From 711eafef717c54520b4f5bb360191c27d29a7b3e Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Fri, 17 May 2024 13:11:35 +0800
Subject: [PATCH] add support for connected UDP sockets

---
 wasip1/listen_wasip1.go | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/wasip1/listen_wasip1.go b/wasip1/listen_wasip1.go
index 38ff140..5e5940b 100644
--- a/wasip1/listen_wasip1.go
+++ b/wasip1/listen_wasip1.go
@@ -44,13 +44,37 @@ func ListenPacket(network, address string) (net.PacketConn, error) {
 		addr := &netAddr{network, address}
 		return nil, listenErr(addr, err)
 	}
-	conn, err := listenPacketAddr(addrs[0])
+	conn, err := listenPacketAddr(addrs[0], nil)
 	if err != nil {
 		return nil, listenErr(addrs[0], err)
 	}
 	return conn, nil
 }
 
+// DialUDP connects to the remote UDP network address from the local UDP network address.
+func DialUDP(network, localAddr, remoteAddr string) (net.PacketConn, error) {
+	switch network {
+	case "udp", "udp4", "udp6":
+	default:
+		return nil, unsupportedNetwork(network, localAddr)
+	}
+	laddrs, err := lookupAddr(context.Background(), "listen", network, localAddr)
+	if err != nil {
+		addr := &netAddr{network, localAddr}
+		return nil, listenErr(addr, err)
+	}
+	raddrs, err := lookupAddr(context.Background(), "dial", network, remoteAddr)
+	if err != nil {
+		addr := &netAddr{network, localAddr}
+		return nil, dialErr(addr, err)
+	}
+	conn, err := listenPacketAddr(laddrs[0], raddrs[0])
+	if err != nil {
+		return nil, listenErr(laddrs[0], err)
+	}
+	return conn, nil
+}
+
 func unsupportedNetwork(network, address string) error {
 	return fmt.Errorf("unsupported network: %s://%s", network, address)
 }
@@ -105,7 +129,8 @@ func listenAddr(addr net.Addr) (net.Listener, error) {
 	return makeListener(l, name), nil
 }
 
-func listenPacketAddr(addr net.Addr) (net.PacketConn, error) {
+// If remoteAddr is set, the socket will be connected to that address.
+func listenPacketAddr(addr net.Addr, remoteAddr net.Addr) (net.PacketConn, error) {
 	fd, err := socket(family(addr), SOCK_DGRAM, 0)
 	if err != nil {
 		return nil, os.NewSyscallError("socket", err)
@@ -131,6 +156,16 @@ func listenPacketAddr(addr net.Addr) (net.PacketConn, error) {
 		return nil, os.NewSyscallError("bind", err)
 	}
 
+	if remoteAddr != nil {
+		remoteSockAddr, err := socketAddress(remoteAddr)
+		if err != nil {
+			return nil, os.NewSyscallError("connect", err)
+		}
+		if err := connect(fd, remoteSockAddr); err != nil {
+			return nil, os.NewSyscallError("connect", err)
+		}
+	}
+
 	name, err := getsockname(fd)
 	if err != nil {
 		return nil, os.NewSyscallError("getsockname", err)