func pickLocalAddr(laddrs []ma.Multiaddr, raddr ma.Multiaddr) (laddr ma.Multiaddr) {
if len(laddrs) < 1 {
return nil
}
// make sure that we ONLY use local addrs that match the remote addr.
laddrs = manet.AddrMatch(raddr, laddrs)
if len(laddrs) < 1 {
return nil
}
// make sure that we ONLY use local addrs that CAN dial the remote addr.
// filter out all the local addrs that aren't capable
raddrIPLayer := ma.Split(raddr)[0]
raddrIsLoopback := manet.IsIPLoopback(raddrIPLayer)
raddrIsLinkLocal := manet.IsIP6LinkLocal(raddrIPLayer)
laddrs = addrutil.FilterAddrs(laddrs, func(a ma.Multiaddr) bool {
laddrIPLayer := ma.Split(a)[0]
laddrIsLoopback := manet.IsIPLoopback(laddrIPLayer)
laddrIsLinkLocal := manet.IsIP6LinkLocal(laddrIPLayer)
if laddrIsLoopback { // our loopback addrs can only dial loopbacks.
return raddrIsLoopback
}
if laddrIsLinkLocal {
return raddrIsLinkLocal // out linklocal addrs can only dial link locals.
}
return true
})
// TODO pick with a good heuristic
// we use a random one for now to prevent bad addresses from making nodes unreachable
// with a random selection, multiple tries may work.
return laddrs[rand.Intn(len(laddrs))]
}
// AddrIsShareableOnWAN returns whether the given address should be shareable on the
// wide area network (wide internet).
func AddrIsShareableOnWAN(addr ma.Multiaddr) bool {
s := ma.Split(addr)
if len(s) < 1 {
return false
}
a := s[0]
if manet.IsIPLoopback(a) || manet.IsIP6LinkLocal(a) || manet.IsIPUnspecified(a) {
return false
}
return manet.IsThinWaist(a)
}