github.com/cilium/ebpf@v0.10.0/link/query.go (about)

     1  package link
     2  
     3  import (
     4  	"fmt"
     5  	"os"
     6  	"unsafe"
     7  
     8  	"github.com/cilium/ebpf"
     9  	"github.com/cilium/ebpf/internal/sys"
    10  )
    11  
    12  // QueryOptions defines additional parameters when querying for programs.
    13  type QueryOptions struct {
    14  	// Path can be a path to a cgroup, netns or LIRC2 device
    15  	Path string
    16  	// Attach specifies the AttachType of the programs queried for
    17  	Attach ebpf.AttachType
    18  	// QueryFlags are flags for BPF_PROG_QUERY, e.g. BPF_F_QUERY_EFFECTIVE
    19  	QueryFlags uint32
    20  }
    21  
    22  // QueryPrograms retrieves ProgramIDs associated with the AttachType.
    23  //
    24  // It only returns IDs of programs that were attached using PROG_ATTACH and not bpf_link.
    25  // Returns (nil, nil) if there are no programs attached to the queried kernel resource.
    26  // Calling QueryPrograms on a kernel missing PROG_QUERY will result in ErrNotSupported.
    27  func QueryPrograms(opts QueryOptions) ([]ebpf.ProgramID, error) {
    28  	if haveProgQuery() != nil {
    29  		return nil, fmt.Errorf("can't query program IDs: %w", ErrNotSupported)
    30  	}
    31  
    32  	f, err := os.Open(opts.Path)
    33  	if err != nil {
    34  		return nil, fmt.Errorf("can't open file: %s", err)
    35  	}
    36  	defer f.Close()
    37  
    38  	// query the number of programs to allocate correct slice size
    39  	attr := sys.ProgQueryAttr{
    40  		TargetFd:   uint32(f.Fd()),
    41  		AttachType: sys.AttachType(opts.Attach),
    42  		QueryFlags: opts.QueryFlags,
    43  	}
    44  	if err := sys.ProgQuery(&attr); err != nil {
    45  		return nil, fmt.Errorf("can't query program count: %w", err)
    46  	}
    47  
    48  	// return nil if no progs are attached
    49  	if attr.ProgCount == 0 {
    50  		return nil, nil
    51  	}
    52  
    53  	// we have at least one prog, so we query again
    54  	progIds := make([]ebpf.ProgramID, attr.ProgCount)
    55  	attr.ProgIds = sys.NewPointer(unsafe.Pointer(&progIds[0]))
    56  	attr.ProgCount = uint32(len(progIds))
    57  	if err := sys.ProgQuery(&attr); err != nil {
    58  		return nil, fmt.Errorf("can't query program IDs: %w", err)
    59  	}
    60  
    61  	return progIds, nil
    62  
    63  }