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interfaces: check correct error /proc/net/route

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wrap io.EOF if we hit https://github.com/google/gvisor/issues/5732
Check for the correct err.

Signed-off-by: Denton Gentry <dgentry@tailscale.com>
This commit is contained in:
Denton Gentry 2021-03-30 16:39:20 -07:00 committed by Denton Gentry
parent 47363c95b0
commit 09148c07ba
1 changed files with 6 additions and 4 deletions
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10
net/interfaces/interfaces_linux.go
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@ -8,6 +8,7 @@ import (
"bufio" "bufio"
"bytes" "bytes"
"errors" "errors"
"fmt"
"io" "io"
"log" "log"
"os" "os"
@ -148,7 +149,7 @@ func defaultRouteInterfaceProcNetInternal(bufsize int) (string, error) {
for { for {
line, err := br.ReadSlice('\n') line, err := br.ReadSlice('\n')
if err == io.EOF { if err == io.EOF {
break return "", fmt.Errorf("no default routes found: %w", err)
} }
if err != nil { if err != nil {
return "", err return "", err
@ -170,13 +171,14 @@ func defaultRouteInterfaceProcNetInternal(bufsize int) (string, error) {
return ifc, nil // interface name return ifc, nil // interface name
} }
} }
return "", errors.New("no default routes found")
} }
// returns string interface name and an error.
// io.EOF: full route table processed, no default route found.
// other io error: something went wrong reading the route file.
func defaultRouteInterfaceProcNet() (string, error) { func defaultRouteInterfaceProcNet() (string, error) {
rc, err := defaultRouteInterfaceProcNetInternal(128) rc, err := defaultRouteInterfaceProcNetInternal(128)
if rc == "" && (err == io.EOF || err == nil) { if rc == "" && (errors.Is(err, io.EOF) || err == nil) {
// https://github.com/google/gvisor/issues/5732 // https://github.com/google/gvisor/issues/5732
// On a regular Linux kernel you can read the first 128 bytes of /proc/net/route, // On a regular Linux kernel you can read the first 128 bytes of /proc/net/route,
// then come back later to read the next 128 bytes and so on. // then come back later to read the next 128 bytes and so on.