src/syscall/zx/mxnet/mxnet.go

// Copyright 2017 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 fuchsia

// Package mxnet contains types for talking to Fuchsia's fdio net interface.
package mxnet

import (
	"errors"
	"math"
	"unsafe"
)

// Addr is an IP address.
// It has either len == 4 (if it is IPv4) or len == 16 (IPv6).
type Addr string

// TODO(crawshaw): consider cleaning up these interfaces by migrating to
// an address type that captures everything:
//
//	type Address struct {
//		Addr [16]byte
//		IPv4 bool
//		Port uint16
//	}

const SockaddrLen = c_sockaddr_in6_len

func DecodeSockaddr(data []byte) (addr Addr, port uint16, err error) {
	if len(data) < 2 {
		return "", 0, errors.New("mxnet:DecodeSockaddr: data too short")
	}
	family := uint16(data[0]) | uint16(data[1])<<8
	switch family {
	case AF_INET:
		if len(data) < int(unsafe.Sizeof(c_sockaddr_in{})) {
			return "", 0, errors.New("mxnet:DecodeSockaddr: data too short for ipv4")
		}
		v := (*c_sockaddr_in)(unsafe.Pointer(&data[0]))
		port = uint16(data[3]) | uint16(data[2])<<8
		if !isZeros(v.sin_addr[:]) {
			addr = Addr(v.sin_addr[:])
		}
		return addr, port, nil
	case AF_INET6:
		if len(data) < int(unsafe.Sizeof(c_sockaddr_in6{})) {
			return "", 0, errors.New("mxnet:DecodeSockaddr: data too short for ipv6")
		}
		v := (*c_sockaddr_in6)(unsafe.Pointer(&data[0]))
		port = uint16(data[3]) | uint16(data[2])<<8
		if !isZeros(v.sin6_addr[:]) {
			addr = Addr(v.sin6_addr[:])
		}
		return addr, port, nil
	default:
		return "", 0, errors.New("mxnet:DecodeSockaddr: unknown family")
	}
}

func EncodeSockaddr(dst []byte, addr Addr, port int, zone uint32) (int, error) {
	switch len(addr) {
	case 0, 4:
		if len(dst) < c_sockaddr_in_len {
			return 0, errors.New("mxnet: dst too small for c_sockaddr_in")
		}
		sockaddr := c_sockaddr_in{sin_family: AF_INET}
		if port > math.MaxUint16 {
			return 0, errors.New("port overflow")
		}
		sockaddr.sin_port.setPort(uint16(port))
		copy(sockaddr.sin_addr[:], addr)
		srcb := (*[unsafe.Sizeof(sockaddr)]byte)(unsafe.Pointer(&sockaddr))[:]
		return copy(dst, srcb), nil
	case 16:
		if len(dst) < c_sockaddr_in_len {
			return 0, errors.New("mxnet: dst too small for c_sockaddr_in6")
		}
		sockaddr := c_sockaddr_in6{sin6_family: AF_INET6}
		if port > math.MaxUint16 {
			return 0, errors.New("port overflow")
		}
		sockaddr.sin6_port.setPort(uint16(port))
		sockaddr.sin6_scope_id = zone
		copy(sockaddr.sin6_addr[:], addr)
		srcb := (*[unsafe.Sizeof(sockaddr)]byte)(unsafe.Pointer(&sockaddr))[:]
		return copy(dst, srcb), nil
	default:
		return 0, errors.New("mxnet: bad address length")
	}
}

const (
	c_sockaddr_in_len  = int(unsafe.Sizeof(c_sockaddr_in{}))
	c_sockaddr_in6_len = int(unsafe.Sizeof(c_sockaddr_in6{}))
)

func (v c_in_port) port() uint16 {
	return uint16(v[0])<<8 | uint16(v[1])
}

func (v *c_in_port) setPort(port uint16) {
	v[0] = uint8(port >> 8)
	v[1] = uint8(port)
}

func isZeros(buf []byte) bool {
	for i := 0; i < len(buf); i++ {
		if buf[i] != 0 {
			return false
		}
	}
	return true
}