On 10/16/2020 1:02 PM, Christian Eggers wrote:
Ensure that the skb is not cloned and has enough tail room for the tail
tag. This code will be removed from the drivers in the next commits.
Signed-off-by: Christian Eggers <cegg...@arri.de>
---
[snip]
+ /* We have to pad he packet to the minimum Ethernet frame size,
+ * if necessary, before adding the trailer (tail tagging only).
+ */
+ padlen = (skb->len >= ETH_ZLEN) ? 0 : ETH_ZLEN - skb->len;
+
+ /* To keep the slave's xmit() methods simple, don't pass cloned skbs to
+ * them. Additionally ensure, that suitable room for tail tagging is
+ * available.
+ */
+ if (skb_cloned(skb) ||
+ (p->tail_tag && skb_tailroom(skb) < (padlen + p->overhead))) {
+ struct sk_buff *nskb;
+
+ nskb = alloc_skb(NET_IP_ALIGN + skb->len +
+ padlen + p->overhead, GFP_ATOMIC);
+ if (!nskb) {
+ kfree_skb(skb);
+ return NETDEV_TX_OK;
+ }
+ skb_reserve(nskb, NET_IP_ALIGN);
+
+ skb_reset_mac_header(nskb);
+ skb_set_network_header(nskb,
+ skb_network_header(skb) - skb->head);
+ skb_set_transport_header(nskb,
+ skb_transport_header(skb) - skb->head);
+ skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
+ consume_skb(skb);
+
+ if (padlen)
+ skb_put_zero(nskb, padlen);
+
+ skb = nskb;
+ }
Given the low number of tail taggers, maybe this should be a helper
function that is used by them where applicable? If nothing else you may
want to sprinkle unlikely() conditions to sort of hing the processor
that these are unlikely conditions.
--
Florian
