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f475e5550c
This commit implements UDP offloading for Linux. GSO size is passed to and from the kernel via socket control messages. Support is probed at runtime. UDP GSO is dependent on checksum offload support on the egress netdev. UDP GSO will be disabled in the event sendmmsg() returns EIO, which is a strong signal that the egress netdev does not support checksum offload. Updates tailscale/corp#8734 Signed-off-by: Jordan Whited <jordan@tailscale.com>
83 lines
2.5 KiB
Go
83 lines
2.5 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package neterror classifies network errors.
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package neterror
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import (
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"errors"
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"fmt"
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"runtime"
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"syscall"
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)
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var errEPERM error = syscall.EPERM // box it into interface just once
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// TreatAsLostUDP reports whether err is an error from a UDP send
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// operation that should be treated as a UDP packet that just got
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// lost.
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//
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// Notably, on Linux this reports true for EPERM errors (from outbound
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// firewall blocks) which aren't really send errors; they're just
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// sends that are never going to make it because the local OS blocked
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// it.
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func TreatAsLostUDP(err error) bool {
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if err == nil {
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return false
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}
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switch runtime.GOOS {
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case "linux":
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// Linux, while not documented in the man page,
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// returns EPERM when there's an OUTPUT rule with -j
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// DROP or -j REJECT. We use this very specific
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// Linux+EPERM check rather than something super broad
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// like net.Error.Temporary which could be anything.
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//
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// For now we only do this on Linux, as such outgoing
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// firewall violations mapping to syscall errors
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// hasn't yet been observed on other OSes.
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return errors.Is(err, errEPERM)
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}
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return false
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}
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var packetWasTruncated func(error) bool // non-nil on Windows at least
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// PacketWasTruncated reports whether err indicates truncation but the RecvFrom
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// that generated err was otherwise successful. On Windows, Go's UDP RecvFrom
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// calls WSARecvFrom which returns the WSAEMSGSIZE error code when the received
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// datagram is larger than the provided buffer. When that happens, both a valid
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// size and an error are returned (as per the partial fix for golang/go#14074).
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// If the WSAEMSGSIZE error is returned, then we ignore the error to get
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// semantics similar to the POSIX operating systems. One caveat is that it
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// appears that the source address is not returned when WSAEMSGSIZE occurs, but
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// we do not currently look at the source address.
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func PacketWasTruncated(err error) bool {
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if packetWasTruncated == nil {
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return false
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}
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return packetWasTruncated(err)
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}
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var shouldDisableUDPGSO func(error) bool // non-nil on Linux
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func ShouldDisableUDPGSO(err error) bool {
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if shouldDisableUDPGSO == nil {
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return false
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}
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return shouldDisableUDPGSO(err)
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}
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type ErrUDPGSODisabled struct {
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OnLaddr string
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RetryErr error
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}
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func (e ErrUDPGSODisabled) Error() string {
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return fmt.Sprintf("disabled UDP GSO on %s, NIC(s) may not support checksum offload", e.OnLaddr)
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}
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func (e ErrUDPGSODisabled) Unwrap() error {
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return e.RetryErr
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}
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