[PATCH net-next v03 1/3] af_packet: allow fanout_add when socket is not RUNNING

[Gur Stavi]

PACKET socket can retain its fanout membership through link down and up
and leave a fanout while closed regardless of link state.
However, socket was forbidden from joining a fanout while it was not
RUNNING.

This patch allows PACKET socket to join fanout while not RUNNING.

The previous test for RUNNING also implicitly tested that the socket is
bound to a device. An explicit test of ifindex was added instead.

Signed-off-by: Gur Stavi <gur.stavi@xxxxxxxxxx>
---
 net/packet/af_packet.c | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index f8942062f776..8137c33ab0fd 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1843,26 +1843,29 @@ static int fanout_add(struct sock *sk, struct fanout_args *args)
 		match->prot_hook.ignore_outgoing = type_flags & PACKET_FANOUT_FLAG_IGNORE_OUTGOING;
 		list_add(&match->list, &fanout_list);
 	}
-	err = -EINVAL;
 
 	spin_lock(&po->bind_lock);
-	if (packet_sock_flag(po, PACKET_SOCK_RUNNING) &&
-	    match->type == type &&
-	    match->prot_hook.type == po->prot_hook.type &&
-	    match->prot_hook.dev == po->prot_hook.dev) {
+	if (po->ifindex == -1 || po->num == 0) {
+		/* Socket can not receive packets */
+		err = -ENXIO;
+	} else if (match->type != type ||
+		   match->prot_hook.type != po->prot_hook.type ||
+		   match->prot_hook.dev != po->prot_hook.dev) {
+		/* Joining an existing group, properties must be identical */
+		err = -EINVAL;
+	} else if (refcount_read(&match->sk_ref) >= match->max_num_members) {
 		err = -ENOSPC;
-		if (refcount_read(&match->sk_ref) < match->max_num_members) {
+	} else {
+		/* Paired with packet_setsockopt(PACKET_FANOUT_DATA) */
+		WRITE_ONCE(po->fanout, match);
+		po->rollover = rollover;
+		rollover = NULL;
+		refcount_set(&match->sk_ref, refcount_read(&match->sk_ref) + 1);
+		if (packet_sock_flag(po, PACKET_SOCK_RUNNING)) {
 			__dev_remove_pack(&po->prot_hook);
-
-			/* Paired with packet_setsockopt(PACKET_FANOUT_DATA) */
-			WRITE_ONCE(po->fanout, match);
-
-			po->rollover = rollover;
-			rollover = NULL;
-			refcount_set(&match->sk_ref, refcount_read(&match->sk_ref) + 1);
 			__fanout_link(sk, po);
-			err = 0;
 		}
+		err = 0;
 	}
 	spin_unlock(&po->bind_lock);
 
@@ -3452,8 +3455,12 @@ static int packet_create(struct net *net, struct socket *sock, int protocol,
 	po->prot_hook.af_packet_net = sock_net(sk);
 
 	if (proto) {
+		/* Implicitly bind socket to "any interface" */
+		po->ifindex = 0;
 		po->prot_hook.type = proto;
 		__register_prot_hook(sk);
+	} else {
+		po->ifindex = -1;
 	}
 
 	mutex_lock(&net->packet.sklist_lock);
-- 
2.45.2