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 <linux/gfp.h> 8 #include <net/route.h> 9 #include <net/xfrm.h> 10 #include <net/ip.h> 11 #include <net/netfilter/nf_queue.h> 12 13 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */ 14 int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type) 15 { 16 struct net *net = dev_net(skb_dst(skb)->dev); 17 const struct iphdr *iph = ip_hdr(skb); 18 struct rtable *rt; 19 struct flowi4 fl4 = {}; 20 unsigned long orefdst; 21 unsigned int hh_len; 22 unsigned int type; 23 24 type = inet_addr_type(net, iph->saddr); 25 if (skb->sk && inet_sk(skb->sk)->transparent) 26 type = RTN_LOCAL; 27 if (addr_type == RTN_UNSPEC) 28 addr_type = type; 29 30 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause 31 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. 32 */ 33 if (addr_type == RTN_LOCAL) { 34 fl4.daddr = iph->daddr; 35 if (type == RTN_LOCAL) 36 fl4.saddr = iph->saddr; 37 fl4.flowi4_tos = RT_TOS(iph->tos); 38 fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0; 39 fl4.flowi4_mark = skb->mark; 40 fl4.flowi4_flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0; 41 rt = ip_route_output_key(net, &fl4); 42 if (IS_ERR(rt)) 43 return -1; 44 45 /* Drop old route. */ 46 skb_dst_drop(skb); 47 skb_dst_set(skb, &rt->dst); 48 } else { 49 /* non-local src, find valid iif to satisfy 50 * rp-filter when calling ip_route_input. */ 51 fl4.daddr = iph->saddr; 52 rt = ip_route_output_key(net, &fl4); 53 if (IS_ERR(rt)) 54 return -1; 55 56 orefdst = skb->_skb_refdst; 57 if (ip_route_input(skb, iph->daddr, iph->saddr, 58 RT_TOS(iph->tos), rt->dst.dev) != 0) { 59 dst_release(&rt->dst); 60 return -1; 61 } 62 dst_release(&rt->dst); 63 refdst_drop(orefdst); 64 } 65 66 if (skb_dst(skb)->error) 67 return -1; 68 69 #ifdef CONFIG_XFRM 70 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && 71 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) { 72 struct dst_entry *dst = skb_dst(skb); 73 skb_dst_set(skb, NULL); 74 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0); 75 if (IS_ERR(dst)) 76 return -1; 77 skb_dst_set(skb, dst); 78 } 79 #endif 80 81 /* Change in oif may mean change in hh_len. */ 82 hh_len = skb_dst(skb)->dev->hard_header_len; 83 if (skb_headroom(skb) < hh_len && 84 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 85 return -1; 86 87 return 0; 88 } 89 EXPORT_SYMBOL(ip_route_me_harder); 90 91 #ifdef CONFIG_XFRM 92 int ip_xfrm_me_harder(struct sk_buff *skb) 93 { 94 struct flowi fl; 95 unsigned int hh_len; 96 struct dst_entry *dst; 97 98 if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) 99 return 0; 100 if (xfrm_decode_session(skb, &fl, AF_INET) < 0) 101 return -1; 102 103 dst = skb_dst(skb); 104 if (dst->xfrm) 105 dst = ((struct xfrm_dst *)dst)->route; 106 dst_hold(dst); 107 108 dst = xfrm_lookup(dev_net(dst->dev), dst, &fl, skb->sk, 0); 109 if (IS_ERR(dst)) 110 return -1; 111 112 skb_dst_drop(skb); 113 skb_dst_set(skb, dst); 114 115 /* Change in oif may mean change in hh_len. */ 116 hh_len = skb_dst(skb)->dev->hard_header_len; 117 if (skb_headroom(skb) < hh_len && 118 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 119 return -1; 120 return 0; 121 } 122 EXPORT_SYMBOL(ip_xfrm_me_harder); 123 #endif 124 125 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *); 126 EXPORT_SYMBOL(ip_nat_decode_session); 127 128 /* 129 * Extra routing may needed on local out, as the QUEUE target never 130 * returns control to the table. 