net-predictable/loc.go

package main

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

const (
	PathProcPCI = iota
	PathProcUSB
)

func (i *iface) ProcLoc() (err error) {
	spath := strings.Join([]string{i.netpath, "device"}, "/")

	var real string
	if real, err = filepath.EvalSymlinks(spath); err != nil {
		if errors.Is(err, os.ErrNotExist) {
			err = fmt.Errorf("Interface %s isn't a hardware device", i.names[IfNameKern])
			return
		}
		err = fmt.Errorf("Failed to resolve symlink to device: %w", err)
		return
	}

	var devpath string
	var ok bool

	sysdev := strings.Join([]string{SYSFS, "devices/"}, "/")
	if devpath, ok = strings.CutPrefix(real, sysdev); !ok {
		err = fmt.Errorf("Symlink doesn't point to %s\n", sysdev)
		return
	}

	var (
		pci, usb, tmp string
		procmode      int
	)
	for _, v := range strings.Split(devpath, "/") {
		if strings.HasPrefix(v, "pci") {
			procmode = PathProcPCI
			continue
		} else if strings.HasPrefix(v, "usb") {
			procmode = PathProcUSB
			continue
		}

		switch procmode {
		case PathProcPCI:
			{
				if tmp, err = i.ProcPCI(v); err != nil {
					continue
				}
				pci = tmp
			}
		case PathProcUSB:
			{
				if tmp, err = i.ProcUSB(v); err != nil {
					continue
				}
				usb = tmp
			}
		}
	}
	if pci == "" && usb == "" {
		return
	}
	i.names[IfNameLoc] = strings.Join([]string{i.pfx, pci, usb}, "")

	return
}