Bug fix from audit.

peer/control/ping.go

@@ -41,6 +41,8 @@ func (p Ping) Marshal(buf []byte) []byte {
 
 	buf[0] = version
 	binary.BigEndian.PutUint64(buf[1:9], uint64(p.PingTS))
+
+	// SrcV4.
 	if p.SrcV4.IsValid() {
 		a4 := p.SrcV4.Addr().As4()
 		copy(buf[9:13], a4[:])
@@ -48,9 +50,13 @@ func (p Ping) Marshal(buf []byte) []byte {
 	} else {
 		clear(buf[9:15])
 	}
+
+	// SrcV6.
 	a16 := p.SrcV6.Addr().As16()
 	copy(buf[15:31], a16[:])
 	binary.BigEndian.PutUint16(buf[31:33], p.SrcV6.Port())
+
+	// Dst.
 	a16 = p.Dst.Addr().As16()
 	copy(buf[33:49], a16[:])
 	binary.BigEndian.PutUint16(buf[49:51], p.Dst.Port())
@@ -72,7 +78,7 @@ func Unmarshal(buf [Size]byte) (Ping, error) {
 	}
 
 	addr = netip.AddrFrom16([16]byte(buf[15:31])).Unmap()
-	if addr.IsUnspecified() && addr.Is6() {
+	if !addr.IsUnspecified() && addr.Is6() {
 		p.SrcV6 = netip.AddrPortFrom(addr, binary.BigEndian.Uint16(buf[31:33]))
 	}