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130 lines
3.8 KiB
Go
130 lines
3.8 KiB
Go
// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package chirp implements a client to communicate with the BIRD Internet
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// Routing Daemon.
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package chirp
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import (
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"bufio"
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"fmt"
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"net"
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"strings"
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)
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// New creates a BIRDClient.
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func New(socket string) (*BIRDClient, error) {
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conn, err := net.Dial("unix", socket)
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if err != nil {
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return nil, fmt.Errorf("failed to connect to BIRD: %w", err)
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}
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b := &BIRDClient{socket: socket, conn: conn, scanner: bufio.NewScanner(conn)}
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// Read and discard the first line as that is the welcome message.
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if _, err := b.readResponse(); err != nil {
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return nil, err
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}
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return b, nil
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}
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// BIRDClient handles communication with the BIRD Internet Routing Daemon.
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type BIRDClient struct {
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socket string
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conn net.Conn
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scanner *bufio.Scanner
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}
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// Close closes the underlying connection to BIRD.
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func (b *BIRDClient) Close() error { return b.conn.Close() }
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// DisableProtocol disables the provided protocol.
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func (b *BIRDClient) DisableProtocol(protocol string) error {
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out, err := b.exec("disable %s", protocol)
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if err != nil {
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return err
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}
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if strings.Contains(out, fmt.Sprintf("%s: already disabled", protocol)) {
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return nil
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} else if strings.Contains(out, fmt.Sprintf("%s: disabled", protocol)) {
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return nil
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}
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return fmt.Errorf("failed to disable %s: %v", protocol, out)
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}
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// EnableProtocol enables the provided protocol.
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func (b *BIRDClient) EnableProtocol(protocol string) error {
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out, err := b.exec("enable %s", protocol)
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if err != nil {
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return err
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}
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if strings.Contains(out, fmt.Sprintf("%s: already enabled", protocol)) {
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return nil
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} else if strings.Contains(out, fmt.Sprintf("%s: enabled", protocol)) {
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return nil
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}
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return fmt.Errorf("failed to enable %s: %v", protocol, out)
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}
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// BIRD CLI docs from https://bird.network.cz/?get_doc&v=20&f=prog-2.html#ss2.9
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// Each session of the CLI consists of a sequence of request and replies,
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// slightly resembling the FTP and SMTP protocols.
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// Requests are commands encoded as a single line of text,
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// replies are sequences of lines starting with a four-digit code
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// followed by either a space (if it's the last line of the reply) or
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// a minus sign (when the reply is going to continue with the next line),
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// the rest of the line contains a textual message semantics of which depends on the numeric code.
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// If a reply line has the same code as the previous one and it's a continuation line,
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// the whole prefix can be replaced by a single white space character.
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//
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// Reply codes starting with 0 stand for ‘action successfully completed’ messages,
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// 1 means ‘table entry’, 8 ‘runtime error’ and 9 ‘syntax error’.
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func (b *BIRDClient) exec(cmd string, args ...interface{}) (string, error) {
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if _, err := fmt.Fprintf(b.conn, cmd, args...); err != nil {
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return "", err
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}
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fmt.Fprintln(b.conn)
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return b.readResponse()
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}
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// hasResponseCode reports whether the provided byte slice is
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// prefixed with a BIRD response code.
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// Equivalent regex: `^\d{4}[ -]`.
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func hasResponseCode(s []byte) bool {
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if len(s) < 5 {
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return false
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}
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for _, b := range s[:4] {
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if '0' <= b && b <= '9' {
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continue
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}
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return false
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}
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return s[4] == ' ' || s[4] == '-'
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}
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func (b *BIRDClient) readResponse() (string, error) {
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var resp strings.Builder
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var done bool
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for !done {
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if !b.scanner.Scan() {
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return "", fmt.Errorf("reading response from bird failed: %q", resp.String())
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}
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if err := b.scanner.Err(); err != nil {
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return "", err
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}
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out := b.scanner.Bytes()
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if _, err := resp.Write(out); err != nil {
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return "", err
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}
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if hasResponseCode(out) {
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done = out[4] == ' '
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}
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if !done {
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resp.WriteRune('\n')
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}
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}
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return resp.String(), nil
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}
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