From c55d26967b1b4646e80a7c1c11700373dc044868 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Thu, 21 Jan 2021 08:05:07 -0800
Subject: [PATCH] wgengine/magicsock: log more details of endpoints learned
 over disco

Also, don't try to use IPv6 LinkLocalUnicast addresses for now. Like endpoints
exchanged with control, we share them but don't yet use them.

Updates #1172
---
 wgengine/magicsock/magicsock.go | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/wgengine/magicsock/magicsock.go b/wgengine/magicsock/magicsock.go
index 9cead1c61..06cf1e0d5 100644
--- a/wgengine/magicsock/magicsock.go
+++ b/wgengine/magicsock/magicsock.go
@@ -1850,7 +1850,10 @@ func (c *Conn) handleDiscoMessage(msg []byte, src netaddr.IPPort) bool {
 			return true
 		}
 		if de != nil {
-			c.logf("magicsock: disco: %v<-%v (%v, %v)  got call-me-maybe", c.discoShort, de.discoShort, de.publicKey.ShortString(), derpStr(src.String()))
+			c.logf("magicsock: disco: %v<-%v (%v, %v)  got call-me-maybe, %d endpoints",
+				c.discoShort, de.discoShort,
+				de.publicKey.ShortString(), derpStr(src.String()),
+				len(dm.MyNumber))
 			go de.handleCallMeMaybe(dm)
 		}
 	}
@@ -3464,14 +3467,35 @@ func (de *discoEndpoint) handleCallMeMaybe(m *disco.CallMeMaybe) {
 	if de.isCallMeMaybeEP == nil {
 		de.isCallMeMaybeEP = map[netaddr.IPPort]bool{}
 	}
+	var newEPs []netaddr.IPPort
 	for _, ep := range m.MyNumber {
+		if ep.IP.Is6() && ep.IP.IsLinkLocalUnicast() {
+			// We send these out, but ignore them for now.
+			// TODO: teach the ping code to ping on all interfaces
+			// for these.
+			continue
+		}
 		de.isCallMeMaybeEP[ep] = true
 		if es, ok := de.endpointState[ep]; ok {
 			es.callMeMaybeTime = now
 		} else {
 			de.endpointState[ep] = &endpointState{callMeMaybeTime: now}
-		}
+			newEPs = append(newEPs, ep)
+		}
+	}
+	if len(newEPs) > 0 {
+		de.c.logf("magicsock: disco: call-me-maybe from %v %v added new endpoints: %v",
+			de.publicKey.ShortString(), de.discoShort,
+			logger.ArgWriter(func(w *bufio.Writer) {
+				for i, ep := range newEPs {
+					if i > 0 {
+						w.WriteString(", ")
+					}
+					w.WriteString(ep.String())
+				}
+			}))
 	}
+
 	// Delete any prior CalllMeMaybe endpoints that weren't included
 	// in this message.
 	for ep, want := range de.isCallMeMaybeEP {