Exemplo n.º 1
0
void nf_nat_set_seq_adjust(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
			   __be32 seq, s16 off)
{
	if (!off)
		return;
	set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
	adjust_tcp_sequence(ntohl(seq), off, ct, ctinfo);
}
Exemplo n.º 2
0
/* Generic function for mangling variable-length address changes inside
 * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
 * command in FTP).
 *
 * Takes care about all the nasty sequence number changes, checksumming,
 * skb enlargement, ...
 *
 * */
int
nf_nat_mangle_tcp_packet(struct sk_buff **pskb,
			 struct nf_conn *ct,
			 enum ip_conntrack_info ctinfo,
			 unsigned int match_offset,
			 unsigned int match_len,
			 const char *rep_buffer,
			 unsigned int rep_len)
{
	struct iphdr *iph;
	struct tcphdr *tcph;
	int oldlen, datalen;

	if (!skb_make_writable(pskb, (*pskb)->len))
		return 0;

	if (rep_len > match_len &&
	    rep_len - match_len > skb_tailroom(*pskb) &&
	    !enlarge_skb(pskb, rep_len - match_len))
		return 0;

	SKB_LINEAR_ASSERT(*pskb);

	iph = (*pskb)->nh.iph;
	tcph = (void *)iph + iph->ihl*4;

	oldlen = (*pskb)->len - iph->ihl*4;
	mangle_contents(*pskb, iph->ihl*4 + tcph->doff*4,
			match_offset, match_len, rep_buffer, rep_len);

	datalen = (*pskb)->len - iph->ihl*4;
	if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) {
		tcph->check = 0;
		tcph->check = tcp_v4_check(datalen,
					   iph->saddr, iph->daddr,
					   csum_partial((char *)tcph,
							datalen, 0));
	} else
		nf_proto_csum_replace2(&tcph->check, *pskb,
				       htons(oldlen), htons(datalen), 1);

	if (rep_len != match_len) {
		set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
		adjust_tcp_sequence(ntohl(tcph->seq),
				    (int)rep_len - (int)match_len,
				    ct, ctinfo);
		/* Tell TCP window tracking about seq change */
		nf_conntrack_tcp_update(*pskb, (*pskb)->nh.iph->ihl*4,
					ct, CTINFO2DIR(ctinfo));
	}
	return 1;
}