You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: interface_plan9.go
    path of file: ./repos/gccrs/libgo/go/net
    
    the code of the file until where you have to start completion: // Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package net

import (
	"errors"
	"internal/itoa"
	"os"
)

// If the ifindex is zero, interfaceTable returns mappings of all
// network interfaces. Otherwise it returns a mapping of a specific
// interface.
func interfaceTable(ifindex int) ([]Interface, error) {
	if ifindex == 0 {
		n, err := interfaceCount()
		if err != nil {
			return nil, err
		}
		ifcs := make([]Interface, n)
		for i := range ifcs {
			ifc, err := readInterface(i)
			if err != nil {
				return nil, err
		
    
func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
	var ifcs []Interface
	if ifi == nil {
		var err error
		ifcs, err = interfaceTable(0)
		if err != nil {
			return nil, err
		}
	} else {
		ifcs = []Interface{*ifi}
	}

	var addrs []Addr
	for _, ifc := range ifcs {
		status := ifc.Name + "/status"
		statusf, err := open(status)
		if err != nil {
			return nil, err
		}
		defer statusf.close()

		// Read but ignore first line as it only contains the table header.
		// See https://9p.io/magic/man2html/3/ip
		if _, ok := statusf.readLine(); !ok {
			return nil, errors.New("cannot read header line for interface: " + status)
		}

		for line, ok := statusf.readLine(); ok; line, ok = statusf.readLine() {
			fields := getFields(line)
			if len(fields) < 1 {
				return nil, errors.New("cannot parse IP address for interface: " + status)
			}
			addr := fields[0]
			ip := ParseIP(addr)
			if ip == nil {
				return nil, errors.New("cannot parse IP address for interface: " + status)
			}

			// The mask is represented as CIDR relative to the IPv6 address.
			// Plan 9 internal representation is always IPv6.
			maskfld := fields[1]
			maskfld = maskfld[1:]
			pfxlen, _, ok := dtoi(maskfld)
			if !ok {
				return nil, errors.New("cannot parse network mask for interface: " + status)
			}
			var mask IPMask
			if ip.To4() != nil { // IPv4 or IPv6 IPv4-mapped address
				mask = CIDRMask(pfxlen-8*len(v4InV6Prefix), 8*IPv4len)
			}
			if ip.To16() != nil && ip.To4() == nil { // IPv6 address
				mask = CIDRMask(pfxlen, 8*IPv6len)
			}

			addrs = append(addrs, &IPNet{IP: ip, Mask: mask})
		}
	}

	return addrs, nil
}