Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* Amanda extension for TCP NAT alteration. |
| 2 | * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca> |
| 3 | * based on a copy of HW's ip_nat_irc.c as well as other modules |
| 4 | * |
| 5 | * This program is free software; you can redistribute it and/or |
| 6 | * modify it under the terms of the GNU General Public License |
| 7 | * as published by the Free Software Foundation; either version |
| 8 | * 2 of the License, or (at your option) any later version. |
| 9 | * |
| 10 | * Module load syntax: |
| 11 | * insmod ip_nat_amanda.o |
| 12 | */ |
| 13 | |
| 14 | #include <linux/kernel.h> |
| 15 | #include <linux/module.h> |
| 16 | #include <linux/netfilter.h> |
| 17 | #include <linux/skbuff.h> |
| 18 | #include <linux/ip.h> |
| 19 | #include <linux/udp.h> |
| 20 | #include <net/tcp.h> |
| 21 | #include <net/udp.h> |
| 22 | |
| 23 | #include <linux/netfilter_ipv4.h> |
| 24 | #include <linux/netfilter_ipv4/ip_nat.h> |
| 25 | #include <linux/netfilter_ipv4/ip_nat_helper.h> |
| 26 | #include <linux/netfilter_ipv4/ip_conntrack_helper.h> |
| 27 | #include <linux/netfilter_ipv4/ip_conntrack_amanda.h> |
| 28 | |
| 29 | |
| 30 | MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>"); |
| 31 | MODULE_DESCRIPTION("Amanda NAT helper"); |
| 32 | MODULE_LICENSE("GPL"); |
| 33 | |
| 34 | static unsigned int help(struct sk_buff **pskb, |
| 35 | enum ip_conntrack_info ctinfo, |
| 36 | unsigned int matchoff, |
| 37 | unsigned int matchlen, |
| 38 | struct ip_conntrack_expect *exp) |
| 39 | { |
| 40 | char buffer[sizeof("65535")]; |
| 41 | u_int16_t port; |
| 42 | unsigned int ret; |
| 43 | |
| 44 | /* Connection comes from client. */ |
| 45 | exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; |
| 46 | exp->dir = IP_CT_DIR_ORIGINAL; |
| 47 | |
| 48 | /* When you see the packet, we need to NAT it the same as the |
| 49 | * this one (ie. same IP: it will be TCP and master is UDP). */ |
| 50 | exp->expectfn = ip_nat_follow_master; |
| 51 | |
| 52 | /* Try to get same port: if not, try to change it. */ |
| 53 | for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { |
| 54 | exp->tuple.dst.u.tcp.port = htons(port); |
| 55 | if (ip_conntrack_expect_related(exp) == 0) |
| 56 | break; |
| 57 | } |
| 58 | |
| 59 | if (port == 0) { |
| 60 | ip_conntrack_expect_free(exp); |
| 61 | return NF_DROP; |
| 62 | } |
| 63 | |
| 64 | sprintf(buffer, "%u", port); |
| 65 | ret = ip_nat_mangle_udp_packet(pskb, exp->master, ctinfo, |
| 66 | matchoff, matchlen, |
| 67 | buffer, strlen(buffer)); |
| 68 | if (ret != NF_ACCEPT) |
| 69 | ip_conntrack_unexpect_related(exp); |
| 70 | return ret; |
| 71 | } |
| 72 | |
| 73 | static void __exit fini(void) |
| 74 | { |
| 75 | ip_nat_amanda_hook = NULL; |
| 76 | /* Make sure noone calls it, meanwhile. */ |
| 77 | synchronize_net(); |
| 78 | } |
| 79 | |
| 80 | static int __init init(void) |
| 81 | { |
| 82 | BUG_ON(ip_nat_amanda_hook); |
| 83 | ip_nat_amanda_hook = help; |
| 84 | return 0; |
| 85 | } |
| 86 | |
| 87 | module_init(init); |
| 88 | module_exit(fini); |