ssh: add packetTypeNames map for better debug info

Change-Id: Ie1f58e00982568382e09d8f1dd12bf8a1dc1a9ed
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/171679
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

ssh/messages.go

diff --git a/ssh/messages.go b/ssh/messages.go
index 08d2811..5ec42af 100644
--- a/ssh/messages.go
+++ b/ssh/messages.go
@@ -764,3 +764,29 @@
 	}
 	return msg, nil
 }
+
+var packetTypeNames = map[byte]string{
+	msgDisconnect:          "disconnectMsg",
+	msgServiceRequest:      "serviceRequestMsg",
+	msgServiceAccept:       "serviceAcceptMsg",
+	msgKexInit:             "kexInitMsg",
+	msgKexDHInit:           "kexDHInitMsg",
+	msgKexDHReply:          "kexDHReplyMsg",
+	msgUserAuthRequest:     "userAuthRequestMsg",
+	msgUserAuthSuccess:     "userAuthSuccessMsg",
+	msgUserAuthFailure:     "userAuthFailureMsg",
+	msgUserAuthPubKeyOk:    "userAuthPubKeyOkMsg",
+	msgGlobalRequest:       "globalRequestMsg",
+	msgRequestSuccess:      "globalRequestSuccessMsg",
+	msgRequestFailure:      "globalRequestFailureMsg",
+	msgChannelOpen:         "channelOpenMsg",
+	msgChannelData:         "channelDataMsg",
+	msgChannelOpenConfirm:  "channelOpenConfirmMsg",
+	msgChannelOpenFailure:  "channelOpenFailureMsg",
+	msgChannelWindowAdjust: "windowAdjustMsg",
+	msgChannelEOF:          "channelEOFMsg",
+	msgChannelClose:        "channelCloseMsg",
+	msgChannelRequest:      "channelRequestMsg",
+	msgChannelSuccess:      "channelRequestSuccessMsg",
+	msgChannelFailure:      "channelRequestFailureMsg",
+}