iter.go

Documentation: github.com/cilium/ebpf/link

     1  package link
     2  
     3  import (
     4  	"fmt"
     5  	"io"
     6  	"unsafe"
     7  
     8  	"github.com/cilium/ebpf"
     9  	"github.com/cilium/ebpf/internal/sys"
    10  )
    11  
    12  type IterOptions struct {
    13  	// Program must be of type Tracing with attach type
    14  	// AttachTraceIter. The kind of iterator to attach to is
    15  	// determined at load time via the AttachTo field.
    16  	//
    17  	// AttachTo requires the kernel to include BTF of itself,
    18  	// and it to be compiled with a recent pahole (>= 1.16).
    19  	Program *ebpf.Program
    20  
    21  	// Map specifies the target map for bpf_map_elem and sockmap iterators.
    22  	// It may be nil.
    23  	Map *ebpf.Map
    24  }
    25  
    26  // AttachIter attaches a BPF seq_file iterator.
    27  func AttachIter(opts IterOptions) (*Iter, error) {
    28  	if err := haveBPFLink(); err != nil {
    29  		return nil, err
    30  	}
    31  
    32  	progFd := opts.Program.FD()
    33  	if progFd < 0 {
    34  		return nil, fmt.Errorf("invalid program: %s", sys.ErrClosedFd)
    35  	}
    36  
    37  	var info bpfIterLinkInfoMap
    38  	if opts.Map != nil {
    39  		mapFd := opts.Map.FD()
    40  		if mapFd < 0 {
    41  			return nil, fmt.Errorf("invalid map: %w", sys.ErrClosedFd)
    42  		}
    43  		info.map_fd = uint32(mapFd)
    44  	}
    45  
    46  	attr := sys.LinkCreateIterAttr{
    47  		ProgFd:      uint32(progFd),
    48  		AttachType:  sys.AttachType(ebpf.AttachTraceIter),
    49  		IterInfo:    sys.NewPointer(unsafe.Pointer(&info)),
    50  		IterInfoLen: uint32(unsafe.Sizeof(info)),
    51  	}
    52  
    53  	fd, err := sys.LinkCreateIter(&attr)
    54  	if err != nil {
    55  		return nil, fmt.Errorf("can't link iterator: %w", err)
    56  	}
    57  
    58  	return &Iter{RawLink{fd, ""}}, err
    59  }
    60  
    61  // Iter represents an attached bpf_iter.
    62  type Iter struct {
    63  	RawLink
    64  }
    65  
    66  // Open creates a new instance of the iterator.
    67  //
    68  // Reading from the returned reader triggers the BPF program.
    69  func (it *Iter) Open() (io.ReadCloser, error) {
    70  	attr := &sys.IterCreateAttr{
    71  		LinkFd: it.fd.Uint(),
    72  	}
    73  
    74  	fd, err := sys.IterCreate(attr)
    75  	if err != nil {
    76  		return nil, fmt.Errorf("can't create iterator: %w", err)
    77  	}
    78  
    79  	return fd.File("bpf_iter"), nil
    80  }
    81  
    82  // union bpf_iter_link_info.map
    83  type bpfIterLinkInfoMap struct {
    84  	map_fd uint32
    85  }
    86
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