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1 | 1 | //go:build linux |
2 | 2 |
|
| 3 | +// Copyright 2012 Google, Inc. All rights reserved. |
| 4 | +// |
| 5 | +// Use of this source code is governed by a BSD-style license |
| 6 | +// that can be found in the LICENSE file in the root of the source |
| 7 | +// tree. |
| 8 | + |
| 9 | +// Package routing provides a very basic but mostly functional implementation of |
| 10 | +// a routing table for IPv4/IPv6 addresses. It uses a routing table pulled from |
| 11 | +// the kernel via netlink to find the correct interface, gateway, and preferred |
| 12 | +// source IP address for packets destined to a particular location. |
| 13 | +// |
| 14 | +// The routing package is meant to be used with applications that are sending |
| 15 | +// raw packet data, which don't have the benefit of having the kernel route |
| 16 | +// packets for them. |
3 | 17 | package routing |
4 | 18 |
|
5 | 19 | import ( |
| 20 | + "bytes" |
| 21 | + "errors" |
| 22 | + "fmt" |
6 | 23 | "net" |
7 | | - |
8 | | - "github.com/google/gopacket/routing" |
| 24 | + "sort" |
| 25 | + "strings" |
| 26 | + "syscall" |
| 27 | + "unsafe" |
9 | 28 | ) |
10 | 29 |
|
11 | | -// New creates a https://github.com/google/gopacket instance for Linux |
12 | | -func New() (Router, error) { |
13 | | - router, err := routing.New() |
14 | | - if err != nil { |
15 | | - return nil, err |
| 30 | +// Pulled from http://man7.org/linux/man-pages/man7/rtnetlink.7.html |
| 31 | +// See the section on RTM_NEWROUTE, specifically 'struct rtmsg'. |
| 32 | +type routeInfoInMemory struct { |
| 33 | + Family byte |
| 34 | + DstLen byte |
| 35 | + SrcLen byte |
| 36 | + TOS byte |
| 37 | + |
| 38 | + Table byte |
| 39 | + Protocol byte |
| 40 | + Scope byte |
| 41 | + Type byte |
| 42 | + |
| 43 | + Flags uint32 |
| 44 | +} |
| 45 | + |
| 46 | +// rtInfo contains information on a single route. |
| 47 | +type rtInfo struct { |
| 48 | + Src, Dst *net.IPNet |
| 49 | + Gateway, PrefSrc net.IP |
| 50 | + // We currently ignore the InputIface. |
| 51 | + InputIface, OutputIface uint32 |
| 52 | + Priority uint32 |
| 53 | +} |
| 54 | + |
| 55 | +// routeSlice implements sort.Interface to sort routes by Priority. |
| 56 | +type routeSlice []*rtInfo |
| 57 | + |
| 58 | +func (r routeSlice) Len() int { |
| 59 | + return len(r) |
| 60 | +} |
| 61 | +func (r routeSlice) Less(i, j int) bool { |
| 62 | + return r[i].Priority < r[j].Priority |
| 63 | +} |
| 64 | +func (r routeSlice) Swap(i, j int) { |
| 65 | + r[i], r[j] = r[j], r[i] |
| 66 | +} |
| 67 | + |
| 68 | +type router struct { |
| 69 | + ifaces map[int]*net.Interface |
| 70 | + addrs map[int]ipAddrs |
| 71 | + v4, v6 routeSlice |
| 72 | +} |
| 73 | + |
| 74 | +func (r *router) String() string { |
| 75 | + strs := []string{"ROUTER", "--- V4 ---"} |
| 76 | + for _, route := range r.v4 { |
| 77 | + strs = append(strs, fmt.Sprintf("%+v", *route)) |
16 | 78 | } |
17 | | - return RouterLinux{router: router}, nil |
| 79 | + strs = append(strs, "--- V6 ---") |
| 80 | + for _, route := range r.v6 { |
| 81 | + strs = append(strs, fmt.Sprintf("%+v", *route)) |
| 82 | + } |
| 83 | + return strings.Join(strs, "\n") |
18 | 84 | } |
19 | 85 |
|
20 | | -type RouterLinux struct { |
