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cmd/lopower: set ultimate fallback DNS servers

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Change-Id: I044d6c7b9dc4b874f3c60d2c6ce2105bafc00639
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2024-11-03 14:21:57 -08:00
parent 44570dabda
commit 510f0745ea
2 changed files with 34 additions and 3 deletions
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18
cmd/lopower/lopower.go
View File

@ -50,6 +50,7 @@
"tailscale.com/net/tsaddr"
"tailscale.com/syncs"
"tailscale.com/tsnet"
"tailscale.com/types/dnstype"
"tailscale.com/types/ipproto"
"tailscale.com/types/key"
"tailscale.com/types/logger"
@ -638,7 +639,22 @@ func (lp *lpServer) startTSNet(ctx context.Context) {
}
lp.tsnet = ts
ts.PreStart = func() error {
ts.Sys().DNSManager.Get().SetForceAAAA(true)
dnsMgr := ts.Sys().DNSManager.Get()
dnsMgr.SetForceAAAA(true)
// Force fallback resolvers to Google and Cloudflare as an ultimate
// fallback in case the Tailnet DNS servers are not set/forced. Normally
// tailscaled would resort to using the OS DNS resolvers, but
// tsnet/userspace binaries don't do that (yet?), so this is the
// "Opionated" part of the "LOPOWER" name. The opinion is just using
// big providers known to work. (Normally stock tailscaled never
// makes such opinions and never defaults to any big provider, unless
// you're already running on that big provider's network so have
// already indicated you're fine with them.))
dnsMgr.SetForceFallbackResolvers([]*dnstype.Resolver{
{Addr: "8.8.8.8"},
{Addr: "1.1.1.1"},
})
return nil
}

19
net/dns/manager.go
View File

@ -63,8 +63,9 @@ type Manager struct {
mu sync.Mutex // guards following
// config is the last configuration we successfully compiled or nil if there
// was any failure applying the last configuration.
config *Config
forceAAAA bool // whether client wants MagicDNS AAAA even if unsure of host's IPv6 status
config *Config
forceAAAA bool // whether client wants MagicDNS AAAA even if unsure of host's IPv6 status
forceFallbackResolvers []*dnstype.Resolver
}
// NewManagers created a new manager from the given config.
@ -141,6 +142,16 @@ func (m *Manager) SetForceAAAA(v bool) {
m.forceAAAA = v
}
// SetForceFallbackResolvers sets the resolvers to use to override
// the fallback resolvers if the control plane doesn't send any.
//
// It takes ownership of the provided slice.
func (m *Manager) SetForceFallbackResolvers(resolvers []*dnstype.Resolver) {
m.mu.Lock()
defer m.mu.Unlock()
m.forceFallbackResolvers = resolvers
}
// setLocked sets the DNS configuration.
//
// m.mu must be held.
@ -159,6 +170,10 @@ func (m *Manager) setLocked(cfg Config) error {
return err
}
if _, ok := rcfg.Routes["."]; !ok && len(m.forceFallbackResolvers) > 0 {
rcfg.Routes["."] = m.forceFallbackResolvers
}
m.logf("Resolvercfg: %v", logger.ArgWriter(func(w *bufio.Writer) {
rcfg.WriteToBufioWriter(w)
}))