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 const struct sock *sk = skb_to_full_sk(skb); 27 __u8 flags = sk ? inet_sk_flowi_flags(sk) : 0; 28 struct net_device *dev = skb_dst(skb)->dev; 29 unsigned int hh_len; 30 31 if (addr_type == RTN_UNSPEC) 32 addr_type = inet_addr_type_dev_table(net, dev, saddr); 33 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST) 34 flags |= FLOWI_FLAG_ANYSRC; 35 else 36 saddr = 0; 37 38 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause 39 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. 40 */ 41 fl4.daddr = iph->daddr; 42 fl4.saddr = saddr; 43 fl4.flowi4_tos = RT_TOS(iph->tos); 44 fl4.flowi4_oif = sk ? sk->sk_bound_dev_if : 0; 45 if (!fl4.flowi4_oif) 46 fl4.flowi4_oif = l3mdev_master_ifindex(dev); 47 fl4.flowi4_mark = skb->mark; 48 fl4.flowi4_flags = flags; 49 rt = ip_route_output_key(net, &fl4); 50 if (IS_ERR(rt)) 51 return PTR_ERR(rt); 52 53 /* Drop old route. */ 54 skb_dst_drop(skb); 55 skb_dst_set(skb, &rt->dst); 56 57 if (skb_dst(skb)->error) 58 return skb_dst(skb)->error; 59 60 #ifdef CONFIG_XFRM 61 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && 62 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) { 63 struct dst_entry *dst = skb_dst(skb); 64 skb_dst_set(skb, NULL); 65 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0); 66 if (IS_ERR(dst)) 67 return PTR_ERR(dst); 68 skb_dst_set(skb, dst); 69 } 70 #endif 71 72 /* Change in oif may mean change in hh_len. */ 73 hh_len = skb_dst(skb)->dev->hard_header_len; 74 if (skb_headroom(skb) < hh_len && 75 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)), 76 0, GFP_ATOMIC)) 77 return -ENOMEM; 78 79 return 0; 80 } 81 EXPORT_SYMBOL(ip_route_me_harder); 82 83 int nf_ip_reroute(struct sk_buff *skb, const struct nf_queue_entry *entry) 84 { 85 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry); 86 87 if (entry->state.hook == NF_INET_LOCAL_OUT) { 88 const struct iphdr *iph = ip_hdr(skb); 89 90 if (!(iph->tos == rt_info->tos && 91 skb->mark == rt_info->mark && 92 iph->daddr == rt_info->daddr && 93 iph->saddr == rt_info->saddr)) 94 return ip_route_me_harder(entry->state.net, skb, 95 RTN_UNSPEC); 96 } 97 return 0; 98 } 99 EXPORT_SYMBOL_GPL(nf_ip_reroute); 100 101 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook, 102 unsigned int dataoff, u_int8_t protocol) 103 { 104 const struct iphdr *iph = ip_hdr(skb); 105 __sum16 csum = 0; 106 107 switch (skb->ip_summed) { 108 case CHECKSUM_COMPLETE: 109 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN) 110 break; 111 if ((protocol == 0 && !csum_fold(skb->csum)) || 112 !csum_tcpudp_magic(iph->saddr, iph->daddr, 113 skb->len - dataoff, protocol, 114 skb->csum)) { 115 skb->ip_summed = CHECKSUM_UNNECESSARY; 116 break; 117 } 118 /* fall through */ 119 case CHECKSUM_NONE: 120 if (protocol == 0) 121 skb->csum = 0; 122 else 123 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, 124 skb->len - dataoff, 125 protocol, 0); 126 csum = __skb_checksum_complete(skb); 127 } 128 return csum; 129 } 130 EXPORT_SYMBOL(nf_ip_checksum); 131 132 __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook, 133 unsigned int dataoff, unsigned int len, 134 u_int8_t protocol) 135 { 136 const struct iphdr *iph = ip_hdr(skb); 137 __sum16 csum = 0; 138 139 switch (skb->ip_summed) { 140 case CHECKSUM_COMPLETE: 141 if (len == skb->len - dataoff) 142 return nf_ip_checksum(skb, hook, dataoff, protocol); 143 /* fall through */ 144 case CHECKSUM_NONE: 145 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol, 146 skb->len - dataoff, 0); 147 skb->ip_summed = CHECKSUM_NONE; 148 return __skb_checksum_complete_head(skb, dataoff + len); 149 } 150 return csum; 151 } 152 EXPORT_SYMBOL_GPL(nf_ip_checksum_partial); 153 154 int nf_ip_route(struct net *net, struct dst_entry **dst, struct flowi *fl, 155 bool strict __always_unused) 156 { 157 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4); 158 if (IS_ERR(rt)) 159 return PTR_ERR(rt); 160 *dst = &rt->dst; 161 return 0; 162 } 163 EXPORT_SYMBOL_GPL(nf_ip_route); 164