tcp raw socket programming recvfrom()

[Alin-Adrian Anton]

Kip Macy wrote:

>Usually if your looking at raw packets you want to use BPF.
>
>		-Kip
>
>On Wed, 9 Jul 2003, Alin-Adrian Anton wrote:
>
>  
>
>>Hey folks,
>>
>>I wrote my piece of code to play with, and it uses raw sockets to send 
>>TCP packets. It sends packets okay, everything tested with a sniffer, 
>>everything is really really fine, but it seems I cannot recvfrom 
>>anything. I mean, it just keeps waiting and doesn't see the reply the 
>>server is actually sending (can be seen with a sniffer). I read that the 
>>freebsd kernel does not duplicate any incoming TCP/UDP packets to any of 
>>the opened raw sockets. Is that true? So the only solution is to use the 
>>interface in promiscuous mode and sniff like a sniffer for the expected 
>>packet? Is there any other way?
>>
>>PS: ICMP gets received well with recvfrom (tested).
>>
>>On Linux, it does work for tcp/udp too with recvfrom.
>>
>>
>>I was also wondering if anyone could help me understand why this 
>>behaviour in freebsd? (or *BSD)
>>
>>Thanks!
>>
>>Best Regards,
>>Alin.
>>
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>>    
>>
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>  
>
Usually? What does usually mean? I know I can use bpf. But is there 
another way to look at incoming TCP packet ? What I did is I sent a TCP 
SYN packet and the server answers with a TCP SYN_ACK packet. How can I 
look at the SYN_ACK packet using raw sockets?

Alin.