| 1 | /* IPv4 specific functions of netfilter core */ |
| 2 | #include <linux/kernel.h> |
| 3 | #include <linux/netfilter.h> |
| 4 | #include <linux/netfilter_ipv4.h> |
| 5 | #include <linux/ip.h> |
| 6 | #include <linux/skbuff.h> |
| 7 | #include <net/route.h> |
| 8 | #include <net/xfrm.h> |
| 9 | #include <net/ip.h> |
| 10 | #include <net/netfilter/nf_queue.h> |
| 11 | |
| 12 | /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */ |
| 13 | int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type) |
| 14 | { |
| 15 | const struct iphdr *iph = ip_hdr(skb); |
| 16 | struct rtable *rt; |
| 17 | struct flowi fl = {}; |
| 18 | struct dst_entry *odst; |
| 19 | unsigned int hh_len; |
| 20 | unsigned int type; |
| 21 | |
| 22 | type = inet_addr_type(&init_net, iph->saddr); |
| 23 | if (addr_type == RTN_UNSPEC) |
| 24 | addr_type = type; |
| 25 | |
| 26 | /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause |
| 27 | * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. |
| 28 | */ |
| 29 | if (addr_type == RTN_LOCAL) { |
| 30 | fl.nl_u.ip4_u.daddr = iph->daddr; |
| 31 | if (type == RTN_LOCAL) |
| 32 | fl.nl_u.ip4_u.saddr = iph->saddr; |
| 33 | fl.nl_u.ip4_u.tos = RT_TOS(iph->tos); |
| 34 | fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0; |
| 35 | fl.mark = skb->mark; |
| 36 | if (ip_route_output_key(&init_net, &rt, &fl) != 0) |
| 37 | return -1; |
| 38 | |
| 39 | /* Drop old route. */ |
| 40 | dst_release(skb->dst); |
| 41 | skb->dst = &rt->u.dst; |
| 42 | } else { |
| 43 | /* non-local src, find valid iif to satisfy |
| 44 | * rp-filter when calling ip_route_input. */ |
| 45 | fl.nl_u.ip4_u.daddr = iph->saddr; |
| 46 | if (ip_route_output_key(&init_net, &rt, &fl) != 0) |
| 47 | return -1; |
| 48 | |
| 49 | odst = skb->dst; |
| 50 | if (ip_route_input(skb, iph->daddr, iph->saddr, |
| 51 | RT_TOS(iph->tos), rt->u.dst.dev) != 0) { |
| 52 | dst_release(&rt->u.dst); |
| 53 | return -1; |
| 54 | } |
| 55 | dst_release(&rt->u.dst); |
| 56 | dst_release(odst); |
| 57 | } |
| 58 | |
| 59 | if (skb->dst->error) |
| 60 | return -1; |
| 61 | |
| 62 | #ifdef CONFIG_XFRM |
| 63 | if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && |
| 64 | xfrm_decode_session(skb, &fl, AF_INET) == 0) |
| 65 | if (xfrm_lookup(&skb->dst, &fl, skb->sk, 0)) |
| 66 | return -1; |
| 67 | #endif |
| 68 | |
| 69 | /* Change in oif may mean change in hh_len. */ |
| 70 | hh_len = skb->dst->dev->hard_header_len; |
| 71 | if (skb_headroom(skb) < hh_len && |
| 72 | pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) |
| 73 | return -1; |
| 74 | |
| 75 | return 0; |
| 76 | } |
| 77 | EXPORT_SYMBOL(ip_route_me_harder); |
| 78 | |
| 79 | #ifdef CONFIG_XFRM |
| 80 | int ip_xfrm_me_harder(struct sk_buff *skb) |
| 81 | { |
| 82 | struct flowi fl; |
| 83 | unsigned int hh_len; |
| 84 | struct dst_entry *dst; |
| 85 | |
| 86 | if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) |
| 87 | return 0; |
| 88 | if (xfrm_decode_session(skb, &fl, AF_INET) < 0) |
| 89 | return -1; |
| 90 | |
| 91 | dst = skb->dst; |
| 92 | if (dst->xfrm) |
| 93 | dst = ((struct xfrm_dst *)dst)->route; |
| 94 | dst_hold(dst); |
| 95 | |
| 96 | if (xfrm_lookup(&dst, &fl, skb->sk, 0) < 0) |
| 97 | return -1; |
| 98 | |
| 99 | dst_release(skb->dst); |
| 100 | skb->dst = dst; |
| 101 | |
| 102 | /* Change in oif may mean change in hh_len. */ |
| 103 | hh_len = skb->dst->dev->hard_header_len; |
| 104 | if (skb_headroom(skb) < hh_len && |
| 105 | pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) |
| 106 | return -1; |
| 107 | return 0; |
| 108 | } |
| 109 | EXPORT_SYMBOL(ip_xfrm_me_harder); |
| 110 | #endif |
| 111 | |
| 112 | void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *); |
