Merge branch 'packet-fanout-unique-id'

Mike Maloney says:

====================
packet: Add option to create new fanout group with unique id.

Fanout uses a per net global namespace. A process that intends to create a
new fanout group can accidentally join an existing group. It is
not possible to detect this.

Add a socket option to specify on the first call to
setsockopt(..., PACKET_FANOUT, ...) to ensure that a new group is created.
Also add tests.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 44 insertions, 0 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 8489beff5c25..94052f42058b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1496,6 +1496,7 @@ static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
 DEFINE_MUTEX(fanout_mutex);
 EXPORT_SYMBOL_GPL(fanout_mutex);
 static LIST_HEAD(fanout_list);
+static u16 fanout_next_id;
 
 static void __fanout_link(struct sock *sk, struct packet_sock *po)
 {
@@ -1629,6 +1630,36 @@ static void fanout_release_data(struct packet_fanout *f)
 	};
 }
 
+static bool __fanout_id_is_free(struct sock *sk, u16 candidate_id)
+{
+	struct packet_fanout *f;
+
+	list_for_each_entry(f, &fanout_list, list) {
+		if (f->id == candidate_id &&
+		    read_pnet(&f->net) == sock_net(sk)) {
+			return false;
+		}
+	}
+	return true;
+}
+
+static bool fanout_find_new_id(struct sock *sk, u16 *new_id)
+{
+	u16 id = fanout_next_id;
+
+	do {
+		if (__fanout_id_is_free(sk, id)) {
+			*new_id = id;
+			fanout_next_id = id + 1;
+			return true;
+		}
+
+		id++;
+	} while (id != fanout_next_id);
+
+	return false;
+}
+
 static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
 {
 	struct packet_rollover *rollover = NULL;
@@ -1676,6 +1707,19 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
 		po->rollover = rollover;
 	}
 
+	if (type_flags & PACKET_FANOUT_FLAG_UNIQUEID) {
+		if (id != 0) {
+			err = -EINVAL;
+			goto out;
+		}
+		if (!fanout_find_new_id(sk, &id)) {
+			err = -ENOMEM;
+			goto out;
+		}
+		/* ephemeral flag for the first socket in the group: drop it */
+		flags &= ~(PACKET_FANOUT_FLAG_UNIQUEID >> 8);
+	}
+
 	match = NULL;
 	list_for_each_entry(f, &fanout_list, list) {
 		if (f->id == id &&