| /* |
| * IP6 tables REJECT target module |
| * Linux INET6 implementation |
| * |
| * Copyright (C)2003 USAGI/WIDE Project |
| * |
| * Authors: |
| * Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp> |
| * |
| * Based on net/ipv4/netfilter/ipt_REJECT.c |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License |
| * as published by the Free Software Foundation; either version |
| * 2 of the License, or (at your option) any later version. |
| */ |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/gfp.h> |
| #include <linux/module.h> |
| #include <linux/skbuff.h> |
| #include <linux/icmpv6.h> |
| #include <linux/netdevice.h> |
| #include <net/ipv6.h> |
| #include <net/tcp.h> |
| #include <net/icmp.h> |
| #include <net/ip6_checksum.h> |
| #include <net/ip6_fib.h> |
| #include <net/ip6_route.h> |
| #include <net/flow.h> |
| #include <linux/netfilter/x_tables.h> |
| #include <linux/netfilter_ipv6/ip6_tables.h> |
| #include <linux/netfilter_ipv6/ip6t_REJECT.h> |
| |
| MODULE_AUTHOR("Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>"); |
| MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv6"); |
| MODULE_LICENSE("GPL"); |
| |
| /* Send RST reply */ |
| static void send_reset(struct net *net, struct sk_buff *oldskb) |
| { |
| struct sk_buff *nskb; |
| struct tcphdr otcph, *tcph; |
| unsigned int otcplen, hh_len; |
| int tcphoff, needs_ack; |
| const struct ipv6hdr *oip6h = ipv6_hdr(oldskb); |
| struct ipv6hdr *ip6h; |
| #define DEFAULT_TOS_VALUE 0x0U |
| const __u8 tclass = DEFAULT_TOS_VALUE; |
| struct dst_entry *dst = NULL; |
| u8 proto; |
| struct flowi6 fl6; |
| |
| if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) || |
| (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) { |
| pr_debug("addr is not unicast.\n"); |
| return; |
| } |
| |
| proto = oip6h->nexthdr; |
| tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto); |
| |
| if ((tcphoff < 0) || (tcphoff > oldskb->len)) { |
| pr_debug("Cannot get TCP header.\n"); |
| return; |
| } |
| |
| otcplen = oldskb->len - tcphoff; |
| |
| /* IP header checks: fragment, too short. */ |
| if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) { |
| pr_debug("proto(%d) != IPPROTO_TCP, " |
| "or too short. otcplen = %d\n", |
| proto, otcplen); |
| return; |
| } |
| |
| if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr))) |
| BUG(); |
| |
| /* No RST for RST. */ |
| if (otcph.rst) { |
| pr_debug("RST is set\n"); |
| return; |
| } |
| |
| /* Check checksum. */ |
| if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP, |
| skb_checksum(oldskb, tcphoff, otcplen, 0))) { |
| pr_debug("TCP checksum is invalid\n"); |
| return; |
| } |
| |
| memset(&fl6, 0, sizeof(fl6)); |
| fl6.flowi6_proto = IPPROTO_TCP; |
| ipv6_addr_copy(&fl6.saddr, &oip6h->daddr); |
| ipv6_addr_copy(&fl6.daddr, &oip6h->saddr); |
| fl6.fl6_sport = otcph.dest; |
| fl6.fl6_dport = otcph.source; |
| security_skb_classify_flow(oldskb, flowi6_to_flowi(&fl6)); |
| dst = ip6_route_output(net, NULL, &fl6); |
| if (dst == NULL || dst->error) { |
| dst_release(dst); |
| return; |
| } |
| dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0); |
| if (IS_ERR(dst)) |
| return; |
| |
| hh_len = (dst->dev->hard_header_len + 15)&~15; |
| nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr) |
| + sizeof(struct tcphdr) + dst->trailer_len, |
| GFP_ATOMIC); |
| |
| if (!nskb) { |
| if (net_ratelimit()) |
| pr_debug("cannot alloc skb\n"); |
| dst_release(dst); |
| return; |
| } |
| |
| skb_dst_set(nskb, dst); |
| |
| skb_reserve(nskb, hh_len + dst->header_len); |
| |
| skb_put(nskb, sizeof(struct ipv6hdr)); |
| skb_reset_network_header(nskb); |
| ip6h = ipv6_hdr(nskb); |
| *(__be32 *)ip6h = htonl(0x60000000 | (tclass << 20)); |
