1// Copyright 2016 The Go Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style 3// license that can be found in the LICENSE file. 4 5//go:build darwin || dragonfly || freebsd || netbsd || openbsd 6// +build darwin dragonfly freebsd netbsd openbsd 7 8// Package route provides basic functions for the manipulation of 9// packet routing facilities on BSD variants. 10// 11// The package supports any version of Darwin, any version of 12// DragonFly BSD, FreeBSD 7 and above, NetBSD 6 and above, and OpenBSD 13// 5.6 and above. 14package route 15 16import ( 17 "errors" 18 "os" 19 "syscall" 20) 21 22var ( 23 errUnsupportedMessage = errors.New("unsupported message") 24 errMessageMismatch = errors.New("message mismatch") 25 errMessageTooShort = errors.New("message too short") 26 errInvalidMessage = errors.New("invalid message") 27 errInvalidAddr = errors.New("invalid address") 28 errShortBuffer = errors.New("short buffer") 29) 30 31// A RouteMessage represents a message conveying an address prefix, a 32// nexthop address and an output interface. 33// 34// Unlike other messages, this message can be used to query adjacency 35// information for the given address prefix, to add a new route, and 36// to delete or modify the existing route from the routing information 37// base inside the kernel by writing and reading route messages on a 38// routing socket. 39// 40// For the manipulation of routing information, the route message must 41// contain appropriate fields that include: 42// 43// Version = <must be specified> 44// Type = <must be specified> 45// Flags = <must be specified> 46// Index = <must be specified if necessary> 47// ID = <must be specified> 48// Seq = <must be specified> 49// Addrs = <must be specified> 50// 51// The Type field specifies a type of manipulation, the Flags field 52// specifies a class of target information and the Addrs field 53// specifies target information like the following: 54// 55// route.RouteMessage{ 56// Version: RTM_VERSION, 57// Type: RTM_GET, 58// Flags: RTF_UP | RTF_HOST, 59// ID: uintptr(os.Getpid()), 60// Seq: 1, 61// Addrs: []route.Addrs{ 62// RTAX_DST: &route.Inet4Addr{ ... }, 63// RTAX_IFP: &route.LinkAddr{ ... }, 64// RTAX_BRD: &route.Inet4Addr{ ... }, 65// }, 66// } 67// 68// The values for the above fields depend on the implementation of 69// each operating system. 70// 71// The Err field on a response message contains an error value on the 72// requested operation. If non-nil, the requested operation is failed. 73type RouteMessage struct { 74 Version int // message version 75 Type int // message type 76 Flags int // route flags 77 Index int // interface index when attached 78 ID uintptr // sender's identifier; usually process ID 79 Seq int // sequence number 80 Err error // error on requested operation 81 Addrs []Addr // addresses 82 83 extOff int // offset of header extension 84 raw []byte // raw message 85} 86 87// Marshal returns the binary encoding of m. 88func (m *RouteMessage) Marshal() ([]byte, error) { 89 return m.marshal() 90} 91 92// A RIBType represents a type of routing information base. 93type RIBType int 94 95const ( 96 RIBTypeRoute RIBType = syscall.NET_RT_DUMP 97 RIBTypeInterface RIBType = syscall.NET_RT_IFLIST 98) 99 100// FetchRIB fetches a routing information base from the operating 101// system. 102// 103// The provided af must be an address family. 104// 105// The provided arg must be a RIBType-specific argument. 106// When RIBType is related to routes, arg might be a set of route 107// flags. When RIBType is related to network interfaces, arg might be 108// an interface index or a set of interface flags. In most cases, zero 109// means a wildcard. 110func FetchRIB(af int, typ RIBType, arg int) ([]byte, error) { 111 try := 0 112 for { 113 try++ 114 mib := [6]int32{sysCTL_NET, sysAF_ROUTE, 0, int32(af), int32(typ), int32(arg)} 115 n := uintptr(0) 116 if err := sysctl(mib[:], nil, &n, nil, 0); err != nil { 117 return nil, os.NewSyscallError("sysctl", err) 118 } 119 if n == 0 { 120 return nil, nil 121 } 122 b := make([]byte, n) 123 if err := sysctl(mib[:], &b[0], &n, nil, 0); err != nil { 124 // If the sysctl failed because the data got larger 125 // between the two sysctl calls, try a few times 126 // before failing. (golang.org/issue/45736). 127 const maxTries = 3 128 if err == syscall.ENOMEM && try < maxTries { 129 continue 130 } 131 return nil, os.NewSyscallError("sysctl", err) 132 } 133 return b[:n], nil 134 } 135} 136