From 61b361bac0c606746eaf051a865a35ab855091a7 Mon Sep 17 00:00:00 2001
From: David Anderson <danderson@tailscale.com>
Date: Sat, 10 Apr 2021 19:37:11 -0700
Subject: [PATCH] net/dns: teach the openresolv manager to read DNS config.
Signed-off-by: David Anderson <danderson@tailscale.com>
---
net/dns/direct.go | 25 +++++++++++++++----------
net/dns/openresolv.go | 22 +++++++++++++++++++++-
2 files changed, 36 insertions(+), 11 deletions(-)
diff --git a/net/dns/direct.go b/net/dns/direct.go
index c58a1907c..6da43bc4a 100644
--- a/net/dns/direct.go
+++ b/net/dns/direct.go
@@ -44,15 +44,8 @@ func writeResolvConf(w io.Writer, servers []netaddr.IP, domains []dnsname.FQDN)
}
}
-func readResolvFile(path string) (OSConfig, error) {
- var config OSConfig
-
- f, err := os.Open(path)
- if err != nil {
- return config, err
- }
-
- scanner := bufio.NewScanner(f)
+func readResolv(r io.Reader) (config OSConfig, err error) {
+ scanner := bufio.NewScanner(r)
for scanner.Scan() {
line := strings.TrimSpace(scanner.Text())
@@ -61,7 +54,7 @@ func readResolvFile(path string) (OSConfig, error) {
nameserver = strings.TrimSpace(nameserver)
ip, err := netaddr.ParseIP(nameserver)
if err != nil {
- return config, err
+ return OSConfig{}, err
}
config.Nameservers = append(config.Nameservers, ip)
continue
@@ -82,6 +75,18 @@ func readResolvFile(path string) (OSConfig, error) {
return config, nil
}
+func readResolvFile(path string) (OSConfig, error) {
+ var config OSConfig
+
+ f, err := os.Open(path)
+ if err != nil {
+ return config, err
+ }
+ defer f.Close()
+
+ return readResolv(f)
+}
+
// readResolvConf reads DNS configuration from /etc/resolv.conf.
func readResolvConf() (OSConfig, error) {
return readResolvFile(resolvConf)
diff --git a/net/dns/openresolv.go b/net/dns/openresolv.go
index 1d7083ec9..855f65dd3 100644
--- a/net/dns/openresolv.go
+++ b/net/dns/openresolv.go
@@ -8,6 +8,7 @@ import (
"bytes"
"fmt"
"os/exec"
+ "strings"
)
// resolvconfIsOpenresolv reports whether the `resolvconf` binary on
@@ -48,7 +49,26 @@ func (m openresolvManager) SupportsSplitDNS() bool {
}
func (m openresolvManager) GetBaseConfig() (OSConfig, error) {
- return OSConfig{}, ErrGetBaseConfigNotSupported
+ bs, err := exec.Command("resolvconf", "-i").CombinedOutput()
+ if err != nil {
+ return OSConfig{}, err
+ }
+
+ args := []string{"-l"}
+ for _, f := range strings.Split(strings.TrimSpace(string(bs)), " ") {
+ if f == "tailscale" {
+ continue
+ }
+ args = append(args, f)
+ }
+
+ var buf bytes.Buffer
+ cmd := exec.Command("resolvconf", args...)
+ cmd.Stdout = &buf
+ if err := cmd.Run(); err != nil {
+ return OSConfig{}, err
+ }
+ return readResolv(&buf)
}
func (m openresolvManager) Close() error {