usb: gadget: NCM: Stop RX TCP Bursts getting dropped.

This fixes a problem with dropped packets over 16k CDC-NCM
when the connection is being heavily used.

The issue was that the extracted frames cloned from the
received frame were consuming more memory than necessary
resulting in the truesize being ~32KB instead of ~2KB, this
meant there was a high chance of reaching the sk_rcvbuf
limit.

Signed-off-by: Jim Baxter <jim_baxter@mentor.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

diff --git a/drivers/usb/gadget/f_ncm.c b/drivers/usb/gadget/f_ncm.c
index 5452fb663762694c284efcb7a8ca3a7612b2a287..bcdc882cd4157af2a0bd56a89248b7d3969d4b35 100644 (file)
--- a/drivers/usb/gadget/f_ncm.c
+++ b/drivers/usb/gadget/f_ncm.c
@@ -1229,16 +1229,17 @@ static int ncm_unwrap_ntb(struct gether *port,
                        index2 = get_ncm(&tmp, opts->dgram_item_len);
                        dg_len2 = get_ncm(&tmp, opts->dgram_item_len);
 
-                       skb2 = skb_clone(skb, GFP_ATOMIC);
+                       /*
+                        * Copy the data into a new skb.
+                        * This ensures the truesize is correct
+                        */
+                       skb2 = netdev_alloc_skb_ip_align(ncm->netdev,
+                                                        dg_len - crc_len);
                        if (skb2 == NULL)
                                goto err;
+                       memcpy(skb_put(skb2, dg_len - crc_len),
+                              skb->data + index, dg_len - crc_len);
 
-                       if (!skb_pull(skb2, index)) {
-                               ret = -EOVERFLOW;
-                               goto err;
-                       }
-
-                       skb_trim(skb2, dg_len - crc_len);
                        skb_queue_tail(list, skb2);
 
                        ndp_len -= 2 * (opts->dgram_item_len * 2);