Re: [PATCH] libbpf: Don't error out if getsockopt() fails for XDP_OPTIONS

On 9/13/19 8:53 PM, Yonghong Song wrote:

On 9/10/19 12:06 AM, Toke Høiland-Jørgensen wrote:

quoted

Yonghong Song [off-list ref] writes:

quoted

On 9/9/19 10:46 AM, Toke Høiland-Jørgensen wrote:

quoted

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,
there really is no need to error out if the getsockopt() call fails.

Signed-off-by: Toke Høiland-Jørgensen <redacted>
---
    tools/lib/bpf/xsk.c | 8 ++------
    1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index 680e63066cf3..598e487d9ce8 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c

@@ -603,12 +603,8 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
    
    	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 (!err)
+		xsk->zc = opts.flags & XDP_OPTIONS_ZEROCOPY;
    
    	if (!(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) {
    		err = xsk_setup_xdp_prog(xsk);

Since 'zc' is not used by anybody, maybe all codes 'zc' related can be
removed? It can be added back back once there is an interface to use
'zc'?

Fine with me; up to the maintainers what they prefer, I guess? :)

Given this is not exposed to applications at this point and we don't do anything
useful with it, lets just remove the zc cruft until there is a proper interface
added to libbpf. Toke, please respin with the suggested removal, thanks!