| /* (C) 1999-2001 Paul `Rusty' Russell |
| * (C) 2002-2004 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/netfilter.h> |
| #include <linux/ip.h> |
| #include <linux/tcp.h> |
| #include <linux/if.h> |
| #include <linux/netfilter/nfnetlink_conntrack.h> |
| #include <linux/netfilter_ipv4/ip_nat.h> |
| #include <linux/netfilter_ipv4/ip_nat_rule.h> |
| #include <linux/netfilter_ipv4/ip_nat_protocol.h> |
| #include <linux/netfilter_ipv4/ip_nat_core.h> |
| |
| static int |
| tcp_in_range(const struct ip_conntrack_tuple *tuple, |
| enum ip_nat_manip_type maniptype, |
| const union ip_conntrack_manip_proto *min, |
| const union ip_conntrack_manip_proto *max) |
| { |
| __be16 port; |
| |
| if (maniptype == IP_NAT_MANIP_SRC) |
| port = tuple->src.u.tcp.port; |
| else |
| port = tuple->dst.u.tcp.port; |
| |
| return ntohs(port) >= ntohs(min->tcp.port) |
| && ntohs(port) <= ntohs(max->tcp.port); |
| } |
| |
| static int |
| tcp_unique_tuple(struct ip_conntrack_tuple *tuple, |
| const struct ip_nat_range *range, |
| enum ip_nat_manip_type maniptype, |
| const struct ip_conntrack *conntrack) |
| { |
| static u_int16_t port; |
| __be16 *portptr; |
| unsigned int range_size, min, i; |
| |
| if (maniptype == IP_NAT_MANIP_SRC) |
| portptr = &tuple->src.u.tcp.port; |
| else |
| portptr = &tuple->dst.u.tcp.port; |
| |
| /* If no range specified... */ |
| if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)) { |
| /* If it's dst rewrite, can't change port */ |
| if (maniptype == IP_NAT_MANIP_DST) |
| return 0; |
| |
| /* Map privileged onto privileged. */ |
| if (ntohs(*portptr) < 1024) { |
| /* Loose convention: >> 512 is credential passing */ |
| if (ntohs(*portptr)<512) { |
| min = 1; |
| range_size = 511 - min + 1; |
| } else { |
| min = 600; |
| range_size = 1023 - min + 1; |
| } |
| } else { |
| min = 1024; |
| range_size = 65535 - 1024 + 1; |
| } |
| } else { |
| min = ntohs(range->min.tcp.port); |
| range_size = ntohs(range->max.tcp.port) - min + 1; |
| } |
| |
| for (i = 0; i < range_size; i++, port++) { |
| *portptr = htons(min + port % range_size); |
| if (!ip_nat_used_tuple(tuple, conntrack)) { |
| return 1; |
| } |
| } |
| return 0; |
| } |
| |
| static int |
| tcp_manip_pkt(struct sk_buff **pskb, |
| unsigned int iphdroff, |
| const struct ip_conntrack_tuple *tuple, |
| enum ip_nat_manip_type maniptype) |
| { |
| struct iphdr *iph = (struct iphdr *)((*pskb)->data + iphdroff); |
| struct tcphdr *hdr; |
| unsigned int hdroff = iphdroff + iph->ihl*4; |
| __be32 oldip, newip; |
| __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 ((*pskb)->len >= hdroff + sizeof(struct tcphdr)) |
| hdrsize = sizeof(struct tcphdr); |
| |
| if (!skb_make_writable(pskb, hdroff + hdrsize)) |
| return 0; |
| |
| iph = (struct iphdr *)((*pskb)->data + iphdroff); |
| hdr = (struct tcphdr *)((*pskb)->data + hdroff); |
| |
| if (maniptype == IP_NAT_MANIP_SRC) { |
| /* Get rid of src ip and src pt */ |
| oldip = iph->saddr; |
| newip = tuple->src.ip; |
| newport = tuple->src.u.tcp.port; |
| portptr = &hdr->source; |
| } else { |
| /* Get rid of dst ip and dst pt */ |
| oldip = iph->daddr; |
| newip = tuple->dst.ip; |
| newport = tuple->dst.u.tcp.port; |
| portptr = &hdr->dest; |
| } |
| |
| oldport = *portptr; |
| *portptr = newport; |
| |
| if (hdrsize < sizeof(*hdr)) |
| return 1; |
| |
| nf_proto_csum_replace4(&hdr->check, *pskb, oldip, newip, 1); |
| nf_proto_csum_replace2(&hdr->check, *pskb, oldport, newport, 0); |
| return 1; |
| } |
| |
| struct ip_nat_protocol ip_nat_protocol_tcp = { |
| .name = "TCP", |
| .protonum = IPPROTO_TCP, |
| .me = THIS_MODULE, |
| .manip_pkt = tcp_manip_pkt, |
| .in_range = tcp_in_range, |
| .unique_tuple = tcp_unique_tuple, |
| #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \ |
| defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE) |
| .range_to_nfattr = ip_nat_port_range_to_nfattr, |
| .nfattr_to_range = ip_nat_port_nfattr_to_range, |
| #endif |
| }; |