[PATCH v3 6/6] net: ipv6: allow setting address on interface outside current namespace

[Jonas Bonn]

This patch allows an interface outside of the current namespace to be
selected when setting a new IPv6 address for a device.  This uses the
IFA_TARGET_NETNSID attribute to select the namespace in which to search
for the interface to act upon.

Signed-off-by: Jonas Bonn <jonas@xxxxxxxxxxx>
---
 net/ipv6/addrconf.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 34ccef18b40e..06a49670fe62 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4721,6 +4721,7 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 		  struct netlink_ext_ack *extack)
 {
 	struct net *net = sock_net(skb->sk);
+	struct net *tgt_net;
 	struct ifaddrmsg *ifm;
 	struct nlattr *tb[IFA_MAX+1];
 	struct in6_addr *peer_pfx;
@@ -4758,6 +4759,18 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 		cfg.preferred_lft = ci->ifa_prefered;
 	}
 
+	if (tb[IFA_TARGET_NETNSID]) {
+		s32 netnsid = nla_get_s32(tb[IFA_TARGET_NETNSID]);
+
+		tgt_net = rtnl_get_net_ns_capable(NETLINK_CB(skb).sk, netnsid);
+		if (IS_ERR(tgt_net)) {
+			NL_SET_ERR_MSG(extack,
+				"ipv6: Invalid target network namespace id");
+			return PTR_ERR(tgt_net);
+		}
+		net = tgt_net;
+	}
+
 	dev =  __dev_get_by_index(net, ifm->ifa_index);
 	if (!dev)
 		return -ENODEV;
-- 
2.20.1