@@ -4548,6 +4548,11 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
xdp->data_meta = xdp->data;
xdp->data_end = xdp->data + hlen;
xdp->data_hard_start = skb->data - skb_headroom(skb);
+
+ /* SKB "head" area always have tailroom for skb_shared_info */
+ xdp->frame_sz = (void *)skb_end_pointer(skb) - xdp->data_hard_start;
+ xdp->frame_sz += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+
orig_data_end = xdp->data_end;
orig_data = xdp->data;
eth = (struct ethhdr *)xdp->data;
@@ -4571,14 +4576,11 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
skb_reset_network_header(skb);
}
- /* check if bpf_xdp_adjust_tail was used. it can only "shrink"
- * pckt.
- */
- off = orig_data_end - xdp->data_end;
+ /* check if bpf_xdp_adjust_tail was used */
+ off = xdp->data_end - orig_data_end;
if (off != 0) {
skb_set_tail_pointer(skb, xdp->data_end - xdp->data);
- skb->len -= off;
-
+ skb->len += off; /* positive on grow, negative on shrink */
}
/* check if XDP changed eth hdr such SKB needs update */
The SKB "head" pointer points to the data area that contains skb_shared_info, that can be found via skb_end_pointer(). Given xdp->data_hard_start have been established (basically pointing to skb->head), frame size is between skb_end_pointer() and data_hard_start, plus the size reserved to skb_shared_info. Change the bpf_xdp_adjust_tail offset adjust of skb->len, to be a positive offset number on grow, and negative number on shrink. As this seems more natural when reading the code. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> --- net/core/dev.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)