net/ipv4/netfilter.c

   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 <net/route.h>
   7 #include <net/xfrm.h>
   8 #include <net/ip.h>
   9
  10 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
  11 int ip_route_me_harder(struct sk_buff **pskb, unsigned addr_type)
  12 {
  13         struct iphdr *iph = (*pskb)->nh.iph;
  14         struct rtable *rt;
  15         struct flowi fl = {};
  16         struct dst_entry *odst;
  17         unsigned int hh_len;
  18
  19         if (addr_type == RTN_UNSPEC)
  20                 addr_type = inet_addr_type(iph->saddr);
  21
  22         /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
  23          * packets with foreign saddr to appear on the NF_IP_LOCAL_OUT hook.
  24          */
  25         if (addr_type == RTN_LOCAL) {
  26                 fl.nl_u.ip4_u.daddr = iph->daddr;
  27                 fl.nl_u.ip4_u.saddr = iph->saddr;
  28                 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
  29                 fl.oif = (*pskb)->sk ? (*pskb)->sk->sk_bound_dev_if : 0;
  30 #ifdef CONFIG_IP_ROUTE_FWMARK
  31                 fl.nl_u.ip4_u.fwmark = (*pskb)->mark;
  32 #endif
  33                 if (ip_route_output_key(&rt, &fl) != 0)
  34                         return -1;
  35
  36                 /* Drop old route. */
  37                 dst_release((*pskb)->dst);
  38                 (*pskb)->dst = &rt->u.dst;
  39         } else {
  40                 /* non-local src, find valid iif to satisfy
  41                  * rp-filter when calling ip_route_input. */
  42                 fl.nl_u.ip4_u.daddr = iph->saddr;
  43                 if (ip_route_output_key(&rt, &fl) != 0)
  44                         return -1;
  45
  46                 odst = (*pskb)->dst;
  47                 if (ip_route_input(*pskb, iph->daddr, iph->saddr,
  48                                    RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
  49                         dst_release(&rt->u.dst);
  50                         return -1;
  51                 }
  52                 dst_release(&rt->u.dst);
  53                 dst_release(odst);
  54         }
  55
  56         if ((*pskb)->dst->error)
  57                 return -1;
  58
  59 #ifdef CONFIG_XFRM
  60         if (!(IPCB(*pskb)->flags & IPSKB_XFRM_TRANSFORMED) &&
  61             xfrm_decode_session(*pskb, &fl, AF_INET) == 0)
  62                 if (xfrm_lookup(&(*pskb)->dst, &fl, (*pskb)->sk, 0))
  63                         return -1;
  64 #endif
  65
  66         /* Change in oif may mean change in hh_len. */
  67         hh_len = (*pskb)->dst->dev->hard_header_len;
  68         if (skb_headroom(*pskb) < hh_len) {
  69                 struct sk_buff *nskb;
  70
  71                 nskb = skb_realloc_headroom(*pskb, hh_len);
  72                 if (!nskb)
  73                         return -1;
  74                 if ((*pskb)->sk)
  75                         skb_set_owner_w(nskb, (*pskb)->sk);
  76                 kfree_skb(*pskb);
  77                 *pskb = nskb;
  78         }
  79
  80         return 0;
  81 }
  82 EXPORT_SYMBOL(ip_route_me_harder);
  83
  84 #ifdef CONFIG_XFRM
  85 int ip_xfrm_me_harder(struct sk_buff **pskb)
  86 {
  87         struct flowi fl;
  88         unsigned int hh_len;
  89         struct dst_entry *dst;
  90
  91         if (IPCB(*pskb)->flags & IPSKB_XFRM_TRANSFORMED)
  92                 return 0;
  93         if (xfrm_decode_session(*pskb, &fl, AF_INET) < 0)
  94                 return -1;
  95
  96         dst = (*pskb)->dst;
  97         if (dst->xfrm)
  98                 dst = ((struct xfrm_dst *)dst)->route;
  99         dst_hold(dst);
 100
 101         if (xfrm_lookup(&dst, &fl, (*pskb)->sk, 0) < 0)
 102                 return -1;
 103
 104         dst_release((*pskb)->dst);
 105         (*pskb)->dst = dst;
 106
 107         /* Change in oif may mean change in hh_len. */
 108         hh_len = (*pskb)->dst->dev->hard_header_len;
 109         if (skb_headroom(*pskb) < hh_len) {
 110                 struct sk_buff *nskb;
 111
 112                 nskb = skb_realloc_headroom(*pskb, hh_len);
 113                 if (!nskb)
 114                         return -1;
 115                 if ((*pskb)->sk)
 116                         skb_set_owner_w(nskb, (*pskb)->sk);
 117                 kfree_skb(*pskb);
 118                 *pskb = nskb;
 119         }
 120         return 0;
 121 }
 122 EXPORT_SYMBOL(ip_xfrm_me_harder);
 123 #endif
 124
 125 void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
 126 EXPORT_SYMBOL(ip_nat_decode_session);
 127
 128 /*
 129  * Extra routing may needed on local out, as the QUEUE target never
 130  * returns control to the table.
