}
	_, _, err = ucw.WriteMsgUnix(nil, rights, nil)
	if err != nil {
		t.Fatalf("UnixConn readMsg: %v", err)
	}
	err = ucr.SetReadDeadline(time.Now().Add(5 * time.Second))
	if err != nil {
		t.Fatalf("Can't set unix connection timeout: %v", err)
	}
	_, oobn, _, _, err := ucr.ReadMsgUnix(nil, oob)
	if err != nil {
		t.Fatalf("UnixConn readMsg: %v", err)
	}

	scms, err := syscall.ParseSocketControlMessage(oob[:oobn])

	if 20 > l || l > len(b) {
		return n
	}
	if b[0]>>4 != 4 {
		return n
	}
	copy(b, b[l:])
	return n - l
}

func (c *IPConn) readMsg(b, oob []byte) (n, oobn, flags int, addr *IPAddr, err error) {
	var sa syscall.Sockaddr
	n, oobn, flags, sa, err = c.fd.readMsg(b, oob, 0)
	switch sa := sa.(type) {
	case *syscall.SockaddrInet4:
		addr = &IPAddr{IP: sa.Addr[0:]}
	case *syscall.SockaddrInet6:

package net

import (
	"context"
	"syscall"
)

func (c *IPConn) readFrom(b []byte) (int, *IPAddr, error) {
	return 0, nil, syscall.EPLAN9
}

func (c *IPConn) readMsg(b, oob []byte) (n, oobn, flags int, addr *IPAddr, err error) {
	return 0, 0, 0, nil, syscall.EPLAN9
}

func (c *IPConn) writeTo(b []byte, addr *IPAddr) (int, error) {
	return 0, syscall.EPLAN9
}

package net

import (
	"context"
	"os"
	"syscall"
)

func (c *UnixConn) readFrom(b []byte) (int, *UnixAddr, error) {
	return 0, nil, syscall.EPLAN9
}

func (c *UnixConn) readMsg(b, oob []byte) (n, oobn, flags int, addr *UnixAddr, err error) {
	return 0, 0, 0, nil, syscall.EPLAN9
}

func (c *UnixConn) writeTo(b []byte, addr *UnixAddr) (int, error) {
	return 0, syscall.EPLAN9
}

	n, err = fd.pfd.ReadFromInet6(p, from)
	runtime.KeepAlive(fd)
	return n, wrapSyscallError(readFromSyscallName, err)
}

func (fd *netFD) readMsg(p []byte, oob []byte, flags int) (n, oobn, retflags int, sa syscall.Sockaddr, err error) {
	n, oobn, retflags, sa, err = fd.pfd.ReadMsg(p, oob, flags)
	runtime.KeepAlive(fd)
	return n, oobn, retflags, sa, wrapSyscallError(readMsgSyscallName, err)
}

		if sa.Name != "" {
			addr = &UnixAddr{Name: sa.Name, Net: sotypeToNet(c.fd.sotype)}
		}
	}
	return n, addr, err
}

func (c *UnixConn) readMsg(b, oob []byte) (n, oobn, flags int, addr *UnixAddr, err error) {
	var sa syscall.Sockaddr
	n, oobn, flags, sa, err = c.fd.readMsg(b, oob, readMsgFlags)
	if readMsgFlags == 0 && err == nil && oobn > 0 {
		setReadMsgCloseOnExec(oob[:oobn])
	}

	switch sa := sa.(type) {

				if err = fd.pd.waitRead(fd.isFile); err == nil {
					continue
				}
			}
		}
		err = fd.eofError(n, err)
		return n, err
	}
}

// ReadMsg wraps the recvmsg network call.
func (fd *FD) ReadMsg(p []byte, oob []byte, flags int) (int, int, int, syscall.Sockaddr, error) {
	if err := fd.readLock(); err != nil {
		return 0, 0, 0, nil, err
	}
	defer fd.readUnlock()

	}
	buf = buf[:m]

	h, buf := unmarshalUDPHeader(buf)
	n := copy(b, buf)
	ip, _ := netip.AddrFromSlice(h.raddr)
	addr := netip.AddrPortFrom(ip, h.rport)
	return n, addr, nil
}

func (c *UDPConn) readMsg(b, oob []byte) (n, oobn, flags int, addr netip.AddrPort, err error) {
	return 0, 0, 0, netip.AddrPort{}, syscall.EPLAN9
}

func (c *UDPConn) writeTo(b []byte, addr *UDPAddr) (int, error) {
	if addr == nil {

func (c *IPConn) ReadMsgIP(b, oob []byte) (n, oobn, flags int, addr *IPAddr, err error) {
	if !c.ok() {
		return 0, 0, 0, nil, syscall.EINVAL
	}
	n, oobn, flags, addr, err = c.readMsg(b, oob)
	if err != nil {
		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return
}

// WriteToIP acts like [IPConn.WriteTo] but takes an [IPAddr].

			port = from.Port
		}
	}
	if err == nil {
		addr = netip.AddrPortFrom(ip, uint16(port))
	}
	return n, addr, err
}

func (c *UDPConn) readMsg(b, oob []byte) (n, oobn, flags int, addr netip.AddrPort, err error) {
	switch c.fd.family {
	case syscall.AF_INET:
		var sa syscall.SockaddrInet4
		n, oobn, flags, err = c.fd.readMsgInet4(b, oob, 0, &sa)