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package ndp
import (
"fmt"
"net"
"net/netip"
)
// An Addr is an IPv6 unicast address.
type Addr string
// Possible Addr types for an IPv6 unicast address.
const (
Unspecified Addr = "unspecified"
LinkLocal Addr = "linklocal"
UniqueLocal Addr = "uniquelocal"
Global Addr = "global"
)
// chooseAddr selects an Addr from the interface based on the specified Addr type.
func chooseAddr(addrs []net.Addr, zone string, addr Addr) (netip.Addr, error) {
// Does the caller want an unspecified address?
if addr == Unspecified {
return netip.IPv6Unspecified().WithZone(zone), nil
}
// Select an IPv6 address from the interface's addresses.
var match func(ip netip.Addr) bool
switch addr {
case LinkLocal:
match = (netip.Addr).IsLinkLocalUnicast
case UniqueLocal:
match = (netip.Addr).IsPrivate
case Global:
match = func(ip netip.Addr) bool {
// Specifically exclude the ULA range.
return ip.IsGlobalUnicast() && !ip.IsPrivate()
}
default:
// Special case: try to match Addr as a literal IPv6 address.
ip, err := netip.ParseAddr(string(addr))
if err != nil {
return netip.Addr{}, fmt.Errorf("ndp: invalid IPv6 address: %q", addr)
}
if err := checkIPv6(ip); err != nil {
return netip.Addr{}, err
}
match = func(check netip.Addr) bool {
return ip == check
}
}
return findAddr(addrs, addr, zone, match)
}
// findAddr searches for a valid IPv6 address in the slice of net.Addr that
// matches the input function. If none is found, the IPv6 unspecified address
// "::" is returned.
func findAddr(addrs []net.Addr, addr Addr, zone string, match func(ip netip.Addr) bool) (netip.Addr, error) {
for _, a := range addrs {
ipn, ok := a.(*net.IPNet)
if !ok {
continue
}
ip, ok := netip.AddrFromSlice(ipn.IP)
if !ok {
panicf("ndp: failed to convert net.IPNet: %v", ipn.IP)
}
if err := checkIPv6(ip); err != nil {
continue
}
// From here on, we can assume that only IPv6 addresses are
// being checked.
if match(ip) {
return ip.WithZone(zone), nil
}
}
// No matching address on this interface.
return netip.Addr{}, fmt.Errorf("ndp: address %q not found on interface %q", addr, zone)
}
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