| /* (C) 1999-2001 Paul `Rusty' Russell |
| * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org> |
| * |
| * 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/types.h> |
| #include <linux/init.h> |
| #include <linux/export.h> |
| #include <linux/tcp.h> |
| |
| #include <linux/netfilter.h> |
| #include <linux/netfilter/nfnetlink_conntrack.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> |
| |
| static u16 tcp_port_rover; |
| |
| static void |
| tcp_unique_tuple(const struct nf_nat_l3proto *l3proto, |
| struct nf_conntrack_tuple *tuple, |
| const struct nf_nat_range *range, |
| enum nf_nat_manip_type maniptype, |
| const struct nf_conn *ct) |
| { |
| nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct, |
| &tcp_port_rover); |
| } |
| |
| static bool |
| tcp_manip_pkt(struct sk_buff *skb, |
| const struct nf_nat_l3proto *l3proto, |
| unsigned int iphdroff, unsigned int hdroff, |
| const struct nf_conntrack_tuple *tuple, |
| enum nf_nat_manip_type maniptype) |
| { |
| struct tcphdr *hdr; |
| __be16 *portptr, newport, oldport; |
| int hdrsize = 8; /* TCP connection tracking guarantees this much */ |
| |
| /* this could be a inner header returned in icmp packet; in such |
| cases we cannot update the checksum field since it is outside of |
| the 8 bytes of transport layer headers we are guaranteed */ |
| if (skb->len >= hdroff + sizeof(struct tcphdr)) |
| hdrsize = sizeof(struct tcphdr); |
| |
| if (!skb_make_writable(skb, hdroff + hdrsize)) |
| return false; |
| |
| hdr = (struct tcphdr *)(skb->data + hdroff); |
| |
| if (maniptype == NF_NAT_MANIP_SRC) { |
| /* Get rid of src port */ |
| newport = tuple->src.u.tcp.port; |
| portptr = &hdr->source; |
| } else { |
| /* Get rid of dst port */ |
| newport = tuple->dst.u.tcp.port; |
| portptr = &hdr->dest; |
| } |
| |
| oldport = *portptr; |
| *portptr = newport; |
| |
| if (hdrsize < sizeof(*hdr)) |
| return true; |
| |
| l3proto->csum_update(skb, iphdroff, &hdr->check, tuple, maniptype); |
| inet_proto_csum_replace2(&hdr->check, skb, oldport, newport, false); |
| return true; |
| } |
| |
| const struct nf_nat_l4proto nf_nat_l4proto_tcp = { |
| .l4proto = IPPROTO_TCP, |
| .manip_pkt = tcp_manip_pkt, |
| .in_range = nf_nat_l4proto_in_range, |
| .unique_tuple = tcp_unique_tuple, |
| #if IS_ENABLED(CONFIG_NF_CT_NETLINK) |
| .nlattr_to_range = nf_nat_l4proto_nlattr_to_range, |
| #endif |
| }; |