| /* nf_nat_helper.c - generic support functions for NAT helpers |
| * |
| * (C) 2000-2002 Harald Welte <laforge@netfilter.org> |
| * (C) 2003-2006 Netfilter Core Team <coreteam@netfilter.org> |
| * (C) 2007-2012 Patrick McHardy <kaber@trash.net> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| */ |
| #include <linux/module.h> |
| #include <linux/gfp.h> |
| #include <linux/types.h> |
| #include <linux/skbuff.h> |
| #include <linux/tcp.h> |
| #include <linux/udp.h> |
| #include <net/tcp.h> |
| |
| #include <net/netfilter/nf_conntrack.h> |
| #include <net/netfilter/nf_conntrack_helper.h> |
| #include <net/netfilter/nf_conntrack_ecache.h> |
| #include <net/netfilter/nf_conntrack_expect.h> |
| #include <net/netfilter/nf_conntrack_seqadj.h> |
| #include <net/netfilter/nf_nat.h> |
| #include <net/netfilter/nf_nat_l3proto.h> |
| #include <net/netfilter/nf_nat_l4proto.h> |
| #include <net/netfilter/nf_nat_core.h> |
| #include <net/netfilter/nf_nat_helper.h> |
| |
| /* Frobs data inside this packet, which is linear. */ |
| static void mangle_contents(struct sk_buff *skb, |
| unsigned int dataoff, |
| unsigned int match_offset, |
| unsigned int match_len, |
| const char *rep_buffer, |
| unsigned int rep_len) |
| { |
| unsigned char *data; |
| |
| BUG_ON(skb_is_nonlinear(skb)); |
| data = skb_network_header(skb) + dataoff; |
| |
| /* move post-replacement */ |
| memmove(data + match_offset + rep_len, |
| data + match_offset + match_len, |
| skb_tail_pointer(skb) - (skb_network_header(skb) + dataoff + |
| match_offset + match_len)); |
| |
| /* insert data from buffer */ |
| memcpy(data + match_offset, rep_buffer, rep_len); |
| |
| /* update skb info */ |
| if (rep_len > match_len) { |
| pr_debug("nf_nat_mangle_packet: Extending packet by " |
| "%u from %u bytes\n", rep_len - match_len, skb->len); |
| skb_put(skb, rep_len - match_len); |
| } else { |
| pr_debug("nf_nat_mangle_packet: Shrinking packet from " |
| "%u from %u bytes\n", match_len - rep_len, skb->len); |
| __skb_trim(skb, skb->len + rep_len - match_len); |
| } |
| |
| if (nf_ct_l3num((struct nf_conn *)skb_nfct(skb)) == NFPROTO_IPV4) { |
| /* fix IP hdr checksum information */ |
| ip_hdr(skb)->tot_len = htons(skb->len); |
| ip_send_check(ip_hdr(skb)); |
| } else |
| ipv6_hdr(skb)->payload_len = |
| htons(skb->len - sizeof(struct ipv6hdr)); |
| } |
| |
| /* Unusual, but possible case. */ |
| static bool enlarge_skb(struct sk_buff *skb, unsigned int extra) |
| { |
| if (skb->len + extra > 65535) |
| return false; |
| |
| if (pskb_expand_head(skb, 0, extra - skb_tailroom(skb), GFP_ATOMIC)) |
| return false; |
| |
| return true; |
| } |
| |
| /* 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, ... |
| * |
| * */ |
| bool __nf_nat_mangle_tcp_packet(struct sk_buff *skb, |
| struct nf_conn *ct, |
| enum ip_conntrack_info ctinfo, |
| unsigned int protoff, |
| unsigned int match_offset, |
| unsigned int match_len, |
| const char *rep_buffer, |
| unsigned int rep_len, bool adjust) |
| { |
| const struct nf_nat_l3proto *l3proto; |
| struct tcphdr *tcph; |
| int oldlen, datalen; |
| |
| if (!skb_make_writable(skb, skb->len)) |
| return false; |
| |
| if (rep_len > match_len && |
| rep_len - match_len > skb_tailroom(skb) && |
| !enlarge_skb(skb, rep_len - match_len)) |
