On 3/19/20 6:13 AM, Toke Høiland-Jørgensen wrote:
From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
While it is currently possible for userspace to specify that an existing
XDP program should not be replaced when attaching to an interface, there is
no mechanism to safely replace a specific XDP program with another.
This patch adds a new netlink attribute, IFLA_XDP_EXPECTED_FD, which can be
set along with IFLA_XDP_FD. If set, the kernel will check that the program
currently loaded on the interface matches the expected one, and fail the
operation if it does not. This corresponds to a 'cmpxchg' memory operation.
The patch set itself looks good to me. But previously there is a
discussion regarding a potential similar functionality through bpf_link.
I guess maintainers (Alexei and Daniel) need to weigh in as some
future vision is involved.
A new companion flag, XDP_FLAGS_EXPECT_FD, is also added to explicitly
request checking of the EXPECTED_FD attribute. This is needed for userspace
to discover whether the kernel supports the new attribute.
Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
---
include/linux/netdevice.h | 2 +-
include/uapi/linux/if_link.h | 4 +++-
net/core/dev.c | 25 ++++++++++++++++++++-----
net/core/rtnetlink.c | 11 +++++++++++
4 files changed, 35 insertions(+), 7 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index b6fedd54cd8e..40b12bd93913 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3767,7 +3767,7 @@ struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
typedef int (*bpf_op_t)(struct net_device *dev, struct netdev_bpf *bpf);
int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
- int fd, u32 flags);
+ int fd, int expected_fd, u32 flags);
u32 __dev_xdp_query(struct net_device *dev, bpf_op_t xdp_op,
enum bpf_netdev_command cmd);
int xdp_umem_query(struct net_device *dev, u16 queue_id);
[...]
