| 1 | /* |
| 2 | * IPv4 specific functions of netfilter core |
| 3 | * |
| 4 | * Rusty Russell (C) 2000 -- This code is GPL. |
| 5 | * Patrick McHardy (C) 2006-2012 |
| 6 | */ |
| 7 | #include <linux/kernel.h> |
| 8 | #include <linux/netfilter.h> |
| 9 | #include <linux/netfilter_ipv4.h> |
| 10 | #include <linux/ip.h> |
| 11 | #include <linux/skbuff.h> |
| 12 | #include <linux/gfp.h> |
| 13 | #include <linux/export.h> |
| 14 | #include <net/route.h> |
| 15 | #include <net/xfrm.h> |
| 16 | #include <net/ip.h> |
| 17 | #include <net/netfilter/nf_queue.h> |
| 18 | |
| 19 | /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */ |
| 20 | int ip_route_me_harder(struct sk_buff *skb, unsigned int addr_type) |
| 21 | { |
| 22 | struct net *net = dev_net(skb_dst(skb)->dev); |
| 23 | const struct iphdr *iph = ip_hdr(skb); |
| 24 | struct rtable *rt; |
| 25 | struct flowi4 fl4 = {}; |
| 26 | __be32 saddr = iph->saddr; |
| 27 | __u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0; |
| 28 | unsigned int hh_len; |
| 29 | |
| 30 | if (addr_type == RTN_UNSPEC) |
| 31 | addr_type = inet_addr_type(net, saddr); |
| 32 | if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST) |
| 33 | flags |= FLOWI_FLAG_ANYSRC; |
| 34 | else |
| 35 | saddr = 0; |
| 36 | |
| 37 | /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause |
| 38 | * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. |
| 39 | */ |
| 40 | fl4.daddr = iph->daddr; |
| 41 | fl4.saddr = saddr; |
| 42 | fl4.flowi4_tos = RT_TOS(iph->tos); |
| 43 | fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0; |
| 44 | fl4.flowi4_mark = skb->mark; |
| 45 | fl4.flowi4_flags = flags; |
| 46 | rt = ip_route_output_key(net, &fl4); |
| 47 | if (IS_ERR(rt)) |
| 48 | return PTR_ERR(rt); |
| 49 | |
| 50 | /* Drop old route. */ |
| 51 | skb_dst_drop(skb); |
| 52 | skb_dst_set(skb, &rt->dst); |
| 53 | |
| 54 | if (skb_dst(skb)->error) |
| 55 | return skb_dst(skb)->error; |
| 56 | |
| 57 | #ifdef CONFIG_XFRM |
| 58 | if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && |
| 59 | xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) { |
| 60 | struct dst_entry *dst = skb_dst(skb); |
| 61 | skb_dst_set(skb, NULL); |
| 62 | dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0); |
| 63 | if (IS_ERR(dst)) |
| 64 | return PTR_ERR(dst); |
| 65 | skb_dst_set(skb, dst); |
| 66 | } |
| 67 | #endif |
| 68 | |
| 69 | /* Change in oif may mean change in hh_len. */ |
| 70 | hh_len = skb_dst(skb)->dev->hard_header_len; |
| 71 | if (skb_headroom(skb) < hh_len && |
| 72 | pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)), |
| 73 | 0, GFP_ATOMIC)) |
| 74 | return -ENOMEM; |
| 75 | |
| 76 | return 0; |
| 77 | } |
| 78 | EXPORT_SYMBOL(ip_route_me_harder); |
| 79 | |
| 80 | /* |
| 81 | * Extra routing may needed on local out, as the QUEUE target never |
| 82 | * returns control to the table. |
| 83 | */ |
| 84 | |
| 85 | struct ip_rt_info { |
| 86 | __be32 daddr; |
| 87 | __be32 saddr; |
| 88 | u_int8_t tos; |
| 89 | u_int32_t mark; |
| 90 | }; |
| 91 | |
| 92 | static void nf_ip_saveroute(const struct sk_buff *skb, |
| 93 | struct nf_queue_entry *entry) |
| 94 | { |
| 95 | struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); |
| 96 | |
| 97 | if (entry->hook == NF_INET_LOCAL_OUT) { |
| 98 | const struct iphdr *iph = ip_hdr(skb); |
| 99 | |
| 100 | rt_info->tos = iph->tos; |
| 101 | rt_info->daddr = iph->daddr; |
