Add support for bootstrapping upstream DNS servers by hostname.

dnsforward/upstream_pool.go

@@ -2,9 +2,7 @@ package dnsforward
 
 import (
 	"crypto/tls"
-	"fmt"
 	"net"
-	"net/url"
 	"sync"
 
 	"github.com/joomcode/errorx"
@@ -27,51 +25,29 @@ import (
 //  log.Println(r)
 //  pool.Put(c.Conn)
 type TLSPool struct {
-	Address            string
-	parsedAddress      *url.URL
-	parsedAddressMutex sync.RWMutex
+	boot *bootstrapper
 
+	// connections
 	conns      []net.Conn
-	sync.Mutex // protects conns
-}
-
-func (n *TLSPool) getHost() (string, error) {
-	n.parsedAddressMutex.RLock()
-	if n.parsedAddress != nil {
-		n.parsedAddressMutex.RUnlock()
-		return n.parsedAddress.Host, nil
-	}
-	n.parsedAddressMutex.RUnlock()
-
-	n.parsedAddressMutex.Lock()
-	defer n.parsedAddressMutex.Unlock()
-	url, err := url.Parse(n.Address)
-	if err != nil {
-		return "", errorx.Decorate(err, "Failed to parse %s", n.Address)
-	}
-	if url.Scheme != "tls" {
-		return "", fmt.Errorf("TLSPool only supports TLS")
-	}
-	n.parsedAddress = url
-	return n.parsedAddress.Host, nil
+	connsMutex sync.Mutex // protects conns
 }
 
 func (n *TLSPool) Get() (net.Conn, error) {
-	host, err := n.getHost()
+	address, tlsConfig, err := n.boot.get()
 	if err != nil {
 		return nil, err
 	}
 
 	// get the connection from the slice inside the lock
 	var c net.Conn
-	n.Lock()
+	n.connsMutex.Lock()
 	num := len(n.conns)
 	if num > 0 {
 		last := num - 1
 		c = n.conns[last]
 		n.conns = n.conns[:last]
 	}
-	n.Unlock()
+	n.connsMutex.Unlock()
 
 	// if we got connection from the slice, return it
 	if c != nil {
@@ -80,10 +56,10 @@ func (n *TLSPool) Get() (net.Conn, error) {
 	}
 
 	// we'll need a new connection, dial now
-	// log.Printf("Dialing to %s", host)
-	conn, err := tls.Dial("tcp", host, nil)
+	// log.Printf("Dialing to %s", address)
+	conn, err := tls.Dial("tcp", address, tlsConfig)
 	if err != nil {
-		return nil, errorx.Decorate(err, "Failed to connect to %s", host)
+		return nil, errorx.Decorate(err, "Failed to connect to %s", address)
 	}
 	return conn, nil
 }
@@ -92,7 +68,7 @@ func (n *TLSPool) Put(c net.Conn) {
 	if c == nil {
 		return
 	}
-	n.Lock()
+	n.connsMutex.Lock()
 	n.conns = append(n.conns, c)
-	n.Unlock()
+	n.connsMutex.Unlock()
 }