VLAN problem

[Daniel Bujnik]

Hello,

I have been trying to serialize and deserialize an ARP packet encapsulated in VLAN tagged Ethernet frame. While serialization seems to be working correctly I have been struggling with deserialization bit.

Please have a look at the code snipped below. After deserialization the pArp pointer is NULL. Could you please point out what I am doing wrong?

Many thanks in advance,

Daniel B

-------------------------------------------------------------------------------------
Ethernet ethHeader;
ethHeader.SetDestinationMAC("01:01:01:01:01:01");
ethHeader.SetSourceMAC("02:02:02:02:02:02");

Dot1Q vlan;
vlan.SetDEI(0);
vlan.SetPCP(0);
vlan.SetVID(1000);

ARP arp;
arp.SetHardwareType(1);
arp.SetProtocolType(IP::PROTO);
arp.SetHardwareLength(6);
arp.SetProtocolLength(4);
arp.SetOperation(ARP::Reply);
arp.SetSenderMAC("03:03:03:03:03:03");
arp.SetSenderIP("4.4.4.4");
arp.SetTargetMAC("05:05:05:05:05:05");
arp.SetTargetIP("6.6.6.6");

Packet packetA;
packetA.PushLayer(ethHeader);
packetA.PushLayer(vlan);
packetA.PushLayer(arp);

unsigned char buf[100];
packetA.Craft();
unsigned short len = packetA.GetData(buf);

Packet packetB;
packetB.PacketFromEthernet(buf, len);

Ethernet* pEth = packetB.GetLayer<Ethernet>();
Dot1Q* pVlan = packetB.GetLayer<Dot1Q>();
ARP* pArp = packetB.GetLayer<ARP>();

unsigned short vid = pVlan->GetVID();
string ip = pArp->GetTargetIP();
-------------------------------------------------------------------------------------

[Esteban Pellegrino]

I see... I'm not able to test the code but I guess this is happening because the Dot1Q Craft method is not getting information about the layer on the bottom. I'll check that out and see if can be fixed. For now you can probably force the Type on the Dot1Q to be ARP when you create the first packet :

vlan.SetType(ARP::PROTO)

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Esteban Pellegrino | Mobile Team Leader
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[Daniel Bujnik]

Hi Esteban,

You are right. In my case Dot1Q layer serializes Type field as 0x0800, which is IPv4. Calling the setter method you advice solves the problem for me.

Cheers,

Daniel B