[PATCH v3 1/1] net: ipv6: allow setting address on interface outside current namespace

[Jonas Bonn <jonas@norrbonn.se>]

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@norrbonn.se>
---

I messed up this patch and the cleanup code path wasn't included.  It
should look like this.  Sorry for the noise.

/Jonas

 net/ipv6/addrconf.c | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 34ccef18b40e..8ef8297db150 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 = NULL;
 	struct ifaddrmsg *ifm;
 	struct nlattr *tb[IFA_MAX+1];
 	struct in6_addr *peer_pfx;
@@ -4758,9 +4759,23 @@ 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;
+	if (!dev) {
+		err = -ENODEV;
+		goto out;
+	}
 
 	if (tb[IFA_FLAGS])
 		cfg.ifa_flags = nla_get_u32(tb[IFA_FLAGS]);
@@ -4773,8 +4788,10 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 			 IFA_F_MCAUTOJOIN | IFA_F_OPTIMISTIC;
 
 	idev = ipv6_find_idev(dev);
-	if (IS_ERR(idev))
-		return PTR_ERR(idev);
+	if (IS_ERR(idev)) {
+		err = PTR_ERR(idev);
+		goto out;
+	}
 
 	if (!ipv6_allow_optimistic_dad(net, idev))
 		cfg.ifa_flags &= ~IFA_F_OPTIMISTIC;
@@ -4782,7 +4799,8 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (cfg.ifa_flags & IFA_F_NODAD &&
 	    cfg.ifa_flags & IFA_F_OPTIMISTIC) {
 		NL_SET_ERR_MSG(extack, "IFA_F_NODAD and IFA_F_OPTIMISTIC are mutually exclusive");
-		return -EINVAL;
+		err = -EINVAL;
+		goto out;
 	}
 
 	ifa = ipv6_get_ifaddr(net, cfg.pfx, dev, 1);
@@ -4791,7 +4809,8 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 		 * It would be best to check for !NLM_F_CREATE here but
 		 * userspace already relies on not having to provide this.
 		 */
-		return inet6_addr_add(net, ifm->ifa_index, &cfg, extack);
+		err = inet6_addr_add(net, ifm->ifa_index, &cfg, extack);
+		goto out;
 	}
 
 	if (nlh->nlmsg_flags & NLM_F_EXCL ||
@@ -4802,6 +4821,9 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	in6_ifa_put(ifa);
 
+out:
+	if (tgt_net)
+		put_net(tgt_net);
 	return err;
 }
 
-- 
2.20.1