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 struct net *net = dev_net(skb_dst(skb)->dev); 16 const struct iphdr *iph = ip_hdr(skb); 17 struct rtable *rt; 18 struct flowi fl = {}; 19 struct dst_entry *odst; 20 unsigned int hh_len; 21 unsigned int type; 22 23 type = inet_addr_type(net, iph->saddr); 24 if (skb->sk && inet_sk(skb->sk)->transparent) 25 type = RTN_LOCAL; 26 if (addr_type == RTN_UNSPEC) 27 addr_type = type; 28 29 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause 30 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. 31 */ 32 if (addr_type == RTN_LOCAL) { 33 fl.nl_u.ip4_u.daddr = iph->daddr; 34 if (type == RTN_LOCAL) 35 fl.nl_u.ip4_u.saddr = iph->saddr; 36 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos); 37 fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0; 38 fl.mark = skb->mark; 39 fl.flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0; 40 if (ip_route_output_key(net, &rt, &fl) != 0) 41 return -1; 42 43 /* Drop old route. */ 44 skb_dst_drop(skb); 45 skb_dst_set(skb, &rt->u.dst); 46 } else { 47 /* non-local src, find valid iif to satisfy 48 * rp-filter when calling ip_route_input. */ 49 fl.nl_u.ip4_u.daddr = iph->saddr; 50 if (ip_route_output_key(net, &rt, &fl) != 0) 51 return -1; 52 53 odst = skb_dst(skb); 54 if (ip_route_input(skb, iph->daddr, iph->saddr, 55 RT_TOS(iph->tos), rt->u.dst.dev) != 0) { 56 dst_release(&rt->u.dst); 57 return -1; 58 } 59 dst_release(&rt->u.dst); 60 dst_release(odst); 61 } 62 63 if (skb_dst(skb)->error) 64 return -1; 65 66 #ifdef CONFIG_XFRM 67 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && 68 xfrm_decode_session(skb, &fl, AF_INET) == 0) { 69 struct dst_entry *dst = skb_dst(skb); 70 skb_dst_set(skb, NULL); 71 if (xfrm_lookup(net, &dst, &fl, skb->sk, 0)) 72 return -1; 73 skb_dst_set(skb, dst); 74 } 75 #endif 76 77 /* Change in oif may mean change in hh_len. */ 78 hh_len = skb_dst(skb)->dev->hard_header_len; 79 if (skb_headroom(skb) < hh_len && 80 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 81 return -1; 82 83 return 0; 84 } 85 EXPORT_SYMBOL(ip_route_me_harder); 86 87 #ifdef CONFIG_XFRM 88 int ip_xfrm_me_harder(struct sk_buff *skb) 89 { 90 struct flowi fl; 91 unsigned int hh_len; 92 struct dst_entry *dst; 93 94 if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) 95 return 0; 96 if (xfrm_decode_session(skb, &fl, AF_INET) < 0) 97 return -1; 98 99 dst = skb_dst(skb); 100 if (dst->xfrm) 101 dst = ((struct xfrm_dst *)dst)->route; 102 dst_hold(dst); 103 104 if (xfrm_lookup(dev_net(dst->dev), &dst, &fl, skb->sk, 0) < 0) 105 return -1; 106 107 skb_dst_drop(skb); 108 skb_dst_set(skb, dst); 109 110 /* Change in oif may mean change in hh_len. */ 111 hh_len = skb_dst(skb)->dev->hard_header_len; 112 if (skb_headroom(skb) < hh_len && 113 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 114 return -1; 115 return 0; 116 } 117 EXPORT_SYMBOL(ip_xfrm_me_harder); 118 #endif 119 120 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *); 121 EXPORT_SYMBOL(ip_nat_decode_session); 122 123 /* 124 * Extra routing may needed on local out, as the QUEUE target never 125 * returns control to the table. 