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 __be32 saddr = iph->saddr; 21 __u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0; 22 unsigned int hh_len; 23 24 if (addr_type == RTN_UNSPEC) 25 addr_type = inet_addr_type(net, saddr); 26 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST) 27 flags |= FLOWI_FLAG_ANYSRC; 28 else 29 saddr = 0; 30 31 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause 32 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. 33 */ 34 fl4.daddr = iph->daddr; 35 fl4.saddr = saddr; 36 fl4.flowi4_tos = RT_TOS(iph->tos); 37 fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0; 38 fl4.flowi4_mark = skb->mark; 39 fl4.flowi4_flags = flags; 40 rt = ip_route_output_key(net, &fl4); 41 if (IS_ERR(rt)) 42 return -1; 43 44 /* Drop old route. */ 45 skb_dst_drop(skb); 46 skb_dst_set(skb, &rt->dst); 47 48 if (skb_dst(skb)->error) 49 return -1; 50 51 #ifdef CONFIG_XFRM 52 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && 53 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) { 54 struct dst_entry *dst = skb_dst(skb); 55 skb_dst_set(skb, NULL); 56 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0); 57 if (IS_ERR(dst)) 58 return -1; 59 skb_dst_set(skb, dst); 60 } 61 #endif 62 63 /* Change in oif may mean change in hh_len. */ 64 hh_len = skb_dst(skb)->dev->hard_header_len; 65 if (skb_headroom(skb) < hh_len && 66 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 67 return -1; 68 69 return 0; 70 } 71 EXPORT_SYMBOL(ip_route_me_harder); 72 73 #ifdef CONFIG_XFRM 74 int ip_xfrm_me_harder(struct sk_buff *skb) 75 { 76 struct flowi fl; 77 unsigned int hh_len; 78 struct dst_entry *dst; 79 80 if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) 81 return 0; 82 if (xfrm_decode_session(skb, &fl, AF_INET) < 0) 83 return -1; 84 85 dst = skb_dst(skb); 86 if (dst->xfrm) 87 dst = ((struct xfrm_dst *)dst)->route; 88 dst_hold(dst); 89 90 dst = xfrm_lookup(dev_net(dst->dev), dst, &fl, skb->sk, 0); 91 if (IS_ERR(dst)) 92 return -1; 93 94 skb_dst_drop(skb); 95 skb_dst_set(skb, dst); 96 97 /* Change in oif may mean change in hh_len. */ 98 hh_len = skb_dst(skb)->dev->hard_header_len; 99 if (skb_headroom(skb) < hh_len && 100 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 101 return -1; 102 return 0; 103 } 104 EXPORT_SYMBOL(ip_xfrm_me_harder); 105 #endif 106 107 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *); 108 EXPORT_SYMBOL(ip_nat_decode_session); 109 110 /* 111 * Extra routing may needed on local out, as the QUEUE target never 112 * returns control to the table. 113 */ 114 115 struct ip_rt_info { 116 __be32 daddr; 117 __be32 saddr; 118 u_int8_t tos; 119 u_int32_t mark; 120 }; 121 122 static void nf_ip_saveroute(const struct sk_buff *skb, 123 struct nf_queue_entry *entry) 124 { 125 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 126 127 if (entry->hook == NF_INET_LOCAL_OUT) { 128 const struct iphdr *iph = ip_hdr(skb); 129 130 rt_info->tos = iph->tos; 131 rt_info->daddr = iph->daddr; 132 rt_info->saddr = iph->saddr; 133 rt_info->mark = skb->mark; 134 } 135 } 136 137 static int nf_ip_reroute(struct sk_buff *skb, 138 const struct nf_queue_entry *entry) 139 { 140 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 141 142 if (entry->hook == NF_INET_LOCAL_OUT) { 143 const struct iphdr *iph = ip_hdr(skb); 144 145 if (!(iph->tos == rt_info->tos && 146 skb->mark == rt_info->mark && 147 iph->daddr == rt_info->daddr && 148 iph->saddr == rt_info->saddr)) 149 return ip_route_me_harder(skb, RTN_UNSPEC); 150 } 151 return 0; 152 } 153 154 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, 155 unsigned int dataoff, u_int8_t protocol) 156 { 157 const struct iphdr *iph = ip_hdr(skb); 158 __sum16 csum = 0; 159 160 switch (skb->ip_summed) { 161 case CHECKSUM_COMPLETE: 162 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) 163 break; 164 if ((protocol == 0 && !csum_fold(skb->csum)) || 165 !csum_tcpudp_magic(iph->saddr, iph->daddr, 166 skb->len - dataoff, protocol, 167 skb->csum)) { 168 skb->ip_summed = CHECKSUM_UNNECESSARY; 169 break; 170 } 171 /* fall through */ 172 case CHECKSUM_NONE: 173 if (protocol == 0) 174 skb->csum = 0; 175 else 176 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, 177 skb->len - dataoff, 178 protocol, 0); 179 csum = __skb_checksum_complete(skb); 180 } 181 return csum; 182 } 183 EXPORT_SYMBOL(nf_ip_checksum); 184 185 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, 186 unsigned int dataoff, unsigned int len, 187 u_int8_t protocol) 188 { 189 const struct iphdr *iph = ip_hdr(skb); 190 __sum16 csum = 0; 191 192 switch (skb->ip_summed) { 193 case CHECKSUM_COMPLETE: 194 if (len == skb->len - dataoff) 195 return nf_ip_checksum(skb, hook, dataoff, protocol); 196 /* fall through */ 197 case CHECKSUM_NONE: 198 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, 199 skb->len - dataoff, 0); 200 skb->ip_summed = CHECKSUM_NONE; 201 return __skb_checksum_complete_head(skb, dataoff + len); 202 } 203 return csum; 204 } 205 206 static int nf_ip_route(struct net *net, struct dst_entry **dst, 207 struct flowi *fl, bool strict __always_unused) 208 { 209 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4); 210 if (IS_ERR(rt)) 211 return PTR_ERR(rt); 212 *dst = &rt->dst; 213 return 0; 214 } 215 216 static const struct nf_afinfo nf_ip_afinfo = { 217 .family = AF_INET, 218 .checksum = nf_ip_checksum, 219 .checksum_partial = nf_ip_checksum_partial, 220 .route = nf_ip_route, 221 .saveroute = nf_ip_saveroute, 222 .reroute = nf_ip_reroute, 223 .route_key_size = sizeof(struct ip_rt_info), 224 }; 225 226 static int ipv4_netfilter_init(void) 227 { 228 return nf_register_afinfo(&nf_ip_afinfo); 229 } 230 231 static void ipv4_netfilter_fini(void) 232 { 233 nf_unregister_afinfo(&nf_ip_afinfo); 234 } 235 236 module_init(ipv4_netfilter_init); 237 module_exit(ipv4_netfilter_fini); 238 239 #ifdef CONFIG_SYSCTL 240 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = { 241 { .procname = "net", }, 242 { .procname = "ipv4", }, 243 { .procname = "netfilter", }, 244 { } 245 }; 246 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path); 247 #endif /* CONFIG_SYSCTL */ 248