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 return 0; 71 } 72 73 NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, 74 dev_net(skb->dev), NULL, skb, skb->dev, NULL, 75 xfrm4_rcv_encap_finish); 76 return 0; 77 } 78 79 /* If it's a keepalive packet, then just eat it. 80 * If it's an encapsulated packet, then pass it to the 81 * IPsec xfrm input. 82 * Returns 0 if skb passed to xfrm or was dropped. 83 * Returns >0 if skb should be passed to UDP. 84 * Returns <0 if skb should be resubmitted (-ret is protocol) 85 */ 86 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb) 87 { 88 struct udp_sock *up = udp_sk(sk); 89 struct udphdr *uh; 90 struct iphdr *iph; 91 int iphlen, len; 92 93 __u8 *udpdata; 94 __be32 *udpdata32; 95 __u16 encap_type = up->encap_type; 96 97 /* if this is not encapsulated socket, then just return now */ 98 if (!encap_type) 99 return 1; 100 101 /* If this is a paged skb, make sure we pull up 102 * whatever data we need to look at. */ 103 len = skb->len - sizeof(struct udphdr); 104 if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8))) 105 return 1; 106 107 /* Now we can get the pointers */ 108 uh = udp_hdr(skb); 109 udpdata = (__u8 *)uh + sizeof(struct udphdr); 110 udpdata32 = (__be32 *)udpdata; 111 112 switch (encap_type) { 113 default: 114 case UDP_ENCAP_ESPINUDP: 115 /* Check if this is a keepalive packet. If so, eat it. */ 116 if (len == 1 && udpdata[0] == 0xff) { 117 goto drop; 118 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) { 119 /* ESP Packet without Non-ESP header */ 120 len = sizeof(struct udphdr); 121 } else 122 /* Must be an IKE packet.. pass it through */ 123 return 1; 124 break; 125 case UDP_ENCAP_ESPINUDP_NON_IKE: 126 /* Check if this is a keepalive packet. If so, eat it. */ 127 if (len == 1 && udpdata[0] == 0xff) { 128 goto drop; 129 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) && 130 udpdata32[0] == 0 && udpdata32[1] == 0) { 131 132 /* ESP Packet with Non-IKE marker */ 133 len = sizeof(struct udphdr) + 2 * sizeof(u32); 134 } else 135 /* Must be an IKE packet.. pass it through */ 136 return 1; 137 break; 138 } 139 140 /* At this point we are sure that this is an ESPinUDP packet, 141 * so we need to remove 'len' bytes from the packet (the UDP 142 * header and optional ESP marker bytes) and then modify the 143 * protocol to ESP, and then call into the transform receiver. 144 */ 145 if (skb_unclone(skb, GFP_ATOMIC)) 146 goto drop; 147 148 /* Now we can update and verify the packet length... */ 149 iph = ip_hdr(skb); 150 iphlen = iph->ihl << 2; 151 iph->tot_len = htons(ntohs(iph->tot_len) - len); 152 if (skb->len < iphlen + len) { 153 /* packet is too small!?! */ 154 goto drop; 155 } 156 157 /* pull the data buffer up to the ESP header and set the 158 * transport header to point to ESP. Keep UDP on the stack 159 * for later. 160 */ 161 __skb_pull(skb, len); 162 skb_reset_transport_header(skb); 163 164 /* process ESP */ 165 return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type); 166 167 drop: 168 kfree_skb(skb); 169 return 0; 170 } 171 172 int xfrm4_rcv(struct sk_buff *skb) 173 { 174 return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0); 175 } 176 EXPORT_SYMBOL(xfrm4_rcv); 177