BGP: Fix IPv4 listen addr configuration and generalize addr conversion (

#451)

This removes some duplicate code and introduces a new helper function

    netTCPAddrToSockAddr(*net.TCPAddrr) unix.Sockaddr

  to do the conversaion on one place, including regression tests.

  Closes #450

Signed-off-by: Maximilian Wilhelm <[email protected]>

net/tcp/listen.go

@@ -76,17 +76,7 @@ func (lf *ListenerFactory) NewListener(v *vrf.VRF, laddr *net.TCPAddr, ttl uint8
 		}
 	}
 
-	if laddr.IP.To4() != nil {
-		err = unix.Bind(fd, &unix.SockaddrInet4{
-			Port: laddr.Port,
-			Addr: ipv4AddrToArray(laddr.IP),
-		})
-	} else {
-		err = unix.Bind(fd, &unix.SockaddrInet6{
-			Port: laddr.Port,
-			Addr: ipv6AddrToArray(laddr.IP),
-		})
-	}
+	err = unix.Bind(fd, netTCPAddrToSockAddr(laddr))
 	if err != nil {
 		unix.Close(fd)
 		return nil, fmt.Errorf("bind failed: %w", err)

net/tcp/tcpsock_posix.go

@@ -47,22 +47,7 @@ func dialTCP(afi uint16, laddr, raddr *net.TCPAddr, ttl uint8, md5secret string,
 	}
 
 	if laddr != nil && laddr.IP != nil {
-		var bindSA unix.Sockaddr
-		if laddr.IP.To4() != nil {
-			la := ipv4AddrToArray(laddr.IP)
-			bindSA = &unix.SockaddrInet4{
-				Port: laddr.Port,
-				Addr: la,
-			}
-		} else {
-			la := ipv6AddrToArray(laddr.IP)
-			bindSA = &unix.SockaddrInet6{
-				Port: laddr.Port,
-				Addr: la,
-			}
-		}
-
-		err := unix.Bind(fd, bindSA)
+		err := unix.Bind(fd, netTCPAddrToSockAddr(laddr))
 		if err != nil {
 			return nil, fmt.Errorf("bind() failed: %w", err)
 		}
@@ -78,20 +63,7 @@ func dialTCP(afi uint16, laddr, raddr *net.TCPAddr, ttl uint8, md5secret string,
 		}
 	}
 
-	var connectSA unix.Sockaddr
-	if raddr.IP.To4() != nil {
-		connectSA = &unix.SockaddrInet4{
-			Port: raddr.Port,
-			Addr: ipv4AddrToArray(raddr.IP),
-		}
-	} else {
-		connectSA = &unix.SockaddrInet6{
-			Port: raddr.Port,
-			Addr: ipv6AddrToArray(raddr.IP),
-		}
-	}
-
-	err = unix.Connect(fd, connectSA)
+	err = unix.Connect(fd, netTCPAddrToSockAddr(raddr))
 	if err != nil {
 		return nil, fmt.Errorf("connect() failed: %w", err)
 	}
@@ -103,15 +75,23 @@ func dialTCP(afi uint16, laddr, raddr *net.TCPAddr, ttl uint8, md5secret string,
 	}, nil
 }
 
-func ipv6AddrToArray(x net.IP) [16]byte {
-	return [16]byte{
-		x[0], x[1], x[2], x[3], x[4], x[5], x[6], x[7],
-		x[8], x[9], x[10], x[11], x[12], x[13], x[14], x[15],
+func netTCPAddrToSockAddr(tcpAddr *net.TCPAddr) unix.Sockaddr {
+	ip := tcpAddr.IP
+	ip4 := ip.To4()
+	if ip4 != nil {
+		return &unix.SockaddrInet4{
+			Port: tcpAddr.Port,
+			Addr: [4]byte{
+				ip4[0], ip4[1], ip4[2], ip4[3],
+			},
+		}
 	}
-}
 
-func ipv4AddrToArray(x net.IP) [4]byte {
-	return [4]byte{
-		x[0], x[1], x[2], x[3],
+	return &unix.SockaddrInet6{
+		Port: tcpAddr.Port,
+		Addr: [16]byte{
+			ip[0], ip[1], ip[2], ip[3], ip[4], ip[5], ip[6], ip[7],
+			ip[8], ip[9], ip[10], ip[11], ip[12], ip[13], ip[14], ip[15],
+		},
 	}
 }

net/tcp/tcpsock_posix_test.go

@@ -0,0 +1,50 @@
+package tcp
+
+import (
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/sys/unix"
+)
+
+func TestNetTCPAddrToSockAddr(t *testing.T) {
+	tests := []struct {
+		name     string
+		addr     string
+		expected unix.Sockaddr
+	}{
+		{
+			name: "IPv4 / 0.0.0.0",
+			addr: "0.0.0.0:179",
+			expected: &unix.SockaddrInet4{
+				Port: 179,
+				Addr: [4]byte{0, 0, 0, 0},
+			},
+		},
+		{
+			name: "IPv4 / 192.0.2.42",
+			addr: "192.0.2.42:179",
+			expected: &unix.SockaddrInet4{
+				Port: 179,
+				Addr: [4]byte{192, 0, 2, 42},
+			},
+		},
+		{
+			name: "IPv6 / 2001:db8::$2",
+			addr: "[2001:db8::42]:179",
+			expected: &unix.SockaddrInet6{
+				Port: 179,
+				Addr: [16]byte{0x20, 0x01, 0x0d, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x42},
+			},
+		},
+	}
+
+	for _, test := range tests {
+		tcpaddr, err := net.ResolveTCPAddr("tcp", test.addr)
+		if err != nil {
+			t.Fatalf("Failed to resolve TCPAddr: %v", err)
+		}
+		assert.Equal(t, test.expected, netTCPAddrToSockAddr(tcpaddr), test.name)
+	}
+}