[PATCH net-next v04 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.

Socket can be RUNNING if it has a specified protocol. Either directly
from packet_create (being implicitly bound to any interface) or following
a successful bind. Socket RUNNING state is switched off if it is bound to
an interface that went down.

Instead of the test for RUNNING, this patch adds a test that socket can
become RUNNING.

Signed-off-by: Gur Stavi <gur.stavi@xxxxxxxxxx>
---
 net/packet/af_packet.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index f8942062f776..2ff4b251842d 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1846,21 +1846,22 @@ static int fanout_add(struct sock *sk, struct fanout_args *args)
 	err = -EINVAL;
 
 	spin_lock(&po->bind_lock);
-	if (packet_sock_flag(po, PACKET_SOCK_RUNNING) &&
+	if (po->num &&
 	    match->type == type &&
 	    match->prot_hook.type == po->prot_hook.type &&
 	    match->prot_hook.dev == po->prot_hook.dev) {
 		err = -ENOSPC;
 		if (refcount_read(&match->sk_ref) < match->max_num_members) {
-			__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);
+			if (packet_sock_flag(po, PACKET_SOCK_RUNNING)) {
+				__dev_remove_pack(&po->prot_hook);
+				__fanout_link(sk, po);
+			}
 			err = 0;
 		}
 	}
-- 
2.45.2