From 90c59eda68e10d5fee97d2e523198a64a0a94b24 Mon Sep 17 00:00:00 2001
From: Pierre LALET <pierre.lalet@cea.fr>
Date: Sun, 27 Aug 2017 02:14:11 +0200
Subject: [PATCH] bridge_and_sniff(): introduce packet transformation functions
---
scapy/sendrecv.py | 39 +++++++++++++++++++++++++++++++++++----
1 file changed, 35 insertions(+), 4 deletions(-)
diff --git a/scapy/sendrecv.py b/scapy/sendrecv.py
index 5258a21c..12cb6654 100644
--- a/scapy/sendrecv.py
+++ b/scapy/sendrecv.py
@@ -735,7 +735,8 @@ Examples:
@conf.commands.register
-def bridge_and_sniff(if1, if2, prn=None, L2socket=None, *args, **kargs):
+def bridge_and_sniff(if1, if2, xfrm12=None, xfrm21=None, prn=None, L2socket=None,
+ *args, **kargs):
"""Forward traffic between interfaces if1 and if2, sniff and return
the exchanged packets.
@@ -743,8 +744,16 @@ Arguments:
if1, if2: the interfaces to use (interface names or opened sockets).
+ xfrm12: a function to call when forwarding a packet from if1 to
+ if2. If it returns True, the packet is forwarded as it. If it
+ returns False or None, the packet is discarded. If it returns a
+ packet, this packet is forwarded instead of the original packet
+ one.
+
+ xfrm21: same as xfrm12 for packets forwarded from if2 to if1.
+
The other arguments are the same than for the function sniff(),
- except for opened_socket, offline and iface that are ignored.
+ except for offline, opened_socket and iface that are ignored.
See help(sniff) for more.
"""
@@ -761,15 +770,37 @@ Arguments:
sckt1, if1 = _init_socket(if1, 1)
sckt2, if2 = _init_socket(if2, 2)
peers = {if1: sckt2, if2: sckt1}
+ xfrms = {}
+ if xfrm12 is not None:
+ xfrms[if1] = xfrm12
+ if xfrm21 is not None:
+ xfrms[if2] = xfrm21
def prn_send(pkt):
try:
sendsock = peers[pkt.sniffed_on]
except KeyError:
return
+ if pkt.sniffed_on in xfrms:
+ try:
+ newpkt = xfrms[pkt.sniffed_on](pkt)
+ except:
+ log_runtime.warning(
+ 'Exception in transformation function for packet [%s] '
+ 'received on %s -- dropping',
+ pkt.summary(), pkt.sniffed_on, exc_info=True
+ )
+ return
+ else:
+ if newpkt is True:
+ newpkt = pkt.original
+ elif not newpkt:
+ return
+ else:
+ newpkt = pkt.original
try:
- sendsock.send(pkt.original)
+ sendsock.send(newpkt)
except:
- log_runtime.warning('Cannot forward packet [%s] received from %s',
+ log_runtime.warning('Cannot forward packet [%s] received on %s',
pkt.summary(), pkt.sniffed_on, exc_info=True)
if prn is None:
prn = prn_send
--
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