From 34ae479b3e7f67ee80fc58880e7192f5c6f8e4ce Mon Sep 17 00:00:00 2001
From: Lars Ekman <lars.g.ekman@est.tech>
Date: Fri, 9 Nov 2018 10:41:23 +0100
Subject: [PATCH] Generate a router-id from a hash on the hostname as fallback

This may be necessary in a true ipv6-only cluster.
---
 internal/bgp/bgp.go       | 26 ++++++++++++++++----------
 speaker/bgp_controller.go |  6 +++---
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/internal/bgp/bgp.go b/internal/bgp/bgp.go
index 5f75cbf5705..965f46efe98 100644
--- a/internal/bgp/bgp.go
+++ b/internal/bgp/bgp.go
@@ -1,10 +1,12 @@
 package bgp // import "go.universe.tf/metallb/internal/bgp"
 
 import (
+	"bytes"
 	"context"
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"hash/crc32"
 	"io"
 	"io/ioutil"
 	"net"
@@ -25,6 +27,7 @@ var errClosed = errors.New("session closed")
 type Session struct {
 	asn      uint32
 	routerID net.IP // May be nil, meaning "derive from context"
+	myNode   string
 	addr     string
 	peerASN  uint32
 	holdTime time.Duration
@@ -184,11 +187,7 @@ func (s *Session) connect() error {
 
 	routerID := s.routerID
 	if routerID == nil {
-		routerID = getRouterID(s.defaultNextHop)
-		if routerID == nil {
-			conn.Close()
-			return fmt.Errorf("cannot automatically derive router ID for IPv6 connection to %q", s.addr)
-		}
+		routerID = getRouterID(s.defaultNextHop, s.myNode)
 	}
 
 	if err = sendOpen(conn, s.asn, routerID, s.holdTime); err != nil {
@@ -235,16 +234,22 @@ func (s *Session) connect() error {
 	return nil
 }
 
+func hashRouterId(hostname string) net.IP {
+	buf := new(bytes.Buffer)
+	binary.Write(buf, binary.LittleEndian, crc32.ChecksumIEEE([]byte(hostname)))
+	return net.IP(buf.Bytes())
+}
+
 // Ipv4; Use the address as-is.
 // Ipv6; Pick the first ipv4 address on the same interface as the address
-func getRouterID(addr net.IP) net.IP {
+func getRouterID(addr net.IP, myNode string) net.IP {
 	if addr.To4() != nil {
 		return addr
 	}
 
 	ifaces, err := net.Interfaces()
 	if err != nil {
-		return nil
+		return hashRouterId(myNode)
 	}
 	for _, i := range ifaces {
 		addrs, err := i.Addrs()
@@ -274,12 +279,12 @@ func getRouterID(addr net.IP) net.IP {
 					if ip.To4() != nil {
 						return ip
 					}
-					return nil
 				}
+				return hashRouterId(myNode)
 			}
 		}
 	}
-	return nil
+	return hashRouterId(myNode)
 }
 
 // sendKeepalives sends BGP KEEPALIVE packets at the negotiated rate
@@ -339,11 +344,12 @@ func (s *Session) sendKeepalive() error {
 //
 // The session will immediately try to connect and synchronize its
 // local state with the peer.
-func New(l log.Logger, addr string, asn uint32, routerID net.IP, peerASN uint32, holdTime time.Duration, password string) (*Session, error) {
+func New(l log.Logger, addr string, asn uint32, routerID net.IP, peerASN uint32, holdTime time.Duration, password string, myNode string) (*Session, error) {
 	ret := &Session{
 		addr:        addr,
 		asn:         asn,
 		routerID:    routerID.To4(),
+		myNode:      myNode,
 		peerASN:     peerASN,
 		holdTime:    holdTime,
 		logger:      log.With(l, "peer", addr, "localASN", asn, "peerASN", peerASN),
diff --git a/speaker/bgp_controller.go b/speaker/bgp_controller.go
index 306a0e3fac1..ddd86c42f23 100644
--- a/speaker/bgp_controller.go
+++ b/speaker/bgp_controller.go
@@ -184,7 +184,7 @@ func (c *bgpController) syncPeers(l log.Logger) error {
 			if p.cfg.RouterID != nil {
 				routerID = p.cfg.RouterID
 			}
-			s, err := newBGP(c.logger, net.JoinHostPort(p.cfg.Addr.String(), strconv.Itoa(int(p.cfg.Port))), p.cfg.MyASN, routerID, p.cfg.ASN, p.cfg.HoldTime, p.cfg.Password)
+			s, err := newBGP(c.logger, net.JoinHostPort(p.cfg.Addr.String(), strconv.Itoa(int(p.cfg.Port))), p.cfg.MyASN, routerID, p.cfg.ASN, p.cfg.HoldTime, p.cfg.Password, c.myNode)
 			if err != nil {
 				l.Log("op", "syncPeers", "error", err, "peer", p.cfg.Addr, "msg", "failed to create BGP session")
 				errs++
@@ -286,6 +286,6 @@ func (c *bgpController) SetNode(l log.Logger, node *v1.Node) error {
 	return c.syncPeers(l)
 }
 
-var newBGP = func(logger log.Logger, addr string, myASN uint32, routerID net.IP, asn uint32, hold time.Duration, password string) (session, error) {
-	return bgp.New(logger, addr, myASN, routerID, asn, hold, password)
+var newBGP = func(logger log.Logger, addr string, myASN uint32, routerID net.IP, asn uint32, hold time.Duration, password string, myNode string) (session, error) {
+	return bgp.New(logger, addr, myASN, routerID, asn, hold, password, myNode)
 }