samples/bpf: Fix MAC address swapping in xdp2_kern

xdp2_kern rewrites and forwards packets out on the same interface.
Forwarding still works but rewrite got broken when xdp multibuffer
support has been added.

With xdp multibuffer a local copy of the packet has been introduced. The
MAC address is now swapped in the local copy, but the local copy in not
written back.

Fix MAC address swapping be adding write back of modified packet.

Fixes: 772251742262 ("samples/bpf: fixup some tools to be able to support xdp multibuffer")
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Reviewed-by: Andy Gospodarek <gospo@broadcom.com>
Link: https://lore.kernel.org/r/20221015213050.65222-1-gerhard@engleder-embedded.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

diff --git a/samples/bpf/xdp2_kern.c b/samples/bpf/xdp2_kern.c
index 3332ba6bb95fb14d04507bde56cf0a514bd2ac92..67804ecf7ce376c318c0ba3332ebed3b7462268e 100644 (file)
--- a/samples/bpf/xdp2_kern.c
+++ b/samples/bpf/xdp2_kern.c
@@ -112,6 +112,10 @@ int xdp_prog1(struct xdp_md *ctx)
 
        if (ipproto == IPPROTO_UDP) {
                swap_src_dst_mac(data);
+
+               if (bpf_xdp_store_bytes(ctx, 0, pkt, sizeof(pkt)))
+                       return rc;
+
                rc = XDP_TX;
        }