xfrm4_input.c

  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#include <net/protocol.h>
 21#include <net/gro.h>
 22
 23static int xfrm4_rcv_encap_finish2(struct net *net, struct sock *sk,
 24				   struct sk_buff *skb)
 25{
 26	return dst_input(skb);
 27}
 28
 29static inline int xfrm4_rcv_encap_finish(struct net *net, struct sock *sk,
 30					 struct sk_buff *skb)
 31{
 32	if (!skb_dst(skb)) {
 33		const struct iphdr *iph = ip_hdr(skb);
 34
 35		if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
 36					 ip4h_dscp(iph), skb->dev))
 37			goto drop;
 38	}
 39
 40	if (xfrm_trans_queue(skb, xfrm4_rcv_encap_finish2))
 41		goto drop;
 42
 43	return 0;
 44drop:
 45	kfree_skb(skb);
 46	return NET_RX_DROP;
 47}
 48
 49int xfrm4_transport_finish(struct sk_buff *skb, int async)
 50{
 51	struct xfrm_offload *xo = xfrm_offload(skb);
 52	struct iphdr *iph = ip_hdr(skb);
 53	struct net_device *dev = skb->dev;
 54
 55	iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
 56
 57#ifndef CONFIG_NETFILTER
 58	if (!async)
 59		return -iph->protocol;
 60#endif
 61
 62	__skb_push(skb, -skb_network_offset(skb));
 63	iph->tot_len = htons(skb->len);
 64	ip_send_check(iph);
 65
 66	if (xo && (xo->flags & XFRM_GRO)) {
 67		/* The full l2 header needs to be preserved so that re-injecting the packet at l2
 68		 * works correctly in the presence of vlan tags.
 69		 */
 70		skb_mac_header_rebuild_full(skb, xo->orig_mac_len);
 71		skb_reset_network_header(skb);
 72		skb_reset_transport_header(skb);
 73		return 0;
 74	}
 75
 76	NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
 77		dev_net(dev), NULL, skb, dev, NULL,
 78		xfrm4_rcv_encap_finish);
 79	if (async)
 80		dev_put(dev);
 81	return 0;
 82}
 83
 84static int __xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb, bool pull)
 85{
 86	struct udp_sock *up = udp_sk(sk);
 87	struct udphdr *uh;
 88	struct iphdr *iph;
 89	int iphlen, len;
 90	__u8 *udpdata;
 91	__be32 *udpdata32;
 92	u16 encap_type;
 93
 94	encap_type = READ_ONCE(up->encap_type);
 95	/* if this is not encapsulated socket, then just return now */
 96	if (!encap_type)
 97		return 1;
 98
 99	/* If this is a paged skb, make sure we pull up
100	 * whatever data we need to look at. */
101	len = skb->len - sizeof(struct udphdr);
102	if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
103		return 1;
104
105	/* Now we can get the pointers */
106	uh = udp_hdr(skb);
107	udpdata = (__u8 *)uh + sizeof(struct udphdr);
108	udpdata32 = (__be32 *)udpdata;
109
110	switch (encap_type) {
111	default:
112	case UDP_ENCAP_ESPINUDP:
113		/* Check if this is a keepalive packet.  If so, eat it. */
114		if (len == 1 && udpdata[0] == 0xff) {
115			return -EINVAL;
116		} else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
117			/* ESP Packet without Non-ESP header */
118			len = sizeof(struct udphdr);
119		} else
120			/* Must be an IKE packet.. pass it through */
121			return 1;
122		break;
123	}
124
125	/* At this point we are sure that this is an ESPinUDP packet,
126	 * so we need to remove 'len' bytes from the packet (the UDP
127	 * header and optional ESP marker bytes) and then modify the
128	 * protocol to ESP, and then call into the transform receiver.
129	 */
130	if (skb_unclone(skb, GFP_ATOMIC))
131		return -EINVAL;
132
133	/* Now we can update and verify the packet length... */
134	iph = ip_hdr(skb);
135	iphlen = iph->ihl << 2;
136	iph->tot_len = htons(ntohs(iph->tot_len) - len);
137	if (skb->len < iphlen + len) {
138		/* packet is too small!?! */
139		return -EINVAL;
140	}
141
142	/* pull the data buffer up to the ESP header and set the
143	 * transport header to point to ESP.  Keep UDP on the stack
144	 * for later.
145	 */
146	if (pull) {
147		__skb_pull(skb, len);
148		skb_reset_transport_header(skb);
149	} else {
150		skb_set_transport_header(skb, len);
151	}
152
153	/* process ESP */
154	return 0;
155}
156
157/* If it's a keepalive packet, then just eat it.
158 * If it's an encapsulated packet, then pass it to the
159 * IPsec xfrm input.
160 * Returns 0 if skb passed to xfrm or was dropped.
161 * Returns >0 if skb should be passed to UDP.
162 * Returns <0 if skb should be resubmitted (-ret is protocol)
163 */
164int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
165{
166	int ret;
167
168	ret = __xfrm4_udp_encap_rcv(sk, skb, true);
169	if (!ret)
170		return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0,
171				       udp_sk(sk)->encap_type);
172
173	if (ret < 0) {
174		kfree_skb(skb);
175		return 0;
176	}
177
178	return ret;
179}
180EXPORT_SYMBOL(xfrm4_udp_encap_rcv);
181
182struct sk_buff *xfrm4_gro_udp_encap_rcv(struct sock *sk, struct list_head *head,
183					struct sk_buff *skb)
184{
185	int offset = skb_gro_offset(skb);
186	const struct net_offload *ops;
187	struct sk_buff *pp = NULL;
188	int len, dlen;
189	__u8 *udpdata;
190	__be32 *udpdata32;
191
192	len = skb->len - offset;
193	dlen = offset + min(len, 8);
194	udpdata = skb_gro_header(skb, dlen, offset);
195	udpdata32 = (__be32 *)udpdata;
196	if (unlikely(!udpdata))
197		return NULL;
198
199	rcu_read_lock();
200	ops = rcu_dereference(inet_offloads[IPPROTO_ESP]);
201	if (!ops || !ops->callbacks.gro_receive)
202		goto out;
203
204	/* check if it is a keepalive or IKE packet */
205	if (len <= sizeof(struct ip_esp_hdr) || udpdata32[0] == 0)
206		goto out;
207
208	/* set the transport header to ESP */
209	skb_set_transport_header(skb, offset);
210
211	NAPI_GRO_CB(skb)->proto = IPPROTO_UDP;
212
213	pp = call_gro_receive(ops->callbacks.gro_receive, head, skb);
214	rcu_read_unlock();
215
216	return pp;
217
218out:
219	rcu_read_unlock();
220	NAPI_GRO_CB(skb)->same_flow = 0;
221	NAPI_GRO_CB(skb)->flush = 1;
222
223	return NULL;
224}
225EXPORT_SYMBOL(xfrm4_gro_udp_encap_rcv);
226
227int xfrm4_rcv(struct sk_buff *skb)
228{
229	return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
230}
231EXPORT_SYMBOL(xfrm4_rcv);