I had some success in walking thru the mbufs constituting the packet with some code modifications . The 1st mbuf is the 
header foloowed by the data mbufs . I am able to traverse thru the mbufs and extract some info related to length of data
 & packet . But I cant figure out the location of the ip layer information inside the data mbufs . when I access some of the char sequence members of the mbuf such as MH_databuf & M_databuf using mtod I get some sequence of chars . Am I looking in the wrong place ?
Pls give me some pointers . 

Below is the code of the hook for reference : 

static int output_hook(void *arg, struct mbuf **m,
                       struct ifnet *ifp, int dir)
{
    out_bytes += (*m)->m_len;
    struct mbuf* trav = (*m);
do{
	short mbuf_type = trav->m_type;
    int mbuf_length = trav->m_len;
    int mbuf_flags = trav->m_flags;

    //char * mbuf_hdrdata = (*m)->m_data;
    //struct	mowner * mbuf_owner = (*m)->m_owner;
    //char * mbuf_data = (*m)->m_dat;
    //char *mdata = (char *)malloc(mbuf_length+1);
    //strncpy(mdata,mbuf_hdrdata,mbuf_length);
    //mdata[mbuf_length]='\0';

    slogf( _SLOG_SETCODE(_SLOGC_TEST, 2),
            	           _SLOG_ERROR,
            	           "in our output_hook() mbuf len:%d type:%d flags:%d",
            	           	   	   	   	   	   mbuf_length,mbuf_type,mbuf_flags);

    // found a packet header mbuf
    if(M_PKTHDR == mbuf_flags)
    {
    	struct	pkthdr pkthdr_data = trav->m_pkthdr;
    	slogf( _SLOG_SETCODE(_SLOGC_TEST, 2),
							   _SLOG_ERROR,
							   "in our output_hook() packet hdr len:%d csumflags:%d csumdata:%u segsize:%u",
							   pkthdr_data.len,pkthdr_data.csum_flags,pkthdr_data.csum_data,pkthdr_data.segsz);

    	struct	ifnet *if_data = NULL;
	    if_data = pkthdr_data.rcvif;
		if(if_data)
		{
			struct sockaddr *dest_sa = NULL;
			int fam = -1;
			int port = -1;
			if(if_data->if_dl && if_data->if_dl->ifa_dstaddr)
			{
				dest_sa = if_data->if_dl->ifa_dstaddr;
				if(dest_sa){
					port = ntohs(((struct sockaddr_in*)dest_sa)->sin_port);
					fam = ((struct sockaddr_in*)dest_sa)->sin_family;
				}
			}
			slogf( _SLOG_SETCODE(_SLOGC_TEST, 2),
							   _SLOG_ERROR,
							   "in our output_hook() socket info:%d %d",port,fam);
		}
    }
    // found a data packet mbuf but where is it ???
    else if(MT_DATA == mbuf_type )
    {
    	//char databuffer[MLEN]= {0};
    	//strcpy(databuffer,trav->m_dat);
    	//char * databuffer = trav->m_dat;
		//char *pdata = (char *)malloc(mbuf_length+1);
		//strncpy(pdata,databuffer,mbuf_length);
		//pdata[mbuf_length]='\0';

    	slogf( _SLOG_SETCODE(_SLOGC_TEST, 2),_SLOG_ERROR,
    						"in our output_hook() i m databuffer");
    }
    // go to next buf in chain
    trav=trav->m_next;
}while(NULL != trav);

    return 0; // 0 means allow, 1 means block
}