refactor(netcore): separate resolver and dialer code (#5)

No functional change, just more clear separation of concerns.

netcore/dialer.go

@@ -54,51 +54,6 @@ func (nx *Network) sequentialDial(
 	return nil, errors.Join(errv...)
 }
 
-// maybeLookupEndpoint resolves the domain name inside an endpoint into
-// a list of TCP/UDP endpoints. If the domain name is already an IP
-// address, we short circuit the lookup.
-func (nx *Network) maybeLookupEndpoint(ctx context.Context, endpoint string) ([]string, error) {
-	domain, port, err := net.SplitHostPort(endpoint)
-	if err != nil {
-		return nil, err
-	}
-
-	addrs, err := nx.maybeLookupHost(ctx, domain)
-	if err != nil {
-		return nil, err
-	}
-
-	var endpoints []string
-	for _, addr := range addrs {
-		endpoints = append(endpoints, net.JoinHostPort(addr, port))
-	}
-	return endpoints, nil
-}
-
-// maybeLookupHost resolves a domain name to IP addresses unless the domain
-// is already an IP address, in which case we short circuit the lookup.
-func (nx *Network) maybeLookupHost(ctx context.Context, domain string) ([]string, error) {
-	// handle the case where domain is already an IP address
-	if net.ParseIP(domain) != nil {
-		return []string{domain}, nil
-	}
-
-	// TODO(bassosimone): we should probably ensure we nonetheless
-	// include the lookup event inside the logs.
-	return nx.doLookupHost(ctx, domain)
-}
-
-func (nx *Network) doLookupHost(ctx context.Context, domain string) ([]string, error) {
-	// if there is a custom LookupHostFunc, use it
-	if nx.LookupHostFunc != nil {
-		return nx.LookupHostFunc(ctx, domain)
-	}
-
-	// otherwise fallback to the system resolver
-	reso := &net.Resolver{}
-	return reso.LookupHost(ctx, domain)
-}
-
 func (nx *Network) dialLog(ctx context.Context, network, address string) (net.Conn, error) {
 	// TODO(bassosimone): emit structured logs
 	return nx.dialNet(ctx, network, address)

netcore/network.go

@@ -1,4 +1,8 @@
+//
 // SPDX-License-Identifier: GPL-3.0-or-later
+//
+// Definition of Network.
+//
 
 package netcore
 

netcore/resolver.go

@@ -0,0 +1,60 @@
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+// Adapted from: https://github.com/ooni/probe-cli/blob/v3.20.1/internal/netxlite/dialer.go
+//
+// Internal code for DNS lookups.
+//
+
+package netcore
+
+import (
+	"context"
+	"net"
+)
+
+// maybeLookupEndpoint resolves the domain name inside an endpoint into
+// a list of TCP/UDP endpoints. If the domain name is already an IP
+// address, we short circuit the lookup.
+func (nx *Network) maybeLookupEndpoint(ctx context.Context, endpoint string) ([]string, error) {
+	domain, port, err := net.SplitHostPort(endpoint)
+	if err != nil {
+		return nil, err
+	}
+
+	addrs, err := nx.maybeLookupHost(ctx, domain)
+	if err != nil {
+		return nil, err
+	}
+
+	var endpoints []string
+	for _, addr := range addrs {
+		endpoints = append(endpoints, net.JoinHostPort(addr, port))
+	}
+	return endpoints, nil
+}
+
+// maybeLookupHost resolves a domain name to IP addresses unless the domain
+// is already an IP address, in which case we short circuit the lookup.
+func (nx *Network) maybeLookupHost(ctx context.Context, domain string) ([]string, error) {
+	// handle the case where domain is already an IP address
+	if net.ParseIP(domain) != nil {
+		return []string{domain}, nil
+	}
+
+	// TODO(bassosimone): we should probably ensure we nonetheless
+	// include the lookup event inside the logs.
+	return nx.doLookupHost(ctx, domain)
+}
+
+// doLookupHost performs the DNS lookup.
+func (nx *Network) doLookupHost(ctx context.Context, domain string) ([]string, error) {
+	// if there is a custom LookupHostFunc, use it
+	if nx.LookupHostFunc != nil {
+		return nx.LookupHostFunc(ctx, domain)
+	}
+
+	// otherwise fallback to the system resolver
+	reso := &net.Resolver{}
+	return reso.LookupHost(ctx, domain)
+}

netcore/tlsconfig.go

@@ -1,4 +1,8 @@
+//
 // SPDX-License-Identifier: GPL-3.0-or-later
+//
+// TLS config code.
+//
 
 package netcore
 

netcore/tlsdialer.go

@@ -1,4 +1,8 @@
+//
 // SPDX-License-Identifier: GPL-3.0-or-later
+//
+// TLS dialing code
+//
 
 package netcore