Add warnings when using SigType fallbacks

txi2p/sam/session.py

@@ -1,8 +1,10 @@
 # Copyright (c) str4d <str4d@mail.i2p>
 # See COPYING for details.
+from __future__ import print_function
 
 import os
 from parsley import makeProtocol
+import sys
 from twisted.internet import defer, error
 from twisted.python import failure, log
 
@@ -12,6 +14,10 @@
 from txi2p.sam.base import cmpSAM, SAMSender, SAMReceiver, SAMFactory
 
 
+def eprint(*args, **kwargs):
+    print(*args, file=sys.stderr, **kwargs)
+
+
 class SessionCreateSender(SAMSender):
     def sendSessionCreate(self, samVersion, style, id, privKey=None, localPort=None, options={}, sigType=None):
         msg = 'SESSION CREATE'
@@ -52,6 +58,7 @@ def create(self, result, destination=None, message=None):
                     message.startswith('SIGNATURE_TYPE') and \
                     not self.factory.sigType:
                 fallback = 'ECDSA_SHA256_P256' in message and 'DSA_SHA1' or 'ECDSA_SHA256_P256'
+                eprint('Warning: %s, falling back to %s' % (message, fallback))
                 self.sender.sendSessionCreate(
                     self.factory.samVersion,
                     self.factory.style,
@@ -76,7 +83,7 @@ def postLookup(self, dest):
             try:
                 self.sender.transport.setTcpKeepAlive(1)
             except AttributeError as e:
-                print e
+                eprint(e)
         self.factory.sessionCreated(self, dest)
 
 
@@ -274,6 +281,7 @@ def destGenerated(self, result=None, pub=None, priv=None, message=None):
                     message.startswith('SIGNATURE_TYPE') and \
                     not self.factory.sigType:
                 fallback = 'ECDSA_SHA256_P256' in message and 'DSA_SHA1' or 'ECDSA_SHA256_P256'
+                eprint('Warning: %s, falling back to %s' % (message, fallback))
                 self.sender.sendDestGenerate(
                     self.factory.samVersion,
                     fallback)