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 */ 224