| 102 | rt_info->saddr = iph->saddr; |
| 103 | rt_info->mark = skb->mark; |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | static int nf_ip_reroute(struct sk_buff *skb, |
| 108 | const struct nf_queue_entry *entry) |
| 109 | { |
| 110 | const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); |
| 111 | |
| 112 | if (entry->hook == NF_INET_LOCAL_OUT) { |
| 113 | const struct iphdr *iph = ip_hdr(skb); |
| 114 | |
| 115 | if (!(iph->tos == rt_info->tos && |
| 116 | skb->mark == rt_info->mark && |
| 117 | iph->daddr == rt_info->daddr && |
| 118 | iph->saddr == rt_info->saddr)) |
| 119 | return ip_route_me_harder(skb, RTN_UNSPEC); |
| 120 | } |
| 121 | return 0; |
| 122 | } |
| 123 | |
| 124 | __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, |
| 125 | unsigned int dataoff, u_int8_t protocol) |
| 126 | { |
| 127 | const struct iphdr *iph = ip_hdr(skb); |
| 128 | __sum16 csum = 0; |
| 129 | |
| 130 | switch (skb->ip_summed) { |
| 131 | case CHECKSUM_COMPLETE: |
| 132 | if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) |
| 133 | break; |
| 134 | if ((protocol == 0 && !csum_fold(skb->csum)) || |
| 135 | !csum_tcpudp_magic(iph->saddr, iph->daddr, |
| 136 | skb->len - dataoff, protocol, |
| 137 | skb->csum)) { |
| 138 | skb->ip_summed = CHECKSUM_UNNECESSARY; |
| 139 | break; |
| 140 | } |
| 141 | /* fall through */ |
| 142 | case CHECKSUM_NONE: |
| 143 | if (protocol == 0) |
| 144 | skb->csum = 0; |
| 145 | else |
| 146 | skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, |
| 147 | skb->len - dataoff, |
| 148 | protocol, 0); |
| 149 | csum = __skb_checksum_complete(skb); |
| 150 | } |
| 151 | return csum; |
| 152 | } |
| 153 | EXPORT_SYMBOL(nf_ip_checksum); |
| 154 | |
| 155 | static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, |
| 156 | unsigned int dataoff, unsigned int len, |
| 157 | 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 (len == skb->len - dataoff) |
| 165 | return nf_ip_checksum(skb, hook, dataoff, protocol); |
| 166 | /* fall through */ |
| 167 | case CHECKSUM_NONE: |
| 168 | skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, |
| 169 | skb->len - dataoff, 0); |
| 170 | skb->ip_summed = CHECKSUM_NONE; |
| 171 | return __skb_checksum_complete_head(skb, dataoff + len); |
| 172 | } |
| 173 | return csum; |
| 174 | } |
| 175 | |
| 176 | static int nf_ip_route(struct net *net, struct dst_entry **dst, |
| 177 | struct flowi *fl, bool strict __always_unused) |
| 178 | { |
| 179 | struct rtable *rt = ip_route_output_key(net, &fl->u.ip4); |
| 180 | if (IS_ERR(rt)) |
| 181 | return PTR_ERR(rt); |
| 182 | *dst = &rt->dst; |
| 183 | return 0; |
| 184 | } |
| 185 | |
| 186 | static const struct nf_afinfo nf_ip_afinfo = { |
| 187 | .family = AF_INET, |
| 188 | .checksum = nf_ip_checksum, |
| 189 | .checksum_partial = nf_ip_checksum_partial, |
| 190 | .route = nf_ip_route, |
| 191 | .saveroute = nf_ip_saveroute, |
| 192 | .reroute = nf_ip_reroute, |
| 193 | .route_key_size = sizeof(struct ip_rt_info), |
| 194 | }; |
| 195 | |
| 196 | static int __init ipv4_netfilter_init(void) |
| 197 | { |
| 198 | return nf_register_afinfo(&nf_ip_afinfo); |
| 199 | } |
| 200 | |
| 201 | static void __exit ipv4_netfilter_fini(void) |
| 202 | { |
| 203 | nf_unregister_afinfo(&nf_ip_afinfo); |
| 204 | } |
| 205 | |
| 206 | module_init(ipv4_netfilter_init); |
| 207 | module_exit(ipv4_netfilter_fini); |