108 lines
2.5 KiB
Go
108 lines
2.5 KiB
Go
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package dnsforward
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import (
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"context"
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"crypto/tls"
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"fmt"
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"net"
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"net/url"
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"strings"
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"sync"
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"github.com/joomcode/errorx"
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)
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type bootstrapper struct {
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address string // in form of "tls://one.one.one.one:853"
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resolver *net.Resolver // resolver to use to resolve hostname, if neccessary
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resolved string // in form "IP:port"
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resolvedConfig *tls.Config
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sync.Mutex
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}
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func toBoot(address, bootstrapAddr string) bootstrapper {
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var resolver *net.Resolver
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if bootstrapAddr != "" {
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resolver = &net.Resolver{
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PreferGo: true,
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Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
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d := net.Dialer{}
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return d.DialContext(ctx, network, bootstrapAddr)
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},
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}
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}
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return bootstrapper{
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address: address,
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resolver: resolver,
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}
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}
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// will get usable IP address from Address field, and caches the result
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func (n *bootstrapper) get() (string, *tls.Config, error) {
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// TODO: RLock() here but atomically upgrade to Lock() if fast path doesn't work
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n.Lock()
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if n.resolved != "" { // fast path
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retval, tlsconfig := n.resolved, n.resolvedConfig
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n.Unlock()
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return retval, tlsconfig, nil
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}
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//
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// slow path
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//
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defer n.Unlock()
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justHostPort := n.address
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if strings.Contains(n.address, "://") {
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url, err := url.Parse(n.address)
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if err != nil {
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return "", nil, errorx.Decorate(err, "Failed to parse %s", n.address)
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}
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justHostPort = url.Host
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}
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// convert host to IP if neccessary, we know that it's scheme://hostname:port/
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// get a host without port
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host, port, err := net.SplitHostPort(justHostPort)
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if err != nil {
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return "", nil, fmt.Errorf("bootstrapper requires port in address %s", n.address)
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}
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// if it's an IP
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ip := net.ParseIP(host)
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if ip != nil {
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n.resolved = justHostPort
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return n.resolved, nil, nil
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}
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//
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// if it's a hostname
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//
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resolver := n.resolver // no need to check for nil resolver -- documented that nil is default resolver
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addrs, err := resolver.LookupIPAddr(context.TODO(), host)
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if err != nil {
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return "", nil, errorx.Decorate(err, "Failed to lookup %s", host)
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}
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for _, addr := range addrs {
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// TODO: support ipv6, support multiple ipv4
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if addr.IP.To4() == nil {
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continue
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}
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ip = addr.IP
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break
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}
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if ip == nil {
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// couldn't find any suitable IP address
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return "", nil, fmt.Errorf("Couldn't find any suitable IP address for host %s", host)
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}
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n.resolved = net.JoinHostPort(ip.String(), port)
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n.resolvedConfig = &tls.Config{ServerName: host}
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return n.resolved, n.resolvedConfig, nil
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}
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