1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	Handle firewalling
4 *	Linux ethernet bridge
5 *
6 *	Authors:
7 *	Lennert Buytenhek		<buytenh@gnu.org>
8 *	Bart De Schuymer		<bdschuym@pandora.be>
9 *
10 *	Lennert dedicates this file to Kerstin Wurdinger.
11 */
12
13#include <linux/module.h>
14#include <linux/kernel.h>
15#include <linux/slab.h>
16#include <linux/ip.h>
17#include <linux/netdevice.h>
18#include <linux/skbuff.h>
19#include <linux/if_arp.h>
20#include <linux/if_ether.h>
21#include <linux/if_vlan.h>
22#include <linux/if_pppox.h>
23#include <linux/ppp_defs.h>
24#include <linux/netfilter_bridge.h>
25#include <linux/netfilter_ipv4.h>
26#include <linux/netfilter_ipv6.h>
27#include <linux/netfilter_arp.h>
28#include <linux/in_route.h>
29#include <linux/inetdevice.h>
30
31#include <net/ip.h>
32#include <net/ipv6.h>
33#include <net/addrconf.h>
34#include <net/route.h>
35#include <net/netfilter/br_netfilter.h>
36
37#include <linux/uaccess.h>
38#include "br_private.h"
39#ifdef CONFIG_SYSCTL
40#include <linux/sysctl.h>
41#endif
42
43int br_validate_ipv6(struct net *net, struct sk_buff *skb)
44{
45	const struct ipv6hdr *hdr;
46	struct inet6_dev *idev = __in6_dev_get(skb->dev);
47	u32 pkt_len;
48	u8 ip6h_len = sizeof(struct ipv6hdr);
49
50	if (!pskb_may_pull(skb, ip6h_len))
51		goto inhdr_error;
52
53	if (skb->len < ip6h_len)
54		goto drop;
55
56	hdr = ipv6_hdr(skb);
57
58	if (hdr->version != 6)
59		goto inhdr_error;
60
61	pkt_len = ntohs(hdr->payload_len);
62	if (hdr->nexthdr == NEXTHDR_HOP && nf_ip6_check_hbh_len(skb, &pkt_len))
63		goto drop;
64
65	if (pkt_len + ip6h_len > skb->len) {
66		__IP6_INC_STATS(net, idev,
67				IPSTATS_MIB_INTRUNCATEDPKTS);
68		goto drop;
69	}
70	if (pskb_trim_rcsum(skb, pkt_len + ip6h_len)) {
71		__IP6_INC_STATS(net, idev,
72				IPSTATS_MIB_INDISCARDS);
73		goto drop;
74	}
75
76	memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
77	/* No IP options in IPv6 header; however it should be
78	 * checked if some next headers need special treatment
79	 */
80	return 0;
81
82inhdr_error:
83	__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
84drop:
85	return -1;
86}
87
88static inline bool
89br_nf_ipv6_daddr_was_changed(const struct sk_buff *skb,
90			     const struct nf_bridge_info *nf_bridge)
91{
92	return memcmp(&nf_bridge->ipv6_daddr, &ipv6_hdr(skb)->daddr,
93		      sizeof(ipv6_hdr(skb)->daddr)) != 0;
94}
95
96/* PF_BRIDGE/PRE_ROUTING: Undo the changes made for ip6tables
97 * PREROUTING and continue the bridge PRE_ROUTING hook. See comment
98 * for br_nf_pre_routing_finish(), same logic is used here but
99 * equivalent IPv6 function ip6_route_input() called indirectly.
100 */
101static int br_nf_pre_routing_finish_ipv6(struct net *net, struct sock *sk, struct sk_buff *skb)
102{
103	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
104	struct rtable *rt;
105	struct net_device *dev = skb->dev, *br_indev;
106	const struct nf_ipv6_ops *v6ops = nf_get_ipv6_ops();
107
108	br_indev = nf_bridge_get_physindev(skb, net);
109	if (!br_indev) {
110		kfree_skb(skb);
111		return 0;
112	}
113
114	nf_bridge->frag_max_size = IP6CB(skb)->frag_max_size;
115
116	if (nf_bridge->pkt_otherhost) {
117		skb->pkt_type = PACKET_OTHERHOST;
118		nf_bridge->pkt_otherhost = false;
119	}
120	nf_bridge->in_prerouting = 0;
121	if (br_nf_ipv6_daddr_was_changed(skb, nf_bridge)) {
122		skb_dst_drop(skb);
123		v6ops->route_input(skb);
124
125		if (skb_dst(skb)->error) {
126			kfree_skb(skb);
127			return 0;
128		}
129
130		if (skb_dst(skb)->dev == dev) {
131			skb->dev = br_indev;
132			nf_bridge_update_protocol(skb);
133			nf_bridge_push_encap_header(skb);
134			br_nf_hook_thresh(NF_BR_PRE_ROUTING,
135					  net, sk, skb, skb->dev, NULL,
136					  br_nf_pre_routing_finish_bridge);
137			return 0;
138		}
139		ether_addr_copy(eth_hdr(skb)->h_dest, dev->dev_addr);
140		skb->pkt_type = PACKET_HOST;
141	} else {
142		rt = bridge_parent_rtable(br_indev);
143		if (!rt) {
144			kfree_skb(skb);
145			return 0;
146		}
147		skb_dst_drop(skb);
148		skb_dst_set_noref(skb, &rt->dst);
149	}
150
151	skb->dev = br_indev;
152	nf_bridge_update_protocol(skb);
153	nf_bridge_push_encap_header(skb);
154	br_nf_hook_thresh(NF_BR_PRE_ROUTING, net, sk, skb,
155			  skb->dev, NULL, br_handle_frame_finish);
156
157	return 0;
158}
159
160/* Replicate the checks that IPv6 does on packet reception and pass the packet
161 * to ip6tables.
162 */
163unsigned int br_nf_pre_routing_ipv6(void *priv,
164				    struct sk_buff *skb,
165				    const struct nf_hook_state *state)
166{
167	struct nf_bridge_info *nf_bridge;
168
169	if (br_validate_ipv6(state->net, skb))
170		return NF_DROP_REASON(skb, SKB_DROP_REASON_IP_INHDR, 0);
171
172	nf_bridge = nf_bridge_alloc(skb);
173	if (!nf_bridge)
174		return NF_DROP_REASON(skb, SKB_DROP_REASON_NOMEM, 0);
175	if (!setup_pre_routing(skb, state->net))
176		return NF_DROP_REASON(skb, SKB_DROP_REASON_DEV_READY, 0);
177
178	nf_bridge = nf_bridge_info_get(skb);
179	nf_bridge->ipv6_daddr = ipv6_hdr(skb)->daddr;
180
181	skb->protocol = htons(ETH_P_IPV6);
182	skb->transport_header = skb->network_header + sizeof(struct ipv6hdr);
183
184	NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, state->net, state->sk, skb,
185		skb->dev, NULL,
186		br_nf_pre_routing_finish_ipv6);
187
188	return NF_STOLEN;
189}
190