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"martian source" mixes up source and destination

 

 

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grawity at gmail

Apr 28, 2012, 10:37 AM

Post #1 of 2 (132 views)
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"martian source" mixes up source and destination

After enabling the /proc/sys/net/ipv4/conf/all/log_martians sysctl, I've
been receiving the following messages on dmesg:

> martian source 255.255.255.255 from 192.168.1.115, on dev wlan0
> ll header: ff:ff:ff:ff:ff:ff:f4:6d:04:85:fc:d7:08:00
> martian source 192.168.1.255 from 192.168.1.115, on dev wlan0
> ll header: ff:ff:ff:ff:ff:ff:f4:6d:04:85:fc:d7:08:00
> martian source 192.168.1.255 from 192.168.1.115, on dev wlan0
> ll header: ff:ff:ff:ff:ff:ff:f4:6d:04:85:fc:d7:08:00
> <later>
> martian source 255.255.255.255 from 192.168.1.183, on dev eth0
> ll header: ff:ff:ff:ff:ff:ff:48:5d:60:e8:65:8f:08:00

However, the packets are *not* martians, but legitimate broadcast
UDP/IPv4 packets: they have the *destination* as 255.255.255.255 or
192.168.1.255, with the source being 192.168.1.115 (wlan0 on this
device) for the first three packets, and 192.168.1.183 (eth0) on the
fourth.

Linux 3.3.4-1-ARCH on Arch Linux

--
Mantas M. <grawity [at] gmail>

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mjt at tls

Apr 28, 2012, 9:52 PM

Post #2 of 2 (129 views)
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Re: "martian source" mixes up source and destination [In reply to]

On 28.04.2012 21:37, Mantas M. wrote:
> After enabling the /proc/sys/net/ipv4/conf/all/log_martians sysctl, I've
> been receiving the following messages on dmesg:

Cc'ing netdev [at] vge for network-related question.

>> martian source 255.255.255.255 from 192.168.1.115, on dev wlan0
>> ll header: ff:ff:ff:ff:ff:ff:f4:6d:04:85:fc:d7:08:00
>> martian source 192.168.1.255 from 192.168.1.115, on dev wlan0
>> ll header: ff:ff:ff:ff:ff:ff:f4:6d:04:85:fc:d7:08:00
>> martian source 192.168.1.255 from 192.168.1.115, on dev wlan0
>> ll header: ff:ff:ff:ff:ff:ff:f4:6d:04:85:fc:d7:08:00
>> <later>
>> martian source 255.255.255.255 from 192.168.1.183, on dev eth0
>> ll header: ff:ff:ff:ff:ff:ff:48:5d:60:e8:65:8f:08:00

It has been this way since very long time. The meaning of this
message is:

there is a martian source sending packets to 255.255.255.255
from 192.168.1.183 on dev eth0

> However, the packets are *not* martians, but legitimate broadcast
> UDP/IPv4 packets: they have the *destination* as 255.255.255.255 or
> 192.168.1.255, with the source being 192.168.1.115 (wlan0 on this
> device) for the first three packets, and 192.168.1.183 (eth0) on the
> fourth.

log_martians does not check destination address, it checks _source_
address. At least it did so in the past. Please show output of
`ip route' from your machine.

> Linux 3.3.4-1-ARCH on Arch Linux

Thanks,

/mjt

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