On Wed, Jun 24, 2020 at 03:06:10PM -0600, Jason A. Donenfeld wrote:

Hi Alexander,

This patch introduced a behavior change around GRO_DROP:

napi_skb_finish used to sometimes return GRO_DROP:

quoted

-static gro_result_t napi_skb_finish(gro_result_t ret, struct sk_buff *skb)
+static gro_result_t napi_skb_finish(struct napi_struct *napi,
+				    struct sk_buff *skb,
+				    gro_result_t ret)
 {
 	switch (ret) {
 	case GRO_NORMAL:
-		if (netif_receive_skb_internal(skb))
-			ret = GRO_DROP;
+		gro_normal_one(napi, skb);

But under your change, gro_normal_one and the various calls that makes
never propagates its return value, and so GRO_DROP is never returned to
the caller, even if something drops it.

Was this intentional? Or should I start looking into how to restore it?

Thanks,
Jason

For some context, I'm consequently mulling over this change in my code,
since checking for GRO_DROP now constitutes dead code:

diff --git a/drivers/net/wireguard/receive.c b/drivers/net/wireguard/receive.c
index 91438144e4f7..9b2ab6fc91cd 100644
--- a/drivers/net/wireguard/receive.c
+++ b/drivers/net/wireguard/receive.c

@@ -414,14 +414,8 @@ static void wg_packet_consume_data_done(struct wg_peer *peer,
 	if (unlikely(routed_peer != peer))
 		goto dishonest_packet_peer;

-	if (unlikely(napi_gro_receive(&peer->napi, skb) == GRO_DROP)) {
-		++dev->stats.rx_dropped;
-		net_dbg_ratelimited("%s: Failed to give packet to userspace from peer %llu (%pISpfsc)\n",
-				    dev->name, peer->internal_id,
-				    &peer->endpoint.addr);
-	} else {
-		update_rx_stats(peer, message_data_len(len_before_trim));
-	}
+	napi_gro_receive(&peer->napi, skb);
+	update_rx_stats(peer, message_data_len(len_before_trim));
 	return;

 dishonest_packet_peer: