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tailscale/net/netutil/routes.go

95 lines
2.9 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package netutil
import (
"encoding/binary"
"fmt"
"net/netip"
"sort"
"strings"
"tailscale.com/net/tsaddr"
)
var (
ipv4default = netip.MustParsePrefix("0.0.0.0/0")
ipv6default = netip.MustParsePrefix("::/0")
)
func validateViaPrefix(ipp netip.Prefix) error {
if !tsaddr.IsViaPrefix(ipp) {
return fmt.Errorf("%v is not a 4-in-6 prefix", ipp)
}
if ipp.Bits() < (128 - 32) {
return fmt.Errorf("%v 4-in-6 prefix must be at least a /%v", ipp, 128-32)
}
a := ipp.Addr().As16()
// The first 64 bits of a are the via prefix.
// The next 32 bits are the "site ID".
// The last 32 bits are the IPv4.
//
// We used to only allow advertising site IDs from 0-255, but we have
// since relaxed this (as of 2024-01) to allow IDs from 0-65535.
siteID := binary.BigEndian.Uint32(a[8:12])
if siteID > 0xFFFF {
return fmt.Errorf("route %v contains invalid site ID %08x; must be 0xffff or less", ipp, siteID)
}
return nil
}
// CalcAdvertiseRoutes calculates the requested routes to be advertised by a node.
// advertiseRoutes is the user-provided, comma-separated list of routes (IP addresses or CIDR prefixes) to advertise.
// advertiseDefaultRoute indicates whether the node should act as an exit node and advertise default routes.
func CalcAdvertiseRoutes(advertiseRoutes string, advertiseDefaultRoute bool) ([]netip.Prefix, error) {
routeMap := map[netip.Prefix]bool{}
if advertiseRoutes != "" {
var default4, default6 bool
advroutes := strings.Split(advertiseRoutes, ",")
for _, s := range advroutes {
ipp, err := netip.ParsePrefix(s)
if err != nil {
return nil, fmt.Errorf("%q is not a valid IP address or CIDR prefix", s)
}
if ipp != ipp.Masked() {
return nil, fmt.Errorf("%s has non-address bits set; expected %s", ipp, ipp.Masked())
}
if tsaddr.IsViaPrefix(ipp) {
if err := validateViaPrefix(ipp); err != nil {
return nil, err
}
}
if ipp == ipv4default {
default4 = true
} else if ipp == ipv6default {
default6 = true
}
routeMap[ipp] = true
}
if default4 && !default6 {
return nil, fmt.Errorf("%s advertised without its IPv6 counterpart, please also advertise %s", ipv4default, ipv6default)
} else if default6 && !default4 {
return nil, fmt.Errorf("%s advertised without its IPv4 counterpart, please also advertise %s", ipv6default, ipv4default)
}
}
if advertiseDefaultRoute {
routeMap[netip.MustParsePrefix("0.0.0.0/0")] = true
routeMap[netip.MustParsePrefix("::/0")] = true
}
if len(routeMap) == 0 {
return nil, nil
}
routes := make([]netip.Prefix, 0, len(routeMap))
for r := range routeMap {
routes = append(routes, r)
}
sort.Slice(routes, func(i, j int) bool {
if routes[i].Bits() != routes[j].Bits() {
return routes[i].Bits() < routes[j].Bits()
}
return routes[i].Addr().Less(routes[j].Addr())
})
return routes, nil
}