21 | | - router routing.Router |
| 86 | +type ipAddrs struct { |
| 87 | + v4, v6 net.IP |
22 | 88 | } |
23 | 89 |
|
24 | | -func (r RouterLinux) Route(dst net.IP) (iface *net.Interface, gateway, preferredSrc net.IP, err error) { |
25 | | - return r.router.Route(dst) |
| 90 | +func (r *router) Route(dst net.IP) (iface *net.Interface, gateway, preferredSrc net.IP, err error) { |
| 91 | + return r.RouteWithSrc(nil, nil, dst) |
26 | 92 | } |
27 | 93 |
|
28 | | -func (r RouterLinux) RouteWithSrc(input net.HardwareAddr, src, dst net.IP) (iface *net.Interface, gateway, preferredSrc net.IP, err error) { |
29 | | - return r.router.RouteWithSrc(input, src, dst) |
| 94 | +func (r *router) RouteWithSrc(input net.HardwareAddr, src, dst net.IP) (iface *net.Interface, gateway, preferredSrc net.IP, err error) { |
| 95 | + var ifaceIndex int |
| 96 | + switch { |
| 97 | + case dst.To4() != nil: |
| 98 | + ifaceIndex, gateway, preferredSrc, err = r.route(r.v4, input, src, dst) |
| 99 | + case dst.To16() != nil: |
| 100 | + ifaceIndex, gateway, preferredSrc, err = r.route(r.v6, input, src, dst) |
| 101 | + default: |
| 102 | + err = errors.New("IP is not valid as IPv4 or IPv6") |
| 103 | + } |
| 104 | + |
| 105 | + if err != nil { |
| 106 | + return |
| 107 | + } |
| 108 | + |
| 109 | + iface = r.ifaces[ifaceIndex] |
| 110 | + |
| 111 | + if preferredSrc == nil { |
| 112 | + switch { |
| 113 | + case dst.To4() != nil: |
| 114 | + preferredSrc = r.addrs[ifaceIndex].v4 |
| 115 | + case dst.To16() != nil: |
| 116 | + preferredSrc = r.addrs[ifaceIndex].v6 |
| 117 | + } |
| 118 | + } |
| 119 | + return |
| 120 | +} |
| 121 | + |
| 122 | +func (r *router) route(routes routeSlice, input net.HardwareAddr, src, dst net.IP) (iface int, gateway, preferredSrc net.IP, err error) { |
| 123 | + var inputIndex uint32 |
| 124 | + if input != nil { |
| 125 | + for i, iface := range r.ifaces { |
| 126 | + if bytes.Equal(input, iface.HardwareAddr) { |
| 127 | + inputIndex = uint32(i) |
| 128 | + break |
| 129 | + } |
| 130 | + } |
| 131 | + } |
| 132 | + var defaultGateway *rtInfo = nil |
| 133 | + for _, rt := range routes { |
| 134 | + if rt.InputIface != 0 && rt.InputIface != inputIndex { |
| 135 | + continue |
| 136 | + } |
| 137 | + if rt.Src == nil && rt.Dst == nil { |
| 138 | + defaultGateway = rt |
| 139 | + continue |
| 140 | + } |
| 141 | + if rt.Src != nil && !rt.Src.Contains(src) { |
| 142 | + continue |
| 143 | + } |
| 144 | + if rt.Dst != nil && !rt.Dst.Contains(dst) { |
| 145 | + continue |
| 146 | + } |
| 147 | + return int(rt.OutputIface), rt.Gateway, rt.PrefSrc, nil |
| 148 | + } |
| 149 | + |
| 150 | + if defaultGateway != nil { |
| 151 | + return int(defaultGateway.OutputIface), defaultGateway.Gateway, defaultGateway.PrefSrc, nil |
| 152 | + } |
| 153 | + err = fmt.Errorf("no route found for %v", dst) |
| 154 | + return |
| 155 | +} |
| 156 | + |
| 157 | +// New creates a new router object. The router returned by New currently does |
| 158 | +// not update its routes after construction... care should be taken for |
| 159 | +// long-running programs to call New() regularly to take into account any |
| 160 | +// changes to the routing table which have occurred since the last New() call. |
| 161 | +func New() (Router, error) { |
