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Pad packet when needed #91

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Merged
guedou merged 2 commits into from
Mar 24, 2016
Merged

Pad packet when needed #91

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c2ff2ce
Pad packet when needed (fixes #90)
p-l- Mar 20, 2016
e211d70
Tiny code cleanup
p-l- Mar 24, 2016
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24 changes: 18 additions & 6 deletions scapy/arch/linux.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
from fcntl import ioctl
import scapy.utils
import scapy.utils6
from scapy.packet import Packet, Padding
from scapy.config import conf
from scapy.data import *
from scapy.supersocket import SuperSocket
Expand Down Expand Up @@ -394,18 +395,18 @@ def send(self, x):
sdto = (iff, conf.l3types[type(x)])
if sn[3] in conf.l2types:
ll = lambda x:conf.l2types[sn[3]]()/x
sx = str(ll(x))
x.sent_time = time.time()
try:
sx = str(ll(x))
x.sent_time = time.time()
self.outs.sendto(sx, sdto)
except socket.error,msg:
x.sent_time = time.time() # bad approximation
if conf.auto_fragment and msg[0] == 90:
except socket.error, msg:
if msg[0] == 22 and len(sx) < conf.min_pkt_size:
self.outs.send(sx + "\x00" * (conf.min_pkt_size - len(sx)))
elif conf.auto_fragment and msg[0] == 90:
for p in x.fragment():
self.outs.sendto(str(ll(p)), sdto)
else:
raise




Expand Down Expand Up @@ -460,6 +461,17 @@ def recv(self, x=MTU):
q = conf.raw_layer(pkt)
q.time = get_last_packet_timestamp(self.ins)
return q
def send(self, x):
try:
return SuperSocket.send(self, x)
except socket.error, msg:
if msg[0] == 22 and len(x) < conf.min_pkt_size:
padding = "\x00" * (conf.min_pkt_size - len(x))
if isinstance(x, Packet):
return SuperSocket.send(self, x / Padding(load=padding))
else:
return SuperSocket.send(self, str(x) + padding)
raise


class L2ListenSocket(SuperSocket):
Expand Down
1 change: 1 addition & 0 deletions scapy/config.py
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Original file line number Diff line number Diff line change
Expand Up @@ -345,6 +345,7 @@ class Conf(ConfClass):
L3socket = None
L2socket = None
L2listen = None
min_pkt_size = 60
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@guedou guedou Mar 22, 2016

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Why did you choose 60 ?

According to the page linked in issue #90 this value could be lower. For example, on my laptop sendp("A"*15) works fine while sendp("A"*14) fails. 15 is indeed equal to len(str(Ether())). I wonder if it could be computed dynamically.

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@p-l- p-l- Mar 22, 2016

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That's not the case for every driver, I have one example where 58 bytes are needed.

I don't think that more than 60 bytes could be needed, since that is the minimum ethernet length, and I think it's fine to have the value set to 60 by default as it can be easily configured.

Also, I have not found a way to find this value dynamically (other than by bisecting, and I don't think that trying multiple values is a good option).

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@p-l- p-l- Mar 23, 2016

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@guedou I have updated the description on #90 to give more information.

histfile = os.path.join(os.path.expanduser("~"), ".scapy_history")
padding = 1
except_filter = ""
Expand Down