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Most operating systems add a /32 route for the default gateway address to its routing table This will allow routes to be configured into the system even when the incoming range contains the default gateway. In case a range is a sub-range of an existing route and this range happens to contain the default gateway it attempts to create a default gateway route to prevent loop issues
94 lines
1.9 KiB
Go
94 lines
1.9 KiB
Go
//go:build darwin || dragonfly || freebsd || netbsd || openbsd
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// +build darwin dragonfly freebsd netbsd openbsd
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package routemanager
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import (
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"fmt"
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"net"
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"net/netip"
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"syscall"
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"golang.org/x/net/route"
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)
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// selected BSD Route flags.
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const (
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RTF_UP = 0x1
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RTF_GATEWAY = 0x2
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RTF_HOST = 0x4
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RTF_REJECT = 0x8
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RTF_DYNAMIC = 0x10
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RTF_MODIFIED = 0x20
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RTF_STATIC = 0x800
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RTF_BLACKHOLE = 0x1000
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RTF_LOCAL = 0x200000
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RTF_BROADCAST = 0x400000
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RTF_MULTICAST = 0x800000
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)
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func getRoutesFromTable() ([]netip.Prefix, error) {
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tab, err := route.FetchRIB(syscall.AF_UNSPEC, route.RIBTypeRoute, 0)
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if err != nil {
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return nil, err
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}
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msgs, err := route.ParseRIB(route.RIBTypeRoute, tab)
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if err != nil {
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return nil, err
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}
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var prefixList []netip.Prefix
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for _, msg := range msgs {
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m := msg.(*route.RouteMessage)
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if m.Version < 3 || m.Version > 5 {
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return nil, fmt.Errorf("unexpected RIB message version: %d", m.Version)
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}
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if m.Type != 4 /* RTM_GET */ {
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return nil, fmt.Errorf("unexpected RIB message type: %d", m.Type)
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}
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if m.Flags&RTF_UP == 0 ||
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m.Flags&(RTF_REJECT|RTF_BLACKHOLE) != 0 {
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continue
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}
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addr, ok := toNetIPAddr(m.Addrs[0])
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if !ok {
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continue
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}
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mask, ok := toNetIPMASK(m.Addrs[2])
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if !ok {
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continue
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}
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cidr, _ := mask.Size()
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routePrefix := netip.PrefixFrom(addr, cidr)
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if routePrefix.IsValid() {
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prefixList = append(prefixList, routePrefix)
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}
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}
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return prefixList, nil
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}
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func toNetIPAddr(a route.Addr) (netip.Addr, bool) {
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switch t := a.(type) {
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case *route.Inet4Addr:
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ip := net.IPv4(t.IP[0], t.IP[1], t.IP[2], t.IP[3])
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addr := netip.MustParseAddr(ip.String())
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return addr, true
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default:
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return netip.Addr{}, false
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}
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}
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func toNetIPMASK(a route.Addr) (net.IPMask, bool) {
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switch t := a.(type) {
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case *route.Inet4Addr:
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mask := net.IPv4Mask(t.IP[0], t.IP[1], t.IP[2], t.IP[3])
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return mask, true
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default:
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return nil, false
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}
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}
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