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tailscale/net/netkernelconf/netkernelconf_linux.go

83 lines
3.2 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package netkernelconf
import (
"fmt"
"github.com/safchain/ethtool"
)
const (
rxWantFeature = "rx-udp-gro-forwarding"
rxDoNotWantFeature = "rx-gro-list"
txFeature = "tx-udp-segmentation"
)
// CheckUDPGROForwarding checks if the machine is optimally configured to
// forward UDP packets between the default route and Tailscale TUN interfaces.
// It returns a non-nil warn in the case that the configuration is suboptimal.
// It returns a non-nil err in the case that an error is encountered while
// performing the check.
func CheckUDPGROForwarding(tunInterface, defaultRouteInterface string) (warn, err error) {
const kbLink = "\nSee https://tailscale.com/s/ethtool-config-udp-gro"
errWithPrefix := func(format string, a ...any) error {
const errPrefix = "couldn't check system's UDP GRO forwarding configuration, "
return fmt.Errorf(errPrefix+format, a...)
}
e, err := ethtool.NewEthtool()
if err != nil {
return nil, errWithPrefix("failed to init ethtool: %v", err)
}
defer e.Close()
tunFeatures, err := e.Features(tunInterface)
if err != nil {
return nil, errWithPrefix("failed to retrieve TUN device features: %v", err)
}
if !tunFeatures[txFeature] {
// if txFeature is disabled/nonexistent on the TUN then UDP GRO
// forwarding doesn't matter, we won't be taking advantage of it.
return nil, nil
}
defaultFeatures, err := e.Features(defaultRouteInterface)
if err != nil {
return nil, errWithPrefix("failed to retrieve default route interface features: %v", err)
}
defaultHasRxWant, ok := defaultFeatures[rxWantFeature]
if !ok {
// unlikely the feature is nonexistant with txFeature in the TUN driver
// being added to the kernel later than rxWantFeature, but let's be sure
return nil, nil
}
if !defaultHasRxWant || defaultFeatures[rxDoNotWantFeature] {
return fmt.Errorf("UDP GRO forwarding is suboptimally configured on %s, UDP forwarding throughput capability will increase with a configuration change.%s", defaultRouteInterface, kbLink), nil
}
return nil, nil
}
// SetUDPGROForwarding enables UDP GRO forwarding for the provided default
// interface. It validates if the provided tun interface has UDP segmentation
// enabled and, if not, returns an error. See
// https://tailscale.com/kb/1320/performance-best-practices#linux-optimizations-for-subnet-routers-and-exit-nodes
func SetUDPGROForwarding(tunInterface, defaultInterface string) error {
e, err := ethtool.NewEthtool()
if err != nil {
return fmt.Errorf("failed to init ethtool: %w", err)
}
defer e.Close()
tunFeatures, err := e.Features(tunInterface)
if err != nil {
return fmt.Errorf("failed to retrieve TUN device features: %w", err)
}
if !tunFeatures[txFeature] {
// if txFeature is disabled/nonexistent on the TUN then UDP GRO
// forwarding doesn't matter, we won't be taking advantage of it.
return fmt.Errorf("Not enabling UDP GRO forwarding as UDP segmentation is disabled for Tailscale interface")
}
if err := e.Change(defaultInterface, map[string]bool{rxWantFeature: true, rxDoNotWantFeature: false}); err != nil {
return fmt.Errorf("error enabling UDP GRO forwarding: %w", err)
}
return nil
}