net/dns/resolvd: store nameservers

qbit · bradfitz · commit 59a1b849f002 · 2022-01-20T08:12:22.000-08:00
Currently only search domains are stored. This was an oversight (under?) on my part. As things are now, when MagicDNS is on and "Override local DNS" is off, the dns forwarder has to timeout before names resolve. This introduces a pretty annoying lang that makes everything feel extremely slow. You will also see an error: "upstream nameservers not set". I tested with "Override local DNS" on and off. In both situations things seem to function as expected (and quickly). Signed-off-by: Aaron Bieber <aaron@bolddaemon.com> (cherry picked from commit 411c6c3)
diff --git a/net/dns/resolvd.go b/net/dns/resolvd.go
@@ -16,6 +16,7 @@ import (
 	"regexp"
 	"strings"
 
+	"inet.af/netaddr"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/dnsname"
 )
@@ -130,6 +131,25 @@ func (m resolvdManager) readResolvConf() (config OSConfig, err error) {
 			config.SearchDomains = append(config.SearchDomains, fqdn)
 			continue
 		}
+
+		if strings.HasPrefix(line, "nameserver") {
+			s := strings.TrimPrefix(line, "nameserver")
+			parts := strings.Split(s, " # ")
+			if len(parts) == 0 {
+				return OSConfig{}, err
+			}
+			nameserver := strings.TrimSpace(parts[0])
+			ip, err := netaddr.ParseIP(nameserver)
+			if err != nil {
+				return OSConfig{}, err
+			}
+			config.Nameservers = append(config.Nameservers, ip)
+			continue
+		}
+	}
+
+	if err = scanner.Err(); err != nil {
+		return OSConfig{}, err
 	}
 
 	return config, nil
