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 <linux/export.h> 9 #include <net/route.h> 10 #include <net/xfrm.h> 11 #include <net/ip.h> 12 #include <net/netfilter/nf_queue.h> 13 14 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */ 15 int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type) 16 { 17 struct net *net = dev_net(skb_dst(skb)->dev); 18 const struct iphdr *iph = ip_hdr(skb); 19 struct rtable *rt; 20 struct flowi4 fl4 = {}; 21 __be32 saddr = iph->saddr; 22 __u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0; 23 unsigned int hh_len; 24 25 if (addr_type == RTN_UNSPEC) 26 addr_type = inet_addr_type(net, saddr); 27 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST) 28 flags |= FLOWI_FLAG_ANYSRC; 29 else 30 saddr = 0; 31 32 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause 33 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. 34 */ 35 fl4.daddr = iph->daddr; 36 fl4.saddr = 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 = flags; 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 49 if (skb_dst(skb)->error) 50 return -1; 51 52 #ifdef CONFIG_XFRM 53 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && 54 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) { 55 struct dst_entry *dst = skb_dst(skb); 56 skb_dst_set(skb, NULL); 57 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0); 58 if (IS_ERR(dst)) 59 return -1; 60 skb_dst_set(skb, dst); 61 } 62 #endif 63 64 /* Change in oif may mean change in hh_len. */ 65 hh_len = skb_dst(skb)->dev->hard_header_len; 66 if (skb_headroom(skb) < hh_len && 67 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)), 68 0, GFP_ATOMIC)) 69 return -1; 70 71 return 0; 72 } 73 EXPORT_SYMBOL(ip_route_me_harder); 74 75 #ifdef CONFIG_XFRM 76 int ip_xfrm_me_harder(struct sk_buff *skb) 77 { 78 struct flowi fl; 79 unsigned int hh_len; 80 struct dst_entry *dst; 81 82 if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) 83 return 0; 84 if (xfrm_decode_session(skb, &fl, AF_INET) < 0) 85 return -1; 86 87 dst = skb_dst(skb); 88 if (dst->xfrm) 89 dst = ((struct xfrm_dst *)dst)->route; 90 dst_hold(dst); 91 92 dst = xfrm_lookup(dev_net(dst->dev), dst, &fl, skb->sk, 0); 93 if (IS_ERR(dst)) 94 return -1; 95 96 skb_dst_drop(skb); 97 skb_dst_set(skb, dst); 98 99 /* Change in oif may mean change in hh_len. */ 100 hh_len = skb_dst(skb)->dev->hard_header_len; 101 if (skb_headroom(skb) < hh_len && 102 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 103 return -1; 104 return 0; 105 } 106 EXPORT_SYMBOL(ip_xfrm_me_harder); 107 #endif 108 109 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *); 110 EXPORT_SYMBOL(ip_nat_decode_session); 111 112 /* 113 * Extra routing may needed on local out, as the QUEUE target never 114 * returns control to the table. 115 */ 116 117 struct ip_rt_info { 118 __be32 daddr; 119 __be32 saddr; 120 u_int8_t tos; 121 u_int32_t mark; 122 }; 123 124 static void nf_ip_saveroute(const struct sk_buff *skb, 125 struct nf_queue_entry *entry) 126 { 127 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 128 129 if (entry->hook == NF_INET_LOCAL_OUT) { 130 const struct iphdr *iph = ip_hdr(skb); 131 132 rt_info->tos = iph->tos; 133 rt_info->daddr = iph->daddr; 134 rt_info->saddr = iph->saddr; 135 rt_info->mark = skb->mark; 136 } 137 } 138 139 static int nf_ip_reroute(struct sk_buff *skb, 140 const struct nf_queue_entry *entry) 141 { 142 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 143 144 if (entry->hook == NF_INET_LOCAL_OUT) { 145 const struct iphdr *iph = ip_hdr(skb); 146 147 if (!(iph->tos == rt_info->tos && 148 skb->mark == rt_info->mark && 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 EXPORT_SYMBOL(nf_ip_checksum); 186 187 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, 188 unsigned int dataoff, unsigned int len, 189 u_int8_t protocol) 190 { 191 const struct iphdr *iph = ip_hdr(skb); 192 __sum16 csum = 0; 193 194 switch (skb->ip_summed) { 195 case CHECKSUM_COMPLETE: 196 if (len == skb->len - dataoff) 197 return nf_ip_checksum(skb, hook, dataoff, protocol); 198 /* fall through */ 199 case CHECKSUM_NONE: 200 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, 201 skb->len - dataoff, 0); 202 skb->ip_summed = CHECKSUM_NONE; 203 return __skb_checksum_complete_head(skb, dataoff + len); 204 } 205 return csum; 206 } 207 208 static int nf_ip_route(struct net *net, struct dst_entry **dst, 209 struct flowi *fl, bool strict __always_unused) 210 { 211 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4); 212 if (IS_ERR(rt)) 213 return PTR_ERR(rt); 214 *dst = &rt->dst; 215 return 0; 216 } 217 218 static const struct nf_afinfo nf_ip_afinfo = { 219 .family = AF_INET, 220 .checksum = nf_ip_checksum, 221 .checksum_partial = nf_ip_checksum_partial, 222 .route = nf_ip_route, 223 .saveroute = nf_ip_saveroute, 224 .reroute = nf_ip_reroute, 225 .route_key_size = sizeof(struct ip_rt_info), 226 }; 227 228 static int ipv4_netfilter_init(void) 229 { 230 return nf_register_afinfo(&nf_ip_afinfo); 231 } 232 233 static void ipv4_netfilter_fini(void) 234 { 235 nf_unregister_afinfo(&nf_ip_afinfo); 236 } 237 238 module_init(ipv4_netfilter_init); 239 module_exit(ipv4_netfilter_fini); 240 241 #ifdef CONFIG_SYSCTL 242 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = { 243 { .procname = "net", }, 244 { .procname = "ipv4", }, 245 { .procname = "netfilter", }, 246 { } 247 }; 248 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path); 249 #endif /* CONFIG_SYSCTL */ 250