fn migrate_to_preferred_address()

in neqo-transport/src/connection/mod.rs [1978:2025]

• 38 lines of code
• 7 McCabe index (conditional complexity)

    fn migrate_to_preferred_address(&mut self, now: Instant) -> Res<()> {
        let spa: Option<(tparams::PreferredAddress, ConnectionIdEntry<[u8; 16]>)> = if matches!(
            self.conn_params.get_preferred_address(),
            PreferredAddressConfig::Disabled
        ) {
            qdebug!("[{self}] Preferred address is disabled");
            None
        } else {
            self.tps.borrow_mut().remote().get_preferred_address()
        };
        if let Some((addr, cid)) = spa {
            // The connection ID isn't special, so just save it.
            self.cids.add_remote(cid)?;

            // The preferred address doesn't dictate what the local address is, so this
            // has to use the existing address.  So only pay attention to a preferred
            // address from the same family as is currently in use. More thought will
            // be needed to work out how to get addresses from a different family.
            let prev = self
                .paths
                .primary()
                .ok_or(Error::NoAvailablePath)?
                .borrow()
                .remote_address();
            let remote = match prev.ip() {
                IpAddr::V4(_) => addr.ipv4().map(SocketAddr::V4),
                IpAddr::V6(_) => addr.ipv6().map(SocketAddr::V6),
            };

            if let Some(remote) = remote {
                // Ignore preferred address that move to loopback from non-loopback.
                // `migrate` doesn't enforce this rule.
                if !prev.ip().is_loopback() && remote.ip().is_loopback() {
                    qwarn!("[{self}] Ignoring a move to a loopback address: {remote}");
                    return Ok(());
                }

                if self.migrate(None, Some(remote), false, now).is_err() {
                    qwarn!("[{self}] Ignoring bad preferred address: {remote}");
                }
            } else {
                qwarn!("[{self}] Unable to migrate to a different address family");
            }
        } else {
            qdebug!("[{self}] No preferred address to migrate to");
        }
        Ok(())
    }