Struct TcHook

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pub struct TcHook { /* private fields */ }

Expand description

Represents a location where a TC-BPF filter can be attached.

The BPF TC subsystem has different control paths from other BPF programs. As such a BPF program using a TC Hook (SEC("classifier") or SEC("tc")) must be operated more independently from other Programs.

This struct exposes operations to create, attach, query and destroy a bpf_tc_hook using the TC subsystem.

Documentation about the libbpf TC interface can be found here.

An example of using a BPF TC program can found here.

Implementations§

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impl TcHook

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pub fn new(fd: BorrowedFd<'_>) -> Self

Create a new TcHook given the file descriptor of the loaded SEC("tc") Program.

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pub fn create(&mut self) -> Result<Self>

Create a new TcHook as well as the underlying qdiscs

If a TcHook already exists with the same parameters as the hook calling Self::create(), this function will still succeed.

Will always fail on a TC_CUSTOM hook

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pub fn ifindex(&mut self, idx: i32) -> &mut Self

Set the interface to attach to

Interfaces can be listed by using ip link command from the iproute2 software package

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pub fn attach_point(&mut self, ap: TcAttachPoint) -> &mut Self

Set what type of TC point to attach onto

TC_EGRESS, TC_INGRESS, or TC_CUSTOM

An TC_EGRESS|TC_INGRESS hook can be used as an attach point for calling Self::destroy() to remove the clsact bpf tc qdisc, but cannot be used for an Self::attach() operation

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pub fn parent(&mut self, maj: u32, min: u32) -> &mut Self

Set the parent of a hook

Will cause an EINVAL upon Self::attach() if set upon an TC_EGRESS/TC_INGRESS/(TC_EGRESS|TC_INGRESS) hook

Must be set on a TC_CUSTOM hook

Current acceptable values are TC_H_CLSACT for maj, and TC_H_MIN_EGRESS or TC_H_MIN_INGRESS for min

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pub fn replace(&mut self, replace: bool) -> &mut Self

Set whether this hook should replace an existing hook

If replace is not true upon attach, and a hook already exists an EEXIST error will be returned from Self::attach()

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pub fn handle(&mut self, handle: u32) -> &mut Self

Set the handle of a hook. If unset upon attach, the kernel will assign a handle for the hook

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pub fn get_handle(&self) -> u32

Get the handle of a hook. Only has meaning after hook is attached

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pub fn priority(&mut self, priority: u32) -> &mut Self

Set the priority of a hook If unset upon attach, the kernel will assign a priority for the hook

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pub fn get_priority(&self) -> u32

Get the priority of a hook Only has meaning after hook is attached

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pub fn query(&mut self) -> Result<u32>

Query a hook to inspect the program identifier (prog_id)

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pub fn attach(&mut self) -> Result<Self>

Attach a filter to the TcHook so that the program starts processing

Once the hook is processing, changing the values will have no effect unless the hook is Self::attach()’d again (replace=true being required)

Users can create a second hook by changing the handle, the priority or the attach_point and calling the Self::attach() method again. Beware doing this. It might be better to Copy the TcHook and change the values on the copied hook for easier Self::detach()

NOTE: Once a TcHook is attached, it, and the maps it uses, will outlive the userspace application that spawned them Make sure to detach if this is not desired

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