Re: question when using options in headers..

q1: Yes that is correct ordering. See sample/tcp1.c for a sample 
application using TCP options. To answer the second part: Not using the 
options builder function. Since the options string will actually have 
its own pblock, if you save existing ptags, then call builder functions 
inside of a loop using those ptags, the next call to a builder function 
WITHOUT a saved ptag will generate a new pblock at the end of the list. 
Two things you can try: 1) place your TCP or IP options inside the 
payload and adjust the appropriate header values. 2) try calling an 
options builder with a 0 sized payload and save its ptag. I kinda doubt 
this second one will work though; there is a ton of pointer math and 
indirection going on inside the options builders.

q2: It all depends on your needs. If you're only sending packets one at 
a time with a fire and forget mentality, use only one context. If you 
need to send multiple packets over and over again, use the cq 
interface.

q3: I just tested the advanced mode and it worked fine as of 
1.1.2-rc-05. Can you be more specific with your error? Are you sure you 
initialized the library properly?

On Jan 25, 2004, at 5:14 AM, Mustafa Abu Sedera wrote:

>
> I have a question when sending packets which have header options, as i 
> didn't find any examples on it.
>
> q1:
> Is this order of packet building correct?
> e.g. TCP:
> 1- build_options()
> 2- build_tcp_header-with payload specified, length = paylod_s+20 (or 
> should i add: + option_length)
> 3-build_build_ipv4(LIBNET_RAW4)
> 4-write()
>
> can I send a packet with no options and store the tags of the 
> functions and then later use those tags to send another one WITH 
> options, or would it be considered like a packet with a different 
> protocol? (so I would have to clear() the context first it first)
>
> q2:
> Whats best in sending packets with different protocols:
> a) defining only one libnet context and using it to send pkts of all 
> protocols by calling libnet_clear_packet() after each libnte_write() 
> operation.
> b)defining a libnet context for each type of protocol I use and 
> modifying the parameters later when needed with the tag.
>
> q3:
> even if i use the _ADV suffix the cull pkt returns an error that it 
> was not advanced mode initialized.
>
> Thanks in advance and i REALLY hope this time someone answers me.
>
> Regards
>
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--
Mike Schiffman, CISSP
http://www.packetfactory.net/schiffman
Doveryay No Proveryay