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Handle edge cases in interface and routing config #1136

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Handle edge cases in interface and routing config #1136

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27df986
use the default gateway with the lowest metric
czeumer Oct 4, 2023
16658a4
filter out any non routable addresses
czeumer Oct 4, 2023
06fd248
ensure only the first valid and highest prio default gateway is chosen
czeumer Oct 4, 2023
7a18e9d
go fmt change
czeumer Oct 4, 2023
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1 change: 1 addition & 0 deletions routing/other.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
// that can be found in the LICENSE file in the root of the source
// tree.

//go:build !linux
// +build !linux

// Package routing is currently only supported in Linux, but the build system requires a valid go file for all architectures.
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32 changes: 26 additions & 6 deletions routing/routing.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
// that can be found in the LICENSE file in the root of the source
// tree.

//go:build linux
// +build linux

// Package routing provides a very basic but mostly functional implementation of
Expand Down Expand Up @@ -134,8 +135,11 @@ func (r *router) route(routes routeSlice, input net.HardwareAddr, src, dst net.I
if rt.InputIface != 0 && rt.InputIface != inputIndex {
continue
}
// use the default gateway with lowest metric
if rt.Src == nil && rt.Dst == nil {
defaultGateway = rt
if defaultGateway == nil && rt.Gateway != nil {
defaultGateway = rt
}
continue
}
if rt.Src != nil && !rt.Src.Contains(src) {
Expand Down Expand Up @@ -194,19 +198,31 @@ loop:
for _, attr := range attrs {
switch attr.Attr.Type {
case syscall.RTA_DST:
routeInfo.Dst = &net.IPNet{
inet := net.IPNet{
IP: net.IP(attr.Value),
Mask: net.CIDRMask(int(rt.DstLen), len(attr.Value)*8),
}
if inet.IP.IsMulticast() || inet.IP.IsInterfaceLocalMulticast() || inet.IP.IsLinkLocalMulticast() || inet.IP.IsUnspecified() || inet.IP.IsLinkLocalUnicast() {
continue
}
routeInfo.Dst = &inet
case syscall.RTA_SRC:
routeInfo.Src = &net.IPNet{
inet := net.IPNet{
IP: net.IP(attr.Value),
Mask: net.CIDRMask(int(rt.SrcLen), len(attr.Value)*8),
Mask: net.CIDRMask(int(rt.DstLen), len(attr.Value)*8),
}
if inet.IP.IsMulticast() || inet.IP.IsInterfaceLocalMulticast() || inet.IP.IsLinkLocalMulticast() || inet.IP.IsUnspecified() || inet.IP.IsLinkLocalUnicast() {
continue
}
routeInfo.Src = &inet
case syscall.RTA_GATEWAY:
routeInfo.Gateway = net.IP(attr.Value)
case syscall.RTA_PREFSRC:
routeInfo.PrefSrc = net.IP(attr.Value)
ip := net.IP(attr.Value)
if ip.IsLoopback() || ip.IsMulticast() || ip.IsInterfaceLocalMulticast() || ip.IsLinkLocalMulticast() || ip.IsUnspecified() || ip.IsLinkLocalUnicast() {
continue
}
routeInfo.PrefSrc = ip
case syscall.RTA_IIF:
routeInfo.InputIface = *(*uint32)(unsafe.Pointer(&attr.Value[0]))
case syscall.RTA_OIF:
Expand All @@ -231,8 +247,12 @@ loop:
if err != nil {
return nil, err
}
for _, addr := range ifaceAddrs {
for i, addr := range ifaceAddrs {
if inet, ok := addr.(*net.IPNet); ok {
// filter out any non routable addresses
if i < len(ifaceAddrs)-1 && (inet.IP.IsMulticast() || inet.IP.IsInterfaceLocalMulticast() || inet.IP.IsLinkLocalMulticast() || inet.IP.IsUnspecified() || inet.IP.IsLinkLocalUnicast()) {
continue
}
// 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.
Expand Down
3 changes: 3 additions & 0 deletions routing/routing_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
// that can be found in the LICENSE file in the root of the source
// tree.

//go:build linux
// +build linux

package routing
Expand Down Expand Up @@ -533,6 +534,8 @@ func init() {
testRouter.addrs[2] = ipAddrs{v4: net.IPv4(192, 168, 1, 2)}
defaultRoute := &rtInfo{Gateway: net.IPv4(192, 168, 1, 1), InputIface: 0, OutputIface: 2, Priority: 600}
testRouter.v4 = append(testRouter.v4, defaultRoute)
defaultRouteWithHighPriority := &rtInfo{Gateway: net.IPv4(172, 0, 0, 1), InputIface: 0, OutputIface: 2, Priority: 1000}
testRouter.v4 = append(testRouter.v4, defaultRouteWithHighPriority)
// Configure local route
localHW, _ := net.ParseMAC("01:23:45:67:89:ac")
localInterface := net.Interface{Index: 1, MTU: 1500, Name: "Local", HardwareAddr: localHW, Flags: 1}
Expand Down