bpf, xdp: allow to pass flags to dev_change_xdp_fd
Add an IFLA_XDP_FLAGS attribute that can be passed for setting up
XDP along with IFLA_XDP_FD, which eventually allows user space to
implement typical add/replace/delete logic for programs. Right now,
calling into dev_change_xdp_fd() will always replace previous programs.
When passed XDP_FLAGS_UPDATE_IF_NOEXIST, we can handle this more
graceful when requested by returning -EBUSY in case we try to
attach a new program, but we find that another one is already
attached. This will be used by upcoming front-end for iproute2 as
well.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 048b46b..bffb525 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6692,26 +6692,42 @@ EXPORT_SYMBOL(dev_change_proto_down);
* dev_change_xdp_fd - set or clear a bpf program for a device rx path
* @dev: device
* @fd: new program fd or negative value to clear
+ * @flags: xdp-related flags
*
* Set or clear a bpf program for a device
*/
-int dev_change_xdp_fd(struct net_device *dev, int fd)
+int dev_change_xdp_fd(struct net_device *dev, int fd, u32 flags)
{
const struct net_device_ops *ops = dev->netdev_ops;
struct bpf_prog *prog = NULL;
- struct netdev_xdp xdp = {};
+ struct netdev_xdp xdp;
int err;
+ ASSERT_RTNL();
+
if (!ops->ndo_xdp)
return -EOPNOTSUPP;
if (fd >= 0) {
+ if (flags & XDP_FLAGS_UPDATE_IF_NOEXIST) {
+ memset(&xdp, 0, sizeof(xdp));
+ xdp.command = XDP_QUERY_PROG;
+
+ err = ops->ndo_xdp(dev, &xdp);
+ if (err < 0)
+ return err;
+ if (xdp.prog_attached)
+ return -EBUSY;
+ }
+
prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_XDP);
if (IS_ERR(prog))
return PTR_ERR(prog);
}
+ memset(&xdp, 0, sizeof(xdp));
xdp.command = XDP_SETUP_PROG;
xdp.prog = prog;
+
err = ops->ndo_xdp(dev, &xdp);
if (err < 0 && prog)
bpf_prog_put(prog);