76 lines
2.4 KiB
Go
76 lines
2.4 KiB
Go
package netxlite
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import (
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"errors"
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"net"
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"strings"
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)
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// This file contains weird stuff that we carried over from
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// the original netx implementation and that we cannot remove
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// or change without thinking about the consequences.
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// See https://github.com/ooni/probe/issues/1985
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var errReduceErrorsEmptyList = errors.New("bug: reduceErrors given an empty list")
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// quirkReduceErrors finds a known error in a list of errors since
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// it's probably most relevant. If this error is not found, just
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// return the first error according to this reasoning:
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//
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// If we have a known error, let's consider this the real error
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// since it's probably most relevant. Otherwise let's return the
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// first considering that (1) local resolvers likely will give
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// us IPv4 first and (2) also our resolver does that. So, in case
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// the user has no IPv6 connectivity, an IPv6 error is going to
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// appear later in the list of errors.
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//
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// Honestly, the above reasoning does not feel very solid and
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// we also have an IMPLICIT assumption on our resolver returning
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// IPv4 before IPv6 _which is a really fragile one_. We try to
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// remediate with quirkSortIPAddrs (see below).
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//
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// This is CLEARLY a QUIRK anyway. There may code depending on how
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// we do things here and it's tricky to remove this behavior.
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//
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// See TODO(https://github.com/ooni/probe/issues/1779).
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func quirkReduceErrors(errorslist []error) error {
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if len(errorslist) == 0 {
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// See https://github.com/ooni/probe/issues/1985
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return errReduceErrorsEmptyList
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}
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for _, err := range errorslist {
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var wrapper *ErrWrapper
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if errors.As(err, &wrapper) && !strings.HasPrefix(
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err.Error(), "unknown_failure",
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) {
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return err
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}
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}
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return errorslist[0]
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}
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// quirkSortIPAddrs sorts IP addresses so that IPv4 appears
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// before IPv6. Dialers SHOULD call this code.
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//
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// It saddens me to have this quirk, but it is here to pair
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// with quirkReduceErrors, which assumes that IPv4 addrs
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// appear before IPv6 addrs <facepalm>.
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//
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// Note: this function will skip any input that is not not
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// a valid IPv4 or IPv6 address.
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//
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// See TODO(https://github.com/ooni/probe/issues/1779).
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func quirkSortIPAddrs(addrs []string) (out []string) {
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for _, addr := range addrs {
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if net.ParseIP(addr) != nil && !isIPv6(addr) {
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out = append(out, addr)
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}
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}
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for _, addr := range addrs {
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if net.ParseIP(addr) != nil && isIPv6(addr) {
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out = append(out, addr)
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}
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}
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return
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}
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