| /* |
| * |
| * Copyright 2023 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| |
| // Package internal contains functionality internal to the dns resolver package. |
| package internal |
| |
| import ( |
| "context" |
| "errors" |
| "net" |
| "time" |
| ) |
| |
| // NetResolver groups the methods on net.Resolver that are used by the DNS |
| // resolver implementation. This allows the default net.Resolver instance to be |
| // overidden from tests. |
| type NetResolver interface { |
| LookupHost(ctx context.Context, host string) (addrs []string, err error) |
| LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*net.SRV, err error) |
| LookupTXT(ctx context.Context, name string) (txts []string, err error) |
| } |
| |
| var ( |
| // ErrMissingAddr is the error returned when building a DNS resolver when |
| // the provided target name is empty. |
| ErrMissingAddr = errors.New("dns resolver: missing address") |
| |
| // ErrEndsWithColon is the error returned when building a DNS resolver when |
| // the provided target name ends with a colon that is supposed to be the |
| // separator between host and port. E.g. "::" is a valid address as it is |
| // an IPv6 address (host only) and "[::]:" is invalid as it ends with a |
| // colon as the host and port separator |
| ErrEndsWithColon = errors.New("dns resolver: missing port after port-separator colon") |
| ) |
| |
| // The following vars are overridden from tests. |
| var ( |
| // MinResolutionRate is the minimum rate at which re-resolutions are |
| // allowed. This helps to prevent excessive re-resolution. |
| MinResolutionRate = 30 * time.Second |
| |
| // TimeAfterFunc is used by the DNS resolver to wait for the given duration |
| // to elapse. In non-test code, this is implemented by time.After. In test |
| // code, this can be used to control the amount of time the resolver is |
| // blocked waiting for the duration to elapse. |
| TimeAfterFunc func(time.Duration) <-chan time.Time |
| |
| // NewNetResolver returns the net.Resolver instance for the given target. |
| NewNetResolver func(string) (NetResolver, error) |
| |
| // AddressDialer is the dialer used to dial the DNS server. It accepts the |
| // Host portion of the URL corresponding to the user's dial target and |
| // returns a dial function. |
| AddressDialer func(address string) func(context.Context, string, string) (net.Conn, error) |
| ) |