[PATCH net-next v4 06/33] net: XDP-generic determining XDP frame size
flat view
STALE2355d
LANDED: 1 (0M)
From: Jesper Dangaard Brouer <hidden>
Date: 2020-05-14 10:49:39
Also in:
bpf
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Status: Landed in mainline as a075767bbdc6 on 2020-05-15.
Revision v4 (4 revisions archived); 1 review trailer.
Revisions (4)
- v1 re-posted go to this post
- v2 [diff against previous] re-posted go to this post
- v3 [diff against previous]
- v4 current [diff against previous]
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 <redacted> Acked-by: Toke Høiland-Jørgensen <redacted> --- net/core/dev.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 4c91de39890a..f937a3ff668d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c@@ -4617,6 +4617,11 @@ 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;
@@ -4640,14 +4645,11 @@ 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 */