github.com/cilium/ebpf@v0.15.1-0.20240517100537-8079b37aa138/link/netkit.go (about)

     1  package link
     2  
     3  import (
     4  	"fmt"
     5  	"runtime"
     6  
     7  	"github.com/cilium/ebpf"
     8  	"github.com/cilium/ebpf/internal/sys"
     9  )
    10  
    11  type NetkitOptions struct {
    12  	// Index of the interface to attach to.
    13  	Interface int
    14  	// Program to attach.
    15  	Program *ebpf.Program
    16  	// One of the AttachNetkit* constants.
    17  	Attach ebpf.AttachType
    18  	// Attach relative to an anchor. Optional.
    19  	Anchor Anchor
    20  	// Only attach if the expected revision matches.
    21  	ExpectedRevision uint64
    22  	// Flags control the attach behaviour. Specify an Anchor instead of
    23  	// F_LINK, F_ID, F_BEFORE, F_AFTER and R_REPLACE. Optional.
    24  	Flags uint32
    25  }
    26  
    27  func AttachNetkit(opts NetkitOptions) (Link, error) {
    28  	if opts.Interface < 0 {
    29  		return nil, fmt.Errorf("interface %d is out of bounds", opts.Interface)
    30  	}
    31  
    32  	if opts.Flags&anchorFlags != 0 {
    33  		return nil, fmt.Errorf("disallowed flags: use Anchor to specify attach target")
    34  	}
    35  
    36  	attr := sys.LinkCreateNetkitAttr{
    37  		ProgFd:           uint32(opts.Program.FD()),
    38  		AttachType:       sys.AttachType(opts.Attach),
    39  		TargetIfindex:    uint32(opts.Interface),
    40  		ExpectedRevision: opts.ExpectedRevision,
    41  		Flags:            opts.Flags,
    42  	}
    43  
    44  	if opts.Anchor != nil {
    45  		fdOrID, flags, err := opts.Anchor.anchor()
    46  		if err != nil {
    47  			return nil, fmt.Errorf("attach netkit link: %w", err)
    48  		}
    49  
    50  		attr.RelativeFdOrId = fdOrID
    51  		attr.Flags |= flags
    52  	}
    53  
    54  	fd, err := sys.LinkCreateNetkit(&attr)
    55  	runtime.KeepAlive(opts.Program)
    56  	runtime.KeepAlive(opts.Anchor)
    57  	if err != nil {
    58  		if haveFeatErr := haveNetkit(); haveFeatErr != nil {
    59  			return nil, haveFeatErr
    60  		}
    61  		return nil, fmt.Errorf("attach netkit link: %w", err)
    62  	}
    63  
    64  	return &netkitLink{RawLink{fd, ""}}, nil
    65  }
    66  
    67  type netkitLink struct {
    68  	RawLink
    69  }
    70  
    71  var _ Link = (*netkitLink)(nil)