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net/dns/resolver, net/tsaddr: fix reverse lookups in 4to6 IP range

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Fixes #4439

Signed-off-by: Tom DNetto <tom@tailscale.com>
This commit is contained in:
Tom DNetto
2022-04-20 14:35:20 -07:00
committed by Tom
parent 8d6793fd70
commit df26c63793
3 changed files with 29 additions and 2 deletions
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18
net/dns/resolver/tsdns.go
View File

@@ -725,6 +725,22 @@ func (r *Resolver) resolveLocalReverse(name dnsname.FQDN) (dnsname.FQDN, dns.RCo
return "", dns.RCodeRefused
}
r.mu.Lock()
defer r.mu.Unlock()
// If the requested IP is part of the IPv6 4-to-6 range, it might
// correspond to an IPv4 address (assuming IPv4 is enabled).
if ip4, ok := tsaddr.Tailscale6to4(ip); ok {
fqdn, code := r.fqdnForIPLocked(ip4, name)
if code == dns.RCodeSuccess {
return fqdn, code
}
}
return r.fqdnForIPLocked(ip, name)
}
// r.mu must be held.
func (r *Resolver) fqdnForIPLocked(ip netaddr.IP, name dnsname.FQDN) (dnsname.FQDN, dns.RCode) {
// If someone curiously does a reverse lookup on the DNS IP, we
// return a domain that helps indicate that Tailscale is using
// this IP for a special purpose and it is not a node on their
@@ -733,8 +749,6 @@ func (r *Resolver) resolveLocalReverse(name dnsname.FQDN) (dnsname.FQDN, dns.RCo
return dnsSymbolicFQDN, dns.RCodeSuccess
}
r.mu.Lock()
defer r.mu.Unlock()
ret, ok := r.ipToHost[ip]
if !ok {
for _, suffix := range r.localDomains {

1
net/dns/resolver/tsdns_test.go
View File

@@ -382,6 +382,7 @@ func TestResolveLocalReverse(t *testing.T) {
{"ipv6_nxdomain", dnsname.FQDN("0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.ip6.arpa."), "", dns.RCodeNameError},
{"nxdomain", dnsname.FQDN("2.3.4.5.in-addr.arpa."), "", dns.RCodeRefused},
{"magicdns", dnsname.FQDN("100.100.100.100.in-addr.arpa."), dnsSymbolicFQDN, dns.RCodeSuccess},
{"ipv6_4to6", dnsname.FQDN("4.6.4.6.4.6.2.6.6.9.d.c.3.4.8.4.2.1.b.a.0.e.1.a.c.5.1.1.a.7.d.f.ip6.arpa."), dnsSymbolicFQDN, dns.RCodeSuccess},
}
for _, tt := range tests {