bpf: make generic xdp compatible w/ bpf_xdp_adjust_tail

w/ bpf_xdp_adjust_tail helper xdp's data_end pointer could be changed as
well (only "decrease" of pointer's location is going to be supported).
changing of this pointer will change packet's size.
for generic XDP we need to reflect this packet's length change by
adjusting skb's tail pointer

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index 969462ebb296250fe5f3b7c4621e9ba9720a2dbe..11c789231a034119bf012b93f3fb8686c5562a3b 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3996,9 +3996,9 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
                                     struct bpf_prog *xdp_prog)
 {
        struct netdev_rx_queue *rxqueue;
+       void *orig_data, *orig_data_end;
        u32 metalen, act = XDP_DROP;
        struct xdp_buff xdp;
-       void *orig_data;
        int hlen, off;
        u32 mac_len;
 
@@ -4037,6 +4037,7 @@ 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);
+       orig_data_end = xdp.data_end;
        orig_data = xdp.data;
 
        rxqueue = netif_get_rxqueue(skb);
@@ -4051,6 +4052,13 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
                __skb_push(skb, -off);
        skb->mac_header += off;
 
+       /* check if bpf_xdp_adjust_tail was used. it can only "shrink"
+        * pckt.
+        */
+       off = orig_data_end - xdp.data_end;
+       if (off != 0)
+               skb_set_tail_pointer(skb, xdp.data_end - xdp.data);
+
        switch (act) {
        case XDP_REDIRECT:
        case XDP_TX: