124 lines
2.9 KiB
Go
124 lines
2.9 KiB
Go
package dhcpd
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import (
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"fmt"
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"net"
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"time"
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"github.com/AdguardTeam/golibs/log"
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)
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// ipVersion is a documentational alias for int. Use it when the integer means
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// IP version.
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type ipVersion = int
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// IP version constants.
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const (
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ipVersion4 ipVersion = 4
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ipVersion6 ipVersion = 6
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)
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// netIface is the interface for network interface methods.
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type netIface interface {
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Addrs() ([]net.Addr, error)
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}
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// ifaceIPAddrs returns the interface's IP addresses.
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func ifaceIPAddrs(iface netIface, ipv ipVersion) (ips []net.IP, err error) {
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addrs, err := iface.Addrs()
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if err != nil {
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return nil, err
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}
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for _, a := range addrs {
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var ip net.IP
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switch a := a.(type) {
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case *net.IPAddr:
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ip = a.IP
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case *net.IPNet:
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ip = a.IP
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default:
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continue
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}
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// Assume that net.(*Interface).Addrs can only return valid IPv4
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// and IPv6 addresses. Thus, if it isn't an IPv4 address, it
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// must be an IPv6 one.
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switch ipv {
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case ipVersion4:
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if ip4 := ip.To4(); ip4 != nil {
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ips = append(ips, ip4)
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}
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case ipVersion6:
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if ip6 := ip.To4(); ip6 == nil {
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ips = append(ips, ip)
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}
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default:
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return nil, fmt.Errorf("invalid ip version %d", ipv)
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}
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}
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return ips, nil
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}
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// Currently used defaults for ifaceDNSAddrs.
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const (
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defaultMaxAttempts int = 10
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defaultBackoff time.Duration = 500 * time.Millisecond
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)
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// ifaceDNSIPAddrs returns IP addresses of the interface suitable to send to
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// clients as DNS addresses. If err is nil, addrs contains either no addresses
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// or at least two.
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//
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// It makes up to maxAttempts attempts to get the addresses if there are none,
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// each time using the provided backoff. Sometimes an interface needs a few
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// seconds to really ititialize.
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//
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// See https://github.com/AdguardTeam/AdGuardHome/issues/2304.
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func ifaceDNSIPAddrs(
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iface netIface,
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ipv ipVersion,
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maxAttempts int,
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backoff time.Duration,
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) (addrs []net.IP, err error) {
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var n int
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waitForIP:
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for n = 1; n <= maxAttempts; n++ {
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addrs, err = ifaceIPAddrs(iface, ipv)
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if err != nil {
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return nil, fmt.Errorf("getting ip addrs: %w", err)
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}
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switch len(addrs) {
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case 0:
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log.Debug("dhcpv%d: attempt %d: no ip addresses", ipv, n)
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time.Sleep(backoff)
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case 1:
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// Some Android devices use 8.8.8.8 if there is not
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// a secondary DNS server. Fix that by setting the
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// secondary DNS address to the same address.
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//
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// See https://github.com/AdguardTeam/AdGuardHome/issues/1708.
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log.Debug("dhcpv%d: setting secondary dns ip to itself", ipv)
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addrs = append(addrs, addrs[0])
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fallthrough
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default:
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break waitForIP
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}
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}
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if len(addrs) == 0 {
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// Don't return errors in case the users want to try and enable
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// the DHCP server later.
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log.Error("dhcpv%d: no ip address for interface after %d attempts and %s", ipv, n, time.Duration(n)*backoff)
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} else {
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log.Debug("dhcpv%d: got addresses %s after %d attempts", ipv, addrs, n)
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}
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return addrs, nil
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}
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