TheArchive/tailscale
1
0
Fork 0
mirror of https://github.com/tailscale/tailscale.git synced 2024-11-29 04:55:31 +00:00
Code Issues Packages Projects Releases Wiki Activity

net/dns: on windows, skip site-local v6 resolvers.

Browse Source 
Further refinement for tailscale/corp#1662.

Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson 2021-04-27 18:24:03 -07:00
parent 8554694616
commit 44c2b7dc79
1 changed files with 45 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
net/dns/manager_windows.go
View File

@ -8,6 +8,7 @@
"errors"
"fmt"
"os/exec"
"sort"
"strings"
"syscall"
"time"
@ -343,10 +344,11 @@ func (m windowsManager) getBasePrimaryResolver() (resolvers []netaddr.IP, err er
return nil, err
}
var (
primary winipcfg.LUID
best = ^uint32(0)
)
type candidate struct {
id winipcfg.LUID
metric uint32
}
var candidates []candidate
for _, row := range ifrows {
if !row.Connected {
continue
@ -354,29 +356,57 @@ func (m windowsManager) getBasePrimaryResolver() (resolvers []netaddr.IP, err er
if row.InterfaceLUID == tsLUID {
continue
}
if row.Metric < best {
primary = row.InterfaceLUID
best = row.Metric
candidates = append(candidates, candidate{row.InterfaceLUID, row.Metric})
}
}
if primary == 0 {
if len(candidates) == 0 {
// No resolvers set outside of Tailscale.
return nil, nil
}
ips, err := primary.DNS()
sort.Slice(candidates, func(i, j int) bool { return candidates[i].metric < candidates[j].metric })
for _, candidate := range candidates {
ips, err := candidate.id.DNS()
if err != nil {
return nil, err
}
ipLoop:
for _, stdip := range ips {
if ip, ok := netaddr.FromStdIP(stdip); ok {
ip, ok := netaddr.FromStdIP(stdip)
if !ok {
continue
}
// Skip IPv6 site-local resolvers. These are an ancient
// and obsolete IPv6 RFC, which Windows still faithfully
// implements. The net result is that some low-metric
// interfaces can "have" DNS resolvers, but they're just
// site-local resolver IPs that don't go anywhere. So, we
// skip the site-local resolvers in order to find the
// first interface that has real DNS servers configured.
for _, sl := range siteLocalResolvers {
if ip.WithZone("") == sl {
continue ipLoop
}
}
resolvers = append(resolvers, ip)
}
if len(resolvers) > 0 {
// Found some resolvers, we're done.
break
}
}
return resolvers, nil
}
var siteLocalResolvers = []netaddr.IP{
netaddr.MustParseIP("fec0:0:0:ffff::1"),
netaddr.MustParseIP("fec0:0:0:ffff::2"),
netaddr.MustParseIP("fec0:0:0:ffff::3"),
}
func isWindows7() bool {
key, err := registry.OpenKey(registry.LOCAL_MACHINE, versionKey, registry.READ)
if err != nil {