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ipn/ipnlocal: return early, outdent a bunch in dnsConfigForNetmap

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Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2021-09-07 14:56:45 -07:00
parent 2bb0eb5f7e
commit 30a614f9b9
1 changed files with 68 additions and 65 deletions
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133
ipn/ipnlocal/local.go
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@ -1838,74 +1838,77 @@ func dnsConfigForNetmap(nm *netmap.NetworkMap, prefs *ipn.Prefs, logf logger.Log
dcfg.Hosts[fqdn] = append(dcfg.Hosts[fqdn], ip)
}
if prefs.CorpDNS {
addDefault := func(resolvers []dnstype.Resolver) {
for _, r := range resolvers {
dcfg.DefaultResolvers = append(dcfg.DefaultResolvers, normalizeResolver(r))
}
}
if !prefs.CorpDNS {
return dcfg
}
addDefault(nm.DNS.Resolvers)
for suffix, resolvers := range nm.DNS.Routes {
fqdn, err := dnsname.ToFQDN(suffix)
if err != nil {
logf("[unexpected] non-FQDN route suffix %q", suffix)
}
// Create map entry even if len(resolvers) == 0; Issue 2706.
// This lets the control plane send ExtraRecords for which we
// can authoritatively answer "name not exists" for when the
// control plane also sends this explicit but empty route
// making it as something we handle.
//
// While we're already populating it, might as well size the
// slice appropriately.
dcfg.Routes[fqdn] = make([]dnstype.Resolver, 0, len(resolvers))
for _, r := range resolvers {
dcfg.Routes[fqdn] = append(dcfg.Routes[fqdn], normalizeResolver(r))
}
}
for _, dom := range nm.DNS.Domains {
fqdn, err := dnsname.ToFQDN(dom)
if err != nil {
logf("[unexpected] non-FQDN search domain %q", dom)
}
dcfg.SearchDomains = append(dcfg.SearchDomains, fqdn)
}
if nm.DNS.Proxied { // actually means "enable MagicDNS"
for _, dom := range magicDNSRootDomains(nm) {
dcfg.Routes[dom] = nil // resolve internally with dcfg.Hosts
}
}
// Set FallbackResolvers as the default resolvers in the
// scenarios that can't handle a purely split-DNS config. See
// https://github.com/tailscale/tailscale/issues/1743 for
// details.
switch {
case len(dcfg.DefaultResolvers) != 0:
// Default resolvers already set.
case !prefs.ExitNodeID.IsZero():
// When using exit nodes, it's very likely the LAN
// resolvers will become unreachable. So, force use of the
// fallback resolvers until we implement DNS forwarding to
// exit nodes.
//
// This is especially important on Apple OSes, where
// adding the default route to the tunnel interface makes
// it "primary", and we MUST provide VPN-sourced DNS
// settings or we break all DNS resolution.
//
// https://github.com/tailscale/tailscale/issues/1713
addDefault(nm.DNS.FallbackResolvers)
case len(dcfg.Routes) == 0:
// No settings requiring split DNS, no problem.
case version.OS() == "android":
// We don't support split DNS at all on Android yet.
addDefault(nm.DNS.FallbackResolvers)
addDefault := func(resolvers []dnstype.Resolver) {
for _, r := range resolvers {
dcfg.DefaultResolvers = append(dcfg.DefaultResolvers, normalizeResolver(r))
}
}
addDefault(nm.DNS.Resolvers)
for suffix, resolvers := range nm.DNS.Routes {
fqdn, err := dnsname.ToFQDN(suffix)
if err != nil {
logf("[unexpected] non-FQDN route suffix %q", suffix)
}
// Create map entry even if len(resolvers) == 0; Issue 2706.
// This lets the control plane send ExtraRecords for which we
// can authoritatively answer "name not exists" for when the
// control plane also sends this explicit but empty route
// making it as something we handle.
//
// While we're already populating it, might as well size the
// slice appropriately.
dcfg.Routes[fqdn] = make([]dnstype.Resolver, 0, len(resolvers))
for _, r := range resolvers {
dcfg.Routes[fqdn] = append(dcfg.Routes[fqdn], normalizeResolver(r))
}
}
for _, dom := range nm.DNS.Domains {
fqdn, err := dnsname.ToFQDN(dom)
if err != nil {
logf("[unexpected] non-FQDN search domain %q", dom)
}
dcfg.SearchDomains = append(dcfg.SearchDomains, fqdn)
}
if nm.DNS.Proxied { // actually means "enable MagicDNS"
for _, dom := range magicDNSRootDomains(nm) {
dcfg.Routes[dom] = nil // resolve internally with dcfg.Hosts
}
}
// Set FallbackResolvers as the default resolvers in the
// scenarios that can't handle a purely split-DNS config. See
// https://github.com/tailscale/tailscale/issues/1743 for
// details.
switch {
case len(dcfg.DefaultResolvers) != 0:
// Default resolvers already set.
case !prefs.ExitNodeID.IsZero():
// When using exit nodes, it's very likely the LAN
// resolvers will become unreachable. So, force use of the
// fallback resolvers until we implement DNS forwarding to
// exit nodes.
//
// This is especially important on Apple OSes, where
// adding the default route to the tunnel interface makes
// it "primary", and we MUST provide VPN-sourced DNS
// settings or we break all DNS resolution.
//
// https://github.com/tailscale/tailscale/issues/1713
addDefault(nm.DNS.FallbackResolvers)
case len(dcfg.Routes) == 0:
// No settings requiring split DNS, no problem.
case version.OS() == "android":
// We don't support split DNS at all on Android yet.
addDefault(nm.DNS.FallbackResolvers)
}
return dcfg
}