| 113 | EXPORT_SYMBOL(ip_nat_decode_session); |
| 114 | |
| 115 | /* |
| 116 | * Extra routing may needed on local out, as the QUEUE target never |
| 117 | * returns control to the table. |
| 118 | */ |
| 119 | |
| 120 | struct ip_rt_info { |
| 121 | __be32 daddr; |
| 122 | __be32 saddr; |
| 123 | u_int8_t tos; |
| 124 | }; |
| 125 | |
| 126 | static void nf_ip_saveroute(const struct sk_buff *skb, |
| 127 | struct nf_queue_entry *entry) |
| 128 | { |
| 129 | struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); |
| 130 | |
| 131 | if (entry->hook == NF_INET_LOCAL_OUT) { |
| 132 | const struct iphdr *iph = ip_hdr(skb); |
| 133 | |
| 134 | rt_info->tos = iph->tos; |
| 135 | rt_info->daddr = iph->daddr; |
| 136 | rt_info->saddr = iph->saddr; |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | static int nf_ip_reroute(struct sk_buff *skb, |
| 141 | const struct nf_queue_entry *entry) |
| 142 | { |
| 143 | const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); |
| 144 | |
| 145 | if (entry->hook == NF_INET_LOCAL_OUT) { |
| 146 | const struct iphdr *iph = ip_hdr(skb); |
| 147 | |
| 148 | if (!(iph->tos == rt_info->tos |
| 149 | && iph->daddr == rt_info->daddr |
| 150 | && iph->saddr == rt_info->saddr)) |
| 151 | return ip_route_me_harder(skb, RTN_UNSPEC); |
| 152 | } |
| 153 | return 0; |
| 154 | } |
| 155 | |
| 156 | __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, |
| 157 | unsigned int dataoff, u_int8_t protocol) |
| 158 | { |
| 159 | const struct iphdr *iph = ip_hdr(skb); |
| 160 | __sum16 csum = 0; |
| 161 | |
| 162 | switch (skb->ip_summed) { |
| 163 | case CHECKSUM_COMPLETE: |
| 164 | if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) |
| 165 | break; |
| 166 | if ((protocol == 0 && !csum_fold(skb->csum)) || |
| 167 | !csum_tcpudp_magic(iph->saddr, iph->daddr, |
| 168 | skb->len - dataoff, protocol, |
| 169 | skb->csum)) { |
| 170 | skb->ip_summed = CHECKSUM_UNNECESSARY; |
| 171 | break; |
| 172 | } |
| 173 | /* fall through */ |
| 174 | case CHECKSUM_NONE: |
| 175 | if (protocol == 0) |
| 176 | skb->csum = 0; |
| 177 | else |
| 178 | skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, |
| 179 | skb->len - dataoff, |
| 180 | protocol, 0); |
| 181 | csum = __skb_checksum_complete(skb); |
| 182 | } |
| 183 | return csum; |
| 184 | } |
| 185 | |
| 186 | EXPORT_SYMBOL(nf_ip_checksum); |
| 187 | |
| 188 | static int nf_ip_route(struct dst_entry **dst, struct flowi *fl) |
| 189 | { |
| 190 | return ip_route_output_key(&init_net, (struct rtable **)dst, fl); |
| 191 | } |
| 192 | |
| 193 | static const struct nf_afinfo nf_ip_afinfo = { |
| 194 | .family = AF_INET, |
| 195 | .checksum = nf_ip_checksum, |
| 196 | .route = nf_ip_route, |
| 197 | .saveroute = nf_ip_saveroute, |
| 198 | .reroute = nf_ip_reroute, |
| 199 | .route_key_size = sizeof(struct ip_rt_info), |
| 200 | }; |
| 201 | |
| 202 | static int ipv4_netfilter_init(void) |
| 203 | { |
| 204 | return nf_register_afinfo(&nf_ip_afinfo); |
| 205 | } |
| 206 | |
| 207 | static void ipv4_netfilter_fini(void) |
| 208 | { |
| 209 | nf_unregister_afinfo(&nf_ip_afinfo); |
| 210 | } |
| 211 | |
| 212 | module_init(ipv4_netfilter_init); |
| 213 | module_exit(ipv4_netfilter_fini); |
| 214 | |
| 215 | #ifdef CONFIG_SYSCTL |
| 216 | struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = { |
| 217 | { .procname = "net", .ctl_name = CTL_NET, }, |
| 218 | { .procname = "ipv4", .ctl_name = NET_IPV4, }, |
| 219 | { .procname = "netfilter", .ctl_name = NET_IPV4_NETFILTER, }, |
| 220 | { } |
| 221 | }; |
| 222 | EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path); |
| 223 | #endif /* CONFIG_SYSCTL */ |