martian source on boot up
 

I just noticed a martian source message on boot up:
This is a new one to me. I'm on a home desktop system running through a wireless router.
Is my system under attack?

My understanding of "martian" packets were they were packets coming into an interface that is different than the interface the computer would use to send packets to that source address. For example if a packets comes in on eth0 with and source address of 192.168.5.123, but the routing table routes 192.168.5.0/24 out eth1.

The address specified, 255.255.255.255 is the general broadcast address. I am not sure why this is considered martian.

EDIT: I still don't know why these broadcast packets would be considered martian, but they could be coming from another computer on your network that is doing a DHCP request or from a MS Windows computer that just likes to broadcast some NETBIOS stuff.

Rfc 1812,
Only unicast adresses are allowed for source address. 255.255.255.255 is not a unicast address then it's considered invalid. Linux follows the standard.

Probably it's your wireless router that does strange things. What router is this?
Do you only have 1 ethernet adapter?

You can switch off these warnings with one of these:
net.ipv4.conf.all.log_martians = 0
net.ipv4.conf.default.log_martians = 0
net.ipv4.conf.lo.log_martians = 0
net.ipv4.conf.eth0.log_martians = 0
net.ipv4.conf.eth1.log_martians = 0
net.ipv4.conf.eth2.log_martians = 0
net.ipv4.conf.irda0.log_martians = 0

See your kernel documentation

Use sysctl
 

You should probably use sysctl -w to set those log_martians values to make changes permanent.