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net/dns/resolver: remove deprecated 4via6 magic-dns formats (#20057)

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This removes deprecated magic-dns formats for 4via6 subnet routers.

These are superseded by the current format: Q-R-S-T-via-X.

Fixes #20053

Change-Id: I0eed1f057f856f248c4dc8ce3b751f6c7edcfbfd

Signed-off-by: Becky Pauley <becky@tailscale.com>
This commit is contained in:
BeckyPauley
2026-06-09 18:10:47 +01:00
committed by GitHub
parent 819f3ba7c1
commit 60b935e30f
2 changed files with 18 additions and 51 deletions
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net/dns/resolver/tsdns.go
+17 -46
View File
@@ -763,23 +763,16 @@ func (r *Resolver) resolveLocal(domain dnsname.FQDN, typ dns.Type) (netip.Addr,
}
// resolveViaDomain synthesizes an IP address for quad-A DNS requests of the form
// `<IPv4-address-with-hypens-instead-of-dots>-via-<siteid>[.*]`. Two prior formats that
// didn't pan out (due to a Chrome issue and DNS search ndots issues) were
// `<IPv4-address>.via-<X>` and the older `via-<X>.<IPv4-address>`,
// where X is a decimal, or hex-encoded number with a '0x' prefix.
// `<IPv4-address-with-hypens-instead-of-dots>-via-<siteid>[.*]`.
// For example: "192-168-1-2-via-7" or "192-168-1-2-via-7.foo.ts.net."
//
// This exists as a convenient mapping into Tailscales 'Via Range'.
//
// It returns a zero netip.Addr and true to indicate a successful response with
// an empty answers section if the specified domain is a valid Tailscale 4via6
// domain, but the request type is neither quad-A nor ALL.
//
// TODO(maisem/bradfitz/tom): `<IPv4-address>.via-<X>` was introduced
// (2022-06-02) to work around an issue in Chrome where it would treat
// "http://via-1.1.2.3.4" as a search string instead of a URL. We should rip out
// the old format in early 2023.
func (r *Resolver) resolveViaDomain(domain dnsname.FQDN, typ dns.Type) (netip.Addr, bool) {
fqdn := string(domain.WithoutTrailingDot())
func (r *Resolver) resolveViaDomain(dnsName dnsname.FQDN, typ dns.Type) (netip.Addr, bool) {
fqdn := string(dnsName.WithoutTrailingDot())
switch typ {
case dns.TypeA, dns.TypeAAAA, dns.TypeALL:
// For Type A requests, we should return a successful response
@@ -793,45 +786,23 @@ func (r *Resolver) resolveViaDomain(domain dnsname.FQDN, typ dns.Type) (netip.Ad
default:
return netip.Addr{}, false
}
if len(fqdn) < len("via-X.0.0.0.0") {
if len(fqdn) < len("0-0-0-0-via-0") {
return netip.Addr{}, false // too short to be valid
}
var siteID string
var ip4Str string
switch {
case strings.Contains(fqdn, "-via-"):
// Format number 3: "192-168-1-2-via-7" or "192-168-1-2-via-7.foo.ts.net."
// Third time's a charm. The earlier two formats follow after this block.
firstLabel, domain, _ := strings.Cut(fqdn, ".") // "192-168-1-2-via-7"
if !(domain == "" || dnsname.HasSuffix(domain, "ts.net") || dnsname.HasSuffix(domain, "tailscale.net")) {
return netip.Addr{}, false
}
v4hyphens, suffix, ok := strings.Cut(firstLabel, "-via-")
if !ok {
return netip.Addr{}, false
}
siteID = suffix
ip4Str = strings.ReplaceAll(v4hyphens, "-", ".")
case strings.HasPrefix(fqdn, "via-"):
firstDot := strings.Index(fqdn, ".")
if firstDot < 0 {
return netip.Addr{}, false // missing dot delimiters
}
siteID = fqdn[len("via-"):firstDot]
ip4Str = fqdn[firstDot+1:]
default:
lastDot := strings.LastIndex(fqdn, ".")
if lastDot < 0 {
return netip.Addr{}, false // missing dot delimiters
}
suffix := fqdn[lastDot+1:]
if !strings.HasPrefix(suffix, "via-") {
return netip.Addr{}, false
}
siteID = suffix[len("via-"):]
ip4Str = fqdn[:lastDot]
if !strings.Contains(fqdn, "-via-") {
return netip.Addr{}, false // not a 4via6 domain
}
firstLabel, domain, _ := strings.Cut(fqdn, ".") // "192-168-1-2-via-7"
if !(domain == "" || dnsname.HasSuffix(domain, "ts.net") || dnsname.HasSuffix(domain, "tailscale.net")) {
return netip.Addr{}, false
}
v4hyphens, suffix, ok := strings.Cut(firstLabel, "-via-")
if !ok {
return netip.Addr{}, false
}
siteID := suffix
ip4Str := strings.ReplaceAll(v4hyphens, "-", ".")
ip4, err := netip.ParseAddr(ip4Str)
if err != nil {
net/dns/resolver/tsdns_test.go
+1 -5
View File
@@ -390,12 +390,8 @@ func TestResolveLocal(t *testing.T) {
{"ns-nxdomain", "test3.ipn.dev.", dns.TypeNS, netip.Addr{}, dns.RCodeNameError},
{"onion-domain", "footest.onion.", dns.TypeA, netip.Addr{}, dns.RCodeNameError},
{"magicdns", dnsSymbolicFQDN, dns.TypeA, netip.MustParseAddr("100.100.100.100"), dns.RCodeSuccess},
{"via_hex", dnsname.FQDN("via-0xff.1.2.3.4."), dns.TypeAAAA, netip.MustParseAddr("fd7a:115c:a1e0:b1a:0:ff:1.2.3.4"), dns.RCodeSuccess},
{"via_dec", dnsname.FQDN("via-1.10.0.0.1."), dns.TypeAAAA, netip.MustParseAddr("fd7a:115c:a1e0:b1a:0:1:10.0.0.1"), dns.RCodeSuccess},
{"x_via_hex", dnsname.FQDN("4.3.2.1.via-0xff."), dns.TypeAAAA, netip.MustParseAddr("fd7a:115c:a1e0:b1a:0:ff:4.3.2.1"), dns.RCodeSuccess},
{"x_via_dec", dnsname.FQDN("1.0.0.10.via-1."), dns.TypeAAAA, netip.MustParseAddr("fd7a:115c:a1e0:b1a:0:1:1.0.0.10"), dns.RCodeSuccess},
{"via_invalid", dnsname.FQDN("via-."), dns.TypeAAAA, netip.Addr{}, dns.RCodeRefused},
{"via_invalid_2", dnsname.FQDN("2.3.4.5.via-."), dns.TypeAAAA, netip.Addr{}, dns.RCodeRefused},
{"via_invalid_2", dnsname.FQDN("2-3-4-5-via-."), dns.TypeAAAA, netip.Addr{}, dns.RCodeRefused},
// Hyphenated 4via6 format.
// Without any suffix domain: