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(&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(&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 }; 129 130 static void nf_ip_saveroute(const struct sk_buff *skb, 131 struct nf_queue_entry *entry) 132 { 133 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 134 135 if (entry->hook == NF_INET_LOCAL_OUT) { 136 const struct iphdr *iph = ip_hdr(skb); 137 138 rt_info->tos = iph->tos; 139 rt_info->daddr = iph->daddr; 140 rt_info->saddr = iph->saddr; 141 } 142 } 143 144 static int nf_ip_reroute(struct sk_buff *skb, 145 const struct nf_queue_entry *entry) 146 { 147 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 148 149 if (entry->hook == NF_INET_LOCAL_OUT) { 150 const struct iphdr *iph = ip_hdr(skb); 151 152 if (!(iph->tos == rt_info->tos 153 && iph->daddr == rt_info->daddr 154 && iph->saddr == rt_info->saddr)) 155 return ip_route_me_harder(skb, RTN_UNSPEC); 156 } 157 return 0; 158 } 159 160 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, 161 unsigned int dataoff, u_int8_t protocol) 162 { 163 const struct iphdr *iph = ip_hdr(skb); 164 __sum16 csum = 0; 165 166 switch (skb->ip_summed) { 167 case CHECKSUM_COMPLETE: 168 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) 169 break; 170 if ((protocol == 0 && !csum_fold(skb->csum)) || 171 !csum_tcpudp_magic(iph->saddr, iph->daddr, 172 skb->len - dataoff, protocol, 173 skb->csum)) { 174 skb->ip_summed = CHECKSUM_UNNECESSARY; 175 break; 176 } 177 /* fall through */ 178 case CHECKSUM_NONE: 179 if (protocol == 0) 180 skb->csum = 0; 181 else 182 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, 183 skb->len - dataoff, 184 protocol, 0); 185 csum = __skb_checksum_complete(skb); 186 } 187 return csum; 188 } 189 EXPORT_SYMBOL(nf_ip_checksum); 190 191 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, 192 unsigned int dataoff, unsigned int len, 193 u_int8_t protocol) 194 { 195 const struct iphdr *iph = ip_hdr(skb); 196 __sum16 csum = 0; 197 198 switch (skb->ip_summed) { 199 case CHECKSUM_COMPLETE: 200 if (len == skb->len - dataoff) 201 return nf_ip_checksum(skb, hook, dataoff, protocol); 202 /* fall through */ 203 case CHECKSUM_NONE: 204 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, 205 skb->len - dataoff, 0); 206 skb->ip_summed = CHECKSUM_NONE; 207 csum = __skb_checksum_complete_head(skb, dataoff + len); 208 if (!csum) 209 skb->ip_summed = CHECKSUM_UNNECESSARY; 210 } 211 return csum; 212 } 213 214 static int nf_ip_route(struct dst_entry **dst, struct flowi *fl) 215 { 216 return ip_route_output_key(&init_net, (struct rtable **)dst, fl); 217 } 218 219 static const struct nf_afinfo nf_ip_afinfo = { 220 .family = AF_INET, 221 .checksum = nf_ip_checksum, 222 .checksum_partial = nf_ip_checksum_partial, 223 .route = nf_ip_route, 224 .saveroute = nf_ip_saveroute, 225 .reroute = nf_ip_reroute, 226 .route_key_size = sizeof(struct ip_rt_info), 227 }; 228 229 static int ipv4_netfilter_init(void) 230 { 231 return nf_register_afinfo(&nf_ip_afinfo); 232 } 233 234 static void ipv4_netfilter_fini(void) 235 { 236 nf_unregister_afinfo(&nf_ip_afinfo); 237 } 238 239 module_init(ipv4_netfilter_init); 240 module_exit(ipv4_netfilter_fini); 241 242 #ifdef CONFIG_SYSCTL 243 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = { 244 { .procname = "net", .ctl_name = CTL_NET, }, 245 { .procname = "ipv4", .ctl_name = NET_IPV4, }, 246 { .procname = "netfilter", .ctl_name = NET_IPV4_NETFILTER, }, 247 { } 248 }; 249 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path); 250 #endif /* CONFIG_SYSCTL */ 251