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); }
/* 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; }