Enum IpFamilyPreference 

pub enum IpFamilyPreference {
    Ipv4,
    Ipv6,
    System,
}

Which address family a target name is tried on first, selected by [limits].ip_family_preference.

The default is IPv4, which is deliberately not what the C library hands back. getaddrinfo — glibc and musl alike — orders its answers by RFC 6724, and that ordering puts a global IPv6 address ahead of every IPv4 one whenever the host has a usable IPv6 route. On a host that is only a client of the internet that is the right answer. On a proxy it is an operator policy wearing a resolver’s clothes: a host whose IPv6 egress is tunnelled, or otherwise weaker than its native IPv4 — a common shape on a VPS — would send every dual-stack target down the weaker path first. A TCP tunnel pays for that with the whole IPv6 attempt before IPv4 is even tried, because crate::tunnel::tcp walks the address list in order; a CONNECT-UDP session pays for it outright, because its socket is connected to the first address that has a route and there is no failover behind that choice.

System is the escape hatch back to RFC 6724 ordering, which on glibc an operator can shape further through gai.conf. The knob and its default have precedent: shadowsocks-rust carries the same choice as ipv6_first, likewise off by default.

Variants

Ipv4

Try IPv4 addresses before IPv6 ones. The default.

Ipv6

Try IPv6 addresses before IPv4 ones.

System

Keep the resolver’s own order, which on libc means RFC 6724.

Trait Implementations

impl Clone for IpFamilyPreference

fn clone(&self) -> IpFamilyPreference

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for IpFamilyPreference

impl Debug for IpFamilyPreference

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for IpFamilyPreference

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for IpFamilyPreference

impl PartialEq for IpFamilyPreference

fn eq(&self, other: &IpFamilyPreference) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for IpFamilyPreference