package link
import (
"fmt"
"os"
"unsafe"
"github.com/cilium/ebpf"
"github.com/cilium/ebpf/internal/sys"
)
// QueryOptions defines additional parameters when querying for programs.
type QueryOptions struct {
// Path can be a path to a cgroup, netns or LIRC2 device
Path string
// Attach specifies the AttachType of the programs queried for
Attach ebpf.AttachType
// QueryFlags are flags for BPF_PROG_QUERY, e.g. BPF_F_QUERY_EFFECTIVE
QueryFlags uint32
}
// QueryPrograms retrieves ProgramIDs associated with the AttachType.
//
// Returns (nil, nil) if there are no programs attached to the queried kernel
// resource. Calling QueryPrograms on a kernel missing PROG_QUERY will result in
// ErrNotSupported.
func QueryPrograms(opts QueryOptions) ([]ebpf.ProgramID, error) {
if haveProgQuery() != nil {
return nil, fmt.Errorf("can't query program IDs: %w", ErrNotSupported)
}
f, err := os.Open(opts.Path)
if err != nil {
return nil, fmt.Errorf("can't open file: %s", err)
}
defer f.Close()
// query the number of programs to allocate correct slice size
attr := sys.ProgQueryAttr{
TargetFd: uint32(f.Fd()),
AttachType: sys.AttachType(opts.Attach),
QueryFlags: opts.QueryFlags,
}
if err := sys.ProgQuery(&attr); err != nil {
return nil, fmt.Errorf("can't query program count: %w", err)
}
// return nil if no progs are attached
if attr.ProgCount == 0 {
return nil, nil
}
// we have at least one prog, so we query again
progIds := make([]ebpf.ProgramID, attr.ProgCount)
attr.ProgIds = sys.NewPointer(unsafe.Pointer(&progIds[0]))
attr.ProgCount = uint32(len(progIds))
if err := sys.ProgQuery(&attr); err != nil {
return nil, fmt.Errorf("can't query program IDs: %w", err)
}
return progIds, nil
}