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// Copyright 2010 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build darwin freebsd linux netbsd openbsd windows

// (Raw) IP sockets

package net

import (
        "os"
        "syscall"
        "time"
)

func sockaddrToIP(sa syscall.Sockaddr) Addr {
        switch sa := sa.(type) {
        case *syscall.SockaddrInet4:
                return &IPAddr{sa.Addr[0:]}
        case *syscall.SockaddrInet6:
                return &IPAddr{sa.Addr[0:]}
        }
        return nil
}

func (a *IPAddr) family() int {
        if a == nil || len(a.IP) <= IPv4len {
                return syscall.AF_INET
        }
        if a.IP.To4() != nil {
                return syscall.AF_INET
        }
        return syscall.AF_INET6
}

func (a *IPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
        return ipToSockaddr(family, a.IP, 0)
}

func (a *IPAddr) toAddr() sockaddr {
        if a == nil { // nil *IPAddr
                return nil // nil interface
        }
        return a
}

// IPConn is the implementation of the Conn and PacketConn
// interfaces for IP network connections.
type IPConn struct {
        fd *netFD
}

func newIPConn(fd *netFD) *IPConn { return &IPConn{fd} }

func (c *IPConn) ok() bool { return c != nil && c.fd != nil }

// Implementation of the Conn interface - see Conn for documentation.

// Read implements the Conn Read method.
func (c *IPConn) Read(b []byte) (int, error) {
        n, _, err := c.ReadFrom(b)
        return n, err
}

// Write implements the Conn Write method.
func (c *IPConn) Write(b []byte) (int, error) {
        if !c.ok() {
                return 0, os.EINVAL
        }
        return c.fd.Write(b)
}

// Close closes the IP connection.
func (c *IPConn) Close() error {
        if !c.ok() {
                return os.EINVAL
        }
        err := c.fd.Close()
        c.fd = nil
        return err
}

// LocalAddr returns the local network address.
func (c *IPConn) LocalAddr() Addr {
        if !c.ok() {
                return nil
        }
        return c.fd.laddr
}

// RemoteAddr returns the remote network address, a *IPAddr.
func (c *IPConn) RemoteAddr() Addr {
        if !c.ok() {
                return nil
        }
        return c.fd.raddr
}

// SetDeadline implements the Conn SetDeadline method.
func (c *IPConn) SetDeadline(t time.Time) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setDeadline(c.fd, t)
}

// SetReadDeadline implements the Conn SetReadDeadline method.
func (c *IPConn) SetReadDeadline(t time.Time) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setReadDeadline(c.fd, t)
}

// SetWriteDeadline implements the Conn SetWriteDeadline method.
func (c *IPConn) SetWriteDeadline(t time.Time) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setWriteDeadline(c.fd, t)
}

// SetReadBuffer sets the size of the operating system's
// receive buffer associated with the connection.
func (c *IPConn) SetReadBuffer(bytes int) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setReadBuffer(c.fd, bytes)
}

// SetWriteBuffer sets the size of the operating system's
// transmit buffer associated with the connection.
func (c *IPConn) SetWriteBuffer(bytes int) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setWriteBuffer(c.fd, bytes)
}

// IP-specific methods.

// ReadFromIP reads a IP packet from c, copying the payload into b.
// It returns the number of bytes copied into b and the return address
// that was on the packet.
//
// ReadFromIP can be made to time out and return an error with
// Timeout() == true after a fixed time limit; see SetDeadline and
// SetReadDeadline.
func (c *IPConn) ReadFromIP(b []byte) (int, *IPAddr, error) {
        if !c.ok() {
                return 0, nil, os.EINVAL
        }
        // TODO(cw,rsc): consider using readv if we know the family
        // type to avoid the header trim/copy
        var addr *IPAddr
        n, sa, err := c.fd.ReadFrom(b)
        switch sa := sa.(type) {
        case *syscall.SockaddrInet4:
                addr = &IPAddr{sa.Addr[0:]}
                if len(b) >= IPv4len { // discard ipv4 header
                        hsize := (int(b[0]) & 0xf) * 4
                        copy(b, b[hsize:])
                        n -= hsize
                }
        case *syscall.SockaddrInet6:
                addr = &IPAddr{sa.Addr[0:]}
        }
        return n, addr, err
}

// ReadFrom implements the PacketConn ReadFrom method.
func (c *IPConn) ReadFrom(b []byte) (int, Addr, error) {
        if !c.ok() {
                return 0, nil, os.EINVAL
        }
        n, uaddr, err := c.ReadFromIP(b)
        return n, uaddr.toAddr(), err
}

// WriteToIP writes a IP packet to addr via c, copying the payload from b.
//
// WriteToIP can be made to time out and return
// an error with Timeout() == true after a fixed time limit;
// see SetDeadline and SetWriteDeadline.
// On packet-oriented connections, write timeouts are rare.
func (c *IPConn) WriteToIP(b []byte, addr *IPAddr) (int, error) {
        if !c.ok() {
                return 0, os.EINVAL
        }
        sa, err := addr.sockaddr(c.fd.family)
        if err != nil {
                return 0, &OpError{"write", c.fd.net, addr, err}
        }
        return c.fd.WriteTo(b, sa)
}

// WriteTo implements the PacketConn WriteTo method.
func (c *IPConn) WriteTo(b []byte, addr Addr) (int, error) {
        if !c.ok() {
                return 0, os.EINVAL
        }
        a, ok := addr.(*IPAddr)
        if !ok {
                return 0, &OpError{"write", c.fd.net, addr, os.EINVAL}
        }
        return c.WriteToIP(b, a)
}

// DialIP connects to the remote address raddr on the network protocol netProto,
// which must be "ip", "ip4", or "ip6" followed by a colon and a protocol number or name.
func DialIP(netProto string, laddr, raddr *IPAddr) (*IPConn, error) {
        net, proto, err := parseDialNetwork(netProto)
        if err != nil {
                return nil, err
        }
        switch net {
        case "ip", "ip4", "ip6":
        default:
                return nil, UnknownNetworkError(net)
        }
        if raddr == nil {
                return nil, &OpError{"dial", netProto, nil, errMissingAddress}
        }
        fd, err := internetSocket(net, laddr.toAddr(), raddr.toAddr(), syscall.SOCK_RAW, proto, "dial", sockaddrToIP)
        if err != nil {
                return nil, err
        }
        return newIPConn(fd), nil
}

// ListenIP listens for incoming IP packets addressed to the
// local address laddr.  The returned connection c's ReadFrom
// and WriteTo methods can be used to receive and send IP
// packets with per-packet addressing.
func ListenIP(netProto string, laddr *IPAddr) (*IPConn, error) {
        net, proto, err := parseDialNetwork(netProto)
        if err != nil {
                return nil, err
        }
        switch net {
        case "ip", "ip4", "ip6":
        default:
                return nil, UnknownNetworkError(net)
        }
        fd, err := internetSocket(net, laddr.toAddr(), nil, syscall.SOCK_RAW, proto, "listen", sockaddrToIP)
        if err != nil {
                return nil, err
        }
        return newIPConn(fd), nil
}

// File returns a copy of the underlying os.File, set to blocking mode.
// It is the caller's responsibility to close f when finished.
// Closing c does not affect f, and closing f does not affect c.
func (c *IPConn) File() (f *os.File, err error) { return c.fd.dup() }