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