xfrm4_input.c revision 14bbd6a565e1bcdc240d44687edb93f721cfdf99 
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 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);
35drop:
36	kfree_skb(skb);
37	return NET_RX_DROP;
38}
39
40int 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}
47EXPORT_SYMBOL(xfrm4_rcv_encap);
48
49int 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 */
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
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_unclone(skb, 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
157drop:
158	kfree_skb(skb);
159	return 0;
160}
161
162int xfrm4_rcv(struct sk_buff *skb)
163{
164	return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
165}
166EXPORT_SYMBOL(xfrm4_rcv);
167