STL scapy IGMP issue
andyb...@googlemail.com
Hi,
...I have a problem constructing proper IGMP report messages with scapy. This used to work (don't know when exactly this broke), but my code has been untouched for a pretty long time ?!? Still not sure where the problem lies – any hint on how to troubleshoot that highly appreciated!
the code in question is fairly straight forward:
a=Ether(src=s.dst_mac)/Dot1Q(vlan=s.dst_outer_vlan)/Dot1Q(vlan=s.dst_vlan)
b=IP(src=s.dst_ip)
igmp=scapy.contrib.igmp.IGMP(type=0x16, gaddr=s.dst_mc)
igmp.igmpize(b, a)
pkt = a/b/igmp
s.dst_mac :
The generate scapy packet looks perfect:
###[ Ethernet ]###
dst = 01:00:5e:7f:20:3d
src = 00:33:33:33:00:2a
type = 0x8100
###[ 802.1Q ]###
prio = 0
id = 0
vlan = 601
type = 0x8100
###[ 802.1Q ]###
prio = 0
id = 0
vlan = 32
type = 0x800
###[ IP ]###
version = 4
ihl = None
tos = 0x0
len = None
id = 1
flags =
frag = 0
ttl = 1
proto = igmp
chksum = None
src = 172.17.32.61
dst = 239.255.32.61
\options \
|###[ IP Option Router Alert ]###
| copy_flag = 1
| optclass = control
| option = router_alert
| length = 4
| alert = router_shall_examine_packet
###[ IGMP ]###
type = Version 2 - Membership Report
mrtime = 0
chksum = None
gaddr = 239.255.32.61 ß this is expected
But when capturing at the switch connected to the TRex-Ports I get:
Internet Protocol Version 4, Src: 172.17.32.61 (172.17.32.61), Dst: 239.255.32.61 (239.255.32.61)
Version: 4
Header Length: 24 bytes
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00: Not-ECT (Not ECN-Capable Transport))
0000 00.. = Differentiated Services Codepoint: Default (0x00)
.... ..00 = Explicit Congestion Notification: Not-ECT (Not ECN-Capable Transport) (0x00)
Total Length: 36
Identification: 0x0001 (1)
Flags: 0x00
0... .... = Reserved bit: Not set
.0.. .... = Don't fragment: Not set
..0. .... = More fragments: Not set
Fragment offset: 0
Time to live: 1
Protocol: IGMP (2)
Header checksum: 0x4848 [validation disabled]
[Good: False]
[Bad: False]
Source: 172.17.32.61 (172.17.32.61)
Destination: 239.255.32.61 (239.255.32.61)
[Source GeoIP: Unknown]
[Destination GeoIP: Unknown]
Options: (4 bytes), Router Alert
Router Alert (4 bytes): Router shall examine packet (0)
Type: 148
1... .... = Copy on fragmentation: Yes
.00. .... = Class: Control (0)
...1 0100 = Number: Router Alert (20)
Length: 4
Router Alert: Router shall examine packet (0)
Internet Group Management Protocol
[IGMP Version: 2]
Type: Membership Report (0x16)
Max Resp Time: 0.0 sec (0x00)
Header checksum: 0x3231 [incorrect, should be 0x799a]
Multicast Address: 55.49.57.52 (55.49.57.52) ß this is wrong
VSS-Monitoring ethernet trailer, Source Port: 0
Src Port: 0
I’m currently a bit lost on what to try next ?! MC *did* work in the past, but is not very important, so nobody took a look at this (MC streams are currently not running in production – only in the lab). Might be broken for a longer time already?! Is the wrong igmp header checksum related to this?!
Thanks,
Andreas
Yaroslav Brustinov
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Yaroslav Brustinov
Andreas Bourges
Thanks,
Andreas
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andyb...@googlemail.com
…just pulled master containing the reverted igmp commit and the merged PR for services fmt option.
MC run’s fine – looks good!
Thanks for reacting so fast!
Andreas
