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71029cea2d
This updates all source files to use a new standard header for copyright and license declaration. Notably, copyright no longer includes a date, and we now use the standard SPDX-License-Identifier header. This commit was done almost entirely mechanically with perl, and then some minimal manual fixes. Updates #6865 Signed-off-by: Will Norris <will@tailscale.com>
60 lines
2.0 KiB
Go
60 lines
2.0 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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"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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