[PATCH bpf v2] libbpf: Remove getsockopt() check for XDP_OPTIONS

[PATCH bpf v2] libbpf: Remove getsockopt() check for XDP_OPTIONS

[Toke Høiland-Jørgensen]

The xsk_socket__create() function fails and returns an error if it cannot
get the XDP_OPTIONS through getsockopt(). However, support for XDP_OPTIONS
was not added until kernel 5.3, so this means that creating XSK sockets
always fails on older kernels.

Since the option is just used to set the zero-copy flag in the xsk struct,
and that flag is not really used for anything yet, just remove the
getsockopt() call until a proper use for it is introduced.

Suggested-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
v2:
  - Remove the call entirely.
  
 tools/lib/bpf/xsk.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index 680e63066cf3..14aea315c914 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 {
@@ -481,7 +480,6 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
 	void *rx_map = NULL, *tx_map = NULL;
 	struct sockaddr_xdp sxdp = {};
 	struct xdp_mmap_offsets off;
-	struct xdp_options opts;
 	struct xsk_socket *xsk;
 	socklen_t optlen;
 	int err;
@@ -601,15 +599,6 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
 
 	xsk->prog_fd = -1;
 
-	optlen = sizeof(opts);
-	err = getsockopt(xsk->fd, SOL_XDP, XDP_OPTIONS, &opts, &optlen);
-	if (err) {
-		err = -errno;
-		goto out_mmap_tx;
-	}
-
-	xsk->zc = opts.flags & XDP_OPTIONS_ZEROCOPY;
-
 	if (!(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) {
 		err = xsk_setup_xdp_prog(xsk);
 		if (err)
-- 
2.23.0

Re: [PATCH bpf v2] libbpf: Remove getsockopt() check for XDP_OPTIONS

[Andrii Nakryiko]

On Mon, Sep 16, 2019 at 6:05 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> The xsk_socket__create() function fails and returns an error if it cannot
> get the XDP_OPTIONS through getsockopt(). However, support for XDP_OPTIONS
> was not added until kernel 5.3, so this means that creating XSK sockets
> always fails on older kernels.
>
> Since the option is just used to set the zero-copy flag in the xsk struct,
> and that flag is not really used for anything yet, just remove the
> getsockopt() call until a proper use for it is introduced.
>
> Suggested-by: Yonghong Song <yhs@fb.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---
> v2:
>   - Remove the call entirely.
>
>  tools/lib/bpf/xsk.c | 11 -----------
>  1 file changed, 11 deletions(-)
>

Who doesn't like removal of code?.. :)

Acked-by: Andrii Nakryiko <andriin@fb.com>

[...]

Re: [PATCH bpf v2] libbpf: Remove getsockopt() check for XDP_OPTIONS

[Daniel Borkmann]

On Mon, Sep 16, 2019 at 02:33:42PM +0200, Toke Høiland-Jørgensen wrote:
> The xsk_socket__create() function fails and returns an error if it cannot
> get the XDP_OPTIONS through getsockopt(). However, support for XDP_OPTIONS
> was not added until kernel 5.3, so this means that creating XSK sockets
> always fails on older kernels.
> 
> Since the option is just used to set the zero-copy flag in the xsk struct,
> and that flag is not really used for anything yet, just remove the
> getsockopt() call until a proper use for it is introduced.
> 
> Suggested-by: Yonghong Song <yhs@fb.com>
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>

Applied, thanks!