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// Copyright 2016 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.
//go:build darwin || dragonfly || freebsd || netbsd || openbsd
// +build darwin dragonfly freebsd netbsd openbsd
// Package route provides basic functions for the manipulation of
// packet routing facilities on BSD variants.
//
// The package supports any version of Darwin, any version of
// DragonFly BSD, FreeBSD 7 and above, NetBSD 6 and above, and OpenBSD
// 5.6 and above.
package route
import (
"errors"
"os"
"syscall"
)
var (
errUnsupportedMessage = errors.New("unsupported message")
errMessageMismatch = errors.New("message mismatch")
errMessageTooShort = errors.New("message too short")
errInvalidMessage = errors.New("invalid message")
errInvalidAddr = errors.New("invalid address")
errShortBuffer = errors.New("short buffer")
)
// A RouteMessage represents a message conveying an address prefix, a
// nexthop address and an output interface.
//
// Unlike other messages, this message can be used to query adjacency
// information for the given address prefix, to add a new route, and
// to delete or modify the existing route from the routing information
// base inside the kernel by writing and reading route messages on a
// routing socket.
//
// For the manipulation of routing information, the route message must
// contain appropriate fields that include:
//
// Version = <must be specified>
// Type = <must be specified>
// Flags = <must be specified>
// Index = <must be specified if necessary>
// ID = <must be specified>
// Seq = <must be specified>
// Addrs = <must be specified>
//
// The Type field specifies a type of manipulation, the Flags field
// specifies a class of target information and the Addrs field
// specifies target information like the following:
//
// route.RouteMessage{
// Version: RTM_VERSION,
// Type: RTM_GET,
// Flags: RTF_UP | RTF_HOST,
// ID: uintptr(os.Getpid()),
// Seq: 1,
// Addrs: []route.Addrs{
// RTAX_DST: &route.Inet4Addr{ ... },
// RTAX_IFP: &route.LinkAddr{ ... },
// RTAX_BRD: &route.Inet4Addr{ ... },
// },
// }
//
// The values for the above fields depend on the implementation of
// each operating system.
//
// The Err field on a response message contains an error value on the
// requested operation. If non-nil, the requested operation is failed.
type RouteMessage struct {
Version int // message version
Type int // message type
Flags int // route flags
Index int // interface index when attached
ID uintptr // sender's identifier; usually process ID
Seq int // sequence number
Err error // error on requested operation
Addrs []Addr // addresses
extOff int // offset of header extension
raw []byte // raw message
}
// Marshal returns the binary encoding of m.
func (m *RouteMessage) Marshal() ([]byte, error) {
return m.marshal()
}
// A RIBType represents a type of routing information base.
type RIBType int
const (
RIBTypeRoute RIBType = syscall.NET_RT_DUMP
RIBTypeInterface RIBType = syscall.NET_RT_IFLIST
)
// FetchRIB fetches a routing information base from the operating
// system.
//
// The provided af must be an address family.
//
// The provided arg must be a RIBType-specific argument.
// When RIBType is related to routes, arg might be a set of route
// flags. When RIBType is related to network interfaces, arg might be
// an interface index or a set of interface flags. In most cases, zero
// means a wildcard.
func FetchRIB(af int, typ RIBType, arg int) ([]byte, error) {
try := 0
for {
try++
mib := [6]int32{syscall.CTL_NET, syscall.AF_ROUTE, 0, int32(af), int32(typ), int32(arg)}
n := uintptr(0)
if err := sysctl(mib[:], nil, &n, nil, 0); err != nil {
return nil, os.NewSyscallError("sysctl", err)
}
if n == 0 {
return nil, nil
}
b := make([]byte, n)
if err := sysctl(mib[:], &b[0], &n, nil, 0); err != nil {
// If the sysctl failed because the data got larger
// between the two sysctl calls, try a few times
// before failing. (golang.org/issue/45736).
const maxTries = 3
if err == syscall.ENOMEM && try < maxTries {
continue
}
return nil, os.NewSyscallError("sysctl", err)
}
return b[:n], nil
}
}
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