Re: [PATCH] samples: bpf: xdp1: remove duplicate code to find protocol

On Sun, Aug 8, 2021 at 10:23 PM Yonghong Song [off-list ref] wrote:

On 8/8/21 5:24 AM, Muhammad Falak R Wani wrote:

quoted

The code to find h_vlan_encapsulated_proto is duplicated.
Remove the extra block.

Signed-off-by: Muhammad Falak R Wani <redacted>
---
  samples/bpf/xdp1_kern.c | 9 ---------
  1 file changed, 9 deletions(-)

diff --git a/samples/bpf/xdp1_kern.c b/samples/bpf/xdp1_kern.c
index 34b64394ed9c..a35e064d7726 100644
--- a/samples/bpf/xdp1_kern.c
+++ b/samples/bpf/xdp1_kern.c

@@ -57,15 +57,6 @@ int xdp_prog1(struct xdp_md *ctx)

      h_proto = eth->h_proto;

-     if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
-             struct vlan_hdr *vhdr;
-
-             vhdr = data + nh_off;
-             nh_off += sizeof(struct vlan_hdr);
-             if (data + nh_off > data_end)
-                     return rc;
-             h_proto = vhdr->h_vlan_encapsulated_proto;

No. This is not a duplicate. The h_proto in the above line will be used
in the below "if" condition.

quoted

-     }
      if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
              struct vlan_hdr *vhdr;

Apologies :(
I now realize, it could be double vlan encapsulated.
Would it make sense to add an explicit comment for newbies like me ?
I can send a patch, if it is okay.

-mfrw