diff options
Diffstat (limited to 'vendor/github.com/google/gopacket/routing/routing.go')
-rw-r--r-- | vendor/github.com/google/gopacket/routing/routing.go | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/vendor/github.com/google/gopacket/routing/routing.go b/vendor/github.com/google/gopacket/routing/routing.go new file mode 100644 index 0000000..cbbeb6e --- /dev/null +++ b/vendor/github.com/google/gopacket/routing/routing.go @@ -0,0 +1,241 @@ +// Copyright 2012 Google, Inc. All rights reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the LICENSE file in the root of the source +// tree. + +// +build linux + +// Package routing provides a very basic but mostly functional implementation of +// a routing table for IPv4/IPv6 addresses. It uses a routing table pulled from +// the kernel via netlink to find the correct interface, gateway, and preferred +// source IP address for packets destined to a particular location. +// +// The routing package is meant to be used with applications that are sending +// raw packet data, which don't have the benefit of having the kernel route +// packets for them. +package routing + +import ( + "bytes" + "errors" + "fmt" + "net" + "sort" + "strings" + "syscall" + "unsafe" +) + +// Pulled from http://man7.org/linux/man-pages/man7/rtnetlink.7.html +// See the section on RTM_NEWROUTE, specifically 'struct rtmsg'. +type routeInfoInMemory struct { + Family byte + DstLen byte + SrcLen byte + TOS byte + + Table byte + Protocol byte + Scope byte + Type byte + + Flags uint32 +} + +// rtInfo contains information on a single route. +type rtInfo struct { + Src, Dst *net.IPNet + Gateway, PrefSrc net.IP + // We currently ignore the InputIface. + InputIface, OutputIface uint32 + Priority uint32 +} + +// routeSlice implements sort.Interface to sort routes by Priority. +type routeSlice []*rtInfo + +func (r routeSlice) Len() int { + return len(r) +} +func (r routeSlice) Less(i, j int) bool { + return r[i].Priority < r[j].Priority +} +func (r routeSlice) Swap(i, j int) { + r[i], r[j] = r[j], r[i] +} + +type router struct { + ifaces []net.Interface + addrs []ipAddrs + v4, v6 routeSlice +} + +func (r *router) String() string { + strs := []string{"ROUTER", "--- V4 ---"} + for _, route := range r.v4 { + strs = append(strs, fmt.Sprintf("%+v", *route)) + } + strs = append(strs, "--- V6 ---") + for _, route := range r.v6 { + strs = append(strs, fmt.Sprintf("%+v", *route)) + } + return strings.Join(strs, "\n") +} + +type ipAddrs struct { + v4, v6 net.IP +} + +func (r *router) Route(dst net.IP) (iface *net.Interface, gateway, preferredSrc net.IP, err error) { + return r.RouteWithSrc(nil, nil, dst) +} + +func (r *router) RouteWithSrc(input net.HardwareAddr, src, dst net.IP) (iface *net.Interface, gateway, preferredSrc net.IP, err error) { + var ifaceIndex int + switch { + case dst.To4() != nil: + ifaceIndex, gateway, preferredSrc, err = r.route(r.v4, input, src, dst) + case dst.To16() != nil: + ifaceIndex, gateway, preferredSrc, err = r.route(r.v6, input, src, dst) + default: + err = errors.New("IP is not valid as IPv4 or IPv6") + return + } + + // Interfaces are 1-indexed, but we store them in a 0-indexed array. + ifaceIndex-- + + iface = &r.ifaces[ifaceIndex] + if preferredSrc == nil { + switch { + case dst.To4() != nil: + preferredSrc = r.addrs[ifaceIndex].v4 + case dst.To16() != nil: + preferredSrc = r.addrs[ifaceIndex].v6 + } + } + return +} + +func (r *router) route(routes routeSlice, input net.HardwareAddr, src, dst net.IP) (iface int, gateway, preferredSrc net.IP, err error) { + var inputIndex uint32 + if input != nil { + for i, iface := range r.ifaces { + if bytes.Equal(input, iface.HardwareAddr) { + // Convert from zero- to one-indexed. + inputIndex = uint32(i + 1) + break + } + } + } + for _, rt := range routes { + if rt.InputIface != 0 && rt.InputIface != inputIndex { + continue + } + if rt.Src != nil && !rt.Src.Contains(src) { + continue + } + if rt.Dst != nil && !rt.Dst.Contains(dst) { + continue + } + return int(rt.OutputIface), rt.Gateway, rt.PrefSrc, nil + } + err = fmt.Errorf("no route found for %v", dst) + return +} + +// New creates a new router object. The router returned by New currently does +// not update its routes after construction... care should be taken for +// long-running programs to call New() regularly to take into account any +// changes to the routing table which have occurred since the last New() call. +func New() (Router, error) { + rtr := &router{} + tab, err := syscall.NetlinkRIB(syscall.RTM_GETROUTE, syscall.AF_UNSPEC) + if err != nil { + return nil, err + } + msgs, err := syscall.ParseNetlinkMessage(tab) + if err != nil { + return nil, err + } +loop: + for _, m := range msgs { + switch m.Header.Type { + case syscall.NLMSG_DONE: + break loop + case syscall.RTM_NEWROUTE: + rt := (*routeInfoInMemory)(unsafe.Pointer(&m.Data[0])) + routeInfo := rtInfo{} + attrs, err := syscall.ParseNetlinkRouteAttr(&m) + if err != nil { + return nil, err + } + switch rt.Family { + case syscall.AF_INET: + rtr.v4 = append(rtr.v4, &routeInfo) + case syscall.AF_INET6: + rtr.v6 = append(rtr.v6, &routeInfo) + default: + continue loop + } + for _, attr := range attrs { + switch attr.Attr.Type { + case syscall.RTA_DST: + routeInfo.Dst = &net.IPNet{ + IP: net.IP(attr.Value), + Mask: net.CIDRMask(int(rt.DstLen), len(attr.Value)*8), + } + case syscall.RTA_SRC: + routeInfo.Src = &net.IPNet{ + IP: net.IP(attr.Value), + Mask: net.CIDRMask(int(rt.SrcLen), len(attr.Value)*8), + } + case syscall.RTA_GATEWAY: + routeInfo.Gateway = net.IP(attr.Value) + case syscall.RTA_PREFSRC: + routeInfo.PrefSrc = net.IP(attr.Value) + case syscall.RTA_IIF: + routeInfo.InputIface = *(*uint32)(unsafe.Pointer(&attr.Value[0])) + case syscall.RTA_OIF: + routeInfo.OutputIface = *(*uint32)(unsafe.Pointer(&attr.Value[0])) + case syscall.RTA_PRIORITY: + routeInfo.Priority = *(*uint32)(unsafe.Pointer(&attr.Value[0])) + } + } + } + } + sort.Sort(rtr.v4) + sort.Sort(rtr.v6) + ifaces, err := net.Interfaces() + if err != nil { + return nil, err + } + for i, iface := range ifaces { + if i != iface.Index-1 { + return nil, fmt.Errorf("out of order iface %d = %v", i, iface) + } + rtr.ifaces = append(rtr.ifaces, iface) + var addrs ipAddrs + ifaceAddrs, err := iface.Addrs() + if err != nil { + return nil, err + } + for _, addr := range ifaceAddrs { + if inet, ok := addr.(*net.IPNet); ok { + // Go has a nasty habit of giving you IPv4s as ::ffff:1.2.3.4 instead of 1.2.3.4. + // We want to use mapped v4 addresses as v4 preferred addresses, never as v6 + // preferred addresses. + if v4 := inet.IP.To4(); v4 != nil { + if addrs.v4 == nil { + addrs.v4 = v4 + } + } else if addrs.v6 == nil { + addrs.v6 = inet.IP + } + } + } + rtr.addrs = append(rtr.addrs, addrs) + } + return rtr, nil +} |