| 162 | + rtr := &router{ |
| 163 | + ifaces: make(map[int]*net.Interface), |
| 164 | + addrs: make(map[int]ipAddrs), |
| 165 | + } |
| 166 | + tab, err := syscall.NetlinkRIB(syscall.RTM_GETROUTE, syscall.AF_UNSPEC) |
| 167 | + if err != nil { |
| 168 | + return nil, err |
| 169 | + } |
| 170 | + msgs, err := syscall.ParseNetlinkMessage(tab) |
| 171 | + if err != nil { |
| 172 | + return nil, err |
| 173 | + } |
| 174 | +loop: |
| 175 | + for _, m := range msgs { |
| 176 | + switch m.Header.Type { |
| 177 | + case syscall.NLMSG_DONE: |
| 178 | + break loop |
| 179 | + case syscall.RTM_NEWROUTE: |
| 180 | + rt := (*routeInfoInMemory)(unsafe.Pointer(&m.Data[0])) |
| 181 | + routeInfo := rtInfo{} |
| 182 | + attrs, err := syscall.ParseNetlinkRouteAttr(&m) |
| 183 | + if err != nil { |
| 184 | + return nil, err |
| 185 | + } |
| 186 | + switch rt.Family { |
| 187 | + case syscall.AF_INET: |
| 188 | + rtr.v4 = append(rtr.v4, &routeInfo) |
| 189 | + case syscall.AF_INET6: |
| 190 | + rtr.v6 = append(rtr.v6, &routeInfo) |
| 191 | + default: |
| 192 | + continue loop |
| 193 | + } |
| 194 | + for _, attr := range attrs { |
| 195 | + switch attr.Attr.Type { |
| 196 | + case syscall.RTA_DST: |
| 197 | + routeInfo.Dst = &net.IPNet{ |
| 198 | + IP: net.IP(attr.Value), |
| 199 | + Mask: net.CIDRMask(int(rt.DstLen), len(attr.Value)*8), |
| 200 | + } |
| 201 | + case syscall.RTA_SRC: |
| 202 | + routeInfo.Src = &net.IPNet{ |
| 203 | + IP: net.IP(attr.Value), |
| 204 | + Mask: net.CIDRMask(int(rt.SrcLen), len(attr.Value)*8), |
| 205 | + } |
| 206 | + case syscall.RTA_GATEWAY: |
| 207 | + routeInfo.Gateway = net.IP(attr.Value) |
| 208 | + case syscall.RTA_PREFSRC: |
| 209 | + routeInfo.PrefSrc = net.IP(attr.Value) |
| 210 | + case syscall.RTA_IIF: |
| 211 | + routeInfo.InputIface = *(*uint32)(unsafe.Pointer(&attr.Value[0])) |
| 212 | + case syscall.RTA_OIF: |
| 213 | + routeInfo.OutputIface = *(*uint32)(unsafe.Pointer(&attr.Value[0])) |
| 214 | + case syscall.RTA_PRIORITY: |
| 215 | + routeInfo.Priority = *(*uint32)(unsafe.Pointer(&attr.Value[0])) |
| 216 | + } |
| 217 | + } |
| 218 | + } |
| 219 | + } |
| 220 | + sort.Sort(rtr.v4) |
| 221 | + sort.Sort(rtr.v6) |
| 222 | + ifaces, err := net.Interfaces() |
| 223 | + if err != nil { |
| 224 | + return nil, err |
| 225 | + } |
| 226 | + for _, tmp := range ifaces { |
| 227 | + iface := tmp |
| 228 | + rtr.ifaces[iface.Index] = &iface |
| 229 | + var addrs ipAddrs |
| 230 | + ifaceAddrs, err := iface.Addrs() |
| 231 | + if err != nil { |
| 232 | + return nil, err |
| 233 | + } |
| 234 | + for _, addr := range ifaceAddrs { |
| 235 | + if inet, ok := addr.(*net.IPNet); ok { |
| 236 | + // Go has a nasty habit of giving you IPv4s as ::ffff:1.2.3.4 instead of 1.2.3.4. |
| 237 | + // We want to use mapped v4 addresses as v4 preferred addresses, never as v6 |
| 238 | + // preferred addresses. |
| 239 | + if v4 := inet.IP.To4(); v4 != nil { |
| 240 | + if addrs.v4 == nil { |
| 241 | + addrs.v4 = v4 |
| 242 | + } |
| 243 | + } else if addrs.v6 == nil { |
| 244 | + addrs.v6 = inet.IP |
| 245 | + } |
| 246 | + } |
| 247 | + } |
| 248 | + rtr.addrs[iface.Index] = addrs |
| 249 | + } |
| 250 | + return rtr, nil |
30 | 251 | } |
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