xfrm4_input.c revision 1bf06cd2e338fd6fc29169d30eaf0df982338285 
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/module.h>
13#include <linux/string.h>
14#include <linux/netfilter.h>
15#include <linux/netfilter_ipv4.h>
16#include <net/ip.h>
17#include <net/xfrm.h>
18
19int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
20{
21	return xfrm4_extract_header(skb);
22}
23
24static inline int xfrm4_rcv_encap_finish(struct sk_buff *skb)
25{
26	if (skb->dst == NULL) {
27		const struct iphdr *iph = ip_hdr(skb);
28
29		if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos,
30				   skb->dev))
31			goto drop;
32	}
33	return dst_input(skb);
34drop:
35	kfree_skb(skb);
36	return NET_RX_DROP;
37}
38
39int xfrm4_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,
40		    int encap_type)
41{
42	XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
43	return xfrm_input(skb, nexthdr, spi, encap_type);
44}
45EXPORT_SYMBOL(xfrm4_rcv_encap);
46
47int xfrm4_transport_finish(struct sk_buff *skb, int async)
48{
49	struct iphdr *iph = ip_hdr(skb);
50
51	iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
52
53#ifdef CONFIG_NETFILTER
54	__skb_push(skb, skb->data - skb_network_header(skb));
55	iph->tot_len = htons(skb->len);
56	ip_send_check(iph);
57
58	NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, skb->dev, NULL,
59		xfrm4_rcv_encap_finish);
60	return 0;
61#else
62	if (async)
63		return xfrm4_rcv_encap_finish(skb);
64
65	return -iph->protocol;
66#endif
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 */
76int 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	int ret;
83
84	__u8 *udpdata;
85	__be32 *udpdata32;
86	__u16 encap_type = up->encap_type;
87
88	/* if this is not encapsulated socket, then just return now */
89	if (!encap_type)
90		return 1;
91
92	/* If this is a paged skb, make sure we pull up
93	 * whatever data we need to look at. */
94	len = skb->len - sizeof(struct udphdr);
95	if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
96		return 1;
97
98	/* Now we can get the pointers */
99	uh = udp_hdr(skb);
100	udpdata = (__u8 *)uh + sizeof(struct udphdr);
101	udpdata32 = (__be32 *)udpdata;
102
103	switch (encap_type) {
104	default:
105	case UDP_ENCAP_ESPINUDP:
106		/* Check if this is a keepalive packet.  If so, eat it. */
107		if (len == 1 && udpdata[0] == 0xff) {
108			goto drop;
109		} else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
110			/* ESP Packet without Non-ESP header */
111			len = sizeof(struct udphdr);
112		} else
113			/* Must be an IKE packet.. pass it through */
114			return 1;
115		break;
116	case UDP_ENCAP_ESPINUDP_NON_IKE:
117		/* Check if this is a keepalive packet.  If so, eat it. */
118		if (len == 1 && udpdata[0] == 0xff) {
119			goto drop;
120		} else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
121			   udpdata32[0] == 0 && udpdata32[1] == 0) {
122
123			/* ESP Packet with Non-IKE marker */
124			len = sizeof(struct udphdr) + 2 * sizeof(u32);
125		} else
126			/* Must be an IKE packet.. pass it through */
127			return 1;
128		break;
129	}
130
131	/* At this point we are sure that this is an ESPinUDP packet,
132	 * so we need to remove 'len' bytes from the packet (the UDP
133	 * header and optional ESP marker bytes) and then modify the
134	 * protocol to ESP, and then call into the transform receiver.
135	 */
136	if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
137		goto drop;
138
139	/* Now we can update and verify the packet length... */
140	iph = ip_hdr(skb);
141	iphlen = iph->ihl << 2;
142	iph->tot_len = htons(ntohs(iph->tot_len) - len);
143	if (skb->len < iphlen + len) {
144		/* packet is too small!?! */
145		goto drop;
146	}
147
148	/* pull the data buffer up to the ESP header and set the
149	 * transport header to point to ESP.  Keep UDP on the stack
150	 * for later.
151	 */
152	__skb_pull(skb, len);
153	skb_reset_transport_header(skb);
154
155	/* process ESP */
156	ret = xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
157	return ret;
158
159drop:
160	kfree_skb(skb);
161	return 0;
162}
163
164int xfrm4_rcv(struct sk_buff *skb)
165{
166	return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
167}
168
169EXPORT_SYMBOL(xfrm4_rcv);
170