1 /* 2 * xfrm4_input.c 3 * 4 * Changes: 5 * YOSHIFUJI Hideaki @USAGI 6 * Split up af-specific portion 7 * Derek Atkins <derek@ihtfp.com> 8 * Add Encapsulation support 9 * 10 */ 11 12 #include <linux/slab.h> 13 #include <linux/module.h> 14 #include <linux/string.h> 15 #include <linux/netfilter.h> 16 #include <linux/netfilter_ipv4.h> 17 #include <net/ip.h> 18 #include <net/xfrm.h> 19 20 int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb) 21 { 22 return xfrm4_extract_header(skb); 23 } 24 25 static inline int xfrm4_rcv_encap_finish(struct net *net, struct sock *sk, 26 struct sk_buff *skb) 27 { 28 if (!skb_dst(skb)) { 29 const struct iphdr *iph = ip_hdr(skb); 30 31 if (ip_route_input_noref(skb, iph->daddr, iph->saddr, 32 iph->tos, skb->dev)) 33 goto drop; 34 } 35 return dst_input(skb); 36 drop: 37 kfree_skb(skb); 38 return NET_RX_DROP; 39 } 40 41 int xfrm4_transport_finish(struct sk_buff *skb, int async) 42 { 43 struct iphdr *iph = ip_hdr(skb); 44 45 iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol; 46 47 #ifndef CONFIG_NETFILTER 48 if (!async) 49 return -iph->protocol; 50 #endif 51 52 __skb_push(skb, skb->data - skb_network_header(skb)); 53 iph->tot_len = htons(skb->len); 54 ip_send_check(iph); 55 56 NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, 57 dev_net(skb->dev), NULL, skb, skb->dev, NULL, 58 xfrm4_rcv_encap_finish); 59 return 0; 60 } 61 62 /* If it's a keepalive packet, then just eat it. 63 * If it's an encapsulated packet, then pass it to the 64 * IPsec xfrm input. 65 * Returns 0 if skb passed to xfrm or was dropped. 66 * Returns >0 if skb should be passed to UDP. 67 * Returns <0 if skb should be resubmitted (-ret is protocol) 68 */ 69 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb) 70 { 71 struct udp_sock *up = udp_sk(sk); 72 struct udphdr *uh; 73 struct iphdr *iph; 74 int iphlen, len; 75 76 __u8 *udpdata; 77 __be32 *udpdata32; 78 __u16 encap_type = up->encap_type; 79 80 /* if this is not encapsulated socket, then just return now */ 81 if (!encap_type) 82 return 1; 83 84 /* If this is a paged skb, make sure we pull up 85 * whatever data we need to look at. */ 86 len = skb->len - sizeof(struct udphdr); 87 if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8))) 88 return 1; 89 90 /* Now we can get the pointers */ 91 uh = udp_hdr(skb); 92 udpdata = (__u8 *)uh + sizeof(struct udphdr); 93 udpdata32 = (__be32 *)udpdata; 94 95 switch (encap_type) { 96 default: 97 case UDP_ENCAP_ESPINUDP: 98 /* Check if this is a keepalive packet. If so, eat it. */ 99 if (len == 1 && udpdata[0] == 0xff) { 100 goto drop; 101 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) { 102 /* ESP Packet without Non-ESP header */ 103 len = sizeof(struct udphdr); 104 } else 105 /* Must be an IKE packet.. pass it through */ 106 return 1; 107 break; 108 case UDP_ENCAP_ESPINUDP_NON_IKE: 109 /* Check if this is a keepalive packet. If so, eat it. */ 110 if (len == 1 && udpdata[0] == 0xff) { 111 goto drop; 112 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) && 113 udpdata32[0] == 0 && udpdata32[1] == 0) { 114 115 /* ESP Packet with Non-IKE marker */ 116 len = sizeof(struct udphdr) + 2 * sizeof(u32); 117 } else 118 /* Must be an IKE packet.. pass it through */ 119 return 1; 120 break; 121 } 122 123 /* At this point we are sure that this is an ESPinUDP packet, 124 * so we need to remove 'len' bytes from the packet (the UDP 125 * header and optional ESP marker bytes) and then modify the 126 * protocol to ESP, and then call into the transform receiver. 127 */ 128 if (skb_unclone(skb, GFP_ATOMIC)) 129 goto drop; 130 131 /* Now we can update and verify the packet length... */ 132 iph = ip_hdr(skb); 133 iphlen = iph->ihl << 2; 134 iph->tot_len = htons(ntohs(iph->tot_len) - len); 135 if (skb->len < iphlen + len) { 136 /* packet is too small!?! */ 137 goto drop; 138 } 139 140 /* pull the data buffer up to the ESP header and set the 141 * transport header to point to ESP. Keep UDP on the stack 142 * for later. 143 */ 144 __skb_pull(skb, len); 145 skb_reset_transport_header(skb); 146 147 /* process ESP */ 148 return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type); 149 150 drop: 151 kfree_skb(skb); 152 return 0; 153 } 154 155 int xfrm4_rcv(struct sk_buff *skb) 156 { 157 return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0); 158 } 159 EXPORT_SYMBOL(xfrm4_rcv); 160