net/ipv4/xfrm4_input.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * xfrm4_input.c
   4  *
   5  * Changes:
   6  *      YOSHIFUJI Hideaki @USAGI
   7  *              Split up af-specific portion
   8  *      Derek Atkins <derek@ihtfp.com>
   9  *              Add Encapsulation support
  10  *
  11  */
  12
  13 #include <linux/slab.h>
  14 #include <linux/module.h>
  15 #include <linux/string.h>
  16 #include <linux/netfilter.h>
  17 #include <linux/netfilter_ipv4.h>
  18 #include <net/ip.h>
  19 #include <net/xfrm.h>
  20 #include <net/protocol.h>
  21 #include <net/gro.h>
  22
  23 static int xfrm4_rcv_encap_finish2(struct net *net, struct sock *sk,
  24                                    struct sk_buff *skb)
  25 {
  26         return dst_input(skb);
  27 }
  28
  29 static inline int xfrm4_rcv_encap_finish(struct net *net, struct sock *sk,
  30                                          struct sk_buff *skb)
  31 {
  32         if (!skb_dst(skb)) {
  33                 const struct iphdr *iph = ip_hdr(skb);
  34
  35                 if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
  36                                          ip4h_dscp(iph), skb->dev))
  37                         goto drop;
  38         }
  39
  40         if (xfrm_trans_queue(skb, xfrm4_rcv_encap_finish2))
  41                 goto drop;
  42
  43         return 0;
  44 drop:
  45         kfree_skb(skb);
  46         return NET_RX_DROP;
  47 }
  48
  49 int xfrm4_transport_finish(struct sk_buff *skb, int async)
  50 {
  51         struct xfrm_offload *xo = xfrm_offload(skb);
  52         struct iphdr *iph = ip_hdr(skb);
  53
  54         iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
  55
  56 #ifndef CONFIG_NETFILTER
  57         if (!async)
  58                 return -iph->protocol;
  59 #endif
  60
  61         __skb_push(skb, -skb_network_offset(skb));
  62         iph->tot_len = htons(skb->len);
  63         ip_send_check(iph);
  64
  65         if (xo && (xo->flags & XFRM_GRO)) {
  66                 /* The full l2 header needs to be preserved so that re-injecting the packet at l2
  67                  * works correctly in the presence of vlan tags.
  68                  */
  69                 skb_mac_header_rebuild_full(skb, xo->orig_mac_len);
  70                 skb_reset_network_header(skb);
  71                 skb_reset_transport_header(skb);
  72                 return 0;
  73         }
  74
  75         NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
  76                 dev_net(skb->dev), NULL, skb, skb->dev, NULL,
  77                 xfrm4_rcv_encap_finish);
  78         return 0;
  79 }
  80
  81 static int __xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb, bool pull)
  82 {
  83         struct udp_sock *up = udp_sk(sk);
  84         struct udphdr *uh;
  85         struct iphdr *iph;
  86         int iphlen, len;
  87         __u8 *udpdata;
  88         __be32 *udpdata32;
  89         u16 encap_type;
  90
  91         encap_type = READ_ONCE(up->encap_type);
  92         /* if this is not encapsulated socket, then just return now */
  93         if (!encap_type)
  94                 return 1;
  95
  96         /* If this is a paged skb, make sure we pull up
  97          * whatever data we need to look at. */
  98         len = skb->len - sizeof(struct udphdr);
  99         if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
 100                 return 1;
 101
 102         /* Now we can get the pointers */
 103         uh = udp_hdr(skb);
 104         udpdata = (__u8 *)uh + sizeof(struct udphdr);
 105         udpdata32 = (__be32 *)udpdata;
 106
 107         switch (encap_type) {
 108         default:
 109         case UDP_ENCAP_ESPINUDP:
 110                 /* Check if this is a keepalive packet.  If so, eat it. */
 111                 if (len == 1 && udpdata[0] == 0xff) {
 112                         return -EINVAL;
 113                 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
 114                         /* ESP Packet without Non-ESP header */
 115                         len = sizeof(struct udphdr);
 116                 } else
 117                         /* Must be an IKE packet.. pass it through */
 118                         return 1;
 119                 break;
 120         }
 121
 122         /* At this point we are sure that this is an ESPinUDP packet,
 123          * so we need to remove 'len' bytes from the packet (the UDP
 124          * header and optional ESP marker bytes) and then modify the
 125          * protocol to ESP, and then call into the transform receiver.
