Re: ACC and port numers

[KOVACS Krisztian <hidden@balabit.hu>]

   Hi,

Stanisalv V. Bogatyrev wrote:
>     I added some code, but I get broken port nubers on incoming traffic. 
> I'm new in netfilter/iptables programming and can't find a mistake. Help 
> me please, what do I need to correct to make it work?


> 	  case IPPROTO_TCP: 
> 	    tcp_hdr = (*pskb)->h.th;
> 	    //We don't do ntohs() here. In userspace we trust. So Don't forget to modify ipacc.c
> 	
> 	    sport=tcp_hdr->source;
> 	    dport=tcp_hdr->dest;	    

   The problem lies here: for incoming packets, skb->h.th is not yet set. 
You should try it this way:

struct iphdr *iph = (*pskb)->nh.iph;
struct tcphdr *tcp_hdr = (struct tcphdr *)((u_int32_t *)iph + iph->ihl);

   Of course the code for UDP, ICMP, etc. should also be upgraded (for TCP 
and UDP the ports are at the same location). I didn't check, but you 
should also take care of byte order problems.

-- 
   Regards,
     Krisztian KOVACS