 131  */
 132
 133 struct ip_rt_info {
 134         __be32 daddr;
 135         __be32 saddr;
 136         u_int8_t tos;
 137 };
 138
 139 static void nf_ip_saveroute(const struct sk_buff *skb, struct nf_info *info)
 140 {
 141         struct ip_rt_info *rt_info = nf_info_reroute(info);
 142
 143         if (info->hook == NF_IP_LOCAL_OUT) {
 144                 const struct iphdr *iph = skb->nh.iph;
 145
 146                 rt_info->tos = iph->tos;
 147                 rt_info->daddr = iph->daddr;
 148                 rt_info->saddr = iph->saddr;
 149         }
 150 }
 151
 152 static int nf_ip_reroute(struct sk_buff **pskb, const struct nf_info *info)
 153 {
 154         const struct ip_rt_info *rt_info = nf_info_reroute(info);
 155
 156         if (info->hook == NF_IP_LOCAL_OUT) {
 157                 struct iphdr *iph = (*pskb)->nh.iph;
 158
 159                 if (!(iph->tos == rt_info->tos
 160                       && iph->daddr == rt_info->daddr
 161                       && iph->saddr == rt_info->saddr))
 162                         return ip_route_me_harder(pskb, RTN_UNSPEC);
 163         }
 164         return 0;
 165 }
 166
 167 unsigned int nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
 168                             unsigned int dataoff, u_int8_t protocol)
 169 {
 170         struct iphdr *iph = skb->nh.iph;
 171         unsigned int csum = 0;
 172
 173         switch (skb->ip_summed) {
 174         case CHECKSUM_COMPLETE:
 175                 if (hook != NF_IP_PRE_ROUTING && hook != NF_IP_LOCAL_IN)
 176                         break;
 177                 if ((protocol == 0 && !(u16)csum_fold(skb->csum)) ||
 178                     !csum_tcpudp_magic(iph->saddr, iph->daddr,
 179                                        skb->len - dataoff, protocol,
 180                                        skb->csum)) {
 181                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 182                         break;
 183                 }
 184                 /* fall through */
 185         case CHECKSUM_NONE:
 186                 if (protocol == 0)
 187                         skb->csum = 0;
 188                 else
 189                         skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
 190                                                        skb->len - dataoff,
 191                                                        protocol, 0);
 192                 csum = __skb_checksum_complete(skb);
 193         }
 194         return csum;
 195 }
 196
 197 EXPORT_SYMBOL(nf_ip_checksum);
 198
 199 static struct nf_afinfo nf_ip_afinfo = {
 200         .family         = AF_INET,
 201         .checksum       = nf_ip_checksum,
 202         .saveroute      = nf_ip_saveroute,
 203         .reroute        = nf_ip_reroute,
 204         .route_key_size = sizeof(struct ip_rt_info),
 205 };
 206
 207 static int ipv4_netfilter_init(void)
 208 {
 209         return nf_register_afinfo(&nf_ip_afinfo);
 210 }
 211
 212 static void ipv4_netfilter_fini(void)
 213 {
 214         nf_unregister_afinfo(&nf_ip_afinfo);
 215 }
 216
 217 module_init(ipv4_netfilter_init);
 218 module_exit(ipv4_netfilter_fini);