net/ipv6: Add support for dumping addresses for a specific device

If an RTM_GETADDR dump request has ifa_index set in the ifaddrmsg
header, then return only the addresses for that device.

Since inet6_dump_addr is reused for multicast and anycast addresses,
this adds support for device specfic dumps of RTM_GETMULTICAST and
RTM_GETANYCAST as well.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -4821,6 +4821,7 @@ struct inet6_fill_args {
 	int event;
 	unsigned int flags;
 	int netnsid;
+	int ifindex;
 	enum addr_type_t type;
 };
 
@@ -5018,8 +5019,9 @@ static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb,
 static int inet6_valid_dump_ifaddr_req(const struct nlmsghdr *nlh,
 				       struct inet6_fill_args *fillargs,
 				       struct net **tgt_net, struct sock *sk,
-				       struct netlink_ext_ack *extack)
+				       struct netlink_callback *cb)
 {
+	struct netlink_ext_ack *extack = cb->extack;
 	struct nlattr *tb[IFA_MAX+1];
 	struct ifaddrmsg *ifm;
 	int err, i;
@@ -5034,9 +5036,11 @@ static int inet6_valid_dump_ifaddr_req(const struct nlmsghdr *nlh,
 		NL_SET_ERR_MSG_MOD(extack, "Invalid values in header for address dump request");
 		return -EINVAL;
 	}
-	if (ifm->ifa_index) {
-		NL_SET_ERR_MSG_MOD(extack, "Filter by device index not supported for address dump");
-		return -EINVAL;
+
+	fillargs->ifindex = ifm->ifa_index;
+	if (fillargs->ifindex) {
+		cb->answer_flags |= NLM_F_DUMP_FILTERED;
+		fillargs->flags |= NLM_F_DUMP_FILTERED;
 	}
 
 	err = nlmsg_parse_strict(nlh, sizeof(*ifm), tb, IFA_MAX,
@@ -5094,9 +5098,21 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 		int err;
 
 		err = inet6_valid_dump_ifaddr_req(nlh, &fillargs, &tgt_net,
-						  skb->sk, cb->extack);
+						  skb->sk, cb);
 		if (err < 0)
 			return err;
+
+		if (fillargs.ifindex) {
+			dev = __dev_get_by_index(tgt_net, fillargs.ifindex);
+			if (!dev)
+				return -ENODEV;
+			idev = __in6_dev_get(dev);
+			if (idev) {
+				err = in6_dump_addrs(idev, skb, cb, s_ip_idx,
+						     &fillargs);
+			}
+			goto put_tgt_net;
+		}
 	}
 
 	rcu_read_lock();
@@ -5124,6 +5140,7 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 	rcu_read_unlock();
 	cb->args[0] = h;
 	cb->args[1] = idx;
+put_tgt_net:
 	if (fillargs.netnsid >= 0)
 		put_net(tgt_net);