1 /* 2 * IPv4 specific functions of netfilter core 3 * 4 * Rusty Russell (C) 2000 -- This code is GPL. 5 * Patrick McHardy (C) 2006-2012 6 */ 7 #include <linux/kernel.h> 8 #include <linux/netfilter.h> 9 #include <linux/netfilter_ipv4.h> 10 #include <linux/ip.h> 11 #include <linux/skbuff.h> 12 #include <linux/gfp.h> 13 #include <linux/export.h> 14 #include <net/route.h> 15 #include <net/xfrm.h> 16 #include <net/ip.h> 17 #include <net/netfilter/nf_queue.h> 18 19 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */ 20 int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_type) 21 { 22 const struct iphdr *iph = ip_hdr(skb); 23 struct rtable *rt; 24 struct flowi4 fl4 = {}; 25 __be32 saddr = iph->saddr; 26 __u8 flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0; 27 struct net_device *dev = skb_dst(skb)->dev; 28 unsigned int hh_len; 29 30 if (addr_type == RTN_UNSPEC) 31 addr_type = inet_addr_type_dev_table(net, dev, saddr); 32 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST) 33 flags |= FLOWI_FLAG_ANYSRC; 34 else 35 saddr = 0; 36 37 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause 38 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. 39 */ 40 fl4.daddr = iph->daddr; 41 fl4.saddr = saddr; 42 fl4.flowi4_tos = RT_TOS(iph->tos); 43 fl4.flowi4_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0; 44 if (!fl4.flowi4_oif) 45 fl4.flowi4_oif = l3mdev_master_ifindex(dev); 46 fl4.flowi4_mark = skb->mark; 47 fl4.flowi4_flags = flags; 48 rt = ip_route_output_key(net, &fl4); 49 if (IS_ERR(rt)) 50 return PTR_ERR(rt); 51 52 /* Drop old route. */ 53 skb_dst_drop(skb); 54 skb_dst_set(skb, &rt->dst); 55 56 if (skb_dst(skb)->error) 57 return skb_dst(skb)->error; 58 59 #ifdef CONFIG_XFRM 60 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && 61 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) { 62 struct dst_entry *dst = skb_dst(skb); 63 skb_dst_set(skb, NULL); 64 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), skb->sk, 0); 65 if (IS_ERR(dst)) 66 return PTR_ERR(dst); 67 skb_dst_set(skb, dst); 68 } 69 #endif 70 71 /* Change in oif may mean change in hh_len. */ 72 hh_len = skb_dst(skb)->dev->hard_header_len; 73 if (skb_headroom(skb) < hh_len && 74 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)), 75 0, GFP_ATOMIC)) 76 return -ENOMEM; 77 78 return 0; 79 } 80 EXPORT_SYMBOL(ip_route_me_harder); 81 82 /* 83 * Extra routing may needed on local out, as the QUEUE target never 84 * returns control to the table. 85 */ 86 87 struct ip_rt_info { 88 __be32 daddr; 89 __be32 saddr; 90 u_int8_t tos; 91 u_int32_t mark; 92 }; 93 94 static void nf_ip_saveroute(const struct sk_buff *skb, 95 struct nf_queue_entry *entry) 96 { 97 struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 98 99 if (entry->state.hook == NF_INET_LOCAL_OUT) { 100 const struct iphdr *iph = ip_hdr(skb); 101 102 rt_info->tos = iph->tos; 103 rt_info->daddr = iph->daddr; 104 rt_info->saddr = iph->saddr; 105 rt_info->mark = skb->mark; 106 } 107 } 108 109 static int nf_ip_reroute(struct net *net, struct sk_buff *skb, 110 const struct nf_queue_entry *entry) 111 { 112 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 113 114 if (entry->state.hook == NF_INET_LOCAL_OUT) { 115 const struct iphdr *iph = ip_hdr(skb); 116 117 if (!(iph->tos == rt_info->tos && 118 skb->mark == rt_info->mark && 119 iph->daddr == rt_info->daddr && 120 iph->saddr == rt_info->saddr)) 121 return ip_route_me_harder(net, skb, RTN_UNSPEC); 122 } 123 return 0; 124 } 125 126 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, 127 unsigned int dataoff, u_int8_t protocol) 128 { 129 const struct iphdr *iph = ip_hdr(skb); 130 __sum16 csum = 0; 131 132 switch (skb->ip_summed) { 133 case CHECKSUM_COMPLETE: 134 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) 135 break; 136 if ((protocol == 0 && !csum_fold(skb->csum)) || 137 !csum_tcpudp_magic(iph->saddr, iph->daddr, 138 skb->len - dataoff, protocol, 139 skb->csum)) { 140 skb->ip_summed = CHECKSUM_UNNECESSARY; 141 break; 142 } 143 /* fall through */ 144 case CHECKSUM_NONE: 145 if (protocol == 0) 146 skb->csum = 0; 147 else 148 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, 149 skb->len - dataoff, 150 protocol, 0); 151 csum = __skb_checksum_complete(skb); 152 } 153 return csum; 154 } 155 EXPORT_SYMBOL(nf_ip_checksum); 156 157 static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, 158 unsigned int dataoff, unsigned int len, 159 u_int8_t protocol) 160 { 161 const struct iphdr *iph = ip_hdr(skb); 162 __sum16 csum = 0; 163 164 switch (skb->ip_summed) { 165 case CHECKSUM_COMPLETE: 166 if (len == skb->len - dataoff) 167 return nf_ip_checksum(skb, hook, dataoff, protocol); 168 /* fall through */ 169 case CHECKSUM_NONE: 170 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, 171 skb->len - dataoff, 0); 172 skb->ip_summed = CHECKSUM_NONE; 173 return __skb_checksum_complete_head(skb, dataoff + len); 174 } 175 return csum; 176 } 177 178 static int nf_ip_route(struct net *net, struct dst_entry **dst, 179 struct flowi *fl, bool strict __always_unused) 180 { 181 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4); 182 if (IS_ERR(rt)) 183 return PTR_ERR(rt); 184 *dst = &rt->dst; 185 return 0; 186 } 187 188 static const struct nf_afinfo nf_ip_afinfo = { 189 .family = AF_INET, 190 .checksum = nf_ip_checksum, 191 .checksum_partial = nf_ip_checksum_partial, 192 .route = nf_ip_route, 193 .saveroute = nf_ip_saveroute, 194 .reroute = nf_ip_reroute, 195 .route_key_size = sizeof(struct ip_rt_info), 196 }; 197 198 static int __init ipv4_netfilter_init(void) 199 { 200 return nf_register_afinfo(&nf_ip_afinfo); 201 } 202 subsys_initcall(ipv4_netfilter_init); 203