libbpf: Use AF_LOCAL instead of AF_INET in xsk.c

We have the environments where usage of AF_INET is prohibited
(cgroup/sock_create returns EPERM for AF_INET). Let's use
AF_LOCAL instead of AF_INET, it should perfectly work with SIOCETHTOOL.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Björn Töpel <bjorn.topel@intel.com>
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Link: https://lore.kernel.org/bpf/20210209221826.922940-1-sdf@google.com

tools/lib/bpf/xsk.c

@@ -517,7 +517,7 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
 	struct ifreq ifr = {};
 	int fd, err, ret;
 
-	fd = socket(AF_INET, SOCK_DGRAM, 0);
+	fd = socket(AF_LOCAL, SOCK_DGRAM, 0);
 	if (fd < 0)
 		return -errno;