CODEWITHSUNDEEP
pythonipscapymac-addressarp
geekscrap
geekscrap

Reputation: 1045

Sending scapy IP packet with no interface IP error

I'm currently trying to send an IP packet to an interface using the send(pkt, iface="eth0") function and I'm getting the error:

WARNING: Mac address to reach destination not found. Using broadcast

The interface I am trying to send out on doesn't have an IP address, and thats the way I would prefer it. And if it makes a difference, the interface is a bridge (created with brctl)

There is an ARP entry for the host that is in the IP packet however it seems scapy isn't doing the lookup required to get the MAC from the ARP table...

Thoughts?!

Upvotes: 4

Views: 4531

Answers (2)

FitzChivalry
FitzChivalry

Reputation: 339

The default dst address (MAC address) of an Ethernet frame in scapy is broadcast. This warning is generated whenever you send an Ethernet frame to the broadcast address (ff:ff:ff:ff:ff:ff), as far as I'm concerned. You can see this by creating the packet like this:

Ether()/IP() or Ether()/ARP()

instead of just IP() or ARP().

Upvotes: 1

Pierre
Pierre

Reputation: 6237

I would say this is normal, since making a valid ARP request requires an IP address (and Scapy maintains its own ARP table, independent from the OS one).

You can set the destination address yourself: srp(Ether(dst="[MAC address]")/[...]). If you need to get the MAC address first, create and send an ARP request the same way.

To query Scapy's ARP table, access the element conf.netcache.arp_cache, which is a Scapy-specific dict subclass (called CacheInstance).

For example, to add an entry for your host (and then use sr([...]) instead of srp(Ether(dst="[MAC address])/[...])), use:

conf.netcache.arp_cache['[IP address]'] = '[MAC address]'

Upvotes: 2

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