Add HTTP proxy support to netstack TCP connections

- Import dialers package for proxy support
- Try direct connection first, then fall back to HTTP proxy if configured
- Maintain existing TCP keepalive settings for proxied connections
- Add FARCASTER_FORCE_TCP environment variable to docker-compose

Author: poupas

compose/docker-compose.yml

@@ -9,10 +9,10 @@ services:
     #
     #   FARCASTER_AGENT_TOKEN
     #   The Agent's token is obtained when creating a Scanning Agent in the Probely app.
-    #   Learn more at https://help.probely.com/en/articles/6503388-how-to-install-a-scanning-agent  
+    #   Learn more at https://help.probely.com/en/articles/6503388-how-to-install-a-scanning-agent
     #
-    #   FARCASTER_API_URL 
-    #   Probely's API URL 
+    #   FARCASTER_API_URL
+    #   Probely's API URL
     #
     #   HTTP_PROXY (optional)
     #   An advanced option that can be used to configure an HTTP proxy for the Agent to connect to Probely.
@@ -21,6 +21,7 @@ services:
     - FARCASTER_AGENT_TOKEN
     - FARCASTER_API_URL
     - HTTP_PROXY
+    - FARCASTER_FORCE_TCP
     tmpfs:
     - /run
     cap_add:

farcaster-go/wireguard/netstack/tcp.go

@@ -12,6 +12,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip/adapters/gonet"
 	"gvisor.dev/gvisor/pkg/tcpip/transport/tcp"
 	"gvisor.dev/gvisor/pkg/waiter"
+	"probely.com/farcaster/dialers"
 )
 
 // Forwarder request wrapper to abstract away the details of setting up
@@ -113,20 +114,32 @@ func (r *netstackTCPFwd) ConnectUpstream(timeout time.Duration, count int) (*net
 	// TODO: Add IPv6 support.
 	serverIP := parseIPv4(cr.LocalAddress)
 	serverAddrPort := netip.AddrPortFrom(serverIP, cr.LocalPort)
+	serverAddr := serverAddrPort.String()
 
-	// Dial the upstream server.
+	// Try direct connection first
 	var dialer net.Dialer
-	server, err := dialer.DialContext(*r.ctx, "tcp", serverAddrPort.String())
+	dialer.Timeout = timeout
+	server, err := dialer.DialContext(*r.ctx, "tcp", serverAddr)
+
+	// If direct connection fails, try HTTP proxy if configured
+	if err != nil {
+		if proxyURL := dialers.ParseHTTPProxy(); proxyURL != nil {
+			proxyDialer := dialers.NewHTTPProxyDialer(proxyURL, serverAddr, timeout)
+			server, err = proxyDialer.Connect()
+		}
+	}
+
 	if err != nil {
-		// Reject the connection if dialing fails.
+		// Reject the connection if all attempts fail
 		r.fr.Complete(true)
 		return nil, err
 	}
 
 	// Set TCP keepalive options for the upstream connection.
-	setTCPConnTimeouts(server.(*net.TCPConn), keepaliveInterval, keepaliveCount)
+	tcpConn := server.(*net.TCPConn)
+	setTCPConnTimeouts(tcpConn, keepaliveInterval, keepaliveCount)
 
-	r.upstream = server.(*net.TCPConn)
+	r.upstream = tcpConn
 	return r.upstream, nil
 }