 126          */
 127         if (skb_unclone(skb, GFP_ATOMIC))
 128                 return -EINVAL;
 129
 130         /* Now we can update and verify the packet length... */
 131         iph = ip_hdr(skb);
 132         iphlen = iph->ihl << 2;
 133         iph->tot_len = htons(ntohs(iph->tot_len) - len);
 134         if (skb->len < iphlen + len) {
 135                 /* packet is too small!?! */
 136                 return -EINVAL;
 137         }
 138
 139         /* pull the data buffer up to the ESP header and set the
 140          * transport header to point to ESP.  Keep UDP on the stack
 141          * for later.
 142          */
 143         if (pull) {
 144                 __skb_pull(skb, len);
 145                 skb_reset_transport_header(skb);
 146         } else {
 147                 skb_set_transport_header(skb, len);
 148         }
 149
 150         /* process ESP */
 151         return 0;
 152 }
 153
 154 /* If it's a keepalive packet, then just eat it.
 155  * If it's an encapsulated packet, then pass it to the
 156  * IPsec xfrm input.
 157  * Returns 0 if skb passed to xfrm or was dropped.
 158  * Returns >0 if skb should be passed to UDP.
 159  * Returns <0 if skb should be resubmitted (-ret is protocol)
 160  */
 161 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
 162 {
 163         int ret;
 164
 165         ret = __xfrm4_udp_encap_rcv(sk, skb, true);
 166         if (!ret)
 167                 return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0,
 168                                        udp_sk(sk)->encap_type);
 169
 170         if (ret < 0) {
 171                 kfree_skb(skb);
 172                 return 0;
 173         }
 174
 175         return ret;
 176 }
 177 EXPORT_SYMBOL(xfrm4_udp_encap_rcv);
 178
 179 struct sk_buff *xfrm4_gro_udp_encap_rcv(struct sock *sk, struct list_head *head,
 180                                         struct sk_buff *skb)
 181 {
 182         int offset = skb_gro_offset(skb);
 183         const struct net_offload *ops;
 184         struct sk_buff *pp = NULL;
 185         int ret;
 186
 187         offset = offset - sizeof(struct udphdr);
 188
 189         if (!pskb_pull(skb, offset))
 190                 return NULL;
 191
 192         rcu_read_lock();
 193         ops = rcu_dereference(inet_offloads[IPPROTO_ESP]);
 194         if (!ops || !ops->callbacks.gro_receive)
 195                 goto out;
 196
 197         ret = __xfrm4_udp_encap_rcv(sk, skb, false);
 198         if (ret)
 199                 goto out;
 200
 201         skb_push(skb, offset);
 202         NAPI_GRO_CB(skb)->proto = IPPROTO_UDP;
 203
 204         pp = call_gro_receive(ops->callbacks.gro_receive, head, skb);
 205         rcu_read_unlock();
 206
 207         return pp;
 208
 209 out:
 210         rcu_read_unlock();
 211         skb_push(skb, offset);
 212         NAPI_GRO_CB(skb)->same_flow = 0;
 213         NAPI_GRO_CB(skb)->flush = 1;
 214
 215         return NULL;
 216 }
 217 EXPORT_SYMBOL(xfrm4_gro_udp_encap_rcv);
 218
 219 int xfrm4_rcv(struct sk_buff *skb)
 220 {
 221         return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
 222 }
 223 EXPORT_SYMBOL(xfrm4_rcv);