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Linux/net/ipv4/xfrm4_input.c

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  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 
 21 int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
 22 {
 23         return xfrm4_extract_header(skb);
 24 }
 25 
 26 static int xfrm4_rcv_encap_finish2(struct net *net, struct sock *sk,
 27                                    struct sk_buff *skb)
 28 {
 29         return dst_input(skb);
 30 }
 31 
 32 static inline int xfrm4_rcv_encap_finish(struct net *net, struct sock *sk,
 33                                          struct sk_buff *skb)
 34 {
 35         if (!skb_dst(skb)) {
 36                 const struct iphdr *iph = ip_hdr(skb);
 37 
 38                 if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
 39                                          iph->tos, skb->dev))
 40                         goto drop;
 41         }
 42 
 43         if (xfrm_trans_queue(skb, xfrm4_rcv_encap_finish2))
 44                 goto drop;
 45 
 46         return 0;
 47 drop:
 48         kfree_skb(skb);
 49         return NET_RX_DROP;
 50 }
 51 
 52 int xfrm4_transport_finish(struct sk_buff *skb, int async)
 53 {
 54         struct xfrm_offload *xo = xfrm_offload(skb);
 55         struct iphdr *iph = ip_hdr(skb);
 56 
 57         iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
 58 
 59 #ifndef CONFIG_NETFILTER
 60         if (!async)
 61                 return -iph->protocol;
 62 #endif
 63 
 64         __skb_push(skb, skb->data - skb_network_header(skb));
 65         iph->tot_len = htons(skb->len);
 66         ip_send_check(iph);
 67 
 68         if (xo && (xo->flags & XFRM_GRO)) {
 69                 skb_mac_header_rebuild(skb);
 70                 skb_reset_transport_header(skb);
 71                 return 0;
 72         }
 73 
 74         NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
 75                 dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 76                 xfrm4_rcv_encap_finish);
 77         return 0;
 78 }
 79 
 80 /* If it's a keepalive packet, then just eat it.
 81  * If it's an encapsulated packet, then pass it to the
 82  * IPsec xfrm input.
 83  * Returns 0 if skb passed to xfrm or was dropped.
 84  * Returns >0 if skb should be passed to UDP.
 85  * Returns <0 if skb should be resubmitted (-ret is protocol)
 86  */
 87 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
 88 {
 89         struct udp_sock *up = udp_sk(sk);
 90         struct udphdr *uh;
 91         struct iphdr *iph;
 92         int iphlen, len;
 93 
 94         __u8 *udpdata;
 95         __be32 *udpdata32;
 96         __u16 encap_type = up->encap_type;
 97 
 98         /* if this is not encapsulated socket, then just return now */
 99         if (!encap_type)
100                 return 1;
101 
102         /* If this is a paged skb, make sure we pull up
103          * whatever data we need to look at. */
104         len = skb->len - sizeof(struct udphdr);
105         if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
106                 return 1;
107 
108         /* Now we can get the pointers */
109         uh = udp_hdr(skb);
110         udpdata = (__u8 *)uh + sizeof(struct udphdr);
111         udpdata32 = (__be32 *)udpdata;
112 
113         switch (encap_type) {
114         default:
115         case UDP_ENCAP_ESPINUDP:
116                 /* Check if this is a keepalive packet.  If so, eat it. */
117                 if (len == 1 && udpdata[0] == 0xff) {
118                         goto drop;
119                 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
120                         /* ESP Packet without Non-ESP header */
121                         len = sizeof(struct udphdr);
122                 } else
123                         /* Must be an IKE packet.. pass it through */
124                         return 1;
125                 break;
126         case UDP_ENCAP_ESPINUDP_NON_IKE:
127                 /* Check if this is a keepalive packet.  If so, eat it. */
128                 if (len == 1 && udpdata[0] == 0xff) {
129                         goto drop;
130                 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
131                            udpdata32[0] == 0 && udpdata32[1] == 0) {
132 
133                         /* ESP Packet with Non-IKE marker */
134                         len = sizeof(struct udphdr) + 2 * sizeof(u32);
135                 } else
136                         /* Must be an IKE packet.. pass it through */
137                         return 1;
138                 break;
139         }
140 
141         /* At this point we are sure that this is an ESPinUDP packet,
142          * so we need to remove 'len' bytes from the packet (the UDP
143          * header and optional ESP marker bytes) and then modify the
144          * protocol to ESP, and then call into the transform receiver.
145          */
146         if (skb_unclone(skb, GFP_ATOMIC))
147                 goto drop;
148 
149         /* Now we can update and verify the packet length... */
150         iph = ip_hdr(skb);
151         iphlen = iph->ihl << 2;
152         iph->tot_len = htons(ntohs(iph->tot_len) - len);
153         if (skb->len < iphlen + len) {
154                 /* packet is too small!?! */
155                 goto drop;
156         }
157 
158         /* pull the data buffer up to the ESP header and set the
159          * transport header to point to ESP.  Keep UDP on the stack
160          * for later.
161          */
162         __skb_pull(skb, len);
163         skb_reset_transport_header(skb);
164 
165         /* process ESP */
166         return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
167 
168 drop:
169         kfree_skb(skb);
170         return 0;
171 }
172 
173 int xfrm4_rcv(struct sk_buff *skb)
174 {
175         return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
176 }
177 EXPORT_SYMBOL(xfrm4_rcv);
178 

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