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package main
import (
"net"
"time"
)
func monitor4(conf *config, update4 chan<- *net.IPAddr) {
refresh := time.NewTicker(conf.Interval)
var prevAddr4 *net.IPAddr
for range refresh.C {
link, err := net.InterfaceByName(conf.Link4)
if err != nil {
logger.Printf("can't find interface %s: %w", conf.Link4, err)
continue
}
addrs, err := link.Addrs()
if err != nil {
const format = "can't read IPv4 addresses from %s: %w"
logger.Printf(format, conf.Link4, err)
continue
}
var addr4 *net.IPAddr
for _, netAddr := range addrs {
addr := netAddr.(*net.IPAddr)
if addr.IP.To4() != nil && !addr.IP.IsPrivate() {
addr4 = addr
break
}
}
if !addr4.IP.Equal(prevAddr4.IP) {
logger.Println("detected new IPv4 address:", addr4)
update4 <- addr4
prevAddr4 = addr4
}
}
}
func monitor6(conf *config, update6 chan<- *net.IPNet) {
refresh := time.NewTicker(conf.Interval)
var prevPrefix6 *net.IPNet
for range refresh.C {
link, err := net.InterfaceByName(conf.Link6)
if err != nil {
logger.Printf("can't find interface %s: %w", conf.Link6, err)
continue
}
addrs, err := link.Addrs()
if err != nil {
const format = "can't read IPv6 addresses from %s: %w"
logger.Printf(format, conf.Link6, err)
continue
}
var prefix6 *net.IPNet
for _, netAddr := range addrs {
addr := netAddr.(*net.IPAddr)
if addr.IP.To4() == nil && addr.IP.IsGlobalUnicast() {
cidr := net.CIDRMask(conf.PrefixLen, 128)
prefix6 = &net.IPNet{
IP: addr.IP.Mask(cidr),
Mask: cidr,
}
break
}
}
if !prefix6.IP.Equal(prevPrefix6.IP) {
logger.Println("detected new IPv6 prefix:", prefix6)
update6 <- prefix6
prevPrefix6 = prefix6
}
}
}
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