tcp: fix ooo_okay setting vs Small Queues
TCP Small Queues (tcp_tsq_handler()) can hold one reference on
sk->sk_wmem_alloc, preventing skb->ooo_okay being set.
We should relax test done to set skb->ooo_okay to take care
of this extra reference.
Minimal truesize of skb containing one byte of payload is
SKB_TRUESIZE(1)
Without this fix, we have more chance locking flows into the wrong
transmit queue.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8d4eac7..0a5d97c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -914,9 +914,13 @@
tcp_ca_event(sk, CA_EVENT_TX_START);
/* if no packet is in qdisc/device queue, then allow XPS to select
- * another queue.
+ * another queue. We can be called from tcp_tsq_handler()
+ * which holds one reference to sk_wmem_alloc.
+ *
+ * TODO: Ideally, in-flight pure ACK packets should not matter here.
+ * One way to get this would be to set skb->truesize = 2 on them.
*/
- skb->ooo_okay = sk_wmem_alloc_get(sk) == 0;
+ skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
skb_push(skb, tcp_header_size);
skb_reset_transport_header(skb);