Merge branch 'xdp-offload-mode'

Jakub Kicinski says:

====================
xdp: offload mode

While we discuss the representors.. :)

This set adds XDP flag for forcing offload and a attachment mode
for reporting to user space that program has been offloaded.  The
nfp driver is modified to make use of the new flags, but also to
adhere to the DRV_MODE flag which should disable the HW offload.

The intended driver behaviour is:
            DRV mode   offload
no flags      yes     attempted
DRV_MODE      yes        no
 HW_MODE      no         yes

Where 'yes' means required, and error will be returned if setup fails.
'Attempted' means the offload will only happen automatically if HW is
capable and offloading the program will cause no change in system
behaviour (e.g. maps don't have to bound).

Thanks to loading the program both to the driver and HW by default we
can fallback to the driver mode without disruption in case user replaces
the program with one which cannot be offloaded later.

Note that the NFP driver currently claims XDP offload support but
lacks most basic features like direct packet access.

Only change compared to the RFC is fixing the double bpf_prog_put()
which Daniel has spotted (patch 5).
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 14 insertions, 11 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index df7637733e3c..a91572aa73d5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6934,8 +6934,7 @@ int dev_change_proto_down(struct net_device *dev, bool proto_down)
 }
 EXPORT_SYMBOL(dev_change_proto_down);
 
-bool __dev_xdp_attached(struct net_device *dev, xdp_op_t xdp_op,
-			u32 *prog_id)
+u8 __dev_xdp_attached(struct net_device *dev, xdp_op_t xdp_op, u32 *prog_id)
 {
 	struct netdev_xdp xdp;
 
@@ -6951,14 +6950,18 @@ bool __dev_xdp_attached(struct net_device *dev, xdp_op_t xdp_op,
 }
 
 static int dev_xdp_install(struct net_device *dev, xdp_op_t xdp_op,
-			   struct netlink_ext_ack *extack,
+			   struct netlink_ext_ack *extack, u32 flags,
 			   struct bpf_prog *prog)
 {
 	struct netdev_xdp xdp;
 
 	memset(&xdp, 0, sizeof(xdp));
-	xdp.command = XDP_SETUP_PROG;
+	if (flags & XDP_FLAGS_HW_MODE)
+		xdp.command = XDP_SETUP_PROG_HW;
+	else
+		xdp.command = XDP_SETUP_PROG;
 	xdp.extack = extack;
+	xdp.flags = flags;
 	xdp.prog = prog;
 
 	return xdp_op(dev, &xdp);
@@ -6984,7 +6987,7 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
 	ASSERT_RTNL();
 
 	xdp_op = xdp_chk = ops->ndo_xdp;
-	if (!xdp_op && (flags & XDP_FLAGS_DRV_MODE))
+	if (!xdp_op && (flags & (XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE)))
 		return -EOPNOTSUPP;
 	if (!xdp_op || (flags & XDP_FLAGS_SKB_MODE))
 		xdp_op = generic_xdp_install;
@@ -7003,7 +7006,7 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
 			return PTR_ERR(prog);
 	}
 
-	err = dev_xdp_install(dev, xdp_op, extack, prog);
+	err = dev_xdp_install(dev, xdp_op, extack, flags, prog);
 	if (err < 0 && prog)
 		bpf_prog_put(prog);
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 8da89c1136e5..9a1bd510c812 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -16,6 +16,7 @@
  *	Vitaly E. Lavrov		RTA_OK arithmetics was wrong.
  */
 
+#include <linux/bitops.h>
 #include <linux/errno.h>
 #include <linux/module.h>
 #include <linux/types.h>
@@ -1264,10 +1265,10 @@ static u8 rtnl_xdp_attached_mode(struct net_device *dev, u32 *prog_id)
 		*prog_id = generic_xdp_prog->aux->id;
 		return XDP_ATTACHED_SKB;
 	}
-	if (ops->ndo_xdp && __dev_xdp_attached(dev, ops->ndo_xdp, prog_id))
-		return XDP_ATTACHED_DRV;
+	if (!ops->ndo_xdp)
+		return XDP_ATTACHED_NONE;
 
-	return XDP_ATTACHED_NONE;
+	return __dev_xdp_attached(dev, ops->ndo_xdp, prog_id);
 }
 
 static int rtnl_xdp_fill(struct sk_buff *skb, struct net_device *dev)
@@ -2253,8 +2254,7 @@ static int do_setlink(const struct sk_buff *skb,
 				err = -EINVAL;
 				goto errout;
 			}
-			if ((xdp_flags & XDP_FLAGS_SKB_MODE) &&
-			    (xdp_flags & XDP_FLAGS_DRV_MODE)) {
+			if (hweight32(xdp_flags & XDP_FLAGS_MODES) > 1) {
 				err = -EINVAL;
 				goto errout;
 			}