131 */ 132 133 struct ip_rt_info { 134 __be32 daddr; 135 __be32 saddr; 136 u_int8_t tos; 137 u_int32_t mark; 138 }; 139 140 static void nf_ip_saveroute(const struct sk_buff *skb, 141 struct nf_queue_entry *entry) 142 { 143 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 rt_info->tos = iph->tos; 149 rt_info->daddr = iph->daddr; 150 rt_info->saddr = iph->saddr; 151 rt_info->mark = skb->mark; 152 } 153 } 154 155 static int nf_ip_reroute(struct sk_buff *skb, 156 const struct nf_queue_entry *entry) 157 { 158 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 159 160 if (entry->hook == NF_INET_LOCAL_OUT) { 161 const struct iphdr *iph = ip_hdr(skb); 162 163 if (!(iph->tos == rt_info->tos && 164 skb->mark == rt_info->mark && 165 iph->daddr == rt_info->daddr && 166 iph->saddr == rt_info->saddr)) 167 return ip_route_me_harder(skb, RTN_UNSPEC); 168 } 169 return 0; 170 } 171 172 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, 173 unsigned int dataoff, u_int8_t protocol) 174 { 175 const struct iphdr *iph = ip_hdr(skb); 176 __sum16 csum = 0; 177 178 switch (skb->ip_summed) { 179 case CHECKSUM_COMPLETE: 180 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) 181 break; 182 if ((protocol == 0 && !csum_fold(skb->csum)) || 183 !csum_tcpudp_magic(iph->saddr, iph->daddr, 184 skb->len - dataoff, protocol, 185 skb->csum)) { 186 skb->ip_summed = CHECKSUM_UNNECESSARY; 187 break; 188 } 189 /* fall through */ 190 case CHECKSUM_NONE: 191 if (protocol == 0) 192 skb->csum = 0; 193 else 194 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, 195 skb->len - dataoff, 196 protocol, 0); 197 csum = __skb_checksum_complete(skb); 198 } 199 return csum; 200 } 201 EXPORT_SYMBOL(nf_ip_checksum); 202 203 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, 204 unsigned int dataoff, unsigned int len, 205 u_int8_t protocol) 206 { 207 const struct iphdr *iph = ip_hdr(skb); 208 __sum16 csum = 0; 209 210 switch (skb->ip_summed) { 211 case CHECKSUM_COMPLETE: 212 if (len == skb->len - dataoff) 213 return nf_ip_checksum(skb, hook, dataoff, protocol); 214 /* fall through */ 215 case CHECKSUM_NONE: 216 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, 217 skb->len - dataoff, 0); 218 skb->ip_summed = CHECKSUM_NONE; 219 return __skb_checksum_complete_head(skb, dataoff + len); 220 } 221 return csum; 222 } 223 224 static int nf_ip_route(struct net *net, struct dst_entry **dst, 225 struct flowi *fl, bool strict __always_unused) 226 { 227 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4); 228 if (IS_ERR(rt)) 229 return PTR_ERR(rt); 230 *dst = &rt->dst; 231 return 0; 232 } 233 234 static const struct nf_afinfo nf_ip_afinfo = { 235 .family = AF_INET, 236 .checksum = nf_ip_checksum, 237 .checksum_partial = nf_ip_checksum_partial, 238 .route = nf_ip_route, 239 .saveroute = nf_ip_saveroute, 240 .reroute = nf_ip_reroute, 241 .route_key_size = sizeof(struct ip_rt_info), 242 }; 243 244 static int ipv4_netfilter_init(void) 245 { 246 return nf_register_afinfo(&nf_ip_afinfo); 247 } 248 249 static void ipv4_netfilter_fini(void) 250 { 251 nf_unregister_afinfo(&nf_ip_afinfo); 252 } 253 254 module_init(ipv4_netfilter_init); 255 module_exit(ipv4_netfilter_fini); 256 257 #ifdef CONFIG_SYSCTL 258 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = { 259 { .procname = "net", }, 260 { .procname = "ipv4", }, 261 { .procname = "netfilter", }, 262 { } 263 }; 264 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path); 265 #endif /* CONFIG_SYSCTL */ 266