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->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 dst_release(skb->dst); 45 skb->dst = &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; 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->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 if (xfrm_lookup(net, &skb->dst, &fl, skb->sk, 0)) 70 return -1; 71 #endif 72 73 /* Change in oif may mean change in hh_len. */ 74 hh_len = skb->dst->dev->hard_header_len; 75 if (skb_headroom(skb) < hh_len && 76 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 77 return -1; 78 79 return 0; 80 } 81 EXPORT_SYMBOL(ip_route_me_harder); 82 83 #ifdef CONFIG_XFRM 84 int ip_xfrm_me_harder(struct sk_buff *skb) 85 { 86 struct flowi fl; 87 unsigned int hh_len; 88 struct dst_entry *dst; 89 90 if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) 91 return 0; 92 if (xfrm_decode_session(skb, &fl, AF_INET) < 0) 93 return -1; 94 95 dst = skb->dst; 96 if (dst->xfrm) 97 dst = ((struct xfrm_dst *)dst)->route; 98 dst_hold(dst); 99 100 if (xfrm_lookup(dev_net(dst->dev), &dst, &fl, skb->sk, 0) < 0) 101 return -1; 102 103 dst_release(skb->dst); 104 skb->dst = dst; 105 106 /* Change in oif may mean change in hh_len. */ 107 hh_len = skb->dst->dev->hard_header_len; 108 if (skb_headroom(skb) < hh_len && 109 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 110 return -1; 111 return 0; 112 } 113 EXPORT_SYMBOL(ip_xfrm_me_harder); 114 #endif 115 116 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *); 117 EXPORT_SYMBOL(ip_nat_decode_session); 118 119 /* 120 * Extra routing may needed on local out, as the QUEUE target never 121 * returns control to the table. 122 */ 123 124 struct ip_rt_info { 125 __be32 daddr; 126 __be32 saddr; 127 u_int8_t tos; 128 u_int32_t mark; 129 }; 130 131 static void nf_ip_saveroute(const struct sk_buff *skb, 132 struct nf_queue_entry *entry) 133 { 134 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 135 136 if (entry->hook == NF_INET_LOCAL_OUT) { 137 const struct iphdr *iph = ip_hdr(skb); 138 139 rt_info->tos = iph->tos; 140 rt_info->daddr = iph->daddr; 141 rt_info->saddr = iph->saddr; 142 rt_info->mark = skb->mark; 143 } 144 } 145 146 static int nf_ip_reroute(struct sk_buff *skb, 147 const struct nf_queue_entry *entry) 148 { 149 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 150 151 if (entry->hook == NF_INET_LOCAL_OUT) { 152 const struct iphdr *iph = ip_hdr(skb); 153 154 if (!(iph->tos == rt_info->tos 155 && skb->mark == rt_info->mark 156 && iph->daddr == rt_info->daddr 157 && iph->saddr == rt_info->saddr)) 158 return ip_route_me_harder(skb, RTN_UNSPEC); 159 } 160 return 0; 161 } 162 163 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, 164 unsigned int dataoff, u_int8_t protocol) 165 { 166 const struct iphdr *iph = ip_hdr(skb); 167 __sum16 csum = 0; 168 169 switch (skb->ip_summed) { 170 case CHECKSUM_COMPLETE: 171 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) 172 break; 173 if ((protocol == 0 && !csum_fold(skb->csum)) || 174 !csum_tcpudp_magic(iph->saddr, iph->daddr, 175 skb->len - dataoff, protocol, 176 skb->csum)) { 177 skb->ip_summed = CHECKSUM_UNNECESSARY; 178 break; 179 } 180 /* fall through */ 181 case CHECKSUM_NONE: 182 if (protocol == 0) 183 skb->csum = 0; 184 else 185 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, 186 skb->len - dataoff, 187 protocol, 0); 188 csum = __skb_checksum_complete(skb); 189 } 190 return csum; 191 } 192 EXPORT_SYMBOL(nf_ip_checksum); 193 194 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, 195 unsigned int dataoff, unsigned int len, 196 u_int8_t protocol) 197 { 198 const struct iphdr *iph = ip_hdr(skb); 199 __sum16 csum = 0; 200 201 switch (skb->ip_summed) { 202 case CHECKSUM_COMPLETE: 203 if (len == skb->len - dataoff) 204 return nf_ip_checksum(skb, hook, dataoff, protocol); 205 /* fall through */ 206 case CHECKSUM_NONE: 207 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, 208 skb->len - dataoff, 0); 209 skb->ip_summed = CHECKSUM_NONE; 210 csum = __skb_checksum_complete_head(skb, dataoff + len); 211 if (!csum) 212 skb->ip_summed = CHECKSUM_UNNECESSARY; 213 } 214 return csum; 215 } 216 217 static int nf_ip_route(struct dst_entry **dst, struct flowi *fl) 218 { 219 return ip_route_output_key(&init_net, (struct rtable **)dst, fl); 220 } 221 222 static const struct nf_afinfo nf_ip_afinfo = { 223 .family = AF_INET, 224 .checksum = nf_ip_checksum, 225 .checksum_partial = nf_ip_checksum_partial, 226 .route = nf_ip_route, 227 .saveroute = nf_ip_saveroute, 228 .reroute = nf_ip_reroute, 229 .route_key_size = sizeof(struct ip_rt_info), 230 }; 231 232 static int ipv4_netfilter_init(void) 233 { 234 return nf_register_afinfo(&nf_ip_afinfo); 235 } 236 237 static void ipv4_netfilter_fini(void) 238 { 239 nf_unregister_afinfo(&nf_ip_afinfo); 240 } 241 242 module_init(ipv4_netfilter_init); 243 module_exit(ipv4_netfilter_fini); 244 245 #ifdef CONFIG_SYSCTL 246 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = { 247 { .procname = "net", .ctl_name = CTL_NET, }, 248 { .procname = "ipv4", .ctl_name = NET_IPV4, }, 249 { .procname = "netfilter", .ctl_name = NET_IPV4_NETFILTER, }, 250 { } 251 }; 252 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path); 253 #endif /* CONFIG_SYSCTL */ 254