xfrm4_input.c revision 716062fd4c2f88a33ab409f62a1e7397ad0a7e33 
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
24#ifdef CONFIG_NETFILTER
25static inline int xfrm4_rcv_encap_finish(struct sk_buff *skb)
26{
27	if (skb->dst == NULL) {
28		const struct iphdr *iph = ip_hdr(skb);
29
30		if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos,
31				   skb->dev))
32			goto drop;
33	}
34	return dst_input(skb);
35drop:
36	kfree_skb(skb);
37	return NET_RX_DROP;
38}
39#endif
40
41int xfrm4_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,
42		    int encap_type)
43{
44	XFRM_SPI_SKB_CB(skb)->nhoff = offsetof(struct iphdr, protocol);
45	XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
46	return xfrm_input(skb, nexthdr, spi, encap_type);
47}
48EXPORT_SYMBOL(xfrm4_rcv_encap);
49
50int xfrm4_transport_finish(struct sk_buff *skb, int async)
51{
52#ifdef CONFIG_NETFILTER
53	__skb_push(skb, skb->data - skb_network_header(skb));
54	ip_hdr(skb)->tot_len = htons(skb->len);
55	ip_send_check(ip_hdr(skb));
56
57	NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, skb->dev, NULL,
58		xfrm4_rcv_encap_finish);
59	return 0;
60#else
61	return -ip_hdr(skb)->protocol;
62#endif
63}
64
65/* If it's a keepalive packet, then just eat it.
66 * If it's an encapsulated packet, then pass it to the
67 * IPsec xfrm input.
68 * Returns 0 if skb passed to xfrm or was dropped.
69 * Returns >0 if skb should be passed to UDP.
70 * Returns <0 if skb should be resubmitted (-ret is protocol)
71 */
72int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
73{
74	struct udp_sock *up = udp_sk(sk);
75	struct udphdr *uh;
76	struct iphdr *iph;
77	int iphlen, len;
78	int ret;
79
80	__u8 *udpdata;
81	__be32 *udpdata32;
82	__u16 encap_type = up->encap_type;
83
84	/* if this is not encapsulated socket, then just return now */
85	if (!encap_type)
86		return 1;
87
88	/* If this is a paged skb, make sure we pull up
89	 * whatever data we need to look at. */
90	len = skb->len - sizeof(struct udphdr);
91	if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
92		return 1;
93
94	/* Now we can get the pointers */
95	uh = udp_hdr(skb);
96	udpdata = (__u8 *)uh + sizeof(struct udphdr);
97	udpdata32 = (__be32 *)udpdata;
98
99	switch (encap_type) {
100	default:
101	case UDP_ENCAP_ESPINUDP:
102		/* Check if this is a keepalive packet.  If so, eat it. */
103		if (len == 1 && udpdata[0] == 0xff) {
104			goto drop;
105		} else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
106			/* ESP Packet without Non-ESP header */
107			len = sizeof(struct udphdr);
108		} else
109			/* Must be an IKE packet.. pass it through */
110			return 1;
111		break;
112	case UDP_ENCAP_ESPINUDP_NON_IKE:
113		/* Check if this is a keepalive packet.  If so, eat it. */
114		if (len == 1 && udpdata[0] == 0xff) {
115			goto drop;
116		} else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
117			   udpdata32[0] == 0 && udpdata32[1] == 0) {
118
119			/* ESP Packet with Non-IKE marker */
120			len = sizeof(struct udphdr) + 2 * sizeof(u32);
121		} else
122			/* Must be an IKE packet.. pass it through */
123			return 1;
124		break;
125	}
126
127	/* At this point we are sure that this is an ESPinUDP packet,
128	 * so we need to remove 'len' bytes from the packet (the UDP
129	 * header and optional ESP marker bytes) and then modify the
130	 * protocol to ESP, and then call into the transform receiver.
131	 */
132	if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
133		goto drop;
134
135	/* Now we can update and verify the packet length... */
136	iph = ip_hdr(skb);
137	iphlen = iph->ihl << 2;
138	iph->tot_len = htons(ntohs(iph->tot_len) - len);
139	if (skb->len < iphlen + len) {
140		/* packet is too small!?! */
141		goto drop;
142	}
143
144	/* pull the data buffer up to the ESP header and set the
145	 * transport header to point to ESP.  Keep UDP on the stack
146	 * for later.
147	 */
148	__skb_pull(skb, len);
149	skb_reset_transport_header(skb);
150
151	/* process ESP */
152	ret = xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
153	return ret;
154
155drop:
156	kfree_skb(skb);
157	return 0;
158}
159
160int xfrm4_rcv(struct sk_buff *skb)
161{
162	return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
163}
164
165EXPORT_SYMBOL(xfrm4_rcv);
166