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_len - skb_headroom(skb), 0, GFP_ATOMIC)) 68 return -1; 69 70 return 0; 71 } 72 EXPORT_SYMBOL(ip_route_me_harder); 73 74 #ifdef CONFIG_XFRM 75 int ip_xfrm_me_harder(struct sk_buff *skb) 76 { 77 struct flowi fl; 78 unsigned int hh_len; 79 struct dst_entry *dst; 80 81 if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) 82 return 0; 83 if (xfrm_decode_session(skb, &fl, AF_INET) < 0) 84 return -1; 85 86 dst = skb_dst(skb); 87 if (dst->xfrm) 88 dst = ((struct xfrm_dst *)dst)->route; 89 dst_hold(dst); 90 91 dst = xfrm_lookup(dev_net(dst->dev), dst, &fl, skb->sk, 0); 92 if (IS_ERR(dst)) 93 return -1; 94 95 skb_dst_drop(skb); 96 skb_dst_set(skb, dst); 97 98 /* Change in oif may mean change in hh_len. */ 99 hh_len = skb_dst(skb)->dev->hard_header_len; 100 if (skb_headroom(skb) < hh_len && 101 pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC)) 102 return -1; 103 return 0; 104 } 105 EXPORT_SYMBOL(ip_xfrm_me_harder); 106 #endif 107 108 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *); 109 EXPORT_SYMBOL(ip_nat_decode_session); 110 111 /* 112 * Extra routing may needed on local out, as the QUEUE target never 113 * returns control to the table. 114 */ 115 116 struct ip_rt_info { 117 __be32 daddr; 118 __be32 saddr; 119 u_int8_t tos; 120 u_int32_t mark; 121 }; 122 123 static void nf_ip_saveroute(const struct sk_buff *skb, 124 struct nf_queue_entry *entry) 125 { 126 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 127 128 if (entry->hook == NF_INET_LOCAL_OUT) { 129 const struct iphdr *iph = ip_hdr(skb); 130 131 rt_info->tos = iph->tos; 132 rt_info->daddr = iph->daddr; 133 rt_info->saddr = iph->saddr; 134 rt_info->mark = skb->mark; 135 } 136 } 137 138 static int nf_ip_reroute(struct sk_buff *skb, 139 const struct nf_queue_entry *entry) 140 { 141 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 142 143 if (entry->hook == NF_INET_LOCAL_OUT) { 144 const struct iphdr *iph = ip_hdr(skb); 145 146 if (!(iph->tos == rt_info->tos && 147 skb->mark == rt_info->mark && 148 iph->daddr == rt_info->daddr && 149 iph->saddr == rt_info->saddr)) 150 return ip_route_me_harder(skb, RTN_UNSPEC); 151 } 152 return 0; 153 } 154 155 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, 156 unsigned int dataoff, u_int8_t protocol) 157 { 158 const struct iphdr *iph = ip_hdr(skb); 159 __sum16 csum = 0; 160 161 switch (skb->ip_summed) { 162 case CHECKSUM_COMPLETE: 163 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) 164 break; 165 if ((protocol == 0 && !csum_fold(skb->csum)) || 166 !csum_tcpudp_magic(iph->saddr, iph->daddr, 167 skb->len - dataoff, protocol, 168 skb->csum)) { 169 skb->ip_summed = CHECKSUM_UNNECESSARY; 170 break; 171 } 172 /* fall through */ 173 case CHECKSUM_NONE: 174 if (protocol == 0) 175 skb->csum = 0; 176 else 177 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, 178 skb->len - dataoff, 179 protocol, 0); 180 csum = __skb_checksum_complete(skb); 181 } 182 return csum; 183 } 184 EXPORT_SYMBOL(nf_ip_checksum); 185 186 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, 187 unsigned int dataoff, unsigned int len, 188 u_int8_t protocol) 189 { 190 const struct iphdr *iph = ip_hdr(skb); 191 __sum16 csum = 0; 192 193 switch (skb->ip_summed) { 194 case CHECKSUM_COMPLETE: 195 if (len == skb->len - dataoff) 196 return nf_ip_checksum(skb, hook, dataoff, protocol); 197 /* fall through */ 198 case CHECKSUM_NONE: 199 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, 200 skb->len - dataoff, 0); 201 skb->ip_summed = CHECKSUM_NONE; 202 return __skb_checksum_complete_head(skb, dataoff + len); 203 } 204 return csum; 205 } 206 207 static int nf_ip_route(struct net *net, struct dst_entry **dst, 208 struct flowi *fl, bool strict __always_unused) 209 { 210 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4); 211 if (IS_ERR(rt)) 212 return PTR_ERR(rt); 213 *dst = &rt->dst; 214 return 0; 215 } 216 217 static const struct nf_afinfo nf_ip_afinfo = { 218 .family = AF_INET, 219 .checksum = nf_ip_checksum, 220 .checksum_partial = nf_ip_checksum_partial, 221 .route = nf_ip_route, 222 .saveroute = nf_ip_saveroute, 223 .reroute = nf_ip_reroute, 224 .route_key_size = sizeof(struct ip_rt_info), 225 }; 226 227 static int ipv4_netfilter_init(void) 228 { 229 return nf_register_afinfo(&nf_ip_afinfo); 230 } 231 232 static void ipv4_netfilter_fini(void) 233 { 234 nf_unregister_afinfo(&nf_ip_afinfo); 235 } 236 237 module_init(ipv4_netfilter_init); 238 module_exit(ipv4_netfilter_fini); 239 240 #ifdef CONFIG_SYSCTL 241 struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = { 242 { .procname = "net", }, 243 { .procname = "ipv4", }, 244 { .procname = "netfilter", }, 245 { } 246 }; 247 EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path); 248 #endif /* CONFIG_SYSCTL */ 249