LXR linux/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 <linux/skbuff.h>
   7#include <net/route.h>
   8#include <net/xfrm.h>
   9#include <net/ip.h>
  10#include <net/netfilter/nf_queue.h>
  11
  12/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
  13int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
  14{
  15        struct net *net = dev_net(skb_dst(skb)->dev);
  16        const struct iphdr *iph = ip_hdr(skb);
  17        struct rtable *rt;
  18        struct flowi fl = {};
  19        struct dst_entry *odst;
  20        unsigned int hh_len;
  21        unsigned int type;
  22
  23        type = inet_addr_type(net, iph->saddr);
  24        if (skb->sk && inet_sk(skb->sk)->transparent)
  25                type = RTN_LOCAL;
  26        if (addr_type == RTN_UNSPEC)
  27                addr_type = type;
  28
  29        /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
  30         * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
  31         */
  32        if (addr_type == RTN_LOCAL) {
  33                fl.nl_u.ip4_u.daddr = iph->daddr;
  34                if (type == RTN_LOCAL)
  35                        fl.nl_u.ip4_u.saddr = iph->saddr;
  36                fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
  37                fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
  38                fl.mark = skb->mark;
  39                fl.flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
  40                if (ip_route_output_key(net, &rt, &fl) != 0)
  41                        return -1;
  42
  43                /* Drop old route. */
  44                skb_dst_drop(skb);
  45                skb_dst_set(skb, &rt->u.dst);
  46        } else {
  47                /* non-local src, find valid iif to satisfy
  48                 * rp-filter when calling ip_route_input. */
  49                fl.nl_u.ip4_u.daddr = iph->saddr;
  50                if (ip_route_output_key(net, &rt, &fl) != 0)
  51                        return -1;
  52
  53                odst = skb_dst(skb);
  54                if (ip_route_input(skb, iph->daddr, iph->saddr,
  55                                   RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
  56                        dst_release(&rt->u.dst);
  57                        return -1;
  58                }
  59                dst_release(&rt->u.dst);
  60                dst_release(odst);
  61        }
  62
  63        if (skb_dst(skb)->error)
  64                return -1;
  65
  66#ifdef CONFIG_XFRM
  67        if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
  68            xfrm_decode_session(skb, &fl, AF_INET) == 0) {
  69                struct dst_entry *dst = skb_dst(skb);
  70                skb_dst_set(skb, NULL);
  71                if (xfrm_lookup(net, &dst, &fl, skb->sk, 0))
  72                        return -1;
  73                skb_dst_set(skb, dst);
  74        }
  75#endif
  76
  77        /* Change in oif may mean change in hh_len. */
  78        hh_len = skb_dst(skb)->dev->hard_header_len;
  79        if (skb_headroom(skb) < hh_len &&
  80            pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
  81                return -1;
  82
  83        return 0;
  84}
  85EXPORT_SYMBOL(ip_route_me_harder);
  86
  87#ifdef CONFIG_XFRM
  88int ip_xfrm_me_harder(struct sk_buff *skb)
  89{
  90        struct flowi fl;
  91        unsigned int hh_len;
  92        struct dst_entry *dst;
  93
  94        if (IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
  95                return 0;
  96        if (xfrm_decode_session(skb, &fl, AF_INET) < 0)
  97                return -1;
  98
  99        dst = skb_dst(skb);
 100        if (dst->xfrm)
 101                dst = ((struct xfrm_dst *)dst)->route;
 102        dst_hold(dst);
 103
 104        if (xfrm_lookup(dev_net(dst->dev), &dst, &fl, skb->sk, 0) < 0)
 105                return -1;
 106
 107        skb_dst_drop(skb);
 108        skb_dst_set(skb, dst);
 109
 110        /* Change in oif may mean change in hh_len. */
 111        hh_len = skb_dst(skb)->dev->hard_header_len;
 112        if (skb_headroom(skb) < hh_len &&
 113            pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
 114                return -1;
 115        return 0;
 116}
 117EXPORT_SYMBOL(ip_xfrm_me_harder);
 118#endif
 119
 120void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
 121EXPORT_SYMBOL(ip_nat_decode_session);
 122
 123/*
 124 * Extra routing may needed on local out, as the QUEUE target never
 125 * returns control to the table.
