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guest_ip.go
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guest_ip.go
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package common
import (
"errors"
"fmt"
"io/ioutil"
"log"
"os"
"regexp"
"strings"
"time"
)
// Interface to help find the IP address of a running virtual machine.
type GuestIPFinder interface {
GuestIP() (string, error)
}
// DHCPLeaseGuestLookup looks up the IP address of a guest using DHCP
// lease information from the VMware network devices.
type DHCPLeaseGuestLookup struct {
// Driver that is being used (to find leases path)
Driver Driver
// Device that the guest is connected to.
Device string
// MAC address of the guest.
MACAddress string
}
func (f *DHCPLeaseGuestLookup) GuestIP() (string, error) {
dhcpLeasesPath := f.Driver.DhcpLeasesPath(f.Device)
log.Printf("DHCP leases path: %s", dhcpLeasesPath)
if dhcpLeasesPath == "" {
return "", errors.New("no DHCP leases path found.")
}
fh, err := os.Open(dhcpLeasesPath)
if err != nil {
return "", err
}
defer fh.Close()
dhcpBytes, err := ioutil.ReadAll(fh)
if err != nil {
return "", err
}
var lastIp string
var lastLeaseEnd time.Time
var curIp string
var curLeaseEnd time.Time
ipLineRe := regexp.MustCompile(`^lease (.+?) {$`)
endTimeLineRe := regexp.MustCompile(`^\s*ends \d (.+?);$`)
macLineRe := regexp.MustCompile(`^\s*hardware ethernet (.+?);$`)
for _, line := range strings.Split(string(dhcpBytes), "\n") {
// Need to trim off CR character when running in windows
line = strings.TrimRight(line, "\r")
matches := ipLineRe.FindStringSubmatch(line)
if matches != nil {
lastIp = matches[1]
continue
}
matches = endTimeLineRe.FindStringSubmatch(line)
if matches != nil {
lastLeaseEnd, _ = time.Parse("2006/01/02 15:04:05", matches[1])
continue
}
// If the mac address matches and this lease ends farther in the
// future than the last match we might have, then choose it.
matches = macLineRe.FindStringSubmatch(line)
if matches != nil && strings.EqualFold(matches[1], f.MACAddress) && curLeaseEnd.Before(lastLeaseEnd) {
curIp = lastIp
curLeaseEnd = lastLeaseEnd
}
}
if curIp == "" {
return "", fmt.Errorf("IP not found for MAC %s in DHCP leases at %s", f.MACAddress, dhcpLeasesPath)
}
return curIp, nil
}