aghnet: setsockopt

internal/aghnet/dhcp_unix.go

@@ -112,12 +112,12 @@ func discover4(iface *net.Interface, dstAddr *net.UDPAddr, hostname string) (ok
 	// It's also known that listening on the specified interface's address
 	// ignores broadcasted packets when reading.
 	var c net.PacketConn
-	if c, err = net.ListenPacket("udp4", ":68"); err != nil {
+	if c, err = ListenPacketReusable("udp4", ":68"); err != nil {
 		return false, fmt.Errorf("couldn't listen on :68: %w", err)
 	}
 	defer func() { err = errors.WithDeferred(err, c.Close()) }()
 
-	// Send to resolved broadcast.
+	// Send to broadcast.
 	if _, err = c.WriteTo(req.ToBytes(), dstAddr); err != nil {
 		return false, fmt.Errorf("couldn't send a packet to %s: %w", dstAddr, err)
 	}
@@ -154,9 +154,6 @@ func tryConn4(req *dhcpv4.DHCPv4, c net.PacketConn, iface *net.Interface) (ok, n
 
 	b := make([]byte, 1500)
 	n, _, err := c.ReadFrom(b)
-	if n > 0 {
-		log.Debug("received %d bytes: %v", n, b)
-	}
 	if err != nil {
 		if isTimeout(err) {
 			log.Debug("dhcpv4: didn't receive dhcp response")

internal/aghnet/interfaces.go

@@ -116,3 +116,9 @@ func IfaceDNSIPAddrs(
 
 	return addrs, nil
 }
+
+// ListenPacketReusable announces on the local network address additionally
+// configuring the socket to have a reusable binding.
+func ListenPacketReusable(network, address string) (c net.PacketConn, err error) {
+	return listenPacketReusable(network, address)
+}

internal/aghnet/interfaces_linux.go

@@ -0,0 +1,30 @@
+//go:build linux
+// +build linux
+
+package aghnet
+
+import (
+	"context"
+	"net"
+	"syscall"
+)
+
+// reuseAddrControl is the function to be set to net.ListenConfig.Control.  It
+// configures the socket to have a reusable port binding.
+func reuseAddrControl(network, address string, c syscall.RawConn) (err error) {
+	cerr := c.Control(func(fd uintptr) {
+		err = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
+	})
+	if cerr != nil {
+		return cerr
+	}
+
+	return err
+}
+
+func listenPacketReusable(network, address string) (c net.PacketConn, err error) {
+	var lc net.ListenConfig
+	lc.Control = reuseAddrControl
+
+	return lc.ListenPacket(context.Background(), network, address)
+}

internal/aghnet/interfaces_unix.go

@@ -0,0 +1,34 @@
+//go:build aix || darwin || dragonfly || freebsd || netbsd || openbsd || solaris
+// +build aix darwin dragonfly freebsd netbsd openbsd solaris
+
+package aghnet
+
+import (
+	"context"
+	"net"
+	"os"
+	"syscall"
+)
+
+// reuseAddrCtrl is the function to be set to net.ListenConfig.Control.  It
+// configures the socket to have a reusable port binding.
+func reuseAddrCtrl(network, address string, c syscall.RawConn) (err error) {
+	cerr := c.Control(func(fd uintptr) {
+		err = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_REUSEPORT, 1)
+		if err != nil {
+			err = os.NewSyscallError("setsockopt", err)
+		}
+	})
+	if cerr != nil {
+		return cerr
+	}
+
+	return err
+}
+
+func listenPacketReusable(network, address string) (c net.PacketConn, err error) {
+	var lc net.ListenConfig
+	lc.Control = reuseAddrCtrl
+
+	return lc.ListenPacket(context.Background(), network, address)
+}

internal/aghnet/interfaces_windows.go

@@ -0,0 +1,14 @@
+//go:build windows
+// +build windows
+
+package aghnet
+
+import (
+	"net"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+)
+
+func listenPacketReusable(network, address string) (c net.PacketConn, err error) {
+	return nil, aghos.Unsupported("listening packet reusable")
+}