Re: [PATCH bpf-next] libbpf: remove zc variable as it is not used

[Jonathan Lemon]

On 16 Aug 2019, at 8:37, Yonghong Song wrote:

On 8/16/19 3:26 AM, Magnus Karlsson wrote:
The zc is not used in the xsk part of libbpf, so let us remove it. 
Not
good to have dead code lying around.

Signed-off-by: Magnus Karlsson <magnus.karls...@intel.com>
Reported-by: Yonghong Song <y...@fb.com> > ---
  tools/lib/bpf/xsk.c | 3 ---
  1 file changed, 3 deletions(-)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index 680e630..9687da9 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -65,7 +65,6 @@ struct xsk_socket {
        int xsks_map_fd;
        __u32 queue_id;
        char ifname[IFNAMSIZ];
-       bool zc;
  };

  struct xsk_nl_info {
@@ -608,8 +607,6 @@ int xsk_socket__create(struct xsk_socket 
**xsk_ptr, const char *ifname,
                goto out_mmap_tx;
        }

-       xsk->zc = opts.flags & XDP_OPTIONS_ZEROCOPY;

Since opts.flags usage is removed. Do you think it makes sense to
remove
         optlen = sizeof(opts);
         err = getsockopt(xsk->fd, SOL_XDP, XDP_OPTIONS, &opts, 
&optlen);
         if (err) {
                 err = -errno;
                 goto out_mmap_tx;
         }
as well since nobody then uses opts?

IIRC, this was added specifically in 
2761ed4b6e192820760d5ba913834b2ba05fd08c
so that userland code could know whether the socket was operating in 
zero-copy
mode or not.
--
Jonathan