 126 */
 127
 128struct ip_rt_info {
 129        __be32 daddr;
 130        __be32 saddr;
 131        u_int8_t tos;
 132        u_int32_t mark;
 133};
 134
 135static void nf_ip_saveroute(const struct sk_buff *skb,
 136                            struct nf_queue_entry *entry)
 137{
 138        struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
 139
 140        if (entry->hook == NF_INET_LOCAL_OUT) {
 141                const struct iphdr *iph = ip_hdr(skb);
 142
 143                rt_info->tos = iph->tos;
 144                rt_info->daddr = iph->daddr;
 145                rt_info->saddr = iph->saddr;
 146                rt_info->mark = skb->mark;
 147        }
 148}
 149
 150static int nf_ip_reroute(struct sk_buff *skb,
 151                         const struct nf_queue_entry *entry)
 152{
 153        const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
 154
 155        if (entry->hook == NF_INET_LOCAL_OUT) {
 156                const struct iphdr *iph = ip_hdr(skb);
 157
 158                if (!(iph->tos == rt_info->tos
 159                      && skb->mark == rt_info->mark
 160                      && iph->daddr == rt_info->daddr
 161                      && iph->saddr == rt_info->saddr))
 162                        return ip_route_me_harder(skb, RTN_UNSPEC);
 163        }
 164        return 0;
 165}
 166
 167__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
 168                            unsigned int dataoff, u_int8_t protocol)
 169{
 170        const struct iphdr *iph = ip_hdr(skb);
 171        __sum16 csum = 0;
 172
 173        switch (skb->ip_summed) {
 174        case CHECKSUM_COMPLETE:
 175                if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
 176                        break;
 177                if ((protocol == 0 && !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}
 196EXPORT_SYMBOL(nf_ip_checksum);
 197
 198static __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
 199                                      unsigned int dataoff, unsigned int len,
 200                                      u_int8_t protocol)
 201{
 202        const struct iphdr *iph = ip_hdr(skb);
 203        __sum16 csum = 0;
 204
 205        switch (skb->ip_summed) {
 206        case CHECKSUM_COMPLETE:
 207                if (len == skb->len - dataoff)
 208                        return nf_ip_checksum(skb, hook, dataoff, protocol);
 209                /* fall through */
 210        case CHECKSUM_NONE:
 211                skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
 212                                               skb->len - dataoff, 0);
 213                skb->ip_summed = CHECKSUM_NONE;
 214                csum = __skb_checksum_complete_head(skb, dataoff + len);
 215                if (!csum)
 216                        skb->ip_summed = CHECKSUM_UNNECESSARY;
 217        }
 218        return csum;
 219}
 220
 221static int nf_ip_route(struct dst_entry **dst, struct flowi *fl)
 222{
 223        return ip_route_output_key(&init_net, (struct rtable **)dst, fl);
 224}
 225
 226static const struct nf_afinfo nf_ip_afinfo = {
 227        .family                 = AF_INET,
 228        .checksum               = nf_ip_checksum,
 229        .checksum_partial       = nf_ip_checksum_partial,
 230        .route                  = nf_ip_route,
 231        .saveroute              = nf_ip_saveroute,
 232        .reroute                = nf_ip_reroute,
 233        .route_key_size         = sizeof(struct ip_rt_info),
 234};
 235
 236static int ipv4_netfilter_init(void)
 237{
 238        return nf_register_afinfo(&nf_ip_afinfo);
 239}
 240
 241static void ipv4_netfilter_fini(void)
 242{
 243        nf_unregister_afinfo(&nf_ip_afinfo);
 244}
 245
 246module_init(ipv4_netfilter_init);
 247module_exit(ipv4_netfilter_fini);
 248
 249#ifdef CONFIG_SYSCTL
 250struct ctl_path nf_net_ipv4_netfilter_sysctl_path[] = {
 251        { .procname = "net", .ctl_name = CTL_NET, },
 252        { .procname = "ipv4", .ctl_name = NET_IPV4, },
 253        { .procname = "netfilter", .ctl_name = NET_IPV4_NETFILTER, },
 254        { }
 255};
 256EXPORT_SYMBOL_GPL(nf_net_ipv4_netfilter_sysctl_path);
 257#endif /* CONFIG_SYSCTL */
 258