126 */ 127 128 struct ip_rt_info { 129 __be32 daddr; 130 __be32 saddr; 131 u_int8_t tos; 132 u_int32_t mark; 133 }; 134 135 static void nf_ip_saveroute(const struct sk_buff *skb, 136 struct nf_queue_entry *entry) 137 { 138 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 139 140 if (entry->hook == NF_INET_LOCAL_OUT) { 141 const struct iphdr *iph = ip_hdr(skb); 142 143 rt_info->tos = iph->tos; 144 rt_info->daddr = iph->daddr; 145 rt_info->saddr = iph->saddr; 146 rt_info->mark = skb->mark; 147 } 148 } 149 150 static int nf_ip_reroute(struct sk_buff *skb, 151 const struct nf_queue_entry *entry) 152 { 153 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 154 155 if (entry->hook == NF_INET_LOCAL_OUT) { 156 const struct iphdr *iph = ip_hdr(skb); 157 158 if (!(iph->tos == rt_info->tos 159 && skb->mark == rt_info->mark 160 && iph->daddr == rt_info->daddr 161 && iph->saddr == rt_info->saddr)) 162 return ip_route_me_harder(skb, RTN_UNSPEC); 163 } 164 return 0; 165 } 166 167 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, 168 unsigned int dataoff, u_int8_t protocol) 169 { 170 const struct iphdr *iph = ip_hdr(skb); 171 __sum16 csum = 0; 172 173 switch (skb->ip_summed) { 174 case CHECKSUM_COMPLETE: 175 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) 176 break; 177 if ((protocol == 0 && !csum_fold(skb->csum)) || 178 !csum_tcpudp_magic(iph->saddr, iph->daddr, 179 skb->len - dataoff, protocol, 180 skb->csum)) { 181 skb->ip_summed = CHECKSUM_UNNECESSARY; 182 break; 183 } 184 /* fall through */ 185 case CHECKSUM_NONE: 186 if (protocol == 0) 187 skb->csum = 0; 188 else 189 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, 190 skb->len - dataoff, 191 protocol, 0); 192 csum = __skb_checksum_complete(skb); 193 } 194 return csum; 195 } 196 EXPORT_SYMBOL(nf_ip_checksum); 197 198 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, 199 unsigned int dataoff, unsigned int len, 200 u_int8_t protocol) 201 { 202 const struct iphdr *iph = ip_hdr(skb); 203 __sum16 csum = 0; 204 205 switch (skb->ip_summed) { 206 case CHECKSUM_COMPLETE: 207 if (len == skb->len - dataoff) 208 return nf_ip_checksum(skb, hook, dataoff, protocol); 209 /* fall through */ 210 case CHECKSUM_NONE: 211 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, 212 skb->len - dataoff, 0); 213 skb->ip_summed = CHECKSUM_NONE; 214 csum = __skb_checksum_complete_head(skb, dataoff + len); 215 if (!csum) 216 skb->ip_summed = CHECKSUM_UNNECESSARY; 217 } 218 return csum; 219 } 220 221 static int nf_ip_route(struct dst_entry **dst, struct flowi *fl) 222 { 223 return ip_route_output_key(&init_net, (struct rtable **)dst, fl); 224 } 225 226 static const struct nf_afinfo nf_ip_afinfo = { 227 .family = AF_INET, 228 .checksum = nf_ip_checksum, 229 .checksum_partial = nf_ip_checksum_partial, 230 .route = nf_ip_route, 231 .saveroute = nf_ip_saveroute, 232 .reroute = nf_ip_reroute, 233 .route_key_size = sizeof(struct ip_rt_info), 234 }; 235 236 static int ipv4_netfilter_init(void) 237 { 238 return nf_register_afinfo(&nf_ip_afinfo); 239 } 240 241 static void ipv4_netfilter_fini(void) 242 { 243 nf_unregister_afinfo(&nf_ip_afinfo); 244 } 245 246 module_init(ipv4_netfilter_init); 247 module_exit(ipv4_netfilter_fini); 248 249 #ifdef CONFIG_SYSCTL 250 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = { 251 { .procname = "net", .ctl_name = CTL_NET, }, 252 { .procname = "ipv4", .ctl_name = NET_IPV4, }, 253 { .procname = "netfilter", .ctl_name = NET_IPV4_NETFILTER, }, 254 { } 255 }; 256 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path); 257 #endif /* CONFIG_SYSCTL */ 258