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