| return false; |
| |
| SKB_LINEAR_ASSERT(skb); |
| |
| tcph = (void *)skb->data + protoff; |
| |
| oldlen = skb->len - protoff; |
| mangle_contents(skb, protoff + tcph->doff*4, |
| match_offset, match_len, rep_buffer, rep_len); |
| |
| datalen = skb->len - protoff; |
| |
| l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct)); |
| l3proto->csum_recalc(skb, IPPROTO_TCP, tcph, &tcph->check, |
| datalen, oldlen); |
| |
| if (adjust && rep_len != match_len) |
| nf_ct_seqadj_set(ct, ctinfo, tcph->seq, |
| (int)rep_len - (int)match_len); |
| |
| return true; |
| } |
| EXPORT_SYMBOL(__nf_nat_mangle_tcp_packet); |
| |
| /* Generic function for mangling variable-length address changes inside |
| * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX |
| * command in the Amanda protocol) |
| * |
| * Takes care about all the nasty sequence number changes, checksumming, |
| * skb enlargement, ... |
| * |
| * XXX - This function could be merged with nf_nat_mangle_tcp_packet which |
| * should be fairly easy to do. |
| */ |
| bool |
| nf_nat_mangle_udp_packet(struct sk_buff *skb, |
| struct nf_conn *ct, |
| enum ip_conntrack_info ctinfo, |
| unsigned int protoff, |
| unsigned int match_offset, |
| unsigned int match_len, |
| const char *rep_buffer, |
| unsigned int rep_len) |
| { |
| const struct nf_nat_l3proto *l3proto; |
| struct udphdr *udph; |
| int datalen, oldlen; |
| |
| if (!skb_make_writable(skb, skb->len)) |
| return false; |
| |
| if (rep_len > match_len && |
| rep_len - match_len > skb_tailroom(skb) && |
| !enlarge_skb(skb, rep_len - match_len)) |
| return false; |
| |
| udph = (void *)skb->data + protoff; |
| |
| oldlen = skb->len - protoff; |
| mangle_contents(skb, protoff + sizeof(*udph), |
| match_offset, match_len, rep_buffer, rep_len); |
| |
| /* update the length of the UDP packet */ |
| datalen = skb->len - protoff; |
| udph->len = htons(datalen); |
| |
| /* fix udp checksum if udp checksum was previously calculated */ |
| if (!udph->check && skb->ip_summed != CHECKSUM_PARTIAL) |
| return true; |
| |
| l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct)); |
| l3proto->csum_recalc(skb, IPPROTO_UDP, udph, &udph->check, |
| datalen, oldlen); |
| |
| return true; |
| } |
| EXPORT_SYMBOL(nf_nat_mangle_udp_packet); |
| |
| /* Setup NAT on this expected conntrack so it follows master. */ |
| /* If we fail to get a free NAT slot, we'll get dropped on confirm */ |
| void nf_nat_follow_master(struct nf_conn *ct, |
| struct nf_conntrack_expect *exp) |
| { |
| struct nf_nat_range range; |
| |
| /* This must be a fresh one. */ |
| BUG_ON(ct->status & IPS_NAT_DONE_MASK); |
| |
| /* Change src to where master sends to */ |
| range.flags = NF_NAT_RANGE_MAP_IPS; |
| range.min_addr = range.max_addr |
| = ct->master->tuplehash[!exp->dir].tuple.dst.u3; |
| nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC); |
| |
| /* For DST manip, map port here to where it's expected. */ |
| range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED); |
| range.min_proto = range.max_proto = exp->saved_proto; |
| range.min_addr = range.max_addr |
| = ct->master->tuplehash[!exp->dir].tuple.src.u3; |
| nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST); |
| } |
| EXPORT_SYMBOL(nf_nat_follow_master); |