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
20int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
21{
22	return xfrm4_extract_header(skb);
23}
24
25static inline int xfrm4_rcv_encap_finish(struct sock *sk, struct sk_buff *skb)
26{
27	if (!skb_dst(skb)) {
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);
35drop:
36	kfree_skb(skb);
37	return NET_RX_DROP;
38}
39
40int 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, NULL, skb,
56		skb->dev, NULL,
57		xfrm4_rcv_encap_finish);
58	return 0;
59}
60
61/* If it's a keepalive packet, then just eat it.
62 * If it's an encapsulated packet, then pass it to the
63 * IPsec xfrm input.
64 * Returns 0 if skb passed to xfrm or was dropped.
65 * Returns >0 if skb should be passed to UDP.
66 * Returns <0 if skb should be resubmitted (-ret is protocol)
67 */
68int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
69{
70	struct udp_sock *up = udp_sk(sk);
71	struct udphdr *uh;
72	struct iphdr *iph;
73	int iphlen, len;
74
75	__u8 *udpdata;
76	__be32 *udpdata32;
77	__u16 encap_type = up->encap_type;
78
79	/* if this is not encapsulated socket, then just return now */
80	if (!encap_type)
81		return 1;
82
83	/* If this is a paged skb, make sure we pull up
84	 * whatever data we need to look at. */
85	len = skb->len - sizeof(struct udphdr);
86	if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
87		return 1;
88
89	/* Now we can get the pointers */
90	uh = udp_hdr(skb);
91	udpdata = (__u8 *)uh + sizeof(struct udphdr);
92	udpdata32 = (__be32 *)udpdata;
93
94	switch (encap_type) {
95	default:
96	case UDP_ENCAP_ESPINUDP:
97		/* Check if this is a keepalive packet.  If so, eat it. */
98		if (len == 1 && udpdata[0] == 0xff) {
99			goto drop;
100		} else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
101			/* ESP Packet without Non-ESP header */
102			len = sizeof(struct udphdr);
103		} else
104			/* Must be an IKE packet.. pass it through */
105			return 1;
106		break;
107	case UDP_ENCAP_ESPINUDP_NON_IKE:
108		/* Check if this is a keepalive packet.  If so, eat it. */
109		if (len == 1 && udpdata[0] == 0xff) {
110			goto drop;
111		} else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
112			   udpdata32[0] == 0 && udpdata32[1] == 0) {
113
114			/* ESP Packet with Non-IKE marker */
115			len = sizeof(struct udphdr) + 2 * sizeof(u32);
116		} else
117			/* Must be an IKE packet.. pass it through */
118			return 1;
119		break;
120	}
121
122	/* At this point we are sure that this is an ESPinUDP packet,
123	 * so we need to remove 'len' bytes from the packet (the UDP
124	 * header and optional ESP marker bytes) and then modify the
125	 * protocol to ESP, and then call into the transform receiver.
126	 */
127	if (skb_unclone(skb, GFP_ATOMIC))
128		goto drop;
129
130	/* Now we can update and verify the packet length... */
131	iph = ip_hdr(skb);
132	iphlen = iph->ihl << 2;
133	iph->tot_len = htons(ntohs(iph->tot_len) - len);
134	if (skb->len < iphlen + len) {
135		/* packet is too small!?! */
136		goto drop;
137	}
138
139	/* pull the data buffer up to the ESP header and set the
140	 * transport header to point to ESP.  Keep UDP on the stack
141	 * for later.
142	 */
143	__skb_pull(skb, len);
144	skb_reset_transport_header(skb);
145
146	/* process ESP */
147	return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
148
149drop:
150	kfree_skb(skb);
151	return 0;
152}
153
154int xfrm4_rcv(struct sk_buff *skb)
155{
156	return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
157}
158EXPORT_SYMBOL(xfrm4_rcv);
159