Re: [PATCH bpf-next 1/4] xdp: Support specifying expected existing program when attaching XDP
From: Yonghong Song <hidden>
Date: 2020-03-20 02:13:58
Also in:
bpf
On 3/19/20 6:13 AM, Toke Høiland-Jørgensen wrote:
From: Toke Høiland-Jørgensen <redacted> 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.
quoted hunk ↗ jump to hunk
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 <redacted> --- 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);
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