| ip6h->hop_limit = ip6_dst_hoplimit(dst); |
| ip6h->nexthdr = IPPROTO_TCP; |
| ipv6_addr_copy(&ip6h->saddr, &oip6h->daddr); |
| ipv6_addr_copy(&ip6h->daddr, &oip6h->saddr); |
| |
| tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); |
| /* Truncate to length (no data) */ |
| tcph->doff = sizeof(struct tcphdr)/4; |
| tcph->source = otcph.dest; |
| tcph->dest = otcph.source; |
| |
| if (otcph.ack) { |
| needs_ack = 0; |
| tcph->seq = otcph.ack_seq; |
| tcph->ack_seq = 0; |
| } else { |
| needs_ack = 1; |
| tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin |
| + otcplen - (otcph.doff<<2)); |
| tcph->seq = 0; |
| } |
| |
| /* Reset flags */ |
| ((u_int8_t *)tcph)[13] = 0; |
| tcph->rst = 1; |
| tcph->ack = needs_ack; |
| tcph->window = 0; |
| tcph->urg_ptr = 0; |
| tcph->check = 0; |
| |
| /* Adjust TCP checksum */ |
| tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr, |
| &ipv6_hdr(nskb)->daddr, |
| sizeof(struct tcphdr), IPPROTO_TCP, |
| csum_partial(tcph, |
| sizeof(struct tcphdr), 0)); |
| |
| nf_ct_attach(nskb, oldskb); |
| |
| ip6_local_out(nskb); |
| } |
| |
| static inline void |
| send_unreach(struct net *net, struct sk_buff *skb_in, unsigned char code, |
| unsigned int hooknum) |
| { |
| if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL) |
| skb_in->dev = net->loopback_dev; |
| |
| icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0); |
| } |
| |
| static unsigned int |
| reject_tg6(struct sk_buff *skb, const struct xt_action_param *par) |
| { |
| const struct ip6t_reject_info *reject = par->targinfo; |
| struct net *net = dev_net((par->in != NULL) ? par->in : par->out); |
| |
| pr_debug("%s: medium point\n", __func__); |
| switch (reject->with) { |
| case IP6T_ICMP6_NO_ROUTE: |
| send_unreach(net, skb, ICMPV6_NOROUTE, par->hooknum); |
| break; |
| case IP6T_ICMP6_ADM_PROHIBITED: |
| send_unreach(net, skb, ICMPV6_ADM_PROHIBITED, par->hooknum); |
| break; |
| case IP6T_ICMP6_NOT_NEIGHBOUR: |
| send_unreach(net, skb, ICMPV6_NOT_NEIGHBOUR, par->hooknum); |
| break; |
| case IP6T_ICMP6_ADDR_UNREACH: |
| send_unreach(net, skb, ICMPV6_ADDR_UNREACH, par->hooknum); |
| break; |
| case IP6T_ICMP6_PORT_UNREACH: |
| send_unreach(net, skb, ICMPV6_PORT_UNREACH, par->hooknum); |
| break; |
| case IP6T_ICMP6_ECHOREPLY: |
| /* Do nothing */ |
| break; |
| case IP6T_TCP_RESET: |
| send_reset(net, skb); |
| break; |
| default: |
| if (net_ratelimit()) |
| pr_info("case %u not handled yet\n", reject->with); |
| break; |
| } |
| |
| return NF_DROP; |
| } |
| |
| static int reject_tg6_check(const struct xt_tgchk_param *par) |
| { |
| const struct ip6t_reject_info *rejinfo = par->targinfo; |
| const struct ip6t_entry *e = par->entryinfo; |
| |
| if (rejinfo->with == IP6T_ICMP6_ECHOREPLY) { |
| pr_info("ECHOREPLY is not supported.\n"); |
| return -EINVAL; |
| } else if (rejinfo->with == IP6T_TCP_RESET) { |
| /* Must specify that it's a TCP packet */ |
| if (e->ipv6.proto != IPPROTO_TCP || |
| (e->ipv6.invflags & XT_INV_PROTO)) { |
| pr_info("TCP_RESET illegal for non-tcp\n"); |
| return -EINVAL; |
| } |
| } |
| return 0; |
| } |
| |
| static struct xt_target reject_tg6_reg __read_mostly = { |
| .name = "REJECT", |
| .family = NFPROTO_IPV6, |
| .target = reject_tg6, |
| .targetsize = sizeof(struct ip6t_reject_info), |
| .table = "filter", |
| .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) | |
| (1 << NF_INET_LOCAL_OUT), |
| .checkentry = reject_tg6_check, |
| .me = THIS_MODULE |
| }; |
| |
| static int __init reject_tg6_init(void) |
| { |
| return xt_register_target(&reject_tg6_reg); |
| } |
| |
| static void __exit reject_tg6_exit(void) |
| { |
| xt_unregister_target(&reject_tg6_reg); |
| } |
| |
| module_init(reject_tg6_init); |
| module_exit(reject_tg6_exit); |