
 				netnsid = -1;
@@ -2761,7 +2770,7 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	if (tb[IFLA_IF_NETNSID]) {
 		netnsid = nla_get_s32(tb[IFLA_IF_NETNSID]);
-		tgt_net = get_target_net(NETLINK_CB(skb).sk, netnsid);
+		tgt_net = rtnl_get_net_ns_capable(NETLINK_CB(skb).sk, netnsid);
 		if (IS_ERR(tgt_net))
 			return PTR_ERR(tgt_net);
 	}
@@ -3171,7 +3180,7 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	if (tb[IFLA_IF_NETNSID]) {
 		netnsid = nla_get_s32(tb[IFLA_IF_NETNSID]);
-		tgt_net = get_target_net(NETLINK_CB(skb).sk, netnsid);
+		tgt_net = rtnl_get_net_ns_capable(NETLINK_CB(skb).sk, netnsid);
 		if (IS_ERR(tgt_net))
 			return PTR_ERR(tgt_net);
 	}
-- 
2.17.1