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routetable_linux.go
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routetable_linux.go
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// Copyright (c) 2022 Tailscale Inc & 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 linux
package routetable
import (
"bufio"
"fmt"
"net/netip"
"strconv"
"github.com/tailscale/netlink"
"golang.org/x/sys/unix"
"tailscale.com/net/interfaces"
"tailscale.com/net/netaddr"
"tailscale.com/types/logger"
)
// RouteEntryLinux is the structure that makes up the Sys field of the
// RouteEntry structure.
type RouteEntryLinux struct {
// Type is the raw type of the route.
Type int
// Table is the routing table index of this route.
Table int
// Src is the source of the route (if any).
Src netip.Addr
// Proto describes the source of the route--i.e. what caused this route
// to be added to the route table.
Proto netlink.RouteProtocol
// Priority is the route's priority.
Priority int
// Scope is the route's scope.
Scope int
// InputInterfaceIdx is the input interface index.
InputInterfaceIdx int
// InputInterfaceName is the input interface name (if available).
InputInterfaceName string
}
// Format implements the fmt.Formatter interface.
func (r RouteEntryLinux) Format(f fmt.State, verb rune) {
logger.ArgWriter(func(w *bufio.Writer) {
// TODO(andrew): should we skip printing anything if type is unicast?
fmt.Fprintf(w, "{Type: %s", r.TypeName())
// Match 'ip route' behaviour when printing these fields
if r.Table != unix.RT_TABLE_MAIN {
fmt.Fprintf(w, ", Table: %s", r.TableName())
}
if r.Proto != unix.RTPROT_BOOT {
fmt.Fprintf(w, ", Proto: %s", r.Proto)
}
if r.Src.IsValid() {
fmt.Fprintf(w, ", Src: %s", r.Src)
}
if r.Priority != 0 {
fmt.Fprintf(w, ", Priority: %d", r.Priority)
}
if r.Scope != unix.RT_SCOPE_UNIVERSE {
fmt.Fprintf(w, ", Scope: %s", r.ScopeName())
}
if r.InputInterfaceName != "" {
fmt.Fprintf(w, ", InputInterfaceName: %s", r.InputInterfaceName)
} else if r.InputInterfaceIdx != 0 {
fmt.Fprintf(w, ", InputInterfaceIdx: %d", r.InputInterfaceIdx)
}
w.WriteString("}")
}).Format(f, verb)
}
// TypeName returns the string representation of this route's Type.
func (r RouteEntryLinux) TypeName() string {
switch r.Type {
case unix.RTN_UNSPEC:
return "none"
case unix.RTN_UNICAST:
return "unicast"
case unix.RTN_LOCAL:
return "local"
case unix.RTN_BROADCAST:
return "broadcast"
case unix.RTN_ANYCAST:
return "anycast"
case unix.RTN_MULTICAST:
return "multicast"
case unix.RTN_BLACKHOLE:
return "blackhole"
case unix.RTN_UNREACHABLE:
return "unreachable"
case unix.RTN_PROHIBIT:
return "prohibit"
case unix.RTN_THROW:
return "throw"
case unix.RTN_NAT:
return "nat"
case unix.RTN_XRESOLVE:
return "xresolve"
default:
return strconv.Itoa(r.Type)
}
}
// TableName returns the string representation of this route's Table.
func (r RouteEntryLinux) TableName() string {
switch r.Table {
case unix.RT_TABLE_DEFAULT:
return "default"
case unix.RT_TABLE_MAIN:
return "main"
case unix.RT_TABLE_LOCAL:
return "local"
default:
return strconv.Itoa(r.Table)
}
}
// ScopeName returns the string representation of this route's Scope.
func (r RouteEntryLinux) ScopeName() string {
switch r.Scope {
case unix.RT_SCOPE_UNIVERSE:
return "global"
case unix.RT_SCOPE_NOWHERE:
return "nowhere"
case unix.RT_SCOPE_HOST:
return "host"
case unix.RT_SCOPE_LINK:
return "link"
case unix.RT_SCOPE_SITE:
return "site"
default:
return strconv.Itoa(r.Scope)
}
}
// Get returns route entries from the system route table, limited to at most
// max results.
func Get(max int) ([]RouteEntry, error) {
// Fetching the list of interfaces can race with fetching our route
// table, but we do it anyway since it's helpful for debugging.
ifs, err := interfaces.GetList()
if err != nil {
return nil, err
}
ifsByIdx := make(map[int]interfaces.Interface)
for _, iif := range ifs {
ifsByIdx[iif.Index] = iif
}
filter := &netlink.Route{}
routes, err := netlink.RouteListFiltered(netlink.FAMILY_ALL, filter, netlink.RT_FILTER_TABLE)
if err != nil {
return nil, err
}
var ret []RouteEntry
for _, route := range routes {
if route.Family != netlink.FAMILY_V4 && route.Family != netlink.FAMILY_V6 {
continue
}
re := RouteEntry{}
if route.Family == netlink.FAMILY_V4 {
re.Family = 4
} else {
re.Family = 6
}
switch route.Type {
case unix.RTN_UNSPEC:
re.Type = RouteTypeUnspecified
case unix.RTN_UNICAST:
re.Type = RouteTypeUnicast
case unix.RTN_LOCAL:
re.Type = RouteTypeLocal
case unix.RTN_BROADCAST:
re.Type = RouteTypeBroadcast
case unix.RTN_MULTICAST:
re.Type = RouteTypeMulticast
default:
re.Type = RouteTypeOther
}
if route.Dst != nil {
if d, ok := netaddr.FromStdIPNet(route.Dst); ok {
re.Dst = RouteDestination{Prefix: d}
}
} else if route.Family == netlink.FAMILY_V4 {
re.Dst = RouteDestination{Prefix: netip.PrefixFrom(netip.IPv4Unspecified(), 0)}
} else {
re.Dst = RouteDestination{Prefix: netip.PrefixFrom(netip.IPv6Unspecified(), 0)}
}
if gw := route.Gw; gw != nil {
if gwa, ok := netip.AddrFromSlice(gw); ok {
re.Gateway = gwa
}
}
if outif, ok := ifsByIdx[route.LinkIndex]; ok {
re.Interface = outif.Name
} else if route.LinkIndex > 0 {
re.Interface = fmt.Sprintf("link#%d", route.LinkIndex)
}
reSys := RouteEntryLinux{
Type: route.Type,
Table: route.Table,
Proto: route.Protocol,
Priority: route.Priority,
Scope: int(route.Scope),
InputInterfaceIdx: route.ILinkIndex,
}
if src, ok := netip.AddrFromSlice(route.Src); ok {
reSys.Src = src
}
if iif, ok := ifsByIdx[route.ILinkIndex]; ok {
reSys.InputInterfaceName = iif.Name
}
re.Sys = reSys
ret = append(ret, re)
// Stop after we've reached the maximum number of routes
if len(ret) == max {
break
}
}
return ret, nil
}