netdev - [PATCH net-next v2] net: Add support for filtering neigh dump by master device

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Date:	Tue, 29 Sep 2015 09:32:03 -0700
From:	David Ahern <dsa@...ulusnetworks.com>
To:	netdev@...r.kernel.org
Cc:	David Ahern <dsa@...ulusnetworks.com>
Subject: [PATCH net-next v2] net: Add support for filtering neigh dump by master device

Add support for filtering neighbor dumps by master device by adding
the NDA_MASTER attribute to the dump request. A new netlink flag,
NLM_F_DUMP_FILTERED, is added to indicate the kernel supports the
request and output is filtered as requested.

Signed-off-by: David Ahern <dsa@...ulusnetworks.com>
---
v2
- added NLM_F_DUMP_FILTERED flag for userspace feedback that request is
  supported

This method works for other filters as well and other dump commands.
Works fine for all combinations of new and old kernel and new and old ip:
1. new ip command on old kernel, NDA_MASTER attribute is ignored
2. old ip command on new kernel, NDA_MASTER attribute is not present
3. new ip on new kernel ... goodness ensues by limiting data to
   only what user wants

 include/uapi/linux/netlink.h |  1 +
 net/core/neighbour.c         | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index 6f3fe16cd22a..f095155d8749 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -54,6 +54,7 @@ struct nlmsghdr {
 #define NLM_F_ACK		4	/* Reply with ack, with zero or error code */
 #define NLM_F_ECHO		8	/* Echo this request 		*/
 #define NLM_F_DUMP_INTR		16	/* Dump was inconsistent due to sequence change */
+#define NLM_F_DUMP_FILTERED	32	/* Dump was filtered as requested */
 
 /* Modifiers to GET request */
 #define NLM_F_ROOT	0x100	/* specify tree	root	*/
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 2b515ba7e94f..8c57fdf4d68e 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2235,14 +2235,42 @@ static void neigh_update_notify(struct neighbour *neigh)
 	__neigh_notify(neigh, RTM_NEWNEIGH, 0);
 }
 
+static bool neigh_master_filtered(struct net_device *dev, int master_idx)
+{
+	struct net_device *master;
+
+	if (!master_idx)
+		return false;
+
+	master = netdev_master_upper_dev_get(dev);
+	if (!master || master->ifindex != master_idx)
+		return true;
+
+	return false;
+}
+
 static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
 			    struct netlink_callback *cb)
 {
 	struct net *net = sock_net(skb->sk);
+	const struct nlmsghdr *nlh = cb->nlh;
+	struct nlattr *tb[NDA_MAX + 1];
 	struct neighbour *n;
 	int rc, h, s_h = cb->args[1];
 	int idx, s_idx = idx = cb->args[2];
 	struct neigh_hash_table *nht;
+	int filter_master_idx = 0;
+	unsigned int flags = NLM_F_MULTI;
+	int err;
+
+	err = nlmsg_parse(nlh, sizeof(struct ndmsg), tb, NDA_MAX, NULL);
+	if (!err) {
+		if (tb[NDA_MASTER])
+			filter_master_idx = nla_get_u32(tb[NDA_MASTER]);
+
+		if (filter_master_idx)
+			flags |= NLM_F_DUMP_FILTERED;
+	}
 
 	rcu_read_lock_bh();
 	nht = rcu_dereference_bh(tbl->nht);
@@ -2255,12 +2283,14 @@ static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
 		     n = rcu_dereference_bh(n->next)) {
 			if (!net_eq(dev_net(n->dev), net))
 				continue;
+			if (neigh_master_filtered(n->dev, filter_master_idx))
+				continue;
 			if (idx < s_idx)
 				goto next;
 			if (neigh_fill_info(skb, n, NETLINK_CB(cb->skb).portid,
 					    cb->nlh->nlmsg_seq,
 					    RTM_NEWNEIGH,
-					    NLM_F_MULTI) < 0) {
+					    flags) < 0) {
 				rc = -1;
 				goto out;
 			}
-- 
1.9.1

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