Hello All,
    I have attached the code snippet for extending tproxy to support sctp functionality.

    For the socket lookup I use:

struct sock *nf_tproxy_get_sock_sctp4(const struct sk_buff *skb){

struct sctp_association *asoc;
union sctp_addr *saddr , *daddr;
struct sctp_transport **transport;
struct sctphdr *sh;
struct sock *sk;

void *temp;
void *temp1;

memset(saddr,0,sizeof(saddr));
memset(daddr,0,sizeof(daddr));

saddr->v4.sin_family = AF_INET;
daddr->v4.sin_family = AF_INET;

sh = sctp_hdr(skb);

temp=&ip_hdr(skb)->saddr;
temp1=&ip_hdr(skb)->daddr;

memcpy(&saddr->v4.sin_addr.s_addr,temp, sizeof(struct in_addr));
memcpy(&daddr->v4.sin_addr.s_addr,temp1, sizeof(struct in_addr));

asoc = __sctp_get_association(saddr, daddr, transport);
         if (!asoc)
             sk=NULL;
       sk = asoc->base.sk;

return sk;
}

This function I plan to invoke from both xt_TPROXY.c and xt_socket.c for sctp instead of the existing function for tcp and udp.

if(iph->protocol == IPPROTO_TCP || iph->protocol == IPPROTO_UDP){
        sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
                                   iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr,
                                   hp->source, tgi->lport ? tgi->lport : hp->dest,
                                   par->in, true);
        }

        else
          if(iph->protocol == IPPROTO_SCTP){
               sk = nf_tproxy_get_sock_sctp4(skb);
          }

Have I missed out any condition during the socket lookup ?
What about the icmp support?Can I just reuse the existing functionality by adding sctp to the list of protocols?

Thanks and Regards,
     Maria